Theses - Zoology
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Item Embargo The social environment and the evolution of morphology in the burying beetle, Nicrophorus vespilloidesSmith, Jack MarcusSocial interactions within species are ubiquitous in nature, and cause animals to exist in a social environment. In this thesis, I investigate how the social environment can influence morphological evolution, using a combination of observation and experiments on burying beetles *Nicrophorus vespilloides*. This species exhibits a set of social interactions at all life stages that centre around the acquisition and use of small carrion during reproduction. Larvae grow and develop on an edible carrion nest fashioned from a corpse by their parents. Here they interact with siblings and caring parents as they acquire resources from the carrion to grow and develop. Later, as sexually mature adults, they themselves compete with conspecifics of their own sex for carrion to breed upon. I investigate how these various social interactions influence morphology at these different lifestages. I start by investigating how the social environment influences morphological evolution of offspring, by collecting data from replicate experimental populations that had been evolving for 39 generations in different social environments when I began work. In two populations, parents were able to supply care (‘Full Care’ populations), whereas in two other populations parents were prevented from supplying any post-hatching care (‘No Care’ populations). In Chapter 2, I show that hatchling morphology evolves divergently in these two different social environments. In the Full Care populations, first-hatched larvae have relatively larger head morphology and body size compared with last-hatched larvae. In the No Care populations, by contrast, first- and last-hatched larvae are significantly more uniform in their head morphology and body size throughout the entire brood. In Chapter 3, I show that third instar larval morphology also diverges between the ‘Full Care’ and ‘No Care’ environments. In general, larvae from the Full Care populations have disproportionately larger heads, compared to larvae from the No Care populations. In each case, I suggest that this divergence in the evolution of larval morphology between populations is due to the selection pressures of sibling competition that materialises only in the presence of parents. Next, I investigate how the social environment contributes to morphological change in adult beetles. In Chapter 4, I discover a new form of sexual dimorphism in burying beetles: male burying beetles exhibit disproportionately larger heads than females. I show that this head morphology is directly linked to biting performance, and that beetles with larger heads exert a greater bite force. I then link this to the burying beetle’s natural history and show that head size predicts the outcome of contests over carrion, in both males and females. Finally, in Chapter 5, I investigate how head morphology functions in the preparation of the carrion nest. Males typically invest more than females in nest preparation, though females can prepare a nest singlehandedly if widowed. I use an experimental approach in the laboratory to investigate how parental division of labour influences the evolution of adult morphology; taking advantage of ongoing experimental evolution in a different set of experimental populations, in which females were induced to prepare a carrion nest without any help from the male. I show that females evolve a relatively larger head in response to this additional parental responsibility, whereas males evolve smaller head morphology. In Chapter 6, I discuss how these different results together show that key morphological traits do evolve in response to divergent social environments, whilst highlighting the role of constraints in morphological evolution.Item Open Access Understanding and improving the cost-effectiveness of biodiversity conservationWhite, Thomas; White, Thomas [0000-0002-0536-6162]Biodiversity conservation is currently facing extraordinary challenges but remains severely limited by funding. Thus, the importance of cost-effective conservation is being increasingly realised – requiring information on both the effects and costs of actions taken to conserve biodiversity. Yet, despite progress in collating and using evidence on the effectiveness of conservation in decision-making, the recording and use of cost data has received far less attention. This PhD aims to help bridge this gap by investigating the collection and use of economic data for conservation decision making, as part of wider research into evidence-based conservation. The research presented is structured into several stages: i) investigate the current state of cost reporting and the use of evidence (including costs) in conservation decision making, ii) develop frameworks and approaches to help improve the reporting of the economic costs and benefits of conservation actions, and the use of evidence in decision-making around biodiversity impact mitigation. Lastly, I then apply this thinking to two detailed case studies where I assess the costs and cost-effectiveness of different conservation interventions. Reviewing the published literature on conservation interventions, I identified low rates of detailed cost reporting. Reported costs often lacked important contextual detail necessary to interpret the data and apply it in different contexts. Where detailed costs were provided, they showed considerable variation, with differences in how costs were reported likely to explain much of this variance. I then conducted an interview-based study investigating the use of evidence in business-biodiversity decision making. This revealed a wide range of themes including the high reliance of professionals on experts, policy and guidance as a stamp of cost-effective, evidence-based practice. Several challenges to integrating biodiversity in the private sector were also noted, including the need for better understanding the economic costs and benefits of mitigation action. Building on these studies, I then developed i) a step-by-step framework for the standardised reporting of economic costs and benefits of conservation action, and ii) a set of principles for the use of evidence (including data on costs) to guide actions that businesses and consultants can take to minimize and compensate for their impacts on biodiversity. To demonstrate the complexities and importance of using cost data in decision-making, I then provide two case studies. The first of these studies assesses the costs and cost-effectiveness of actions to avoid and minimize the impacts of power lines on at-risk bird species in Spain. The study identified large variations in the effectiveness and cost-effectiveness of different actions to prevent collisions with at-risk bird species. Changing how cost is measured, by including the costs associated with negative impacts, can improve the apparent cost-effectiveness of mitigation measures, particularly those more effective measures which avoid impact at the outset. In the second case study, I used a dataset of field-level costs of commonly applied agri-environment interventions in the UK to investigate actions to protect and restore biodiversity in farmland. I identified a high variation in costs both between and within different conservation actions. Costs and cost-effectiveness varied depending on the inclusion of several inputs (e.g., fertilizer, pesticide) during implementation, field size, as well as the types of cost and benefit included. Understanding the variability in costs within actions, and how costs and cost-effectiveness are calculated, are critical considerations when assessing the feasibility of different actions to protect and restore biodiversity.Item Embargo Variation in neural crest development contributes to phenotypic diversification of East African cichlid fishesMarconi, AleksandraThe cichlid fishes comprise the largest extant vertebrate family and are the quintessential example of rapid “explosive” adaptive radiations and phenotypic diversification. Despite low genetic divergence, East African cichlids harbour a spectacular intra- and interspecific morphological diversity. Akin to other vertebrates, a considerable proportion of hyper-diverse cichlid traits, such as craniofacial morphologies and pigmentation patterns, originates from a common embryonic migratory progenitor cell population, the neural crest (NC). Although the genetic and developmental basis of these phenotypes has been investigated, understanding of how