Abstract
AbstractHydrology is the main environmental filter in aquatic ecosystems and may result in shared tolerances and functional traits among species in disparate ecosystems. We analyzed the associations between taxonomic and functional facets of diversity within aquatic ecosystems (ponds vs. streams) across a hydroperiod gradient (1–365 d) to untangle the hydrologic drivers of aquatic invertebrate diversity. We used invertebrate assemblage data from seven arid‐land streams in southeastern Arizona, United States collected over 2 yr and nine temperate woodland ponds in Ontario, Canada collected over 2 yr. Our results showed that although invertebrate assemblages from streams and ponds differ taxonomically, hydroperiod had similar influence on invertebrate trait structure regardless of biogeographic and habitat differences. Streams and ponds independently showed strong positive relationships between functional richness and taxonomic richness; however, the relationship showed a shallower slope in ponds, indicating higher functional redundancy. Intermittent ponds and streams tended to have lower functional and taxonomic richness than their perennial counterparts, but harbored greater beta diversity. Our results suggest that even though ponds and streams are fundamentally different habitats with distinct faunas and unique ecological processes, hydrology produces convergent patterns in both trait composition and diversity patterns.
Highlights
Environmental filtering is the process by which a subset of the regional species pool can persist in a local habitat because these species have particular traits or phenotypes suited to local environmental conditions (Southwood 1988, Poff 1997)
Functional diversity is defined as the range of species and traits that influence ecosystem functioning (Tilman 2001). Taxonomic richness and functional richness may respond differently to environmental gradients depending on the composition of the community
The redundancy analysis (RDA) showed 50.3% of the variance was expressed on axis 1 and identified a gradient that contrasted v www.esajournals.org perennial ponds and streams occurring in the right side of the ordination from the intermittent ponds and streams that occupied the top left side of ordination (Fig. 1, Appendix S1)
Summary
Environmental filtering is the process by which a subset of the regional species pool can persist in a local habitat because these species have particular traits or phenotypes suited to local environmental conditions (Southwood 1988, Poff 1997). Filtering works on the principle that species differ in their environmental requirements and tolerances. Communities that have different compositions of species are likely to have different trait diversity. Functional diversity is defined as the range of species and traits that influence ecosystem functioning (Tilman 2001). Taxonomic richness and functional richness may respond differently to environmental gradients depending on the composition of the community (e.g., dominance of generalists or functionally redundant species; Villéger et al 2012). Beta diversity—both ‘turnover’ and ‘variation’ beta (Anderson et al 2011)—may be a more informative measure of the effects of environmental variation than taxonomic richness alone. Variation beta diversity is defined as variation in species composition among sampling locations and turnover beta diversity measures change in community structure along a particular gradient.
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