Biology subjects

Glavaschi, A.

Publications and source records attributed to Glavaschi, A..

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

Sperm attraction by female reproductive fluid in a fish with an unconventional fertilisation strategy

Active sperm guidance towards the eggs is necessary for gametes to meet within the fertilisation window and is usually achieved through the action of female reproductive fluids (FRF hereafter) on sperm flagellar movement. However, it remains unknown whether FRF retains this function in species with unusual fertilisation strategies. Such examples include systems where gametes are released within confined microhabitats characterised by flow-driven physical processes that could facilitate sperm-egg encounters, hence selection on active sperm guidance may be relaxed. Alternatively, sperm attraction could be maintained by pleiotropic effects of genes involved in other reproductive functions of FRF. Here we tested whether FRF of species with unusual modes of fertilisation retain sperm attractant properties using the bitterling, a small cyprinid fish that parasitises freshwater mussels. Bitterling deposit sperm and eggs inside the mussel gills and gamete interactions are facilitated by the water current generated by mussel respiration. Using a recently developed sperm selection chamber and the European bitterling, we find that more sperm accumulate in the FRF channel compared to the water control. Moreover, European bitterling sperm showed no preference for conspecific FRF over that of a distantly related Asian bitterling FRF. Our results suggest that bitterling FRF resembles that of species with conventional fertilisation modes, implying that it could mediate sperm selection and cryptic female choice. We discuss alternative evolutionary scenarios underlying the persistence of sperm attractant properties of bitterling FRF despite the shift to a physically mediated fertilisation environment.

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↗

bioRxiv2022

Immediate predation risk alters the relationship between potential and realised selection on male traits in the Trinidad guppy Poecilia reticulata

Predation risk perception can alter mating behaviours in males and females, but the consequences for sexual selection remain underexplored. We have previously shown that in experimental populations of Trinidadian guppies Poecilia reticulata the opportunity for sexual selection (i.e. the variance in male reproductive fitness) was higher following exposure to a simulated risk of predation than in a no-risk condition. We build upon this result by exploring whether imminent predation risk affects: 1) the relationship between the opportunity for sexual selection and the actual strength of selection on male traits and 2) the traits contributing to male fitness, and he shape of selection on these traits. While predation risk increased the variance in male fitness, realised selection on traits remained unaffected. Pre- and postcopulatory traits follow complex patterns of nonlinear and correlational selection in both treatments. Differences in selection gradients deviate from predictions based on evolutionary responses to predation, the most notable being stronger selection on courtship rate under predation risk. Our results demonstrate that the operation of sexual selection can be altered by perception of an imminent predation risk and reinforce the notion that both trait-based and variance-based metrics should be employed for an informative quantification.

evolutionary biology↗