Genetic diversity is a fundamental component of biodiversity and the medium for speciation events. Examination of global patterns of genetic diversity can help highlight mechanisms underlying species diversity. Here, we compiled 6862 observations of genetic diversity from 492 species of marine fish globally, assessed their associations with macroecological drivers, and tested among three hypotheses for diversity gradients: the founder effect hypothesis, the kinetic energy hypothesis, and the productivity-richness hypothesis. We found that mitochondrial genetic diversity follows latitudinal and longitudinal gradients similar to those of species diversity, being highest near the equator, particularly in the Coral Triangle, while nuclear genetic diversity did not follow clear geographic patterns. Despite these differences, all genetic diversity metrics were positively correlated with chlorophyll, while mitochondrial diversity was also positively associated with sea surface temperature. These findings provide support for the kinetic energy hypothesis, which predicts that elevated metabolic and mutation rates at higher temperatures should increase mitochondrial diversity, and the productivity-richness hypothesis, which posits that resource-rich regions support larger populations with greater genetic diversity. Overall, these findings reveal how environmental controls on mutation and drift in the ocean combine to establish global gradients of genetic diversity within species, and in turn, community assemblages.

Understanding the evolutionary consequences of anthropogenic change is imperative for estimating long-term species resilience. While contemporary genomic data can provide us with important insights into recent demographic histories, investigating past change using present genomic data alone has limitations. In comparison, temporal genomics studies, defined herein as those that incorporate time series genomic data, leverage museum collections and repeated field sampling to directly examine evolutionary change. As temporal genomics is applied to more systems, species, and questions, best practices can be helpful guides to make the most efficient use of limited resources. Here, we conduct a systematic literature review to synthesize the effects of temporal genomics methodology on our ability to detect evolutionary changes. We focus on studies investigating recent change within the past 200 years, highlighting evolutionary processes that have occurred during the past two centuries of accelerated anthropogenic pressure. We first identify the most frequently studied taxa, systems, questions, and drivers, before highlighting overlooked areas where further temporal genomic studies may be particularly enlightening. Then, we provide guidelines for future study and sample designs while identifying key considerations that may influence statistical and analytical power. Our aim is to provide recommendations to a broad array of researchers interested in using temporal genomics in their work.

The survival of animals under global warming strongly depends on their individual thermal niches, which result from the balance between energy loss and gain. Active movement is an important component of this energetic balance, as it affects not only energy gain via food intake but also energy loss via activity metabolism. Here, we develop a novel trait-based approach for how thermal niches arise from temperature-dependent movement. Therefore, we used image-based tracking to quantify the unimodal responses of the movement speed of carabid beetles to temperature. We used these empirical data to parameterize a mathematical model based on metabolic and predator-prey theory for net energy gain to derive a general mechanistic concept of thermal niches. This trait-based approach allows a relatively rapid and cost-effective assessment of climate change vulnerability for a wide range of animal taxa on broad geographic scales.

Understanding range edges is key to addressing fundamental biogeographic questions about abiotic and biotic drivers of species distributions. Range edges are where colonization and extirpation happen, so their dynamics are also important for natural resource management and conservation. We quantified positions for 153 range edges of marine fishes and invertebrates from three US continental shelf regions using decades of survey data and a spatiotemporal model to account for changes in survey design. We analyzed whether range edges maintained their edge thermal niches—temperature extremes at the range edge—over time. Most range edges (86%) maintained either cold or warm temperature extremes; 73% maintained both. However, the substantial fraction of range edges that altered their thermal niche underscore the multiplicity of relevant drivers. This study suggests that temperate marine species largely maintained their edge thermal niches during rapid change and provides a blueprint for testing temperature tracking of species range edges.