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As climatic variation re‐shapes global biodiversity, understanding eco‐evolutionary feedbacks during species range shifts is of increasing importance. Theory on range expansions distinguishes between two different forms: “pulled” and “pushed” waves. Pulled waves occur when the source of the expansion comes from low‐density peripheral populations, while pushed waves occur when recruitment to the expanding edge is supplied by high‐density populations closer to the species' core. How extreme events shape pushed/pulled wave expansion events, as well as trailing‐edge declines/contractions, remains largely unexplored. We examined eco‐evolutionary responses of a marine invertebrate (the owl limpet,Lottia gigantea) that increased in abundance during the 2014–2016 marine heatwaves near the poleward edge of its geographic range in the northeastern Pacific. We used whole‐genome sequencing from 19 populations across >11 degrees of latitude to characterize genomic variation, gene flow, and demographic histories across the species' range. We estimated present‐day dispersal potential and past climatic stability to identify how contemporary and historical seascape features shape genomic characteristics. Consistent with expectations of a pushed wave, we found little genomic differentiation between core and leading‐edge populations, and higher genomic diversity at range edges. A large and well‐mixed population in the northern edge of the species' range is likely a result of ocean current anomalies increasing larval settlement and high‐dispersal potential across biogeographic boundaries. Trailing‐edge populations have higher differentiation from core populations, possibly driven by local selection and limited gene flow, as well as high genomic diversity likely as a result of climatic stability during the Last Glacial Maximum. Our findings suggest that extreme events can drive poleward range expansions that carry the adaptive potential of core populations, while also cautioning that trailing‐edge extirpations may threaten unique evolutionary variation. This work highlights the importance of understanding how both trailing and leading edges respond to global change and extreme events. 

ABSTRACT Coastal organisms live in a dynamic environment where a myriad of environmental stressors, including climate change, ocean acidification, and human harvesting, act on variable spatio‐temporal scales. Each of these stressors may impose unique selective forces on a population, shaping a species' adaptive potential and its ability to persist under future climatic conditions. Genomic investigations of adaptive responses to environmental and anthropogenic disturbances remain rare, especially in marine systems. Here, we use whole genome sequencing data from the owl limpet,Lottia gigantea, and outlier detection methods to pinpoint signals of selection (1) across long‐standing environmental gradients spanning the species' distribution, (2) at the poleward edge of the species' range where it experienced a recent expansion, and (3) between sites vulnerable to or protected from human size‐selective harvesting within California. Loci associated with environmental gradients across the entire range show the strongest differentiation at the southern end of the species' range, potentially driven by adaptation to sea surface temperature and pH. Additionalad‐hocoutlier analyses revealed a distinct set of loci potentially under selection in the expanded range, with different functional roles than the range‐wide outliers. Despite demographic models suggesting that protection from harvesting has a positive impact on the abundance of large individuals, we did not find strong signals of selection or changes in genetic diversity between sites differing in harvesting vulnerability. Our findings suggest that range‐wide environmental selective signals established over longer time scales are distinct from those imposed by climatic anomalies at finer spatio‐temporal scales. We found that climatic variation has a stronger selective imprint than human harvesting, and thus conservation interventions should consider prioritizing the maintenance of climate‐related adaptive potential. Understanding how climatic trends and anomalies interact with anthropogenic pressures will allow us to make more informed decisions to sustain the evolutionary capacity ofL. giganteaand other key coastal species. 

Abstract AimThe biogeography of predator‐induced defences is an understudied area of predator–prey dynamics. Range overlap with predators that induce the response and local demographics (e.g., prey abundances) are likely to be important factors for determining the biogeographic distribution of induced defences within species. However, with climate warming, range‐expanding warm‐water predators are increasingly preying upon temperate species. This is a consequence of a wider phenomenon known as tropicalisation. We aim to determine: (i) if individuals of a temperate barnacle with induced defences (‘bent morphs’) are primarily present where they co‐occur with range‐expanding warm‐water predators (muricid snails) and, (ii) if bent morphs are size‐structured within populations. LocationNorth‐eastern Pacific rocky intertidal zone (~26–40° N). TaxonTetraclita rubescens(Nilsson‐Cantell, 1931), Balanomorpha. MethodsWe use photoquadrats from sites across the range ofT. rubescensto determine the biogeographic distribution of populations with bent morphs and to assess size‐structure. We use a combination of field surveys, literature, and museum occurrences to assess range overlap between cool and warm‐water predators ofT. rubescensand their association with populations with bent morphs and abundance patterns ofT. rubescens. ResultsBent morphs are commonly found within the equatorward portion of the species' range (where abundances are highest), in populations overlapping with range‐expanding warm‐water predators. Bent morphs primarily occur within the smaller size classes. Main conclusionsTo be partly resilient to the effects of tropicalisation, temperate prey must acclimatise/adapt to altered predator–prey dynamics. Predator‐induced defences are one way to do this. We show that bent morphs within a temperate prey species (T. rubescens) are largely restricted to populations that overlap with large‐bodied and range‐expanding warm‐water predators. This is evidence for the partial resilience ofT. rubescensto tropicalisation and provides the rationale for further exploration of the eco‐evolutionary consequences of tropicalisation in this study system and others. 

Abstract Coral reefs worldwide are threatened by thermal stress caused by climate change. Especially devastating periods of coral loss frequently occur during El Niño‐Southern Oscillation (ENSO) events originating in the Eastern Tropical Pacific (ETP). El Niño‐induced thermal stress is considered the primary threat to ETP coral reefs. An increase in the frequency and intensity of ENSO events predicted in the coming decades threatens a pan‐tropical collapse of coral reefs. During the 1982–1983 El Niño, most reefs in the Galapagos Islands collapsed, and many more in the region were decimated by massive coral bleaching and mortality. However, after repeated thermal stress disturbances, such as those caused by the 1997–1998 El Niño, ETP corals reefs have demonstrated regional persistence and resiliency. Using a 44 year dataset (1970–2014) of live coral cover from the ETP, we assess whether ETP reefs exhibit the same decline as seen globally for other reefs. Also, we compare the ETP live coral cover rate of change with data from the maximum Degree Heating Weeks experienced by these reefs to assess the role of thermal stress on coral reef survival. We find that during the period 1970–2014, ETP coral cover exhibited temporary reductions following major ENSO events, but no overall decline. Further, we find that ETP reef recovery patterns allow coral to persist under these El Niño‐stressed conditions, often recovering from these events in 10–15 years. Accumulative heat stress explains 31% of the overall annual rate of change of living coral cover in the ETP. This suggests that ETP coral reefs have adapted to thermal extremes to date, and may have the ability to adapt to near‐term future climate‐change thermal anomalies. These findings for ETP reef resilience may provide general insights for the future of coral reef survival and recovery elsewhere under intensifying El Niño scenarios.