COS 117-6 - Differences in functional group responses to temperature and flooding shape patterns of overall richness in a riverine rock pool metacommunity

Abstract: Climate change presents a threat to biodiversity and the ecosystem services it provides. Future climate models predict changes in precipitation and warming temperatures, which could alter both thermal conditions and the timing, duration, and frequency of flooding in riverine ecosystems, which highlights the need to improve our understanding of how these elements shape diversity. However, responses to temperature and flooding are dependent on the life history traits of species. Therefore, climate change could have a positive, negative, or no effect on overall taxonomic richness depending on the magnitude and direction taxa-specific responses to these climate drivers.


We examined how differences in species traits in response to flooding and environmental conditions shape patterns of taxonomic richness in a metacommunity of riverine rock pools. Rock pools provide habitat for assemblages that include lotic taxa that colonize patches from the river during flood pulses and lentic taxa that colonize patches overland after floodwaters recede. Changes in hydrologic connectivity and temperature are likely to affect both groups of organisms, however due to differences in their life history traits they may respond asymmetrically. Thus, the overall effect of changes in connectivity and thermal conditions on biodiversity may be obscured.


We modeled lentic, lotic, and overall richness as a function of flooding, temperature, pool size, canopy cover, and season using data consisting of 980 samples from 430 pools across 5 years. We predicted that lotic richness would be greater in pools with higher hydrologic connectivity and lower temperatures. We expected to find the opposite pattern for lentic richness. We expected overall richness to be highest in larger pools with more canopy cover because we expected a positive response in both lentic and lotic richness.


We found overall pool diversity reflected key differences in lentic and lotic richness in response to flooding and temperature. Lotic richness was higher in pools with larger surface areas, cooler estimated water temperatures, and lower flood heights, while lentic richness was highest in pools with larger surface areas sampled during the summer months. Overall richness was higher during the summer months in pools with larger surface areas that flood at lower river levels. Interestingly, temperature was not a significant predictor of overall richness, which was the result of the differential responses of the lentic and lotic groups. Given predicted warmer water temperatures and an increase in both high and low flow events we might expect lower overall diversity in the future.