and when, specifically how early, in ontogeny species-specific differences emerge, remains limited. In this PhD thesis, I present a multispecies comparative analysis of the developmental basis of NC-derived phenotypic diversity in Lake Malawi cichlids, focusing on the variation in development of the embryo, NC, and its derivatives. First, I demonstrate fundamental differences in multiple aspects of cichlid embryogenesis, including variation in morphology and timing, duration, and rate of developmental events (heterochrony) concomitant with NC development. Interspecific differences were also identified at the onset of overt formation of craniofacial skeleton and body pigmentation, irrespective of the developmental heterochronies. Second, I characterise the developmental and cellular basis of divergent pigmentation patterns among cichlids, including in the underexplored context of sexual dimorphism in this NC-derived trait. Among the abundant differences between species in many aspects of body colouration, I show that, in contrast to zebrafish, divergent cellular mechanisms underlie formation of analogous phenotypes among closely related cichlids. These results provide a novel perspective on the developmental basis and evolution of vertebrate pigmentation beyond traditional model systems. Finally, I examine the temporal and spatial variation in NC genetic and developmental programme in two divergent cichlids. In addition to spatial-temporal differences in migratory pathways of the NC cells, I identified novel NC subpopulations based on the differential expression of canonical marker of migratory NC sox10 and its duplicate sox10-like. The variation in the spatial distribution of these NC subpopulations implicates neo- and subfunctionalisation as well as partial redundancy between sox10 duplicates, one of which has been lost in the well-studied zebrafish lineage, and thus entirely unexplored role in NC and teleost evolution. The results I present in this thesis offer an integrated perspective on the complex genetic and developmental basis of cichlid morphological variation, spanning from the fundamental processes of embryogenesis to development of the NC and its derivatives. In particular, my work provides compelling evidence of the unprecedented variability in the NC developmental programme between closely related species and therefore contributes to our understanding of the role of this remarkable cell population in evolution of vertebrate morphological diversity.Item Embargo Evolution in a fragmented world: Phenotypic and genetic divergence amongst neighbouring populations of the burying beetle Nicrophorus vespilloidesCatherall-Ostler, AndrewHabitat fragmentation is a leading cause of biodiversity loss, but relatively little is known about its long-term evolutionary consequences. I addressed this problem using neighbouring wild populations of burying beetles (*Nicrophorus* spp.), insects which fight to secure carrion upon which they breed. My work focused on the *Nicrophorus* populations inhabiting a cluster of seven ancient woods west of Cambridge. Whilst the criteria used to identify ancient woods are increasingly controversial, I combined new and existing approaches to show there is strong evidence that these woods have been physically separated for at least a thousand years. I carried out three years of fieldwork in each of the seven woods and found that four different species of burying beetle compete over carrion. The carrion niche is partitioned among burying beetles by size: but despite overlapping spatially and temporally with its larger competitors, the smallest species *N. vespilloides* is the most abundant in each wood. Notwithstanding their similarity in age, ecology and geographic location, I found that the community structure and density of burying beetles varied between the seven woods. I argue that these differences likely cause differences in the intensity of competition between the woods. If this is true, then selection could then favour different levels of investment in competition-related phenotypes between the populations. I tested this hypothesis by establishing seven laboratory populations of *N. vespilloides*, each derived from a different woodland population. I then measured relevant phenotypes from each population in common garden experiments. I found that the contests between burying beetles over carcasses are fought primarily with their mandibles but that there is also a behavioural component of individual fighting ability. Females from woods with more diverse community structures were found to be better fighters. A second set of experiments revealed between-population variation in the behaviour of larvae and adults when breeding on a carcass. In woods that had more diverse community structures, larvae arrived at the carcass sooner after oviposition than did larvae from woods with less diverse community structures. I also found that larval arrival time at the carcass causes a sudden drop in the motivation of potential usurpers to take over a carcass. Together, these results suggest that a quicker larval arrival time might provide a mechanism for evading intense interspecific competition for carrion. Finally, I found that males from woods which support a high density of burying beetles had a shorter duration of parental care, presumably because males departed earlier to secure additional off-carcass mating opportunities. After working with collaborators to obtain pooled whole genome sequencing for the populations, I measured the extent of between population genetic differentiation. I found that the extent of genetic differentiation correlates strongly with the extent of dissimilarity in their community structures. These results suggest that the populations are undergoing divergent adaptation despite gene flow. Together with recent work on other species, the emerging picture is that even populations living in closely-connected habitat fragments can be genetically distinct from one another, at least at some loci. The spatial grain of biodiversity may be far finer than previously believed.Item Open Access Social Evolution in Action: Causes and ConsequencesBladon, EleanorAcross the animal kingdom, social behaviour has been shown to be both a driver of and a response to selection. The question of how social interactions within the family contribute to evolutionary change has received much attention from behavioural ecologists and evolutionary biologists alike, with the former largely focussing on how these interactions are adaptive, and how they impose selection on each member of the partnership, and the latter focussing more on the specific mechanisms of inheritance and how social behaviours of one partner induce the evolution of traits in others. The aim of this thesis is to unite these approaches by asking how adaptive social behaviour (i.e. parental care) can potentially influence evolution: by providing a mechanism for non-genetic inheritance, by constructing the environment in which further social interactions play out, and by influencing trait loss and trait evolvability. The burying beetle *Nicrophorus vespilloides* represents an excellent system for investigating these consequences of parental care. This species exhibits elaborate but variable biparental care, whereby both parents prepare an edible nest for their young from a small vertebrate carcass. They then defend the larvae from predators and competitors and feed them trophallactically with oral fluids. Larvae can survive without any post-hatching care – in the lab at least. I begin in Chapter 2, by examining how burying beetles inherit their gut microbiome, in collaboration with Dr Rahia Mashoodh and Dr Helen Leggett at the University of Cambridge. Previous work suggests this is achieved by two routes: directly from the parents via oral trophallaxis and indirectly via the carcass, through the deposition by parents of oral and anal exudates, which larvae then consume. I eliminated the former mechanism of inheritance, by breeding beetles with and without post-hatching care for two generations, and analysed the resulting gut bacteria of grand-offspring using 16S sequencing. I found that different bacteria are inherited by each route but that gut bacterial communities are just as diverse when vertical transmission happens via the carcass alone. In future work it would be interesting to determine whether beetles have reduced fitness when vertical transmission of the gut bacterial community during post-hatching is prevented. In Chapters 3-6, I extended this approach of comparing populations that had and had not experienced