Examining links between behaviour, plasticity and diversification under environmental heterogeneity using broadly distributed spider species

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Understanding factors that drive and maintain biodiversity is a critical issue in contemporary biology, particularly as species are exposed to rapid climate change, habitat fragmentation, and other environmental alterations that challenge survival. A broad understanding of how organisms respond to environmental heterogeneity at a variety of scales is essential for addressing these contemporary problems. One area that may have predictive power is the study of plasticity-- how and when organisms vary in trait expression under variable environmental conditions. Plasticity may confer resilience for populations despite environmental challenges; allowing survival under a wider range of conditions than would otherwise be possible, and providing sufficient time for adaptation. There are many hypotheses for the evolution of different forms of plasticity, and these have been comprehensively tested in plants and a handful of model systems. Our understanding is hampered however, by the limited taxonomic range of these models. Here I propose studies that will provide a significant leap in understanding by testing hypotheses for the evolution of adaptive plasticity in taxa for which my past work has defined the ecological and social contexts linked to plasticity, and demonstrated the tractability of experimental study in the field and lab. My research personnel and I will use two species of sexually cannibalistic ‘black widow' spiders (Latrodectus hesperus, Latrodectus hasselti) and a mate-guarding jumping spider (Phidippus clarus) to ask about the scale of environmental variation that causes evolutionary adaptation or plasticity. All three species have broad geographic ranges and are exposed to varied environmental conditions in nature, as well as experiencing local shifts in selection as mating seasons progress. All are amenable to study in the field and lab. Moreover, since spiders are top predators of terrestrial invertebrates, they are a critical part of terrestrial food webs. Here I propose studies of multiple populations of each species to test sex-specific hypotheses about the evolution of plasticity. Work will assay how phenotypic variation affects fitness in nature across latitudinal clines, testing my predictions that this is mediated by sexual competition in males and naturally-selected competition over food and refuges in females. Laboratory studies, linked to insights from field work, will quantify (1) clinal divergence in adaptive phenotypes and (2) whether the degree of plasticity across latitudinal gradients is predicted by abiotic conditions versus local variation in demographic context. In this proposal, I leverage my lab's extensive expertise in integrated field and laboratory studies of reproductive fitness to provide new understanding of the conditions that shape the evolution of adaptive plasticity across at a range of temporal and spatial scales.