Aspin, T.W.H., Khamis, K., Matthews, T.J., Williams, G.M.D., Windsor, F.M.,Woodward, G. & Ledger, M.E. (2023) Extra terrestrials: drought creates niche space for rare invertebrates in a large-scale and long-term field experiment.Biology Letters, 19(11), 20230381. DOI:10.1098/rsbl.2023.0381 (IF2022 3,3; Q1 Ecology)
Freshwater habitats are drying more frequently and for longer under thecombined pressures of climate change and overabstraction. Unsurprisingly,many aquatic species decline or become locally extinct as their benthic habi-tat is lost during stream droughts, but less is known about the potential‘winners’: those terrestrial species that may exploit emerging niches indrying riverbeds. In particular, we do not know how these transientecotones will respond as droughts become more extreme in the future. Tofind out we used a large-scale, long-term mesocosm experiment spanninga wide gradient of drought intensity, from permanent flows to fullstreambed dewatering, and analysed terrestrial invertebrate communityassembly after 1 year. Droughts that caused stream fragmentation gaverise to the most diverse terrestrial invertebrate assemblages, including 10species with UK conservation designations, and high species turnoverbetween experimental channels. Droughts that caused streambed dewater-ing produced lower terrestrial invertebrate richness, suggesting that thepersistence of instream pools may benefit these taxa as well as aquaticbiota. Particularly intense droughts may therefore yield relatively few‘winners’among either aquatic or terrestrial species, indicating that thethreat to riverine biodiversity from future drought intensification could bemore pervasive than widely acknowledged.