Species richness and turnover patterns in European tenebrionid beetles



    1. Water Ecology Team, Department of Biotechnology and Biosciences, University of Milano Bicocca, Milan, Italy
    2. Azorean Biodiversity Group, Universidade dos Açores, Departamento de Ciências Agrárias CITA-A, Pico da Urze, Angra do Heroísmo, Portugal
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    1. Departamento de Zoología, Facultad de Biología, Universidad de Santiago de Compostela, Rúa Lope Gómez de Marzoa s/n, 15782 Santiago de Compostela, Spain
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Simone Fattorini, Water Ecology Team, Department of Biotechnology and Biosciences, University of Milano Bicocca, Piazza della Scienza 2, I-20126 Milan, Italy. E-mail: simone_fattorini@virgilio.it


Abstract.  1. We used a hyperdiverse invertebrate group, tenebrionid beetles, to test competing hypotheses about the factors correlated with the spatial variation in species richness and composition across Europe.

2. We considered the following hypotheses for explaining variation in species richness, (i) spatial heterogeneity, (ii) environmental energy, and (iii) dispersal limitation and post-glacial recolonisation, and the following hypotheses for variation in species composition, (i) current climate, (ii) Pleistocene glaciations, and (iii) neutral dynamics.

3. We used inventories of 36 European territories, built from a database containing the distributions of 1010 species or subspecies. Area, spatial position, and topographical and climatic variables were used as predictors in regression (richness) and constrained analysis of principal coordinates (composition) analyses.

4. The latitudinal richness gradient found in European tenebrionids was mostly explained by the joint effect of environmental and spatial variables, supporting the climate and incomplete recolonisation hypotheses.

5. A parabolic relationship of endemism with longitude points to the presence of centres of endemism in the Iberian Peninsula and the Balkans. Current climatic conditions alone were not sufficient to explain spatial turnover patterns of European tenebrionids, which are largely influenced by spatial factors.

6. Both the Pleistocene glaciations and neutral hypotheses were supported, but the fact that turnover is not uniform across Europe suggests that the historical effects of Pleistocene glaciations had a deeper impact on tenebrionid assemblages than neutral dynamics. Thus, variation in species richness seems more directly controlled by climatic factors, whereas geographical constraints related to dispersal limitation or stochastic colonisation events influenced species composition.