On the maintenance of intrapopulation genetic variation: the interplay between sexual selection, chemical communication, and fitness in the wood tiger moth (Arctia plantaginis)

Abstract

The maintenance of intrapopulation phenotypic trait variation often is the result of the interplay between multiple selective forces. Genetic associations between color traits and life-history traits can create context-dependent advantages and affect intrapopulation dynamics. In the polymorphic wood tiger moth (Arctia plantaginis), the two male hindwing phenotypes (genotypes: WW/Wy = white, yy = yellow) show morph-linked advantages that are context-dependent across ecological contexts. Although female hindwing coloration spans continuously from yellow to red they genetically bear the same male color alleles. In this thesis, I investigated the potential contribution of sexual selection, chemical communication, and fitness of the different genetic color morphs (i.e., WW, Wy, yy) in maintaining the two male color morphs. Mate choice and mate recruitment were affected by context-dependent advantages. yy females were more attractive to males in high-density scenarios because of their early calling strategy that likely allowed them to outcompete WW and Wy females. WW females were, instead, more attractive when females were simultaneously calling, perhaps due to their longer calling duration. yy males were faster to reach females than white (WW, Wy) males in low-density scenarios, while white males and males with denser antennae (i.e., higher lamellae count) located females faster in high-density scenarios. At the reproductive level, males and females showed genotype-specific (dis)advantages. Wy females benefit from higher likelihood of reproductive output among female genotypes leading to strong heterozygote advantage. yy males had the lowest reproductive output among male genotypes while pairs with yellow females suffered the lowest mating success. The presence of one or two copies of the yellow allele affected several life-history traits, from pre- to post-copulatory stages. Thus, the color locus has pleiotropic effects on several life-history traits, offering a mechanism of balancing selection that enables the persistence of genetic and phenotypic variation in natural populations.

Keywords: Balancing selection; heterozygote advantage; pleiotropy; receiver antenna variation; signaling strategy variation; wood tiger moth