Larval swimming capacities affect genetic differentiation and range size in demersal marine fishes

Dispersal is a fundamental process governing the ecological and evolutionary dynamics of any given species. Due to inherent challenges associated with measuring dispersal directly, identifying proxies for dispersal capacity has long been an active field of research across ecosystems. In marine systems, pelagic larval duration (PLD) has been one of the most widely used indicators of interspecific dispersal potential. The validity of this proxy, however, relies mostly on the assumption of entirely passive dispersal, a notion that has been challenged by findings of strong larval behavioural capabilities. Here, we assessed the effect of larval swimming capacities measured as mean critical swimming speed (U-crit) on emergent species-level properties related to dispersal potential, population genetic structure and global range size, in demersal marine fishes. In a meta-analytic framework, we tested the relative importance of U-crit versus other intrinsic (PLD, egg type, adult body size) and extrinsic (genetic marker type, study scale) predictors of isolation-by-distance slope, global FST and range size. U-crit showed stronger relationships with all emergent response variables than PLD and was consistently the most important predictor in multi-model inference. Our findings indicate that larval swimming capacities could serve as a powerful indicator of a species’ long-distance dispersal potential

Microplastic exposure increases predictability of predator avoidance strategies in hermit crabs

The contamination of natural systems with plastic debris has become one of the most pressing global environmental issues. Microplastics (MPs) are of particular concern because their ubiquity and small size make them available for ingestion by a range of aquatic biota. MP exposure studies are hence proliferating rapidly but are typically limited to the analyses of population-level responses in toxicity endpoints across treatments. Potential contaminant-induced alterations in behavioural patterns, however, could manifest on numerous levels of variation: at the population-level, between individuals and within individuals. Here, we used repeated measures on startle response durations – a risk-avoidance mechanism – in European hermit crabs, Pagurus bernhardus, to measure behavioural responses to MP exposure across multiple levels of variation. We found that MP exposure led to a significant decrease of startle duration at the population-level as well as a reduction of intra-individual variation. In other words, crabs became less risk averse on average and their behaviour became more predictable with increasing MP concentrations. Collectively, our findings indicate that MP pollution might increase susceptibility to predation in hermit crabs

Sensing coral reef connectivity pathways from space

Coral reefs rely on inter-habitat connectivity to maintain gene flow, biodiversity and ecosystem resilience. Coral reef communities of the Red Sea exhibit remarkable genetic homogeneity across most of the Arabian Peninsula coastline, with a genetic break towards the southern part of the basin. While previous studies have attributed these patterns to environmental heterogeneity, we hypothesize that they may also emerge as a result of dynamic circulation flow; yet, such linkages remain undemonstrated. Here, we integrate satellite-derived biophysical observations, particle dispersion model simulations, genetic population data and ship-borne in situ profiles to assess reef connectivity in the Red Sea. We simulated long-term (>20 yrs.) connectivity patterns driven by remotely-sensed sea surface height and evaluated results against estimates of genetic distance among populations of anemonefish, Amphiprion bicinctus, along the eastern Red Sea coastline. Predicted connectivity was remarkably consistent with genetic population data, demonstrating that circulation features (eddies, surface currents) formulate physical pathways for gene flow. The southern basin has lower physical connectivity than elsewhere, agreeing with known genetic structure of coral reef organisms. The central Red Sea provides key source regions, meriting conservation priority. Our analysis demonstrates a cost-effective tool to estimate biophysical connectivity remotely, supporting coastal management in data-limited regions

High interannual variability in connectivity and genetic pool of a temperate clingfish matches oceanographic transport predictions

Adults of most marine benthic and demersal fish are site-attached, with the dispersal of their larval stages ensuring connectivity among populations. In this study we aimed to infer spatial and temporal variation in population connectivity and dispersal of a marine fish species, using genetic tools and comparing these with oceanographic transport. We focused on an intertidal rocky reef fish species, the shore clingfish Lepadogaster lepadogaster, along the southwest Iberian Peninsula, in 2011 and 2012. We predicted high levels of self-recruitment and distinct populations, due to short pelagic larval duration and because all its developmental stages have previously been found near adult habitats. Genetic analyses based on microsatellites countered our prediction and a biophysical dispersal model showed that oceanographic transport was a good explanation for the patterns observed. Adult sub-populations separated by up to 300 km of coastline displayed no genetic differentiation, revealing a single connected population with larvae potentially dispersing long distances over hundreds of km. Despite this, parentage analysis performed on recruits from one focal site within the Marine Park of Arrabida (Portugal), revealed self-recruitment levels of 2.5% and 7.7% in 2011 and 2012, respectively, suggesting that both long-and short-distance dispersal play an important role in the replenishment of these populations. Population differentiation and patterns of dispersal, which were highly variable between years, could be linked to the variability inherent in local oceanographic processes. Overall, our measures of connectivity based on genetic and oceanographic data highlight the relevance of long-distance dispersal in determining the degree of connectivity, even in species with short pelagic larval durations

Genetic connectivity and self-replenishment of inshore and offshore populations of the endemic anemonefish, Amphiprion latezonatus

Globally, marine species are under increasing pressure from human activities, including ocean warming, acidification, pollution, and overfishing. Species most vulnerable to these pressures tend to be ecological specialists that have low abundance and small distribution ranges (endemics). Marine endemics often exist as meta-populations distributed among few isolated locations. Determining genetic connectivity among these locations is essential to understanding the recovery potential of endemics after local extinction events. This study examined connectivity in the endemic anemonefish, Amphiprion latezonatus, a habitat specialist with low abundance at most locations. Evolutionary and contemporary migration, genetic diversity, and self-replenishment among the four main locations (Sunshine Coast, North Solitary Island, Lord Howe Island, and Norfolk Island) that comprise the entire A. latezonatus geographic range were assessed using mtDNA and microsatellite markers. Though historical gene flow inferred from mtDNA appeared high, population genetic differentiation was evident and contemporary gene flow inferred from microsatellites was limited, alongside very high (=89 %) self-replenishment at all locations. Together, these data suggest prolonged recovery times following severe population decline (or extirpation) and indicate a need to protect this species at all locations, particularly Norfolk Island and Sunshine Coast where marine protected areas are lacking