Species' Distribution and Evolutionary History Influence the Responses of Marine Copepods to Climate Change: A Global Meta-Analysis

Abstract

Ocean acidification (OA) and ocean warming (OW) are predicted to drive changes to the distribution of species and the structure of biological communities globally. Differences in life-history, physical traits, and the phenotypic response of organisms will, however, mean that the effects of OA and OW will differ among species. Geographical differences in environmental characteristics across habitats will also influence the effects of OA and OW, thereby driving inter-population differences in phenotypic response as determined by local adaptations. While is it accepted that the response of species will vary globally, predicting the trends in response of species remains highly uncertain. We undertook a meta-analysis of key biological traits of 47 marine copepod species from 88 studies to identify the intrinsic and extrinsic factors influencing the effects of OA and OW on copepod population demographics. Data from OA and OW were analysed independently due to insufficient two-stressor studies. We found that the large disparity in the response of species to OA and OW is largely defined by their environmental history. Additionally, the response of copepod species to OW is related to their evolutionary history which has less influence on their response to OA. Therefore, our study identified that the response of copepods to OA is driven by a combination of biotic and abiotic factors in their habitats. Under OA alone, copepods from less variable environments may be more susceptible, but the effects of OA will only be strongly negative at extreme low pH (<7). On the other hand, the response to OW is deeply tied to their phylogeny, whereby closely related species share similar costs and trade-offs. However, the effects of near-future OW (+2 to 4°C) seem mainly positive unless these temperatures exceed a species’ thermal limit. Finally, our analysis revealed that OW has a greater influence on key copepod traits than OA. Overall, this study shows that attempting to draw global patterns in the response of species to climate change from a single species or habitat without consideration of environmental and evolutionary history could lead to inaccurate and misleading predictions with respect to the future of biological communities.