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Abstract AimWe studied the niche evolution and diversification modes in transisthmianAlpheusshrimps by examining the interplay between environmental niche divergence and conservatism in allopatric sister species. In a broader perspective, the current study analysed the evolution of climatic niche and the role of the environment in species diversification ofAlpheustransisthmian shrimp. LocationAtlantic and Eastern‐Pacific oceans. TaxonAlpheusshrimps (Caridea: Alpheidae). MethodsWe assembled georeferenced occurrences for 33 species ofAlpheus(with 24 sister species) from a time‐calibrated molecular phylogeny. We modelled their ecological niches and assessed niche overlap through pairwise comparisons. Additionally, we performed phylogenetic reconstructions of the ancestral environmental niche, for each niche axis. ResultsOur results demonstrate that thermal tolerances, food availability and hydrodynamic forces were relevant environmental axes in evolutionary processes in transisthmian species ofAlpheus. Among the 528 paired comparisons, we found that most niches were divergent, including in 12 clades formed by pairs of sister species (in only two of these clades were the niches fully equivalent). Phylogenetic reconstructions of ancestral niches showed an initial niche conservatism in all axes, with divergences intensifying in the last 12 million years. Main ConclusionsWe found evidence that confirms the relevance of the environmental changes that occurred in the West Atlantic and East Pacific for niche evolution in transisthmianAlpheusspecies, as well as for the emergence of some lineages. Our findings provide evidence for different modes ofAlpheusspecies speciation in a period consistent with the closure of the Isthmus of Panama. 

Abstract Snapping shrimps of the genus Alpheus Fabricius, 1798 exhibit remarkable diversity, with over 300 described species. The genus is well-known for its prevalence of species complexes, necessitating the need of new tools to facilitate species discrimination. Traditional taxonomic methods in Alpheus have primarily relied on the examination of morphological traits or comparative morphometric measurements, with an emphasis on variation in the major chela and rostro-orbital region. We applied an integrated approach that combines molecular genetics and geometric morphometrics to investigate the A. gracilipesStimpson, 1860 species complex. We additionally applied geometric morphometric techniques to study the major chela and the rostrum across different species, and used three mitochondrial genes (12S, COI, and 16S) to reconstruct phylogenetic relationships of this complex. Our results demonstrate the first application of geometric morphometric techniques to Alpheus snapping shrimps, and highlight the significance of the major chela and rostrum as taxonomically informative traits. Furthermore, we use DNA barcodes and geometric morphometric techniques to the A. gracilipes species complex to reveal two previously unidentified cryptic species. We present the first phylogenetic reconstruction of this species complex, with new localities and expanded distribution ranges reported for many species. 

Abstract Across plants and animals, genome size is often correlated with life‐history traits: large genomes are correlated with larger seeds, slower development, larger body size and slower cell division. Among decapod crustaceans, caridean shrimps are among the most variable both in terms of genome size variation and life‐history characteristics such as larval development mode and egg size, but the extent to which these traits are associated in a phylogenetic context is largely unknown. In this study, we examine correlations among egg size, larval development and genome size in two different genera of snapping shrimp,AlpheusandSynalpheus, using phylogenetically informed analyses. In bothAlpheusandSynalpheus, egg size is strongly linked to larval development mode: species with abbreviated development had significantly larger eggs than species with extended larval development. We produced the first comprehensive dataset of genome size inAlpheus(n = 37 species) and demonstrated that genome size was strongly and positively correlated with egg size in bothAlpheusandSynalpheus. Correlated trait evolution analyses showed that inAlpheus, changes in genome size were clearly dependent on egg size. InSynalpheus, evolutionary path analyses suggest that changes in development mode (from extended to abbreviated) drove increases in egg volume; larger eggs, in turn, resulted in larger genomes. These data suggest that variation in reproductive traits may underpin the high degree of variation in genome size seen in a wide variety of caridean shrimp groups more generally. 

The global distribution of primary production and consumption by humans (fisheries) is well-documented, but we have no map linking the central ecological process of consumption within food webs to temperature and other ecological drivers. Using standardized assays that span 105° of latitude on four continents, we show that rates of bait consumption by generalist predators in shallow marine ecosystems are tightly linked to both temperature and the composition of consumer assemblages. Unexpectedly, rates of consumption peaked at midlatitudes (25 to 35°) in both Northern and Southern Hemispheres across both seagrass and unvegetated sediment habitats. This pattern contrasts with terrestrial systems, where biotic interactions reportedly weaken away from the equator, but it parallels an emerging pattern of a subtropical peak in marine biodiversity. The higher consumption at midlatitudes was closely related to the type of consumers present, which explained rates of consumption better than consumer density, biomass, species diversity, or habitat. Indeed, the apparent effect of temperature on consumption was mostly driven by temperature-associated turnover in consumer community composition. Our findings reinforce the key influence of climate warming on altered species composition and highlight its implications for the functioning of Earth’s ecosystems.