Cambridgeshire’s elm microspecies support different leaf gall and mine species communities from each other
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Elm tree (Ulmus) populations, once characteristic and commonplace components of the British countryside, were decimated by the arrival of a virulent form of Dutch Elm disease in 1967. The classification of elm species in Britain has so far eluded consensus, with between 1 and 62 species recognised. Resolving British elm taxonomy is important for conservation assessment of the taxa, describing the ecological role and distributions of elm species, and is necessary for assisted breeding programmes aimed at breeding disease-resistant cultivars. None of the British Ulmus classifications has evaluated whether any genetic or ecological characters support the proposed microspecies divisions. We sampled leaves from three individuals from each of three elm microspecies (U. scabra, Ulmus procera and U. cantabrigiensis sensu Sell & Murrell 2018, corresponding to U. glabra, U. glabra x U. minor and U. minor in the Richens 1983 twospecies treatment) at three woodlands (Hayley, Madingley, Cambourne) in Cambridgeshire, identifying and counting leaf mine and leaf gall species. We identified ten leaf mining species and two leaf galling species across the three tree species. The leaf mine Bucculatrix albedinella was recorded in Cambridgeshire for the first time. Leaf gall and mine species composition differed overall between tree species (χ2 =46.7, df=26, p=0.008). Using standardised residuals from the chi squared test of association, Aceria campestricola was strongly overrepresented on U. procera, whilst all other species were overrepresented on U. cantabrigiensis and U. scabra. The number of leaf gall and mine species, and the abundance of leaf gall and mine marks, were both significantly predicted by elm species and not by tree diameter. Notwithstanding the relatively limited sampling of microspecies at this stage, our study supports the hypothesis that elm microspecies support different insect communities from each other, and that leaf mine and gall species are able to discriminate between closely related elm taxa.