Biology subjects

Morbiato, E.

Publications and source records attributed to Morbiato, E..

4 recordsLinked to original sources

bioRxiv2026

Socially-mediated compensatory growth carries hidden sperm costs in male guppies

Phenotypic plasticity allows organisms to mitigate early-life adversity through compensatory growth, yet the long-term costs of such "catch-up" trajectories remain poorly understood, particularly when driven by social factors. While most research focuses on nutritionally induced compensation, we investigate how early social competition--independent of resource availability--shapes adult life-history trade-offs in the guppy (Poecilia reticulata). Our results show that scramble competition among peers during early development triggers compensatory growth once social constraints are removed. Crucially, we reveal a hidden reproductive cost: males exhibiting higher compensatory growth reach a similar adult size but produce significantly fewer sperm at maturity. This deficit persists even when controlling for adult body size, indicating a direct trade-off between somatic recovery and ejaculate investment. Furthermore, we find a negative association between gonopodium length and sperm count, suggesting competing allocations between pre- and postcopulatory traits during growth. These findings reveal a cryptic cost of compensatory growth, where adult morphology conceals underlying differences in reproductive quality. By demonstrating that social environments alone can recalibrate life-history trajectories, we highlight the "ghosts of competition past" as critical determinants of fitness. Our study underscores the necessity of considering ontogenetic history to fully understand the evolution of sexually selected traits in social vertebrates.

evolutionary biology↗

bioRxiv2026

Female reproductive fluid evolves rapidly to favor conspecific sperm

Avoiding fertilization with genetically incompatible partners, whether too similar or too divergent, is a central challenge for sexually reproducing organisms. Selection can favor mechanisms acting before and after mating, with postmating processes potentially compensating for constraints on premating choice. In the postmating context, female reproductive fluid (FRF) can modulate sperm performance and bias fertilization outcomes, but its contribution to reproductive isolation remains unclear. We tested whether FRF mediates discrimination against heterospecific and related sperm in two naturally hybridizing sister species of swordtails, Xiphophorus birchmanni and X. malinche, that diverge in premating behavior towards heterospecifics. Effects of FRF differed sharply between species. In X. malinche, FRF enhanced the velocity of conspecific sperm relative to heterospecifics, consistent with postmating discrimination against hybridization. In contrast, FRF in X. birchmanni did not favor conspecific sperm. Evidence for inbreeding avoidance was weaker, and we found no indication of a trade-off between discrimination against genetically similar and dissimilar sperm. These results show that female reproductive fluid can serve as a rapidly evolving axis of reproductive isolation through postmating female choice.

evolutionary biology↗

bioRxiv2024

Male reproductive phenotype and coercive mating performance in the guppy Poecilia reticulata

In species with fixed alternative male mating tactics, differences between male phenotypes associated with each tactic are well understood. By contrast, in species with fully interchangeable male mating strategies, associations between male phenotypes and fitness when adopting different tactics have received much less attention. One such species is the Trinidad guppy Poecilia reticulata, where males perform high rates of coercive mating attempts (gonopodial thrusts, GTs hereafter) but also switch between GTs and courtship with great flexibility. Male phenotypes favored by females have been described in detail and consist of complex, nonlinear combinations of traits. Coercive tactics also contribute towards male fitness, but no study to date has provided a multivariate description of guppy phenotypes able to obtain fertilizations via GTs, despite evidence suggesting they should be different from phenotypes successful in cooperative mating scenarios. Here we observe male mating behavior in freely interacting mixed-sex groups and compute a GT performance variable based on the closest distance the male approaches the female before abandoning the thrust. We use multivariate selection techniques to relate GT performance to traits and combinations of traits known to contribute towards male fitness. Guppy males that perform best in GTs are small, bold, with large areas of iridescent coloration and fast-swimming sperm, as well as intermediate orange coloration and sperm count. This phenotype only partly confirms our expectation, as it comprises traits advantageous in cooperative mating scenarios. Our study highlights the importance of using multivariate approaches when investigating sexual selection in the context of coercive mating strategies.

animal behavior and cognition↗

bioRxiv2023

Sperm production is negatively associated with muscle and sperm telomere length in a highly polyandrous species

Life history theory suggests that aging is one of the costs of reproduction. Accordingly, a higher reproductive allocation is expected to increase the deterioration of both the somatic and the germinal lines through enhanced telomere attrition. In most species, males reproductive allocation mainly regards traits that increase mating and fertilization success, i.e. sexually selected traits. In the current study, we tested the hypothesis that a higher investment in sexually selected traits is associated with a reduced telomere length in the guppy (Poecilia reticulata), an ectotherm species characterized by strong pre- and postcopulatory sexual selection. We first measured telomere length in both the soma and the sperm over the course of guppys lifespan to see if there was any variation in telomere length associated with age. Secondly, we investigated whether a greater expression of pre- and postcopulatory sexually selected traits is linked to shorter telomere length in both the somatic and the sperm germinal lines, and in young and old males. We found that telomeres lengthened with age in the somatic tissue, but there was no age-dependent variation in telomere length in the sperm cells. Telomere length in guppies was significantly and negatively correlated with sperm production in both tissues and life stages considered in this study. Our findings indicate that telomere erosion in male guppies is more strongly associated with their reproductive investment (sperm production) rather than their age, suggesting a trade-off between reproduction and maintenance is occurring at each stage of males life in this species.

molecular biology↗