Biology subjects

Bonel, N.

Publications and source records attributed to Bonel, N..

7 recordsLinked to original sources

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

Not just mutations: Inbreeding depression persists without genetic variation

Inbreeding depression (ID), the decline in fitness upon inbreeding, is thought to result from a decrease in genetic heterozygosity enhancing phenotypic effects of recessive deleterious mutations. However, emerging evidence suggests that mutations may not explain ID completely. In this study, we test whether ID can emerge even in contexts where genetic heterozygosity does not vary. To that end, highly inbred lines (F=0.99999997) of the freshwater snail Physa acuta were used to produce individuals with varying levels of parental relatedness (self-fertilization, sibling crosses, and cousin crosses), though with identical genomic heterozygosity. Several fitness traits declined significantly with increasing parental relatedness, a pattern characteristic of ID, and quantitatively representing a non-negligible fraction of the ID usually observed in natural, genetically diverse populations of Physa acuta. Individual-based simulations showed that mutation rates compatible with values of ID found in natural populations are way too low to generate as much ID as observed in our experiment. These findings are consistent with the hypothesis that epigenetic changes, in addition to mutations, could contribute to a rapid regeneration of ID and explain the persistence of detectable ID in sets of genetically identical individuals.

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↗

bioRxiv2025

Moving northwards: Invasive Green Crab (Carcinus spp.) Expands into the Southwestern Atlantic

The invasive European green crab (Carcinus maenas) poses a significant ecological threat due to its rapid global spread and disruptive impact on coastal ecosystems. In the Southwestern Atlantic, the northernmost population was recently recorded in the San Matias Gulf, offering a unique opportunity to study its demographic and life-history traits at the leading edge of its range. We assessed sex ratio, population density, size distribution, and the size at which 50% of females were ovigerous (SM50). Our findings revealed a male-biased sex ratio (1.79 males per female) and low population density (0.42 crabs m-2), suggesting early-stage establishment. Size-structure analysis showed a well-structured population with clear cohort separation in both sexes and evidence of two recruitment events. The size at which 50% of females were ovigerous was estimated at 61.48 mm. Although egg-bearing females exhibited a well marked seasonality, with highest prevalence from May to July, their presence nearly year-round suggests an extended reproductive period and adaptability to local conditions, which may be advantageous in recently established populations, facilitating invasion success. These traits, combined with the species ongoing range expansion, highlight the invasive potential of C. maenas and its possible ecological impacts on the San Matias Gulf. Simple SummaryCarcinus maenas is an invasive crab species that threaten coastal ecosystems around the world by competing with native species and damaging habitats. Recently, a population of this species was discovered in the San Matias Gulf in Argentina, marking its northernmost record in the Southwestern Atlantic. We studied its demographic and life-history traits and found a male-biased sex ratio and relatively low population density. Additionally, egg-bearing females were present nearly year-round, with an increase in their abundance from May to July, suggesting that this population is adapting well to local conditions and maintaining an extended reproductive period. Together, these findings point to an early stage of invasion with the potential for further expansion, posing risks to native species and north Patagonian ecosystems.

ecology↗

bioRxiv2020

Pronounced phenotypic differentiation in a wide-dispersing marine snail in response to contrasting selection pressures at a local scale

Heterogeneous environments pose a particular challenge for organisms because the same phenotype is unlikely to perform best regardless of the variety of encountered stressors. To understand how species meet this challenge, we investigated the extent to which contrasting environmental pressures induced ecological and phenotypic responses in a natural population of a wide-dispersing marine snail at a small spatial scale. We analyzed several traits of Heleobia australis (Rissooidea: Cochliopidae) collected from heterogeneous, but highly connected, habitats from the intertidal area of the Bahia Blanca estuary, Argentina. We also conducted molecular analyses by amplifying the COI gene in individuals sampled from each habitat. We found that sympatric subpopulations of H. australis exhibited a strong phenotypic divergence in shell characters and body weight in response to thermal, saline, and dehydration stress, crab predation risk, and parasitic castrators. We proved that this differentiation occurred even early in life as most of the characters observed in juveniles mirrored those found in adults. We also found a divergence in penis size in snails collected from each habitat and raised in common garden laboratory conditions. The molecular analyses confirmed that the individuals studied constituted a single species despite the strong phenotypic differences among subpopulations. The small-scale phenotypic differentiation suggests that H. australis experienced a fine-grained environment where conditions imposed by different sources of stress favored the expression of beneficial traits. We discuss the role of plasticity in shaping adaptive phenotypic responses that increase the likelihood of persistence of subpopulations facing environmental stress conditions.

ecology↗

bioRxiv2019

Freshwater invasive clams grow faster and reproduce earlier in recently introduced populations with reduced growth rates

Many species are shifting their ranges being forced to rapidly respond to novel stressful environmental conditions. Colonizing individuals experience strong selective forces that favor the expression of life history traits notably affecting dispersal and reproductive rates in newly invaded habitats. Limited information is currently available on trait variation within the invasive range despite being critical for understanding ecological and evolutionary factors that drive the process of range expansion of invasive species. Here we evaluated life history shifts of the widely introduced Asian clam Corbicula, within its invaded range. Through an exhaustive literature search, we obtained data for 17 invasive Corbicula populations from different ecosystems worldwide. We tested the relationship between population and individual parameters relevant to the process of range expansion. Our main results are that recently introduced Corbicula populations were characterized by (i) low density and low rate of population increase, (ii) clams reproduced earlier in slow-growing populations, and (iii) density had no effect on population increase. All Corbicula populations analyzed in this study, which are fixed for one genotype (lineage Form A/R), experienced different selective environments in the introduced range. These findings support the perspective that adaptive phenotypic plasticity favored the expression of traits that maximize fitness in recently established populations, which faced stronger r-selective forces relative to long-established ones. We discuss the role of plasticity in facilitating rapid adaptation and increasing the likelihood of populations to overcome difficulties associated with low densities and low population increase in newly invaded areas.

ecology↗

bioRxiv2018

Sexual selection and inbreeding: two efficient ways to limit the accumulation of deleterious mutations

Theory and empirical data showed that two processes can boost selection against deleterious mutations, thus facilitating the purging of the mutation load: inbreeding, by exposing recessive deleterious alleles to selection in homozygous form, and sexual selection, by enhancing the relative reproductive success of males with small mutation loads. These processes tend to be mutually exclusive because sexual selection is reduced under mating systems that promote inbreeding, such as self-fertilization in hermaphrodites. We estimated the relative efficiency of inbreeding and sexual selection at purging the genetic load, using 50 generations of experimental evolution, in a hermaphroditic snail (Physa acuta). To this end, we generated lines that were exposed to various intensities of inbreeding, sexual selection (on the male function) and nonsexual selection (on the female function). We measured how these regimes affected the mutation load, quantified through the survival of outcrossed and selfed juveniles. We found that juvenile survival strongly decreased in outbred lines with reduced male selection, but not when female selection was relaxed, showing that male-specific sexual selection does purge deleterious mutations. However, in lines exposed to inbreeding, where sexual selection was also relaxed, survival did not decrease, and even increased for self-fertilized juveniles, showing that purging through inbreeding can compensate for the absence of sexual selection. Our results point to the further question of whether a mixed strategy combining the advantages of both mechanisms of genetic purging could be evolutionary stable.

evolutionary biology↗