post-hatching care. I analysed replicate experimental burying beetle populations that had evolved for 40 or more generations in the Kilner lab either with or without post-hatching care, respectively the ‘Full Care’ and ‘No Care’ populations. In Chapters 3 and 4, I focused on traits linked to the preparation of the carrion nest. In Chapter 3, I conducted breeding experiments that investigated whether nest construction had evolved divergently between the Full Care and No Care populations. I found that faster nest building in the No Care populations did not compensate for poorer post-hatching care. There was evidence of within-family co-adaptation for nest construction, but the extent of co-adaptation did not diverge between ‘Full Care’ and ‘No Care’ populations. In Chapter 4, in collaboration with Prof. Adria LeBoeuf at the University of Fribourg, Switzerland, I analysed the proteins in oral fluids produced by parents and offspring, which are deposited on the carrion nest. We found that No Care parents had evolved to deposit proteins that could assist their larvae in their absence, but found no evidence of equivalent change in the No Care larvae. Finally, to look at the longer-term evolutionary consequences of parental care, in Chapter 5 I investigated whether traits for supplying and receiving care can persist when they are no longer expressed (as experienced by the No Care populations). I found that No Care fathers and larvae had lower expression of post-hatching care-related traits than their Full Care counterparts, but similar trait loss was not found in mothers. In Chapter 6, I investigated whether evolving with or without care conferred greater resilience when beetles were exposed to increased temperatures during sexual maturation. I found that founder effects were a far better predictor of a population’s resilience than social evolutionary history. I conclude that long-term consequences of social evolution are unpredictable and that the resilience of a population will largely be predicted by the standing genetic variation of its founders.Item Embargo Avian brood parasitism as a model system for studying multispecies interactionsKennerley, James; Kennerley, James [0000-0002-9129-0976]The relationships between avian brood parasites and their hosts are widely recognised as model systems for studying coevolution. Through the examination of tractable interactions between one species of brood parasite and one species of host, important insights have been gained on the processes that shape and regulate the world’s biodiversity. While research has favoured the examination of simpler pairwise interactions, the examination of multispecies interactions remains rare despite most brood parasites being known to parasitise multiple species of host and hosts often subject to parasitism by multiple brood parasite species. With little attention paid to these more complex interactions, important opportunities to understand multispecies interactions go unrealised. In this thesis, I begin by establishing the extent of the opportunities offered by avian brood parasitism as a system for studying multispecies interactions. By compiling data on all known brood parasite–host relationships, I demonstrate that complex interactions are the global norm but most research has focused on pairwise interactions, especially in regions with low brood parasite–host network complexity. I argue that despite brood parasitism’s rich research pedigree, the study of multispecies interactions represents an almost entirely new frontier for the examination of the ecology and evolution of multispecies interactions. Through the following two chapters, I demonstrate how brood parasitism can address questions on multispecies interactions which have important implications for our understanding of the natural world. To understand why some species are targeted by brood parasites while others are not, I assemble a dataset on phenotype and life-history information for all species belonging to the passerine superradiation to examine the behavioural and ecological characteristics associated with host status. I find that brood parasites target species that, in addition to being biologically compatible, are the most conspicuous members of the community and discuss how evolutionary pressures may have facilitated convergence on the same host species by sympatric brood parasites contributing to increased network complexity. Next, I investigate the role and evolutionary origins of the whining vocalisation which is produced in response to observing a brood parasite by a group of distantly related host species found around the world. I find that the whining vocalisation plays an important role in communicating the threat of brood parasitism between species and that the pressure imposed on hosts by multiple species of brood parasites has selected for global convergence on a functionally referential vocalisation that sympatric and allopatric hosts respond to innately but are only able to produce once learned from others. Together, these findings highlight the important role that brood parasite–host networks have had in shaping host phenotypes. Overall, this thesis reveals avian brood parasitism to be a complex global network of interactions rather than a series of pairwise relationships as it has been traditionally treated. Furthermore, by showcasing its applications for addressing longstanding questions in evolutionary ecology, I make the case for avian brood parasitism to be looked at from new perspectives in recognition of its suitability as a model system for studying multispecies interactions.Item Open Access Calcium and actin coordinate egg activation and the metaphase-anaphase transition in Drosophila oocytesWood, BenjaminEgg activation is the process through which the mature oocyte is prepared for embryogenesis, consisting of key cellular changes including, but not limited to: i) Physical and chemical changes to the oocyte’s outer covering; ii) The release of meiotic arrest, enabling the formation of a haploid oocyte; iii) Large-scale changes in the translational landscape; iv) Cytoskeletal rearrangements for regulating downstream events of egg activation and supporting further growth of the zygote. Preceding these events in Drosophila is a single calcium transient observed in the form of a polar wave upon hydration and swelling of the oocyte. A model outlining how the initiation of such a wave is regulated and how it then enacts these downstream effects is not yet fully outlined. The original working model supported by previous research suggested that mechanical triggers during ovulation initiate calcium entry. How this mechanical stimulus is transduced into a calcium wave and what this then means for the source of calcium has not been explored. I first provide an in depth analysis of calcium entry dynamics at egg activation, exploring the significance of seemingly less regulated calcium events. I then investigate the source of calcium and identify an ion channel that is required for calcium entry. By utilising a combination of pharmacological and genetic analysis, I highlight the requirement of Trpm for calcium entry at egg activation. Taken together I demonstrate that calcium enters the oocyte from the peri- vitelline space (between the oolemma and vitelline membrane) through Trpm in the form of a wave. I next ask what mechanisms regulate calcium entry through Trpm channels. I provide detailed visualisation of the actin population in the mature oocyte both before and after egg activation, focusing on the cortical actin. I reveal a clear relationship between calcium entry and the cortical actin- In particular, reduction of the cortical actin density or level of cross-linking promotes the entry of calcium. In the mature oocyte I show that the Arp2/3 machinery and tandem-actin binding domain nucleators are required for maintenance of the cortical actin. I further demonstrate that actin-binding proteins (ABPs) play a role in regulating calcium entry, likely via mediation of cross-linking and density of the cortical actin. This data therefore supports a model in which polar waves are in part a result of a reduced cortical actin density at the poles of the oocyte. I then explore a specific downstream event of egg activation; the resumption of meiosis. I demonstrate the presence of a novel population of actin within the Drosophila oocyte that forms a spindle-like structure. Given this is such a recent discovery, key questions are highlighted: 1) What is the role of this spindle-like apparatus?; 2) How does the spindle-like actin regulate meiosis?; 3) Is there