Elevational biodiversity gradients in the Neotropics: Perspectives from freshwater caddisflies (Insecta: Trichoptera)

diversity of genera and species had a bimodal distribution. Genera β-diversity showed a higher turnover at the lower section of the elevation gradient, between 903 and 1,028 m a.s.l., and a second important shift between 1,874 and 2,281 m a.s.l (Table 4). Species β-diversity showed a bimodal distribution as well, but stronger and at different elevation ranges. The first high turn- over was observed between 1,028 and 1,874 m a.s.l., and the second one between 2,325 and 3,464 m a.s.l (Table 4). The observed changes in community composition along the elevation gradient were not fully supported by the null models, neither at the species nor the generic level. The SES statistics suggest a non-conclusive random distribution of the regional species pool. However, null models strongly support the observed species turnover for localities grouped by elevation (Table 5), but not for genera. The strongest species turnover were at 1,028 to 1,874 and from 2,281 to 3,464 m a.s.l. This change in species composition is in line with the patterns observed when the entire gradient was analyzed. Although not significant, the strongest turnover for genera among elevation groups was observed at 2,281 to 3,464 m a.s. l. Discussion Trichoptera communities showed a higher species and generic diversity at lower localities (500 to 1,000 m a.s.l.) and that then decreased with increasing elevation, confirming our first hypothesis. Although our data are constrained by low sampling effort, the observed patterns are in agreement with the occurrence data for the caddisflies of Ecuador [18]. Further, similar

Fig 3. Non-metric multidimensional scaling of Trichoptera species with correlations to environmental variables (> 0.65) across an elevation gradient (600–3,500 m a.s.l.) in western Ecuador. https://doi.org/10.1371/journal.pone.0272229.g003 PLOS ONE Elevational biodiversity gradients of Neotropical caddisflies PLOS ONE | https://doi.org/10.1371/journal.pone.0272229 August 5, 2022 10 / 17