Arctic biodiversity of stream macroinvertebrates declines in response to latitudinal change in the abiotic template

Abstract

We aimed to determine which processes drive patterns of a and b diversity in Arctic river benthic macrofauna across a broad latitudinal gradient spanning the low to high Arctic of eastern Canada (58 to 81 o N). Further, we examined whether latitudinal differences in taxonomic composition resulted from species replacement with organisms better adapted to northerly conditions or from the loss of taxa unable to tolerate the harsh environments of higher latitudes. We used the bioclimatic envelope concept to provide a first approximation forecast of how climate warming may modify a and b diversity of Arctic rivers and to identify potential changes in environmental variables that will drive future assemblage structure. Benthic macroinvertebrates, environmental supporting variables, and geospatial catchment data were collected to assess drivers of ecological pattern. We compared a diversity (i.e., taxonomic richness) across latitudes and partitioned b diversity into components of nestedness and species turnover to assess their relative contributions to compositional differences. We found sharp declines in taxonomic richness along a latitudinal gradient. This a diversity pattern was not associated with a change in numerical abundance. b diversity was highest when the most distant latitudes were compared, and pairwise latitudinal comparisons indicated that nestedness (loss of species) was the dominant contributor to compositional differences. Biotic-abiotic associations reflected both large-scale climatic drivers, including air temperature and prevalence of vegetated tundra, and small-scale secondary abiotic drivers of assemblage composition (e.g., substrate composition, water chemistry). The importance of nestedness to b diversity across latitudes supports the physiological tolerance hypothesis that a change in environmental tolerance is a key driver of species richness declines with increasing latitude. Distinct taxonomic assemblages among low and high Arctic latitude sites were associated with large-scale, climate-related drivers (e.g., temperature trends, terrestrial vegetation), reflecting the primary structuring of assemblages by bioclimatic envelopes. The abiotic environment was the strongest driver of assemblage structure at high latitudes because of the extreme conditions. With continued warming, biodiversity differences along latitudinal gradients are expected to become less pronounced as temperatures and vegetation become more similar from south to north, with local-scale variables becoming dominant biotic drivers.

Characteristics, Main Impacts, and Stewardship of Natural and Artificial Freshwater Environments: Consequences for Biodiversity Conservation

“…For example, geographical location determines the species pool from which local communities are assembled, and thus local communities show imprints of both regional and local factors [421,432]. Recent studies have also shown that biological communities in northern freshwater ecosystems are clearly affected by climate over broad areas, as has been observed for algae [433], macroinvertebrates [434], and fish [419]. Finally, land use, land cover, and catchment heterogeneity have been found to be associated with both alpha and beta diversity variation of macrophytes (e.g., [435]) and macroinvertebrates (e.g., [428]).…”

Assessment of ecological impairment of Arctic streams: Challenges and future directions

“…Interannual and seasonal variability, as well as the timing of the sampling period, plays a large role in determining the abundance of benthic invertebrates collected using biomonitoring approaches (Hawkins et al., 2010). Depending on yearly precipitation and heat, the abundance of assemblages can vary greatly since there is a clear relationship between variability of macroinvertebrate α diversity and air temperature variation (Culp et al., 2019); this is especially true in Arctic environments where seasonality is known to have significant control over invertebrate abundances (Danks, 2007). Indeed, for Arctic environments, there is an expectation that the natural temporal variability of invertebrates is high (Meyer et al., 2017) and could be based on stochastic factors (Miller & Stout, 1989).…”

Are different benthic communities in Arctic delta lakes distinguishable along a hydrological connectivity gradient using a rapid bioassessment approach?

“…Water samples were sent to the National Laboratory for Environmental Testing (Burlington, Ontario, Canada) for analysis using standardized methods (Environment Canada 2017). The variables were chosen to represent established physical and ecological gradients in the Mackenzie Delta (Lesack et al 1998;Squires et al 2009;Tank et al 2011) and include variables that have been found to structure BMI communities in Arctic regions (e.g., Culp et al 2019) and (or) deltaic floodplain lakes (e.g., Gallardo et al 2008).…”