conservation of this population? I first highlight the requirement of Formins in production of this population. I further reveal that the spindle-like actin is required for regulating the formation and morphology of the spindle and therefore the accurate movement of chromosomes during meiosis, demonstrating remarkable conservation with mammals. Finally, I bring together concepts of calcium and actin signalling explored in the previous chapters, revealing an essential interplay between the two at the metaphase-arrested spindle.Item Open Access Comparative ecology of the endemic Cyprus Warbler and the congeneric Sardinian Warbler: Implications of recent coexistenceJones, Victoria RuthIn 1992 the Sardinian Warbler was first recorded breeding in Cyprus. Since then, survey results from Paphos District suggest that the endemic Cyprus Warbler population has declined, while the Sardinian Warbler breeding population has increased and expanded in Paphos District. Colour-ringed Cyprus and Sardinian Warblers were observed during 2003 to 2005 breeding seasons on seven scrub study plots located across Paphos District. Both species appeared to establish home-ranges without reference to the other species, resulting in considerable interspecific home-range overlap. A playback experiment indicated that Cyprus Warblers reacted equally strongly to conspecific and congeneric song in areas where the two species coexist, but less strongly to congeneric than conspecific song in areas where Sardinian Warblers did not yet breed. The vegetation composition of Cyprus and Sardinian Warbler home-ranges was very similar. There was no indication that the species competed for nest sites. Cyprus and Sardinian Warbler have similar breeding biology; they laid similar sized first clutches and had similar chick output per pair for first nesting attempts. However Sardinian Warblers had a higher frequency of second nesting attempts and this resulted in a higher chick output per pair per year than was achieved by Cyprus Warblers. In both species total chick output per year was higher for pairs that nested early. Nest survival was similar for the two species. Cyprus and Sardinian Warbler diets were very similar. Body condition of both species’ chicks was higher earlier in the breeding season. Cyprus Warblers had higher productivity but lower chick body condition in the zone where their population has declined than in the zone with fewest breeding Sardinian Warblers. Productivity was positively related to arthropod biomass available on different plots for Sardinian Warbler, but not for Cyprus Warbler. There was no evidence of a negative impact of either species on the number or condition of nestlings produced by the congener.Item Open Access A comparison of the costs of delivering conservation through land sharing and land sparingCollas, LydiaGlobally, drastic biodiversity declines and the worsening climate crisis demand overhaul of existing land use policies which have failed to reconcile food production and environmental conservation. In Europe, most existing policies compensate farmers to voluntarily implement land-sharing measures, commonly referred to as wildlife-friendly farming, which seeks to deliver conservation benefits on the farmed land through agri-environment schemes (AES) offering a fixed price per hectare. Investment into sharing has continued despite the accumulation of evidence showing that, for the same amount of lost food production, substantially more would be delivered for conservation and climate change mitigation with the contrasting approach of land sparing, where high-yield farming allows large areas to be spared elsewhere in the landscape as (semi-)natural habitat. Following Brexit, the UK has the opportunity to rethink this approach; but until now policy decisions have had to be made without estimates of the relative taxpayer costs of using sharing and sparing to deliver target conservation outcomes. Addressing this critical research gap was the primary aim of this thesis, as follows. In this thesis, I sought to uncover the taxpayer and food production costs of delivering meaningful conservation outcomes with land sharing and sparing. First, I conducted a novel comparison of the costs of monitoring sharing and sparing schemes for compliance and effectiveness. Monitoring is a fundamental, though often overlooked, taxpayer cost. In terms of effectiveness monitoring, I found current monitoring levels to be insufficient to precisely determine the effects on wild species of sharing schemes; in contrast, the same effort could deliver relatively precise estimates of the much larger effects of sparing. Furthermore, turning to compliance monitoring, I found the cost-effectiveness of existing English AES could be vastly improved with more compliance monitoring; however, this may be politically unpopular with farmers. It is therefore notable that I also found relatively less money was wasted when monitoring sparing at a sub-optimal rate compared to sharing. Second, I used a discrete choice experiment involving 118 arable farmers to establish their willingness to accept (WTA) payment to participate in sharing and sparing schemes that delivered the same biodiversity and carbon outcomes. I found that all but the most farmland-tolerant outcomes were delivered at less taxpayer expense with sparing. Third, combining this assessment of farmer WTA with knowledge of how much schemes must be monitored, I compared the taxpayer costs of delivering the same environmental outcomes with fixed-price sharing and sparing schemes which paid all recruits at the WTA of the least-willing farmer required in the scheme to deliver the target outcome. I found that sparing delivered the same outcomes at less than half the taxpayer cost of sharing; and, importantly, sparing saw only 79% of the food production lost under sharing. Fourth, I examined the distribution of farmer stated WTA, finding that variation in responses was mostly driven by factors other than lost gross margin. Given marked inter-farmer variation in their stated WTA, variable-price schemes, which pay farmers their stated WTA rather than the rate required by the least-willing participant, offered savings to both sharing and sparing schemes. However, even under variable pricing, sharing was not cheaper than sparing in delivering our more farmland-sensitive outcomes. Finally, I examined whether a land-purchase strategy, where the government purchases land and then contracts organisations to manage and create habitat on it, would deliver sparing at less expense than a farm-subsidy approach. I found land purchase was more cost effective than the farm-subsidy approach if long timeframes, low discount rates and large budgets were considered; however the impacts on farming communities of largescale ownership changes warrant further consideration. To conclude, I found overwhelming evidence for UK arable farming that land sparing can deliver biodiversity and carbon outcomes at substantially lower cost than land sharing both in terms of taxpayer costs and lost food production. The relative costs of sharing would increase even more with consideration of species that do not tolerate farmland, in a country with a shorter history of agriculture where fewer habitat specialists have gone extinct compared the UK, and if the production required elsewhere to compensate greater volume of food production lost under sharing was taken into account. Furthermore, the effects of sharing may be near-impossible to precisely determine with current monitoring efforts and continued sub-optimal compliance monitoring would increase the costs of sharing-like options relatively more than the more sparing-like options of existing AES. Whilst variable pricing and land purchase may further reduce the costs of sparing, the costs of delivering meaningful environmental outcomes are most substantially reduced by pursuing a land-sparing, rather than land-sharing, approach. This work is of considerable significance to the UK government, given that prevailing land-sharing policy approaches can at best deliver less than half the environmental outcomes delivered by the same budget spent on land sparing.Item Embargo Ancient origins of the chordate forebrain: Conserved patterning of the anterior neuroectoderm in amphioxusGattoni, GiacomoWhile the general organization of the chordate central nervous system (CNS) is highly conserved and consists of a dorsal neural tube with an anterior brain, the evolutionary origin of this key aspect of the chordate body plan remains obscure. In recent years, a conserved anterior gene regulatory network (aGRN) has been shown to pattern the larval anterior nervous system of several invertebrates, including the two non-chordate deuterostome phyla (echinoderms and hemichordates), in which the aGRN controls the development of the apical organ. Although clear homologs of the apical organ are not present in chordates, most aGRN genes are expressed in the vertebrate forebrain. In this PhD thesis I trace the evolution of the aGRN across deuterostomes using the cephalochordate amphioxus as the main model organism. I first show that during amphioxus development aGRN genes are expressed in a similar pattern to the one found in echinoderms and hemichordates, are regulated by Wnt/b-catenin signalling and are active in the anterior neuroectoderm that forms the larval brain. As a comparative system, I also characterize the development of the apical organ in an understudied group of echinoderms, the crinoids. To follow the fate of the amphioxus anterior neuroectoderm, I next investigate neurogenesis, proliferation and cell type differentiation in larval and adult brains. I demonstrate the presence of a hypothalamic-like region in the anterior cerebral vesicle, which derives from the region where the aGRN is active during development. Finally, I explore how changes in the specification of the body axes and in the expression of one of the upstream aGRN genes, FoxQ2, might have underlined the evolution of the complex vertebrate brain. Taken together, the results presented in this thesis support the conservation across deuterostome evolution of an aGRN that controls the development of the anterior neuroectoderm. In the chordate lineage, the network was integrated to the neurulation program to specify retinal and hypothalamic areas of the forebrain. Furthermore, this work provides a comprehensive characterization of neuroarchitecture and cell type composition across the amphioxus life cycle, facilitating the comparison with other chordate taxa to reconstruct the evolution of the chordate nervous system.Item Open Access The genomics of adaptive colouration in Hypolimnas butterflies and the wood tiger moth, Arctia plantaginisFarré I Orteu, Anna; Farré I Orteu, Anna [0000-0002-3911-0747]Wing phenotypes in butterflies and moths are a striking example of adaptive evolution and are a tractable trait to dissect the genetic mechanisms underlying adaptations. Studies of Lepidoptera, mainly mimetic species from the tropics, have led to two general patterns. First, a limited set of genes have been re-used multiple times in controlling the evolution of wing phenotypes, and second, structural variation often underlies such traits. Clarifying the generality of these two patterns requires the dissection of the genetic architecture of wing phenotypes in a wider variety of species. In this thesis, I explore the genetic basis of wing mimicry in Hypolimnas butterflies and of aposematism in the wood tiger moth using a range of genomics and transcriptomics methods. First, I produce genome assemblies of two Hypolimnas species and investigate the evolution of W chromosomes in Lepidoptera. By comparing the H. misippus genome assembly to multiple Lepidoptera species, I provide evidence that suggests that the W chromosome has a shared origin across the Lepidoptera. Second, I identify the genetic basis of forewing mimicry in H. misippus using a dataset of 335 individuals sequenced using haplotagging, a linked read sequencing technique. To analyse these data, I develop a method called Wrath for the visualisation and exploration of candidate structural variants. I find that transposable element insertions are associated with forewing phenotype and present evidence for the usefulness of Wrath to explore haplotagging data. Third, I examine the evolution of mimicry in the Hypolimnas genus by identifying and comparing the genetic basis of wing phenotypes in H. misippus and H. bolina. Using a dataset of 214 whole genome sequences of H. bolina individuals together with my H. misippus data, I show that cortex, a gene involved in wing colour in many Lepidoptera, is the most likely candidate for the control of white colour elements in the two species. Furthermore, I present evidence that the regulatory elements controlling the presence of hindwing white are likely not homologous between the two species. Additionally, I show that a region close to optix, another well-known colour gene, is associated with orange elements in H. bolina. Finally, I explore the genetic basis of a complex phenotype involving aposematism and behavioural and physiological traits in the wood tiger moth, Arctia plantaginis, and show that this trait is associated with the duplication of a yellow family gene. This work contributes to our understanding of the evolution of wing phenotypes in the Lepidoptera. Overall, my results highlight the importance of structural variation in the evolution of wing colouration while also emphasising the repeatability of the genetic basis of adaptive traits.Item Open Access Phylogenetic inference using ancient environmental DNADe Sanctis, BiancaAncient environmental DNA (aeDNA) has revolutionized our ability to describe and analyze biological communities in space and time by allowing for joint sequencing of entire ecosystems across thousands of years. However, because samples contain damaged, short fragments from multiple individuals or taxa, the field has been so far limited in its scope, and aeDNA has only been applied to population and phylogenetic studies in the last few years. In this thesis, I first build a theoretical coalescent framework to analyze error in supervised binning algorithms, which assign reads from environmental samples to individual taxa in a reference database. Under this framework, I determine the expected error rate under a wide range of parameters and the degradation in assignment accuracy as samples diverge from their closest reference sequence, and with incompleteness of reference sequences. Second, I describe a phylogenetic placement algorithm for non-recombining sequences such as mitochondria or chloroplast DNA, and apply this method to Mammuthus or mammoth and Equus or horse samples from an Arctic-wide aeDNA dataset spanning the last 50,000 years. This analysis demonstrates the potential existence of a previously undiscovered clade of mammoths, and extends the survival of an existing clade. Next, I report one of the first whole genome ancient environmental DNA studies, using DNA extracted from 14-16,000 year old cave soil with material from two closely related species, Ursus arctos or the American black bear and Arctodus simus or the extinct giant short-faced bear. By comparing the ancient sequence against a modern reference panel of black bears and a high-quality fossil giant short-faced bear reference, I infer evolutionary relationships between the Late Pleistocene populations and their modern relatives. Lastly, I molecularly date an ancient environmental Betula or birch tree chloroplast sequence from Northern Greenland, confirming that it was approximately 2 million years old, the oldest DNA to be successfully sequenced so far. All together, this work demonstrates the ability to infer phylogenies and population histories of individual taxa from ancient environmental DNA.Item Embargo The Sea is the Limit: Foraging Ecology of Breeding Antarctic ProcellariiformesBentley, LilyIn the dynamic marine environment, highly mobile predators are expected to select profitable foraging areas, especially when provisioning young in addition to meeting their own energy needs. Knowing how and where animals choose to forage is not only important to advance ecological theory, but also to assess and mitigate the impact of anthropogenic threats. In this thesis I examine the breeding-season foraging behaviour of several of the Procellariiformes, a wide-ranging, long-lived group of seabirds, many of which have experienced steep population declines since the mid-20th century. Advances in biologging technologies over the last four decades have made it possible not only to accurately track individual movements, but also to identify important behaviours at sea. In my first data chapter (Chapter 2), I combine data from multiple tag types to describe diving behaviour in three albatross species, and discuss the implications for both foraging ecology and bycatch susceptibility. Moving from foraging capability of the individual to foraging preferences at the level of genus, in Chapter 3 I analyse the divergent niches of a summer- and a winter- breeding species of Procellaria petrel. Here I compare the habitat preferences of Grey Petrels and White-chinned Petrels