Abstract
Aiming to elucidate whether large-scale dispersal factors or environmental species sorting prevail in determining patterns of Trichoptera species composition in mountain lakes, we analyzed the distribution and assembly of the most common Trichoptera (Plectrocnemia laetabilis, Polycentropus flavomaculatus, Drusus rectus, Annitella pyrenaea, and Mystacides azurea) in the mountain lakes of the Pyrenees (Spain, France, Andorra) based on a survey of 82 lakes covering the geographical and environmental extremes of the lake district. Spatial autocorrelation in species composition was determined using Moran’s eigenvector maps (MEM). Redundancy analysis (RDA) was applied to explore the influence of MEM variables and in-lake, and catchment environmental variables on Trichoptera assemblages. Variance partitioning analysis (partial RDA) revealed the fraction of species composition variation that could be attributed uniquely to either environmental variability or MEM variables. Finally, the distribution of individual species was analyzed in relation to specific environmental factors using binomial generalized linear models (GLM). Trichoptera assemblages showed spatial structure. However, the most relevant environmental variables in the RDA (i.e., temperature and woody vegetation in-lake catchments) were also related with spatial variables (i.e., altitude and longitude). Partial RDA revealed that the fraction of variation in species composition that was uniquely explained by environmental variability was larger than that uniquely explained by MEM variables. GLM results showed that the distribution of species with longitudinal bias is related to specific environmental factors with geographical trend. The environmental dependence found agrees with the particular traits of each species. We conclude that Trichoptera species distribution and composition in the lakes of the Pyrenees are governed predominantly by local environmental factors, rather than by dispersal constraints. For boreal lakes, with similar environmental conditions, a strong role of dispersal capacity has been suggested. Further investigation should address the role of spatial scaling, namely absolute geographical distances constraining dispersal and steepness of environmental gradients at short distances.
Highlights
Analyzing the relative importance of local environmental factors with respect to large-scale dispersal restrictions is fundamental for understanding species distributions and community composition at regional scale (e.g., Shurin 2000; Chase 2003; Soininen et al 2007)
Ecology and Evolution published by John Wiley & Sons Ltd
We found 10 Trichoptera taxa (Appendix S1), five of which were considered for statistical analyses as they were present in more than five lakes: Plectrocnemia laetabilis McLachlan and Polycentropus flavomaculatus (Pictet) (Polycentropodidae); Annitella pyrenaea (Navas) and Drusus rectus McLachlan (Limnephilidae); and Mystacides azurea (Linnaeus) (Leptoceridae)
Summary
Analyzing the relative importance of local environmental factors with respect to large-scale dispersal restrictions is fundamental for understanding species distributions and community composition at regional scale (e.g., Shurin 2000; Chase 2003; Soininen et al 2007). Under a scenario purely driven by dispersal, the assembly of communities depends on the stochastic nature of the colonization and the assemblages are prone to multiple stable states driven by priority effects, whereby early colonizers exert a strong influence on the subsequent settlement of new species, eventually affecting community assemblages (Louette et al 2008; Chase 2010). When local environmental factors exert a strong filter for colonizers, the similarity between communities depends less on geographical distance than on the resemblance of key environmental conditions among sites (Chase 2007)
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