Is it possible to detect genetic differences between Antilophia manakins?
One of the outstanding questions in biology is the relationship between genotype and phenotype: how does the genetic make-up of an individual translate into physical characteristics? This question becomes even more daunting when comparing different species. Some species pairs are genetically distinct but look almost exactly the same (so-called cryptic species), whereas other species pairs are genetically nearly identical but look totally different. A recent study in Molecular Ecology explores the latter situation in Antilophia manakins.
Black and White
In Brazil, you can find two species of manakin that look quite distinct. Males of the Araripe manakin (A. bokermanni) are white, whereas the plumage of Helmeted manakin males (A. galeata) is black. Despite the obvious color differences, genetic studies – using mtDNA and introns – could not detect any population structure. This finding could be explained by (1) recent divergence with gene flow or (2) lack of statistical power of these studies.
To differentiate between these two possibilities, Fabio Raposo do Amaral and his colleagues focused on another molecular marker: ultraconserved elements (UCEs). Analyses of these genomic regions revealed clear differentiation between Araripe and helmeted manakin. It thus seems that the statistical power of the previous studies was just too low to pick up any signal of population structure. In addition, demographic modelling indicated that there has been no (or very little) gene flow between these two species.
Araripe and helmeted manakin are genetically distinct, but how did the males of these species evolve different plumage patterns? Perhaps these colors have been under strong sexual selection, with Araripe females preferring white and helmeted females preferring black males. Or maybe the white plumage of Araripe males simply increased in frequency due to genetic drift in a small isolated population.
To answer these questions, a genomic approach might be warranted. Indeed, the authors write that “resequencing of their complete genomes will offer exciting opportunities to identify functionally important regions evolving under selection, which may include candidate genes related to the plumage differences between those two species.”
Amaral, F.A., Coelho, M.M., Aleixo, A., Luna, L.W., Rego, P.S., Araripe, J., Souza, T.O., Silva, W.A.G. & Thom, G. (2018) Recent chapters of Neotropical history overlooked in phylogeography: shallow divergence explains phenotype and genotype uncoupling in Antilophia manakins. Molecular Ecology.