breeding at Gough Island and South Georgia, respectively. Using high-resolution remote sensing environmental data, I identify divergent foraging preferences in dynamic habitats. Finally, in Chapter 4, I compare habitat preferences and accessibility between the two species of Phoebetria albatrosses across six colonies. While most studies of habitat preference consider only a single species or site, here I investigate whether closely- related species inhabit the same ecological niche at sympatric and allopatric colonies throughout their range. I show that Light-mantled Albatrosses have a consistent foraging niche, whereas Sooty Albatrosses select different habitats in sympatry and allopatry. I then discuss the impact of interspecific competition on plasticity in habitat preferences in general. Overall, my thesis examines diverse aspects of seabird foraging ecology from the individual to community level, discusses habitat preferences (and their potential flexibility) in relation to species' evolutionary history and as drivers of community structure, and considers the implications for conservation planning.Item Embargo Fossoriality In Snakes: Perspectives From Morphology And The Fossil RecordHoward, AlexandraSnakes are a speciose clade of squamates that have diversified into almost all habitats, all with the same elongate limbless body plan. This thesis aims to improve scientific understanding of snake evolution by focusing on novel perspectives using both extant snakes and the fossil record. 1. Alternate phylogenetic positions of fossils affects body size estimates in snakes Body size is a readily available metric for both extant and extinct snakes. The competing hypothesis of ecological snake origins also predict different outcomes for the evolution of body size in snakes. I used a combination of ancestral state reconstructions, body size estimates of fossils from regression models, and evolutionary rate modelling to examine the evolution of body size in snakes, with a particular focus on early snake evolution. This project showed that snakes achieve a wide range of diversity of body size during the Cretaceous, trends that are not observed when using data from extant taxa. 2. Cranial osteology of Typhlopidae (Serpentes: Scolecophidia) Scolecophidia are a distinctive group of snakes that occupy the basal most diverging branches of the snake phylogeny. However, due to the small overall size of many taxa, they have been relatively understudied in regards to comparative anatomy. In this project I examined segmented CT scans of 10 different species of Typhlopoidea, the largest clade of Scolecophidia. Using these comparisons I identified variability in several morphological characters not previously thought to be variable in Scolecophidia, as well as the identification of features in large typhlopids such as the lateral wings of the basisphenoid, which were previously thought to be limited only to Alethinophidia. 3. Morphometrics provide evidence for the fossorial origin of snakes The problem of homoplasy, particularly in relation to adaptation to fossoriality, is potentially responsible for the incongruences between phylogenetic hypothesis of snakes that use either morphological or molecular data. In this project I used CT scans of 73 species of alethinophidian snake and geometric morphometrics to examine morphological correlates to fossoriality. I found that there is a clear morphological signal between the parietal of alethinophidian snakes and ecology. In general, the parietal of fossorial snakes is more elongate with a deep u or v shaped fronto-parietal suture, with an elongated posterior shelf that overlaps the braincase. These projects show how integrative research using both extant and palaeontological data can inform questions about the early evolution of clades, particularly the heavily debated ecological origin of snakes.Item Open Access Tradeoffs and co-benefits among impacts of contrasting livestock systemsBartlett, Harriet; Bartlett, Harriet [0000-0002-7389-8785]Livestock farming generates some striking externalities; whilst it provides 30% of human dietary protein, it occupies 75% of agricultural land, emits 14-17% of anthropogenic greenhouse gas emissions, and uses more antimicrobials than human medicine. Demand for livestock products is high and rising, especially for pork which has quadrupled in the past 50 years. Livestock farming systems vary considerably in the scale of their externalities, but our understanding of how multiple externalities co-vary across contrasting production systems is limited. Research typically focuses on impacts in isolation, and the synergies or tradeoffs among them are assumed. To identify and promote the types of systems that best limit impacts or even carry co-benefits we need to explicitly consider multiple externalities and evaluate them across a wide range of alternative production systems. The main aim of my thesis was to do this for pig production. I recruited, visited, and evaluated over 100 pig farms in the UK and Brazil from those considered to be the most “intensive” through to those certified as Organic. My analyses treat a breed-to-finish system as a datapoint, which may consist of one or several farms (e.g. breeding, rearing and finishing farms). I developed metrics which advanced the quantitative characterisation of farm animal welfare to be compatible with life cycle assessments and to account for both quality of life and the quantity of life years required to produce a unit of product (Chapter 2). I systematically evaluated two externality costs that are commonly perceived to trade off against one another: land use and antimicrobial use (Chapter 3). I found weak evidence of a tradeoff between these externalities but importantly also found several systems characterised by low externality costs in both domains. These systems were spread across different label and husbandry types, and no type was an indicator of systems that performed well in both domains. I built upon these assessments of one or two costs by systematically contrasting the land use, greenhouse gas emissions, antimicrobial use and animal welfare of as many of my UK and Brazilian pig systems as possible (Chapter 4). I found evidence of positive associations between land use and greenhouse gas emissions, and antimicrobial use and poor animal welfare, but tradeoffs between these pairs of externalities - systems with low land use generally had low greenhouse gas emissions, but high antimicrobial use and poor welfare. Again however, I found systems that carried relatively low externality costs in all domains. I 6 conclude that contrary to prevailing wisdom, tradeoffs among these externalities are not inevitable. In parallel with this detailed work on pig production, I explored the viral zoonotic emerging infectious disease risks of contrasting ways of meeting livestock product demand (Chapter 5). Analyses to date typically ignore how land use affects emerging infectious disease risks. I created a framework that considered risk factors associated with livestock management and land use. I identified significant knowledge gaps and argued these shortfalls in understanding mean we cannot currently determine whether lower- or higher-yielding systems would better limit the risk of future pandemics. My findings challenge many commonly held perceptions about the externalities of farming systems and have important implications for mitigation strategies. My work illustrates the importance of using empirical evidence rather than relying on patchily supported assumptions. I believe that this warrants the systematic testing of other assumed relationships among externalities. I addressed some important knowledge gaps for the pork sector, and more broadly for emerging infectious disease risks, but the same must be done on a much larger scale, spanning other externalities and sectors.Item Embargo Maximising Return on Investment for Species ConservationCorrea, Roberto JohannesDetermining how best to allocate scarce funds is crucial to the action plans that governments and conservation organizations are developing to prevent species from going extinct. A Return on Investment (ROI) approach that explicitly incorporates the costs, benefits and risks of investment has been shown to improve the effectiveness and efficiency of prioritization schemes, yet has not, to date, been applied to single species. This PhD thesis examines how an ROI approach can be applied at species level, using African elephants as a case study. In order to model the effects of investment, an important first step is being able to estimate