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Macroevolutionary dynamics of nectar spurs, a key evolutionary innovation.

Accepted version
Peer-reviewed

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Authors

Fernández-Mazuecos, Mario  ORCID logo  https://orcid.org/0000-0003-4027-6477
Blanco-Pastor, José Luis  ORCID logo  https://orcid.org/0000-0002-7708-1342
Forrest, Alan 

Abstract

Floral nectar spurs are widely considered a key innovation promoting diversification in angiosperms by means of pollinator shifts. We investigated the macroevolutionary dynamics of nectar spurs in the tribe Antirrhineae (Plantaginaceae), which contains 29 genera and 300-400 species (70-80% spurred). The effect of nectar spurs on diversification was tested, with special focus on Linaria, the genus with the highest number of species. We generated the most comprehensive phylogeny of Antirrhineae to date and reconstructed the evolution of nectar spurs. Diversification rate heterogeneity was investigated using trait-dependent and trait-independent methods, and accounting for taxonomic uncertainty. The association between changes in spur length and speciation was examined within Linaria using model testing and ancestral state reconstructions. We inferred four independent acquisitions of nectar spurs. Diversification analyses revealed that nectar spurs are loosely associated with increased diversification rates. Detected rate shifts were delayed by 5-15 Myr with respect to the acquisition of the trait. Active evolution of spur length, fitting a speciational model, was inferred in Linaria, which is consistent with a scenario of pollinator shifts driving diversification. Nectar spurs played a role in diversification of the Antirrhineae, but diversification dynamics can only be fully explained by the complex interaction of multiple biotic and abiotic factors.

Description

Keywords

Antirrhinum, Linaria, Antirrhineae, diversification, flower, key innovation, nectar spur, speciation, Biodiversity, Biological Evolution, Flowers, Linaria, Models, Biological, Phylogeny, Plant Nectar

Journal Title

New Phytol

Conference Name

Journal ISSN

0028-646X
1469-8137

Volume Title

222

Publisher

Wiley
Sponsorship
European Commission (624396)
Isaac Newton Trust (Minute 1423 (u))
This work was supported by the Marie Curie Intra-European Fellowship LINARIA-SPECIATION (FP7-PEOPLE-2013-IEF, reference 624396), an Isaac Newton Trust Research Grant (Trinity College, Cambridge), a Juan de la Cierva fellowship to M.F.-M. (Spanish Ministry of Economy and Competitivity, reference IJCI-2015-23459) and a Generalitat Valenciana postdoctoral grant to A.J. (Ministry of Education, Culture and Sport, reference BEST/2014/264).