Environmental and spatial filters of zooplankton metacommunities in shallow pools in high‐elevation peatlands in the tropical Andes

Abstract

Understanding metacommunity organisation in freshwater ecosystems is particularly important at high elevation in the tropical Andes, as this region is considered an important biodiversity hotspot with many endemic species threatened by climate change. High levels of dispersal at the regional scale and strong environmental filters at the local scale are thought to structure aquatic communities in these systems. However, metacommunity organisation patterns at the limit of aquatic life (>4,500 m a.s.l.) remain largely unknown. Given the extreme environmental conditions experienced by organisms at high elevation, environment filters would be expected to play a greater role than spatial filters in community assemblages. We assessed the effects of environmental and spatial filters on zooplankton (Cladocera), to gain insight into metacommunity organisation in the shallow high‐elevation pools of the tropical Andes. We sampled zooplankton communities and assessed nine environmental variables, for 200 pools from 20 peatlands in the Cordillera Real of Bolivia. We performed redundancy and variation partitioning analyses on both abundance and presence/absence data, to evaluate the contribution of environmental and spatial processes (geographic and elevation distances) to cladoceran metacommunity assembly at different spatial scales. We identified 18 cladoceran species, eight of which were endemic to the Andes. We found that both environment and spatial filters made a significant contribution to the structuring of cladoceran communities at higher spatial scales (i.e. intervalleys and within valleys), whereas only the environmental filter operated at small spatial scales (i.e. within peatlands). Elevation had a significant effect on cladoceran community variation (e.g. 6.9% within valleys, for abundance data), but not on species diversity. Similar patterns were obtained with presence/absence data. Macrophyte cover, pool area and pH were the most important variables explaining community variation and the species diversity of cladocerans at pool level. These results suggest that species sorting is probably the main process generating variation in cladoceran communities at all spatial scales. At larger spatial scales (intervalleys and within valleys), limited dispersal may also filter species composition. We identified factors significantly contributing to the variation observed, but their overall explanatory power was low. This finding highlights the difficulties involved in evaluating the response of aquatic organisms to their environment and suggests that other environmental variables should be considered. Moreover, frequent and unpredictable disturbances and high stochasticity probably operate simultaneously with environmental filters to structure zooplankton organisation in these unique and harsh aquatic systems.

The joint effects of local, climatic, and spatial variables determine soil oribatid mite community assembly along a temperate forest elevational gradient

“…The balance between deterministic and stochastic processes offers a credible rationale for the genesis and sustenance of spatiotemporal biodiversity patterns, even along elevational gradients (Wang, Hu, et al., 2022 ; Wang, Zhong, et al., 2022 ). This appears especially pertinent for ecosystems subjected to severe and fluctuating conditions, where discerning niche and stochastic processes prove challenging (Quenta Herrera et al., 2018 ).…”

“…Besides geographical distance, elevation also significantly influences oribatid mite community variation. Extreme environmental conditions at high altitudes, such as reduced oxygen pressure, low temperatures, and elevated ultraviolet radiation, restrict soil organism distributions (Liu, Liu, et al., 2023 ; Quenta Herrera et al., 2018 ). We found a direct elevation impact on oribatid mite communities, with marked reductions in abundance and species richness at higher altitudes.…”

“…Most community variation explanatory variables were selected from the assessed environmental factors through forward selection, using the “ordiR2step” function in the R package “vegan” (Blanchet et al., 2008 ). Furthermore, RDA factored in sample elevation values, considering elevation as a surrogate for unmeasured environmental stressors, such as ultraviolet radiation (Quenta Herrera et al., 2018 ).…”

“…MAT and MAP selection as primary climatic variables stemmed from the RDA and random forest analysis findings. The PCNMs, derived from geographic and elevational distances, were considered distinct spatial components (Quenta Herrera et al., 2018 ). Consequently, we established two models: Model 1 related the oribatid mite community to the environment and geographic coordinate‐based distances; Model 2 related the oribatid mite community to the environment and elevation‐based distances.…”