current levels of spend accurately. I used annual spend data, collected for 192 protected areas across sub-Saharan Africa, to assess how the level of spend varies in relation to contextual factors. I found spend per unit area was significantly higher in smaller protected areas that had more range-restricted species, contained rhinos, were managed or received support from non-profit organizations, and were located in more effectively governed countries. I used the model, which explains 78% of the variation in annual spend per unit area, to predict spend across protected areas without data. From this I estimated that a total of US\$367 million is spent annually on the management of protected areas in sub-Saharan Africa, with a median spend of US\$185 km$^{-2}$yr$^{-1}$. Secondly, identifying the level of spend needed to conserve wildlife populations, together with the enabling conditions and barriers, is vital in helping decision-makers improve the allocation of limited financial resources. I collected elephant census data for 90 protected areas (>40% African elephant population) and assessed how population trends vary in relation to level of spend and other contextual factors. I found a strong positive relationship between elephant population growth rate and level of spend (km$^{-2}$yr$^{-1}$) and a smaller positive effect of government effectiveness. Using the best fit model, which explains 53% of the variation in population trends, I estimated that a median spend of US\$1,085 km$^{-2}$yr$^{-1}$ is necessary to stabilize elephant populations within my sample of 90 protected areas. I compared this to current levels of spend and found that 78% of protected areas experienced spend deficits; and overall funding must be increased by an estimated US\$1.5 billion yr$^{-1}$ if elephant numbers are to be stabilized across all sampled sites. Finally, I developed an ROI framework for single species-based priority setting and tested it by evaluating the optimal allocation of funds across protected areas in sub-Saharan Africa under different objectives centred around maximizing (i) the number of elephants and (ii) the number of stable populations at the end of five years of differing levels of external investment (on top of current government spending). I found that the ROI framework substantially increased the number of elephants (n >18,000) or stable populations (n =28) compared to the current external investment. However, there was a considerable trade-off between the number of additional elephants and additional stable populations, particularly at lower levels of external investment. This was driven by the interplay of several factors: (i) the shape of the species response curve to investment, (ii) population sizes in each protected area, (iii) the sizes of the protected areas, (iv) the existing levels of investment, and (v) the available budget. These factors are often not considered in conventional priority-setting approaches, to the detriment of efficient resource allocation. This thesis demonstrates how an ROI framework could be used by governments and conservation organizations that finance species conservation to evaluate the impact that increasing or decreasing their overall investments would have on species recovery. Based on the findings of this thesis, I provide several recommendations and possible solutions to improve the allocation of conservation resources, and thus support more informed and better justified investment in the conservation of speciesItem Embargo The demography of Red Sea reef fishes since the Last Glacial MaximumEmms, MadeleineCoral reefs are at increasing risk of climate-induced mass bleaching events and mass mortality, yet we do not know how coral reef fish species respond to habitat loss on temporal and spatial scales relevant to climate change. The Red Sea represents an ideal model system to address this given that many reef fish populations persisted during the Last Glacial Maximum despite a significant loss of coral reefs. I studied their demogaphic history to determine the impact of environmentally-induced habitat loss. High-throughput sequencing data combined with an Approximate Bayesian Computation framework (including machine learning techniques) provided sufficient power to estimate population parameters for five reef fish species, Dascyllus abudafur, Dascyllus trimaculatus, Dascyllus marginatus, Pomacanthus maculosus, and Carcharhinus melanopterus. The genetic bottleneck experienced during the Last Glacial Maximum (LGM) was not as small as was expected, highlighting the importance of coral reef habitat and refugia. Studying the impact of the LGM on Dascyllus marginatus, a species with a restricted range in the Indian Ocean, enabled me to use this study design to determine that the refugia was unlikely to have been outside the Red Sea, but rather in-situ. The extensiveness of an external population did not appear to affect the response to habitat loss. Lastly, studying the impact of the LGM on Carcharhinus melanopterus, a larger, more motile shark species, showed a similar pattern of response to habitat loss. I then compared the Red Sea barrier with other biogeographic barriers across the Indo-Pacific; in this case it was stronger than some but not as strong as the Indo-Pacific barrier. Overall, the demographic histories showed a similar and mild response to environmentally-induced habitat loss in the Red Sea across species, albeit with some ecological differences. Two case studies allowed me to uncover more about the unique history of the Red Sea, and provided opportunities to discuss other important questions around coral reef refugia and the biogeography of the Indo-Pacific.Item Open Access Evolution of Axial Skeleton Diversity across ReptiliaRoberts, Lucy; Roberts, Lucy [0000-0002-1293-8667]The axial skeleton is a key diagnostic character of vertebrate animals. Comprising the vertebral column and ribs, the axial skeleton is a support structure from which all appendages of the vertebrate body are suspended. Reptilia is a hugely diverse clade of vertebrates, with regards to body form, body size, function, and behaviour. However, despite this established diversity, we know little about the diversity of the axial skeleton across Reptilia, or how axial skeleton evolution is related to development, body form, or function. In this thesis I investigate the diversity and evolution of the axial skeleton across Reptilia, divided into the following chapters: Chapter 1: Introduction; Chapter 2: Axial skeleton morphology; Chapter 3: Combining geometric morphometrics and maximum likelihood modelling to quantify regionalization: Methodology and sensitivity analyses; Chapter 4: Multiple independent trajectories to highly regionalized axial skeleton morphologies across Reptilia: Implications for development and function; Chapter 5: Axial skeletal segmentation across Reptilia: Phylogenetic, ecological, and developmental correlates; and Chapter 6, conclusion: Mammals are not a uniquely regionalized clade: A complex evolutionary history of axial skeleton morphology, function, and development across Reptilia. My results show multiple independent evolutionary trajectories to high degrees of regionalization across Reptilia, demonstrating a greater complexity in axial skeleton evolution, and a greater diversity in axial skeleton morphology across Reptilia, than previously expected. Further to this, I model the evolution of segment counts across Reptilia, comparing segment evolution with body mass and ecological traits. I establish that segmentation played an integral role in the evolution of body form and ecology across Reptilia. High segment counts are associated with aquatic and fossorial ecologies regardless of phylogeny, whereas high relative cervical counts are strongly associated with the acquisition of powered flight in birds, but not in pterosaurs. Overall, I uncover a complex history of axial skeleton evolution across Reptilia. Each extant clade has its own evolutionary trajectory toward highly regionalized forms, and variable trajectories to high and low segment counts. Previous interpretations of axial skeleton diversity across Vertebrata have focused on the origin of mammals, inferring uniquely complex axial skeleton morphologies across Mammalia. However, morphometric analysis here reveals multiple independent gains and losses of regionalization across Reptilia, associated with adaptations to specialised body forms. Amongst sampled taxa, extant crocodilians, most extant squamates, and many extant birds are just as regionalized as sampled mammals. This implies greater degrees of axial