  In the last decades, dispersal studies have benefited from the use of
molecular markers for detecting patterns differing between categories of
individuals and have highlighted sex-biased dispersal in several species. To
explain this phenomenon, several hypotheses implying mating systems,
intrasexual competition or sex-related handicaps have been proposed. In this
context, we investigated sex-biased dispersal in Armadillidium vulgare, a
terrestrial isopod with a promiscuous mating system. As a proxy for effective
dispersal, we performed a fine-scale investigation of the spatial genetic
structure in males and females, using individuals originating from five
sampling points located within 70 meters of each other. Based on microsatellite
markers and spatial autocorrelation analyses, our results revealed that while
males did not present a significant genetic structure at this geographic scale,
females were significantly and genetically more similar to each other when they
were collected in the same sampling point. As females invest more parental care
than males in A. vulgare, but also because this species is promiscuous and
males experience a high intrasexual competition, our results meet the
predictions of most classical hypotheses for sex-biased dispersal. We suggest
that widening dispersal studies to other isopods or crustaceans, differing in
their ecology or mating system and displaying varying levels of parental care,
might shed light on the processes underlying the evolution of sex-biased
dispersal.
