Abstract: Many studies investigating the driving mechanisms of adaptation and its possible ecological consequences focus on a single focal species. It therefore remains largely unknown whether species from the same community differ in their evolutionary effect on ecology and whether these single species’ effects are additive or interact when species co-occur in a community. To address these knowledge gaps, a multi-species approach is needed that integrates evolution-mediated ecological effects on population, community and ecosystem level using multiple species. Here, we used three co-occurring Daphnia species (D. magna, D. pulicaria, and D. galeata) that were exposed to a naturally occurring heat wave. In a previous study, we found signals of micro-evolutionary responses for all three species. In the current study, we assessed the ecological consequences of these micro-evolutionary responses on three ecological scales.
To this end, we conducted a community assembly experiment in outdoor mesocosms. We constructed five communities that were identical in their genetic diversity and starting biomass, but differed in the selection background of the populations: one community with every species exposed, one community with no species exposed and three communities where only one species was exposed. We then quantified the ecological consequences of species selection background at the population (species abundance), community (community composition and total community biomass) and ecosystem (grazing rate and efficiency) level. Additionally, we conducted a full-factorial competition experiment with pairwise competitive trials under laboratory settings.
Our results show that D. pulicaria and D. galeata reached higher abundances in the community with the heat-wave-exposed D. magna population, while D. magna reduced in abundance when the heat-wave-exposed D. galeata population was used. This is indicative for competitive release when D. magna has been exposed to extreme temperatures. The effect rippled through to the higher ecological levels, with significant differences in community composition and grazing pressure across the community types. The interaction between species’ effect sizes varies across ecological scales: species evolutionary effects on ecology were found to interact antagonistically at the community level, but additively at the ecosystem level. The additional competition experiment confirmed that the outcome of interspecific competition is influenced by selection background of the competing species, with a reduced competitive capacity upon heat wave exposure due to the cost of thermal adaptation.
Understanding how evolution-mediated ecological effects of co-occurring species interact, is important in unravelling eco-evolutionary dynamics within communities and will further aid prediction of community-wide and ecosystem responses to global and climate change.
