Viability, behavior, and color expression in the offspring of matings between common wall lizard Podarcis muralis color morphs

Abstract

Colour polymorphisms are widely studied to identify the mechanisms responsible for the origin and maintenance of phenotypic variability in nature. Two of the mechanisms of balancing selection currently thought to explain the long-term persistence of polymorphisms are the evolution of alternative phenotypic optima through correlational selection on suites of traits including colour, and heterosis. Both of these mechanisms can generate differences in offspring viability and fitness arising from different morph combinations. Here, we examined the effect of parental morph combination on fertilisation success, embryonic viability, newborn quality, antipredator and foraging behaviour, as well as inter-annual survival by conducting controlled matings in a polymorphic lacertid Podarcis muralis, where colour morphs are frequently assumed to reflect alternative phenotypic optima (e.g. alternative reproductive strategies). Juveniles were kept in outdoor tubs for a year in order to study inter-annual growth, survival, and morph inheritance. In agreement with a previous genome-wide association analysis, morph frequencies in the year-old juveniles matched the frequencies expected if orange and yellow expression depended on recessive homozygosity at two separate loci. Our findings also agree with previous literature reporting higher reproductive output of heavy females and the higher overall viability of heavy newborn lizards, but we found no evidence for the existence of alternative breeding investment strategies in female morphs, or morph-combination effects on offspring viability and behaviour. We conclude that inter-morph breeding remains entirely viable and genetic incompatibilities are of little significance for the maintenance of discrete colour morphs in P. muralis from the Pyrenees.

No genomic repercussions of assortative pairing in a colour polymorphic lizard

“…Similarly, a recent study indicated that locality is a better predictor of genetic differentiation than colour morph in P. muralis (Andrade et al, 2019). Furthermore, our results are congruent with recent work from Abalos et al (2022) arguing against reduced viability of hatchlings (i.e., post-zygotic barriers) from colour-disassortative matings, which could arise under strong correlational selection and assortative mating (Gray & McKinnon, 2007;Lancaster et al, 2014;Sinervo & Svensson, 2002). However, our results are in contrast with the previous behavioural (Pérez i de Lanuza et al, 2013Lanuza et al, , 2016 and genetic (Bellati, 2011) studies, which suggested some degree of assortative mating in this species.…”

“…Finally, colour alleles may counterbalance the build-up of population structure by acting as genomic bridges between morphs (Comeault et al, 2015). In fact, white individuals can carry orange (o) and yellow alleles (y) in heterozygosity, while orange lizards can present every genotype at the yellow locus (YY, Yy or yy); thus, offspring of P. muralis will not always express the same phenotype as their parents (Abalos et al, 2022;Aguilar et al, 2022;Andrade et al, 2019). Mosaic morphs (i.e., whiteorange and yellow-orange) may also facilitate gene flow between colour morphs, but further work is needed to understand their basis and role in the maintenance of colour morphs of P. muralis.…”

“…Furthermore, several studies have highlighted differences between morphs of P . muralis on their behaviour, morphology, physiology and reproductive strategy (e.g., Calsbeek et al, 2010; Coladonato et al, 2020; Galeotti et al, 2013; Sacchi et al, 2018; Sreelatha et al, 2021), although other studies did not find empirical support for these differences, arguing against the existence of alternative strategies (e.g., Abalos et al, 2020, 2022; Sacchi et al, 2015).…”

Is It Function or Fashion? An Integrative Analysis of Morphology, Performance, and Metabolism in a Colour Polymorphic Lizard

“…For example, in natural sympatric populations in the Pyrenees, no differences were found between morphs in terms of site fidelity, territory size or spatial overlap of males and females [78]. Similarly, colour morph was irrelevant to sociosexual behaviour, habitat, and reproductive success [78,79]. Any ecomorphological trait (head, limbs, boot) that improves reproductive success could also be used to escape from predators or capture prey, so one would expect differences in ecological traits among morphs to be reflected in their morphology and performance traits.…”

Epistatic interactions between pterin and carotenoid genes modulate intra‐morph color variation in a lizard

“…2017; Pérez i de Lanuza & Carretero 2018; but see Abalos et al . 2020, 2021). This variation in color expression is associated with 2 regulatory regions near genes responsible for pterin (sepiapterin reductase [ SPR ]) and carotenoid (beta‐carotene oxygenase 2 [ BCO2 ]) metabolism (Andrade et al .…”