Diversity patterns of aquatic macroinvertebrates in a tropical high-Andean catchment

Abstract

Introduction: Glacierised catchments are remote and hostile environments, in which streams from different water sources (e.g., glacier melt, rain/snowmelt, groundwater) converge, creating a complex mosaic of stream sites with varying levels of glacial influence and environmental conditions. This environmental heterogeneity, in turn, influences the assemblage and composition of aquatic communities and produces complex patterns of species diversity at the catchment scale. Objectives: In this contribution, we assessed biodiversity and community composition of aquatic macroinvertebrate communities from 51 stream site types in a glacierised catchment in the tropical Andes. The aim of our study was to: (1) determine diversity, rarity, commonness and spatial distribution patterns of aquatic macroinvertebrate communities from sites with different water sources, and (2) identify which environmental variables influence the density and presence of macroinvertebrate taxa and, in particular, of the subfamilies of the ubiquitous chironomids. Methods: Our study sites were grouped according to their water source and to their percentage of glacier coverage in the catchment (GCC). At each site we sampled aquatic macroinvertebrates, measured environmental variables and assessed community differences and environmental influence with ordination analyses and generalized linear models. Results: Kryal and mixed sites had an important proportion of rare taxa. Mean richness was highest in the mixed sites and lowest in the sites with the highest glacier cover; while sites with an intermediate percentage of glacier cover, had the highest values of α and β diversity. We found that 13 taxa (15.9%) were common to all stream site types. SIMPER analysis showed that Orthocladiinae, Hyalella sp. and Andesiops sp. contributed the most to the dissimilarity between site types (˃ 45% of cumulative contribution). RDA showed that kryal sites were associated with high turbidity and density of Podonomids, and with low temperature, amount of CPOM and densities of both Anomalocosmoecus sp. and Andesiops sp. Orthocladinae was associated with high current velocity and chlorophyll a concentration, whereas Hyalella sp. had a positive relationship with higher pH and streambed stability. Generalized linear models showed that GCC was the main variable explaining all faunal metrics. Current velocity explained macroinvertebrate abundance, water temperature was related to chironomid density and chlorophyll a influenced Orthocladiinae presence-absence. Conclusions: Our results suggest that by favoring the presence of rare taxa and taxa turnover, glacier influence may increase biodiversity in glacierised catchments. In terms of biodiversity conservation, this study confirms an urgent need to increase knowledge of high-Andean stream biodiversity, especially in highly heterogenous glacierised catchments, to better describe regional biodiversity patterns and community composition of these highly vulnerable freshwater ecosystems. Detailed analyses of benthic communities and development of databases are key for conservation strategies. Water management municipalities and/or enterprises should consider water quality and stream types for more sustainable management of these important ecosystems.

Multi‐taxa colonisation along the foreland of a vanishing equatorial glacier

“…turbidity in the stream) linked to glacial influence will discriminate specialised species adapted to these specific habitats (Milner et al 2008). For example, in agreement with Espinosa et al (2020) at the Antisana volcano, certain aquatic larvae from the beetle families Dytiscidae and Staphylinidae were exclusively observed in the studied glacier‐fed stream, and not in a neighbouring groundwater‐fed stream (unpublished observations from the same sampling dates).…”

Functional Feeding Groups of Macrofauna and Detritus Decomposition along a Gradient of Glacial Meltwater Influence in Tropical High-Andean Streams

“…FFG richness was less affected by GI, since the fewer taxa present at higher GI represented more feeding guilds. The hump-shaped pattern in taxon richness has been found in previous studies from the same region [38,68]. Functional diversity of aquatic macroinvertebrates varies with land cover type in alpine streams [69], and decreases with increasing glacier cover in Arctic-temperate catchment [9].…”

“…Relatively little is known about the ecology of glacier-fed streams in tropical mountains, but overall spatial patterns of macroinvertebrate community structure and diversity seem to follow what is known from temperate-Arctic latitudes [36][37][38]. Additionally, prominent functional traits such as feeding habits and the relationships between functional traits and glacial influence seem to be largely comparable between temperate and tropical glacier-fed streams, with functional diversity lower than expected from a null model close to glaciers [39].…”

The Impacts of Different Anthropogenic Disturbances on Macroinvertebrate Community Structure and Functional Traits of Glacier-Fed Streams in the Tianshan Mountains

“…Our results also showed the diversity and density decreased at sites C-E of the grazing stream when grazing intensity increased. However, there were some taxa sensitive to environmental changes such as EPT species in the grazing stream [62]. Our findings showed that EPT species were also present in the grazing stream, but they decreased with the presence of grazing disturbance.…”