Distinct genetic architectures underlie divergent thorax, leg, and wing pigmentation betweenDrosophila elegansandD. gunungcola

Abstract

<jats:title>Abstract</jats:title><jats:p>Understanding the genetic basis of species differences is a major goal in evolutionary biology. Pigmentation divergence between <jats:italic>Drosophila</jats:italic> species often involves genetic changes in pigmentation candidate genes that pattern the body and wings, but it remains unclear how these changes affect pigmentation evolution in multiple body parts between the same diverging species. <jats:italic>Drosophila elegans</jats:italic> and <jats:italic>D. gunungcola</jats:italic> show pigmentation differences in the thorax, legs, and wings, with <jats:italic>D. elegans</jats:italic> exhibiting male-specific wing spots and <jats:italic>D. gunungcola</jats:italic> lacking wing spots with intensely dark thoraces and legs. Here, we performed QTL mapping to identify the genetic architecture of these differences. We find a large effect QTL on the X chromosome for all three body parts. QTL on Muller Element E were found for thorax pigmentation in both backcrosses but were only marginally significant in one backcross for the legs and wings. Consistent with this observation, we isolated the effects of the Muller Element E QTL by introgressing <jats:italic>D. gunungcola</jats:italic> alleles into a <jats:italic>D. elegans</jats:italic> genetic background and found that <jats:italic>D. gunungcola</jats:italic> alleles linked near the pigmentation candidate gene <jats:italic>ebony</jats:italic> caused intense darkening of the thorax, minimal darkening of legs, and minimal shrinking of wing spots. <jats:italic>D. elegans ebony</jats:italic> mutants showed changes in pigmentation consistent with Ebony having different effects on pigmentation in different tissues. Our results suggest that multiple genes have evolved differential effects on pigmentation levels in different body regions.</jats:p>

Evolution of assortative mating following selective introgression of pigmentation genes between two Drosophila species

“…For nearly 100 years, Drosophila species have been a primary model for the experimental study of speciation (Castillo & Barbash, 2017; Mallet, 2006). Introgression between species with incomplete reproductive isolation has long been used to identify the quantitative trait loci (QTL) responsible for phenotypic differences and reproductive barriers (e.g., Ding et al, 2016; Massey et al, 2021; Shahandeh & Turner, 2020; Tanaka et al, 2015). In those experiments, two species are crossed and their fertile F 1 hybrid females are backcrossed to one parental species for one or a few generations.…”

Evolution of assortative mating following selective introgression of pigmentation genes between two Drosophila species

“…Introgression between species with incomplete reproductive isolation has long been used to identify the quantitative trait loci (QTL) responsible for phenotypic differences and reproductive barriers (e.g., Tanaka et al 2015;Ding et al 2016;Shahandeh and Turner 2020; Massey et al 2021). In those experiments, two species are crossed and their fertile F 1 hybrid females are backcrossed to one parental species for one or a few generations.…”