YnotSing · Evolution of sexual dimorphisms: all about losing not choosing?

Evolution of sexual dimorphisms: all about losing not choosing?

Animals exhibit a diverse array of elaborate communication traits, like flashy colors and song. Such elaborate traits were long thought to have evolved primarily in males through sexual selection. However, females of many animals are ornamented, too. Specifically, research we published in 2014 showed, that female song is surprisingly common and most likely was ancestral in songbirds. Thus, the diversity of bird song we see today must be due, in part, to female song becoming reduced or lost in some lineages. In order to understand how complex bird song evolved in males and females, in this project supported by a MSCA-IF fellowship, our goals were to (1) document and quantify similarities and differences in female and male songs, (2) examine how female and male songs have changed through evolutionary time, and (3) to identify what factors have led to elaborate song in both sexes in some lineages, but losses of female song in others. To quantify the world’s diversity of bird song requires recordings and documentation of female bird song from many different species of songbirds. Female bird song is underrepresented in biological collections, however. To address this, we worked with Xeno-canto, the largest online database of bird songs, sponsored by Naturalis Biodiversity Center, and Cornell’s Macaulay Library of Natural Sounds to create a citizen science project (www.femalebirdsong.org). This project directly addresses citizen scientists, birders, and wildlife recordists encouraging them to submit observations and recordings of female bird song to biological collections and to raise the research community’s awareness of the deficit of female bird song in collections so that they can also work to right this imbalance. The great diversity in singing styles has led to species specific methods to describe individual and sex-specific variation in song. While this has allowed us to zoom in on individual differences within a species, it has hampered comparative work which requires metrics that are standardized across species. To address this we worked with researchers form Queen Mary University of London to devise methods for quantifying female and male song to be compared on a phylogenetic tree of species relationships. Altogether, our research will help us understand how female as well as male songbirds evolved their range of complex songs. Documenting the evolutionary processes responsible for these kinds of diversity are key to understanding how life has been shaped on our planet.

Data: CORDIS, © European Union