Can similar color patterns evolve through different genetic changes in different fruit fly lineages?

Details

Pigmentation is a rapidly evolving trait that can play important roles in mimicry, sexual selection, thermoregulation, and other adaptive processes in many animal groups. In Drosophila, pigmentation can differ dramatically even among closely related taxa, offering an opportunity to investigate the genetic changes underlying species divergence.

This study investigated the genetic basis of color pattern variation between two allopatric—geographically separated—subspecies of Drosophila malerkotliana, a widespread member of the ananassae species subgroup. In D. malerkotliana malerkotliana, males have dark pigmentation on the last three abdominal segments, but females do not. In D. malerkotliana pallens, both sexes lack dark pigmentation.

Composite interval mapping in F2 hybrid progeny showed that this difference is largely controlled by three quantitative trait loci (QTL) on chromosome arm 2L. This arm is homologous to chromosome arm 3R of D. melanogaster, known as Muller element E.

The researchers also used highly recombinant introgression strains produced through repeated backcrossing and phenotypic selection. These showed that the three QTL do not correspond to any of the candidate genes known to be involved in pigment patterning and synthesis in Drosophila.

Together with similar analyses in other Drosophila species, these results indicate that different genetic and molecular changes are responsible for the evolution of similar phenotypic traits in different lineages. This makes Drosophila color patterns a powerful model for investigating how the intrinsic organization of regulatory pathways controlling trait development influences the genetic basis of trait evolution.