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Phenotypic plasticity can buffer organisms against short-term environmental fluctuations. For example, previous exposure to increased temperatures can increase thermal tolerance in many species. Prior studies have found that acclimation to higher temperature can influence the magnitude of transcriptional response to subsequent acute thermal stress (hereafter, transcriptional response modulation). However, mechanisms mediating this gene expression response and, ultimately, phenotypic plasticity remain largely unknown. Epigenetic modifications are good candidates for modulating transcriptional response, as they broadly correlate with gene expression. Here, we investigate changes in DNA methylation as a possible mechanism controlling shifts in gene expression plasticity and thermal acclimation in the reef-building coral Acropora nana. We find that gene expression response to acute stress is altered in corals acclimated to different temperatures, with many genes exhibiting a dampened response to heat stress in corals pre-conditioned to higher temperatures. At the same time, we observe shifts in methylation during both acclimation (11 days) and acute heat stress (24 h). We observed that the acute heat stress results in shifts in gene-level methylation and elicits an acute transcriptional response in distinct gene sets. Further, acclimation-induced shifts in gene expression plasticity and differential methylation also largely occur in separate sets of genes. Counter to our initial hypothesis no overall correlation between the magnitude of differential methylation and the change in gene expression plasticity. We do find a small but statistically significant overlap in genes exhibiting both dampened expression response and shifts in methylation (14 genes), which could be candidates for further inquiry. Overall, our results suggest transcriptional response modulation occurs independently from methylation changes induced by thermal acclimation.

The Yellow Warbler (Setophaga petechia) is a small songbird in the wood-warbler family (Parulidae) that exhibits phenotypic and ecological differences across a widespread distribution and is important to California's riparian habitat conservation. Here, we present a high-quality de novo genome assembly of a vouchered female Yellow Warbler from southern California. Using HiFi long-read and Omni-C proximity sequencing technologies, we generated a 1.22 Gb assembly including 687 scaffolds with a contig N50 of 6.80 Mb, scaffold N50 of 21.18 Mb, and a BUSCO completeness score of 96.0%. This highly contiguous genome assembly provides an essential resource for understanding the history of gene flow, divergence, and local adaptation in Yellow Warblers and can inform conservation management of this charismatic bird species.

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 FROM AUTHOR]