Abstract: Aim We assess biogeographical patterns, population structure and the range of species in the pulmonate genus Siphonaria across the sub-Antarctic. We hypothesized that locally endemic cryptic species will be found across the distribution of these direct-developing limpets in the sub-Antarctic. Location The sub-Antarctic coasts of the Southern Ocean including South America, the Falkland/Malvinas, South Georgia, Kerguelen and Macquarie Islands. Methods Multi-locus phylogenetic reconstructions, mtDNA time-calibrated divergence time estimations and population-based analyses of Siphonaria populations were used at the scale of the Southern Ocean. Results We resolve two widely distributed lineages of Siphonaria (S. lateralis and S. fuegiensis) across the sub-Antarctic. MtDNA divergence time estimates suggest that they were separated around 4.0 Ma (3.0 to 8.0 Ma). Subsequently both species followed different evolutionary pathways across their distributions. Low levels of genetic diversity characterize the populations of both species, reflecting the role of Quaternary glacial cycles during their respective demographic histories, suggesting high levels of dispersal among geographically distant localities. Main conclusions Siphonaria lateralis and S. fuegiensis constitute sister and broadly co-distributed species across the sub-Antarctic. Unexpected transoceanic similarities and low levels of genetic diversity in both these direct-developing species imply recurrent recolonization processes through long-distance dispersal to isolated sub-Antarctic islands. For such groups of Southern Ocean invertebrates, rafting may be more effective for long-distance dispersal than a free-living planktotrophic larval stage. This biogeographical model may explain why many marine species lacking a dispersal phase exhibit broad distributions, low genetic diversity and low population structure over thousands of kilometres.

Abstract: There is widespread evidence that within populations, specialists and generalists can coexist and this is particularly prevalent in marine ecosystems, where foraging specialisations are evident. While individuals may limit niche overlap by consistently foraging in specific areas, site fidelity may also emerge as an artefact of habitat choice, but both drivers and fitness consequences of site fidelity are poorly understood. Here, we examine an individual metric of site and habitat fidelity, using tracking data collected over 11 years for black-browed albatrosses (Thalassarche melanophris). Fidelity was calculated as the similarity between pairs of foraging zones, quantifying measures for within and between years. Foraging areas were identified using area-restricted search, defined as periods during which birds decrease speed and increase turning. Our results demonstrate that birds were considerably more specialised in the habitat in which they forage than the exact location they use within years, and there was a similar pattern between years. However, despite this, it was site fidelity that explained reproductive success. Within a single year, females which were more faithful to a specific location had higher reproductive success than non-specialists, and between years there was a tendency for both sexes. Our results suggest that black-browed albatrosses are highly faithful in their foraging habitat but it is rather site fidelity that is more clearly associated with reproductive success.

Abstract: Animal populations are often comprised of both foraging specialists and generalists. For instance, some individuals show higher foraging site fidelity (spatial specialization) than others. Such individual differences in degree of specialization can persist over time-scales of months or even years in long-lived animals, but the mechanisms leading to these different individual strategies are not fully understood. There is accumulating evidence that individual variation in foraging behaviour is shaped by animal personality traits, such as boldness. Despite this, the potential for boldness to drive differences in the degree of specialization is unknown. In this study, we used novel object tests to measure boldness in black-legged kittiwakes (Rissa tridactyla) breeding at four colonies in Svalbard and deployed GPS loggers to examine their at-sea foraging behaviour. We estimated the repeatability of foraging trips and used a hidden Markov model to identify locations of foraging sites in order to quantify individual foraging site fidelity. Across the breeding season, bolder birds were more repeatable than shy individuals in the distance and range of their foraging trips, and during the incubation period (but not chick rearing), bolder individuals were more site-faithful. Birds exhibited these differences while showing high spatial similarity in foraging areas, indicating that site selection was not driven by personality-dependent spatial partitioning. We instead suggest that a relationship between boldness and site fidelity may be driven by differences in behavioural flexibility between bold and shy individuals. Together, these results provide a potential mechanism by which widely reported individual differences in foraging specialization may emerge.