skeleton diversity across vertebrates than previously thought and presents the potential for uncovering similar complexity in axial skeleton macroevolution across other vertebrate clades, and Vertebrata as a whole.Item Open Access Mushroom body expansion and the cognitive ecology of Heliconius butterfliesYoung, FletcherHeliconius butterflies, a Neotropical genus of approximately 50 species, exhibit a marked expansion of an insect brain structure called the mushroom bodies (MBs), which are 3-4 times larger than in other Lepidoptera, including closely related Heliconiini genera. MBs are known to play a role in learning and memory, particularly in olfactory contexts, however the relative cognitive capabilities of Heliconius remain unknown. The central objective of my PhD is to investigate the behavioural consequences of, and selective pressures that drove, expansion of Heliconius MBs. I have explored these questions by collecting comparative behavioural and neuroanatomical data across Heliconius and closely related Heliconiini. To explore patterns of MB evolution in the Heliconiini, I conducted phylogenetic comparative analyses across a neuroanatomical dataset of 41 species, including 30 Heliconius and representatives of all Heliconiini genera. Phylogenetic generalised linear mixed modelling shows that within the Heliconiini, increased MB size is associated with the Heliconius genus, even when controlling for the size of the central brain, the antennal lobe and the medulla. Moreover, variable rates analyses indicate that the branch leading to Heliconius experienced a significant increase in the rate of evolution of MB size. But what drove this expansion? There are two main adaptive hypotheses to explain this MB expansion. One is that it facilitates an improved shape learning and recognition of Passiflora host plants. To test this, I conducted shape learning assays across six Heliconiini species. However, Heliconius did not, a as group, out-perform the outgroup species. In addition, I conducted geometric morphometric analyses on Passiflora leaf shape to determine the morphospace of host plants Heliconiini species exploit. There was no correlation between host plant morphospace and MB size. Together these findings suggest MB expansion in Heliconius is not associated with an improved ability for the visual identification of host plants. The second relates to Heliconius’ unique foraging strategy. Heliconius are the only Lepidoptera known to actively feed on pollen, which they collect from a limited number of relatively rare plants. In visiting these plants, Heliconius establish “traplines” – routes through the forest that they follow with a high degree of spatial and temporal fidelity, and which seemingly relies on an advanced spatial memory ability. Through a series of behavioural experiments, I show that Heliconius can learn the location of a food resource in a T-maze, in addition to outperforming non-Heliconius Heliconiini in long-term memory and non-elemental learning tasks – cognitive abilities assumed to be crucial for traplining. There was no difference, however, between Heliconius and non-Heliconius in a reversal learning task. Nonetheless, these results are consistent with the elaboration of the Heliconius MB being driven by the cognitive demands of trapline foraging for pollen. Finally, I investigate the possible neural correlates associated with long-term memory performance by comparing the mushroom bodies of Heliconius erato and Dryas iulia individuals involved in the long-term memory assay with control individuals reared in non-learning environments, in addition to a group of freshly-eclosed butterflies. Overall, the mushroom bodies of Heliconius erato exhibited significantly more age- and experience-related plasticity than Dryas iulia. Importantly, an increase in synapse count was associated directly with visual learning in Heliconius erato. At an individual level, within Heliconius erato, but not Dryas iulia, increases in synapse density and count were correlated with improved recall accuracy.Item Open Access Motor control and directional accuracy of phonotaxis in female field cricketsNtelezos, AthanasiosThis thesis addresses two aspects of the phonotactic behavior of female field crickets (Gryllus bimaculatus) as they orient towards singing males: the first one is how the auditory input is integrated into the motor activity underlying their walking responses, and the second one is how accurately they can localize a singing male in a dynamic stimulus situation. Although it has been established that the conspecific calling song is recognized via a circuit in the brain, it is not clear how pattern recognition is linked to descending motor control of phonotaxis. To analyze the auditory-induced motor responses, I recorded high-speed videos of crickets performing phonotaxis and tracked the movement of their bodies and appendages. The video analysis showed that when crickets commence phonotaxis, their body parts and appendages are activated and moved from anterior to posterior in the following order: antennae, head, prothorax, front legs, middle legs. During phonotaxis the antennae move continuously side-to-side in a rhythmic pattern, and on top of this rhythmic movement is superimposed a shift to the side the calling song is presented from. Moreover, the prothorax makes small rhythmic movements that are coupled to the stepping cycle, and on top of these rhythmic movements also steers towards the side the calling song is presented from. Following up on the results of the video analysis, I recorded the activity of the antennal muscles of the scape in crickets that performed phonotaxis. The scape contains two muscles: the adductor muscle that adducts the antenna towards the median line, and the abductor muscle that abducts it laterally. The activity of the adductor muscle is coupled to the adduction movement of the antenna during the contralateral presentation of the calling song, while the activity of the abductor muscle is coupled to the abduction movement during the ipsilateral presentation of the calling song. The antennal movement and muscular activity – especially the abduction movement and the activity of the abductor muscle – are coupled to the calling song on a chirp-to-chirp basis. The neurites of the motoneurons of the antennal muscles are located in the deutocerebrum, while the ascending auditory pathway projects into the protocerebrum. I discuss that additional auditory brain interneurons must be involved for the transfer and processing of the auditory-to-motor signal from the protocerebrum to the deutocerebrum. I also investigated the function of several thoracic muscles for potential contribution to the prothoracic movements contributing to phonotaxis. Of all the muscles tested, only the activity of pronotal muscle 56 was coupled to the prothoracic movements in crickets performing phonotaxis. Specifically, the activity of muscle 56 was coupled both to the rhythmic prothoracic movements that are coupled to the stepping cycle and to the auditory-induced steering of the prothorax. Like the antennae, the prothorax turns to the active speaker and also responds to the calling song on a chirp-to-chirp basis. I discuss that auditory input to the motoneurons of muscle 56 in the prothoracic ganglion is likely indirect via a pathway descending from the brain. Finally, I tested the accuracy of female crickets walking on a trackball as they performed phonotaxis towards a speaker oscillating constantly between 45° left and 45° right relative to their long axis. In a group of crickets, I used a drop of wax to fix the prothorax against the mesothorax and test the effect of the immobilization of the prothorax has on auditory steering. The performance of the crickets with the fixed prothorax was not statistically different from the performance of the crickets that could freely move the prothorax, however, the crickets with the fixed prothorax generally understeered towards the more lateral angles of stimulus. Overall, in this dynamic situation the angular resolution of the crickets was 6-11° in their frontal range, which is less accurate than the previously reported 1-2° for phonotaxis towards a static sound source. The results show that crickets find orientation towards a moving sound source more challenging than towards a static one. This was further corroborated with tests where the crickets steered to the correct side when two speakers positioned 5° to the left and 5° to the right alternated in the presentation of the calling song, meaning their angular resolution for static sound sources was at least 5°.