Abstract
Genetic diversity confers adaptive capacity to populations under changing conditions but its role in mediating impacts of climate change remains unresolved for most ecosystems. This lack of knowledge is particularly acute for foundation species, where impacts may cascade throughout entire ecosystems. We combined population genetics with eco-physiological and ecological field experiments to explore relationships among latitudinal patterns in genetic diversity, physiology and resilience of a kelp ecosystem to climate stress. A subsequent ‘natural experiment’ illustrated the possible influence of latitudinal patterns of genetic diversity on ecosystem vulnerability to an extreme climatic perturbation (marine heatwave). There were strong relationships between physiological versatility, ecological resilience and genetic diversity of kelp forests across latitudes, and genetic diversity consistently outperformed other explanatory variables in contributing to the response of kelp forests to the marine heatwave. Population performance and vulnerability to a severe climatic event were thus strongly related to latitudinal patterns in genetic diversity, with the heatwave extirpating forests with low genetic diversity. Where foundation species control ecological structure and function, impacts of climatic stress can cascade through the ecosystem and, consequently, genetic diversity could contribute to ecosystem vulnerability to climate change.
Highlights
A core tenet of evolutionary theory is that the ability of species to adapt and persist through changing environments is contingent on latent functional responses suited to new conditions[1]
Positive, relationship between latitude and genetic diversity of kelp, measured as both expected heterozygosity (r2 = 0.74, P = 0.002) and number of alleles (r2 = 0.58, P = 0.007), across southwestern Australia (Fig. 1b, see appendix S1 for additional regression statistics)
The latitudinal patterns of genetic diversity, physiological versatility, and ecological resilience were mirrored in kelp forest response to the heatwave (r2 = 0.84, P < 0.001; Fig. 1e), with strikingly different impacts observed across the 12 kelp forests (Figs 1e, 2)
Summary
A core tenet of evolutionary theory is that the ability of species to adapt and persist through changing environments is contingent on latent functional responses suited to new conditions[1]. Our lack of understanding of how genetic diversity mediates population response to climate stress is acute for ‘foundation species’ (trees, corals, kelps, etc.)[4,12], because of their critical influence on community organization and ecosystem functioning. Knowledge of the role of genetic diversity in determining the response of foundation species to climatic stress is, critical for assessing the overall vulnerability of an ecosystem, and to ensure successful conservation and management strategies[2,4,11,13,17,18]. We combined population genetics[19] with eco-physiological and ecological field experiments[14] to examine relationships between latitudinal patterns in genetic diversity, physiological versatility and ecological resilience of kelp forests, one of the most important foundation species of temperate marine habitats globally[20,21]. We documented subsequent responses of kelp (Ecklonia radiata) forests to an extreme climatic perturbation (a marine heatwave), demonstrating through a ‘natural experiment’, the possible influence of latitudinal patterns in genetic diversity on ecosystem vulnerability to climatic stress
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