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

RESEARCH ARTICLE Elevational biodiversity gradients in the Neotropics: Perspectives from freshwater caddisflies (Insecta: Trichoptera) Blanca Rı´os-ToumaID1☯*, Francisco CuestaID1☯*, Ernesto Ra´ zuri-GonzalesID2,3, Ralph Holzenthal2, Andrea Tapia4, Marco Caldero´ n-Loor1,5 1 Facultad de Ingenierı´as y Ciencias Aplicadas, Ingenierı´a Ambiental/ Grupo de Investigacio´ n en Biodiversidad, Medio Ambiente y Salud–BIOMAS-, Universidad de Las Ame´ricas, Quito, Ecuador, 2 Department of Entomology, University of Minnesota, St. Paul, Minnesota, United States of America, 3 Department of Terrestrial Zoology, Entomology III, Senckenberg Research Institute and Natural History Museum, Frankfurt, Germany, 4 Mashpi Reserve, Quito, Ecuador, 5 Centre for Integrative Ecology, School of Life and Environmental Sciences, Deakin University, Melbourne, Australia ☯ These authors contributed equally to this work. * blanca.rios@udla.edu.ec (BRT); francisco.cuesta@udla.edu.ec (FC) Abstract Aquatic insects in the order Trichoptera are extremely diverse in number of species and their trophic roles. However, their distribution and diversity patterns are poorly known in the Neotropics, including the species restricted to tropical mountain ecosystems. Recent stud- ies in tropical mountains have shown high levels of endemism of aquatic insects and changes in the composition of communities over short distances. Still, the incidence of envi- ronmental filters that explain such patterns has not been addressed quantitatively. Given

the relevance of understanding Trichoptera spatial diversity patterns to prioritize conserva- tion areas for freshwaters, as well as to obtain baseline information to predict changes in aquatic communities facing global environmental changes, we assessed the species distri- bution and assemblages of caddisflies along an elevational gradient from 600 to 3,600 m a. s.l. on the equatorial Andes. In this area, we had long-term continuous climate data with hourly resolution. We collected adult caddisflies in seven localities along this gradient using light traps. We sampled each locality for two hours after sunset for three consecutive days. All specimens collected were identified to species or morphospecies. Our results showed an increase in species and genera numbers with decreasing altitude, albeit no significant. Mini- mum air temperature is the main environmental variable explaining Trichoptera community assemblages. β-diversity (taxon turnover among sites), as opposed to species richness, increased with altitude and showed a bimodal distribution along the elevation gradient for both genera and species assemblages, which resulted in a significant shift in community composition of species and genera at 2,000 m a.s.l. Our null-models confirm the observed patterns of B-diversity are non-random and suggest a strong environmental filtering of tropi- cal caddisflies community assemblies and turnover. Geographic distance coupled with changes in environmental conditions along the elevation gradient explained a high percent-

age of community variance, as documented for other taxa (e.g., vascular plants), suggesting PLOS ONE PLOS ONE | https://doi.org/10.1371/journal.pone.0272229 August 5, 2022 1 / 17 a1111111111 a1111111111 a1111111111 a1111111111 a1111111111 OPEN ACCESS Citation: Rı´os-Touma B, Cuesta F, Ra´zuri-Gonzales E, Holzenthal R, Tapia A, Caldero´n-Loor M (2022) Elevational biodiversity gradients in the Neotropics: Perspectives from freshwater caddisflies (Insecta: Trichoptera). PLoS ONE 17(8): e0272229. https:// doi.org/10.1371/journal.pone.0272229 Editor: Frank O. Masese, University of Eldoret, KENYA Received: July 9, 2021 Accepted: July 14, 2022 Published: August 5, 2022 Copyright: © 2022 Rı´os-Touma et al. This is an open access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited. Data Availability Statement: All relevant data are within the manuscript and its Supporting information files (S2 Table). Funding: This paper was developed thanks to the financial support of the EcoAndes Project conducted by CONDESAN and UN-Environment, funded by the Global Environmental Fund (GEF, http://www.thegef.org) (Grant number: 4750), The Swiss Agency for Development and Cooperation (SDC, http://www.eda.admin.ch/sdc) through the Andean Forest Program (Grant number