Abafatori, M. | Search bioRxiv

bioRxiv2026

Distribution and heritable shell differentiation among populations of the sole lymnaeid snail across freshwater habitats of southern Patagonia

Environmental heterogeneity across freshwater systems often promotes phenotypic variation among populations. Yet, the respective contributions of environmentally-induced and heritable variation to population differences are rarely known. We investigated the geographic distribution and morphological differentiation, and heritability of shell traits among populations of the freshwater lymnaeid snail Pectinidens diaphanus in Patagonia. Extensive field surveys across 193 freshwater sites revealed that P. diaphanus is the sole lymnaeid inhabiting southern Patagonia and occupies a broader range of lentic and lotic habitats than previously documented. While reproductive anatomical structures were conserved across populations, shell shape differed markedly among populations from contrasting habitat types, with population origin explaining nearly 50% of total shape variation. Snails from hydrologically unstable habitats (ponds and streams) exhibited more elongated shells and relatively smaller apertures than lake snails, a pattern consistent with functional responses to hydroperiod variability and desiccation risk. To further investigate whether this differentiation was heritable, we conducted a common-garden experiment across two generations. Shell shape differences between permanent- (lake) and temporary- (pond) habitat-derived populations persisted into the G2 generation reared under standardized laboratory conditions, indicating that the observed variation is not solely a response to local environmental conditions but includes a heritable component. Together, our findings demonstrate that P. diaphanus constitutes the sole lymnaeid across southern Patagonia, occupying a broader range than previously documented, and that populations show heritable shell differentiation potentially associated with contrasting freshwater habitats. By integrating large-scale biogeographic surveys with morphometric and experimental approaches, this study provides new insight into how habitat variation may contribute to ecological and evolutionary differentiation in freshwater gastropods.

evolutionary biology↗

bioRxiv2025

Impact of mating strategies on life-history traits in the alien land snail Rumina decollata

AO_SCPLOWBSTRACTC_SCPLOWClimate change and global transport are driving species introductions worldwide, leading to economic and ecological consequences. Hermaphroditic organisms are able to reproduce with any conspecific, and some can self-fertilize, enhancing their potential for population establishment despite low initial densities in colonization events. This study examines how mating strategies influence the life history traits of the alien land snail Rumina decollata by comparing individuals subjected to facultative cross-fertilization or enforced self-fertilization over two laboratory-reared generations. Key life history traits--including size and age at first reproduction, fecundity, hatching time, and juvenile survival--were measured, alongside individual growth and shell morphometry. Self-fertilizing individuals exhibited higher body weight at first clutch but lower fecundity and delayed reproduction compared to cross-fertilizers. Selfing offspring (F2) took longer to hatch and had lower survival rates, indicating significant inbreeding depression. Selfed snails of F1 grew faster than outcrossers, but experienced a decline in growth in F2, consistent with inbreeding depression. Conversely, shell shape remained similar between mating treatments. Although selfing imposed fitness costs, 32% of self-fertilizing individuals produced viable offspring, highlighting their ability to establish in new environments. This study improves our understanding of how R. decollatas reproductive strategies shape life history traits under environmental constraints. SIMPLE SUMMARYSpecies are spreading to new regions due to climate change and global transport, often causing environmental and economic challenges. Hermaphrodite species that can reproduce by cross or self-fertilization can establish populations even when few individuals are present. In our study, we examined how these two reproductive strategies affect a land snails growth, reproduction, and survival. We found that self-fertilizing snails grew larger and heavier but laid fewer eggs and reproduced later than those that mated with others. Additionally, their offspring took longer to hatch and had lower survival rates. These results suggest that self-fertilization comes with costs, likely due to inbreeding depression, but it still allows the species to establish in new environments. Despite lower survival, one-third of the self-fertilizing snails produced viable offspring, showing that this strategy can support population growth when mates are scarce. As this species continues to expand into new areas, our findings help explain how it adapts to different environments. Understanding these reproductive strategies is important for predicting its spread and managing its potential impact on ecosystems.

evolutionary biology↗