The invasive freshwater mussel, the mytilid Limnoperna fortunei (Dunker, 1857), has a great capacity for colonizing a wide range of aquatic environments because of its dispersal ability, high fecundity and wide range of physiological tolerances. Most of the biological and ecological studies of L. fortunei among different habitats. In this investigation, we examined the differences in larval density, density in settlement plates, shell allometry, and growth between two populations from the Río de la Plata basin, Argentina. One of the populations inhabited a heavily polluted area, whereas the other a moderately polluted area. We predicted that the density and growth of the golden mussel would be lower in the heavily polluted environment, expecting therefore to conditions between the sites investigated. We accordingly found that the larval density, the density of settled individuals, and the growth were lower in the more polluted environment. We also observed allometric differences because the individuals from the moderately polluted area with higher population densities were more elongated (i.e., with a higher shell lengthto-width ratio). The golden mussel tolerates a wide range of environmental conditions and presented here support the idea that L. fortunei can inhabit heavily polluted environments,
Sex allocation theory predicts that simultaneous hermaphrodites evolve to an evolutionary stable resource allocation, whereby any increase in investment to male reproduction leads to a disproportionate cost on female reproduction and vice versa. However, empirical evidence for sexual trade-offs in hermaphroditic animals is still limited. Here, we tested how male and female reproductive traits evolved under conditions of reduced selection on either male or female reproduction for 40 generations in a hermaphroditic snail. This selection favors a reinvestment of resources from the sex function under relaxed selection toward the other function. We found no such evolutionary response. Instead, juvenile survival and male reproductive success significantly decreased in lines where selection on the male function (i.e., sexual selection) was relaxed, while relaxing selection on the female function had no effect. Our results suggest that most polymorphisms under selection in these lines were not sex-antagonistic. Rather, they were deleterious mutations affecting juvenile survival (thus reducing both male and female fitness) with strong pleiotropic effects on male success in a sexual selection context. These mutations accumulated when sexual selection was relaxed, which supports the idea that sexual selection in hermaphrodites contributes to purge the mutation load from the genome as in separate-sex organisms.
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