Biology subjects

Sacchi, R.

Publications and source records attributed to Sacchi, R..

3 recordsLinked to original sources

bioRxiv2024

Colour morphs as alternative solutions to the trade-off predicted by the Immuno-Competence Handicap Hypothesis

Colour morphs in polymorphic species represent a suite of heritable traits controlled by separate sets of loci, which correspond to alternative peaks in the fitness surfaces. Pleiotropic effects of hormones have been hypothesized to be involved in the maintenance of morphs, but no experiments have been done to test it so far. In this study, we experimentally increased testosterone plasma levels in colour morph of the common wall lizards to test if white and yellow morphs follow two alternative strategies imposed by trade-off depicted in the Immuno-Competence Handicap Hypotheses. Yellow males invest in a more aggressive behaviour at the expense of a reduced immune function, whereas white males invest in greater survival at the expense of a reduced competitiveness. Plasma T levels were increased through transdermal administration. Before and after treatment, we measured i) the immune-response of lizards through phytohaemoagglutinin (PHA), and ii) the aggressive response by the introduction of a small mirror into the plastic enclosure to mimic the intrusion of a stranger male in its own territory. The hormone administration caused a higher immune-suppression in white than yellow males, and a switch to less aggressive behaviour against the mirrored image. Overall, increased plasma testosterone levels resulted in the disappearance of differences between morphs of both immune-response and aggressive behaviour. These results supplied experimental evidence of the existence of morph-specific strategies in common wall lizards depending on the investment in territorial aggression or in a longer survival, as alternative solutions to the trade-off predicted by the Immuno- Competence Handicap Hypothesis.

animal behavior and cognition↗

bioRxiv2021

Population genomics of wall lizards reflects the dynamic history of the Mediterranean Basin

The Mediterranean Basin has experienced extensive change in geology and climate over the past six million years. Yet, the relative importance of key geological events for the distribution and genetic structure of the Mediterranean fauna remains poorly understood. Here, we use population genomic and phylogenomic analyses to establish the evolutionary history and genetic structure of common wall lizards (Podarcis muralis). This species is particularly informative because, in contrast to other Mediterranean lizards, it is widespread across the Iberian, Italian, and Balkan peninsulas, and in extra-Mediterranean regions. We found strong support for six major lineages within P. muralis, which were largely discordant with the phylogenetic relationship of mitochondrial DNA. The most recent common ancestor of extant P. muralis was likely distributed in the Italian Peninsula, and experienced an "Out-of-Italy" expansion following the Messinian salinity crisis (~5 Mya), resulting in the differentiation into the extant lineages on the Iberian, Italian and Balkan peninsulas. Introgression analysis revealed that both inter- and intraspecific gene flow have been pervasive throughout the evolutionary history of P. muralis. For example, the Southern Italy lineage has a hybrid origin, formed through admixture between the Central Italy lineage and an ancient lineage that was the sister to all other P. muralis. More recent genetic differentiation is associated with the onset of the Quaternary glaciations, which influenced population dynamics and genetic diversity of contemporary lineages. These results demonstrate the pervasive role of Mediterranean geology and climate for the evolutionary history and population genetic structure of extant species.

evolutionary biology↗

bioRxiv2020

Close encounters of the three morphs: does color affect aggression in a polymorphic lizard?

Color polymorphism is genetically controlled and the process generating and maintaining morphs can affect speciation and/or extinction rates. Competition and aggression among morphs can contribute to polymorphism maintenance and color badges are useful signals in intraspecific communication, because they convey information about alternative strategies and avoid unnecessary conflicts. This could lead to an uneven spatial distribution of morphs in a population, because the local frequency of each morph establishes the intensity of the competition in that neighborhood, and then the fitness of each male. We used a polymorphic lizard, Podarcis muralis, to assess if aggression varies among morphs under two contrasting hypotheses: a heteromorphic vs. a homomorphic aggression. We used laboratory mirror tests after lizard color manipulation and we verified the results consistency with the analysis of the spatial distribution of morphs in a wild population. Both the experiments confirmed that aggression is morph-specific and notably homomorphic. The adoption of behavioral alternative strategies that minimize risks and costs of unwanted conflicts could facilitate the stable coexistence of the phenotypes and reduce the resource competition. A bias in aggression to like-coloured males would advantage rarer morph, which would suffer less harassment by common morphs and obtain a fitness advantage. This process would be negatively-frequency-dependent and would stabilize polymorphism in the populations, possibly leading to sympatric speciation.

animal behavior and cognition↗