Living on the edge: Predicting invertebrate richness and rarity in disturbance‐prone aquatic–terrestrial ecosystems

Abstract

1. Temporal fluctuations in cause the spatial extent of wet and dry habitats to vary in aquatic-terrestrial riverine ecosystems, complicating their biomonitoring.As such, biomonitoring efforts may fail to characterize the species that inhabit such habitats, hampering assessments of their biodiversity and implementation of evidence-informed management strategies.2. Relationships between the dynamic characteristics of aquatic-terrestrial habitats and their communities are well known. Thus, habitat characteristics may enable estimation of faunal assemblage characteristics such as taxonomic richness, regardless of in-channel water levels.3. We investigated whether indicators summarizing habitat survey data can predict two metrics representing terrestrial invertebrate assemblages (e.g. taxa richness) in two aquatic-terrestrial habitats: exposed riverine sediments and dry temporary streams. We also compared the performance of unimetric and multimetric habitat indicators in making predictions.4. In exposed riverine sediments, >88% of predictions were correlated with observed taxa richness and an index of conservation status. Values predicted by exposed riverine sediment samples were correlated with those observed in temporary stream channels with comparable riparian (i.e. largely agricultural) land use, but not those observed in channels with contrasting (i.e. more urban) land use. 5. Unimetric habitat indicators performed similarly to more complex multimetric indicators, with each explaining ≤6% of the variability in taxa richness and the index of conservation status. The different spatial scales at which invertebrates respond to habitat conditions and at which indicators record habitat conditions, and a more comprehensive training dataset that incorporates a full range of habitat conditions (i.e. land use), may improve future predictions.6. We demonstrate that invertebrate assemblage characteristics can be predicted regardless of in-channel water levels. Agreement between exposed riverineThis is an open access article under the terms of the Creative Commons Attribution License, which permits use, distribution and reproduction in any medium, provided the original work is properly cited.

Extra terrestrials: drought creates niche space for rare invertebrates in a large-scale and long-term field experiment

“…Notable early riparian colonists of dry streambeds, such as ground beetles (Carabidae) [11], were absent from our samples, but the widespread presence of other common inhabitants of riparian zones, such as rove beetles (Staphylinidae) and money spiders (Linyphiidae), suggests that this is unlikely to reflect the lack of riparian habitat in the mesocosms. It could instead point towards a key difference between the effects of seasonal drying and prolonged drought on terrestrial species composition, with adaptations that allow rapid colonization of newly dry streambeds, such as inundation tolerance and strong flight among some carabids [11,20], becoming significantly less advantageous over longer dry periods. Further studies of prolonged stream droughts are needed to explore this.…”