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

dissimilarity between the two communities (i.e., random). Higher positive SES values could be generated by functionally non-random replacement of species along the elevation gradient [40, 41]. Results Diversity We collected 595 individuals representing 70 species (including morphospecies) in 26 generic- level taxa (i.e., genera and subgenera) across the elevation gradient (S1 Table). The Chao 1 esti- mator and the sample coverage estimator (Table 2) suggest that samples from high elevation localities (> 2,325 m a.s.l.) are less complete (sample coverage between 0.65–0.72) compared to mid and lower elevation localities (with sample coverage between 0.79–0.96). These results indicate that our 3-day sampling strategy performed well at capturing local diversity in general. However, three localities collected less than 50% of the estimated richness, which agrees with the species accumulation curves, the low estimated richness collected coincides with no stabili- zation of species accumulation curves (S2 Fig). However, our sample coverage suggests that species richness is covered in a relatively good proportion, between 0.65 to 0.95 (S3 Fig). Genera across the elevation gradient At the generic level, two clusters were formed; one for genera below 2,000 m a.s.l. and the other for genera above this elevation (SIMPROF test, 5% significance level; Fig 2a, Table 3). These two clusters showed an average dissimilarity of 82%, according to the SIMPER analysis. The genera Nectopsyche, Atopsyche, Helicopsyche, Amphoropsyche, and Rhyacopsyche contrib-

uted the most to this dissimilarity in the high-elevation cluster, whereas Leptonema, Chimarra, Wormaldia, and Smicridea influenced the dissimilarity found in the low-elevation cluster (Fig 2a; Table 3). Nine genera/species were represented by single specimens from a single locality (S2 Table). Average minimum air temperature (T˚ min) is the main variable explaining the resulting ordination (Fig 2b). The first group includes all high elevation localities above 2,000 m, charac- terized by harsh environmental conditions expressed in lower minimum air temperatures, a decrease in annual rainfall, coupled with smaller basins. The second group contains habitats of milder environmental conditions with higher minimum air temperatures, higher precipita- tion, and larger watersheds (Fig 2b, S2 Table). Table 2. Biodiversity metrics across study localities. Locality Elevation (m) Species Genera N N1 Chao 1 (species) Chao 1 (genera) Sample Coverage Mashpi- shungo 619 15 11 86 6.3 21 11 0.9424 Mashpi 1 903 7 5 24 3.5 7 7 0.7917 Mashpi T 1028 35 22 352 12.0 51 38 0.9575 Intillacta 1874 11 9 60 4.9 24 14 0.9172 Bellavista 2281 12 8 42 8.4 15 8 0.9081 Cedral 2325 9 6 17 6.9 27 11 0.6543 Verdecocha 3464 7 4 14 5.6 15 4 0.7249 N = abundance; N1 = Shannon-Wiener diversity index expressed as equally abundant species; Chao 1 = Chao 1 species/genera richness estimator; Sample Coverage = Estimated Sample Coverage, according to Chao and Jost 2012 [27]. https://doi.org/10.1371/journal.pone.0272229.t002 PLOS ONE

Elevational biodiversity gradients of Neotropical caddisflies PLOS ONE | https://doi.org/10.1371/journal.pone.0272229 August 5, 2022 7 / 17