The Interplay Between Local Ecology, Divergent Selection, and Genetic Drift in Population Divergence of a Sexually Antagonistic Female Trait

Abstract

Genetically polymorphic species offer the possibility to study maintenance of genetic variation and the potential role for genetic drift in population divergence. Indirect inference of the selection regimes operating on polymorphic traits can be achieved by comparing population divergence in neutral genetic markers with population divergence in trait frequencies. Such an approach could further be combined with ecological data to better understand agents of selection. Here, we infer the selective regimes acting on a polymorphic mating trait in an insect group; the dorsal structures (either rough or smooth) of female diving beetles. Our recent work suggests that the rough structures have a sexually antagonistic function in reducing male mating attempts. For two species (Dytiscus lapponicus and Graphoderus zonatus), we could not reject genetic drift as an explanation for population divergence in morph frequencies, whereas for the third (Hygrotus impressopunctatus) we found that divergent selection pulls morph frequencies apart across populations. Furthermore, population morph frequencies in H. impressopunctatus were significantly related to local bioclimatic factors, providing an additional line of evidence for local adaptation in this species. These data, therefore, suggest that local ecological factors and sexual conflict interact over larger spatial scales to shape population divergence in the polymorphism. K E Y W O R D S :AFLP, Dytiscidae, frequency-dependent selection, genetic polymorphism, sexual conflict, WorldClim.

Sexual dimorphism and sexual conflict in the diving beetleAgabus uliginosus(L.) (Coleoptera: Dytiscidae)

“…Our findings extend the phylogenetic distribution of pre-insemination sexual conflict and intrasexual dimorphism in diving beetles. Such mating systems have been noted in the Dytiscinae (Miller, 2003) and Hydroporinae (Bilton et al, 2008;Karlsson Green et al, 2014) to which we can now add the more basal Agabinae. Species such as A. uliginosus, where two distinct forms of female occur in allopatry, appear to be rare, although they may prove particularly illuminating for understanding the evolutionary outcomes of such interactions in nature.…”

“…Although the function of surface microreticulation remains unclear, it is a consistent feature of the cuticle of beetles, including many dytiscids (Balfour-Browne, 1940;Crowson, 1981). Similar dimorphisms in dorsal reticulation are seen in the females of a number of hydroporines, including H. memnonius (Bilton et al, 2008) and Hygrotus impressopunctatus Schaller (Karlsson Green et al, 2014), although this is the first time that they have been documented in Agabinae, which occupies a more basal phylogenetic position (Miller & Bergsten, 2014b).…”

“…Differences in female resistance appear to drive the evolution of counter-modifications in male attachment devices, with nonrandom mating between male and female morphs potentially leading to linkage disequilibrium between male and female traits and the coexistence of morphs through negative frequency-dependent selection (H€ ardling & Bergsten, 2006;H€ ardling & Karlsson, 2009). In some species, there is pronounced geographical variation in the relative frequencies of rough and smooth female morphs, although the drivers of these distributions remain poorly understood (Karlsson Green et al, 2014). In a handful of cases, such as Hydroporus memnonius Nicolai (Bilton, Thompson & Foster, 2008), rough and smooth female populations are almost entirely allopatric, with very limited overlap in nature.…”

Using theories of sexual selection and sexual conflict to improve our understanding of plant ecology and evolution

“…This is in contrast to studies in animals, where these theories often are integrated in other fields, such as ecology, behaviour, physiology and immunology (e.g. Eldakar et al 2009; Green et al 2014; Martínez-Padilla et al 2014; van Lieshout et al 2014). …”

“…Similarly, ecology and sexual selection can jointly influence the evolutionary response (e.g. Karlsson et al 2010; Arbuthnott et al 2014; Green et al 2014). Some plant studies have aimed to measure the relative magnitude of sexual selection vs. natural selection, i.e.…”