Biology subjects

Pilastro, A.

Publications and source records attributed to Pilastro, A..

6 recordsLinked to original sources

bioRxiv2026

The BEAC, an epigenetic clock for birds

Epigenetic clocks are powerful tools for estimating both chronological and biological age, enabling the integration of age information into population monitoring, demographic modelling, and research on the ecophysiology and evolution of ageing. Most epigenetic clocks so far have been developed for mammals: here, we present the Bird Epigenetic Ageing Clock (BEAC) for estimating chronological age in avian species. BEAC was established based on genome-wide enzymatic methylation sequencing data of known-age king penguins (Aptenodytes patagonicus), and validated in nine other bird species. The BEAC collects age-informative signals into a bisulfite amplicon sequencing panel of 24 primer pairs, providing a highly accurate and cost-effective alternative to sequencing-intensive approaches. It achieved strong predictive performance in independent king penguin training (R{superscript 2}=0.88; MAE=1.7 years, n=78) and testing data (R{superscript 2}=0.79; MAE=2.3 years, n=41), with negligible batch effects, high longitudinal consistency, and resilience to reduced sample size or missing loci. Importantly, cross-species validation across 180 samples showed that BEAC reliably captures age-associated methylation signals in nine additional bird species across seven clades, demonstrating that a single set of loci can be predictive of ageing across multiple different bird species. BEAC offers a flexible, empirically validated tool and a transferable framework for developing epigenetic clocks in avian species, providing a highly valuable resource for eco-evolutionary studies of ageing in wild species.

molecular biology↗

bioRxiv2026

Allonursing (Co-BreeD): Its prevalence, functions and hypotheses across mammals and human cultures

Allonursing, where dependent young are nursed by females other than their mothers, has been observed across diverse mammalian species and human cultures. Yet, the proximate functions underlying this seemingly altruistic behaviour, and its benefits for the offspring, the mother, and the nursing allomother, remain poorly understood. To facilitate testing hypotheses concerning these questions, we compiled the to date largest allonursing dataset from wild populations (N = 101 species, including 133 populations and 5 human cultures). Using this dataset, we (i) map the taxonomic distribution of allonursing, thereby expanding the list of mammal species qualified as cooperative breeders by 17 additional species, (ii) differentiate cases of non-voluntary from voluntary allonursing and consequently reject the hypothesis that milk stealing explains regular allonursing in most species, (iii) quantify the within-population extent of allonursing to assess its significance across species and evaluate the energy/time saved for mothers, (iv) use phylogenetically controlled analyses to revisit the association between allonursing and polytocy (i.e., litter size >1), and provide an alternative explanation for this association. We conclude by proposing that allonursing has multiple functions, with the most empirically supported ones being provisioning and insurance against maternal loss. Finally, the presented AlloNursing dataset complements the Cooperative-Breeding Database (Co-BreeD) to further expand this integrative resource for cooperative breeding research.

animal behavior and cognition↗

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 length evolution in relation to body mass is shaped by multiple trade-offs in tetrapods

Sperm size is highly variable across species and is influenced by various factors including fertilization mode, female reproductive traits and sperm competition. Despite considerable efforts, many questions about sperm size variation remain open. Variation in body size may affect sperm size evolution through its influence on these factors, but the extent to which sperm size variation is linked to body mass remains elusive. In this study, we use the general theory of Pareto Optimality to investigate the relationship between sperm size and body mass across tetrapods. We find that tetrapods fall within a triangular-shaped Pareto front in the trait space of body mass and sperm length suggesting that the evolution of sperm size in relation to body size is shaped by trade-offs. We then explore the three main factors predicted to influence sperm size evolution, namely sperm competition, clutch size and genome size. Our results demonstrate that body mass optimally shapes sperm size evolution in tetrapods mainly through its association with sperm competition and clutch size. Finally, we show that the triangular-shaped Pareto front is maintained when tested separately within mammals, birds, endothermic species and internal fertilizers, suggesting that similar evolutionary trade-offs characterize the evolution of sperm size in relation to body size within taxonomic/phylogenetic and functional subgroups of tetrapods. This study provides insights into the evolutionary mechanisms driving interspecific sperm size variation and highlights the importance of considering multiple trade-offs in optimizing reproductive traits.

evolutionary biology↗

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↗

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↗