Parallel evolutionary forces influence the evolution of male and female songs in a tropical songbird

Abstract

Given the important role that animal vocalizations play in mate attraction and resource defence, acoustic signals are expected to play a significant role in speciation. Most studies, however, have focused on the acoustic traits of male animals living in the temperate zone. In contrast to temperate environments, in the tropics, it is commonplace for both sexes to produce complex acoustic signals. Therefore, tropical birds offer the opportunity to compare the sexes and provide a more comprehensive understanding of the evolution of animal signals. In this study, we quantified patterns of acoustic variation in Rufous-and-white Wrens (Thryophilus rufalbus) from five populations in Central America. We quantified similarities and differences between male and female songs by comparing the role that acoustic adaptation, cultural isolation and neutral genetic divergence have played in shaping acoustic divergence. We found that males and females showed considerable acoustic variation across populations, although females exhibited greater population divergence than males. Redundancy analysis and partial-redundancy analysis revealed significant relationships between acoustic variation and ecological variables, genetic distance, and geographic distance. Both ambient background noise and geographic distance explained a high proportion of variance for both males and females, suggesting that both acoustic adaptation and cultural isolation influence song. Overall, our results indicate that parallel evolutionary forces act on male and female acoustic signals and highlight the important role that cultural drift and selection play in the evolution of both male and female songs.

Sexually distinct song cultures in a songbird metapopulation

“…Another potential explanation is that genetic diversity has driven population repertoire size. However, sites with low genetic diversity (Baillie, 2011) did not have correspondingly low syllable diversity, suggesting song culture is not tightly constrained by genetic diversity in bellbirds (see also Graham et al, 2018). We suspect that between-site differences in repertoire size are more likely driven by competition level.…”

“…Three later studies on rufous-and-white wrens (Graham et al, 2017a(Graham et al, , 2018(Graham et al, , 2021 showed that song cultures of males and females can be similar in complexity, and appear to evolve in similar directions via acoustic adaptation and cultural drift. However, males and females differ in the relationship between dispersal distance and song-sharing with parents (Graham et al, 2017a), the speed of cultural change, and the relationship between immigration rate and cultural diversity (Graham et al, 2021).…”

Analysis of female song provides insight into the evolution of sex differences in a widely studied songbird

“…Price, 2019), we have few studies within species to guide our understanding of the processes driving these patterns. In contrast to the vast literature on within-species geographic divergence in male signals (McLean & Stuart-Fox, 2014;Podos & Warren, 2007;Slabbekoorn & Smith, 2002;Velásquez, 2014), there are few studies for females in the visual modality (McCoy et al, 1997;McLean & Stuart-Fox, 2014;Obara et al, 2008;Roulin, 2003;Tuomaala et al, 2012) and fewer still in the acoustic modality (Graham et al, 2017(Graham et al, , 2018Mennill & Rogers, 2006;Odom & Mennill, 2012). Yet, it is worth noting that three studies (in butterflies and birds) that considered intraspecific geographic variation in both sexes found greater signal divergence in females than males across populations (Graham et al, 2018;Mennill & Rogers, 2006;Tuomaala et al, 2012).…”

“…In contrast to the vast literature on within-species geographic divergence in male signals (McLean & Stuart-Fox, 2014;Podos & Warren, 2007;Slabbekoorn & Smith, 2002;Velásquez, 2014), there are few studies for females in the visual modality (McCoy et al, 1997;McLean & Stuart-Fox, 2014;Obara et al, 2008;Roulin, 2003;Tuomaala et al, 2012) and fewer still in the acoustic modality (Graham et al, 2017(Graham et al, , 2018Mennill & Rogers, 2006;Odom & Mennill, 2012). Yet, it is worth noting that three studies (in butterflies and birds) that considered intraspecific geographic variation in both sexes found greater signal divergence in females than males across populations (Graham et al, 2018;Mennill & Rogers, 2006;Tuomaala et al, 2012). The implications of female signal evolution, male mate choice/recognition, and their impact on speciation have received little attention in the literature, with a few relevant studies focusing primarily on fish and insects (Chung et al, 2014;Edward & Chapman, 2011;Jiggins et al, 2004;Roberts & Mendelson, 2017.…”

Sexually Distinct Song Cultures Across a Songbird Metapopulation

“…Four later studies on rufous-and-white wrens (Graham et al, 2017a(Graham et al, , 2018a(Graham et al, ,b, 2021 showed that song cultures of males and females can be similar in complexity, and appear to evolve in similar directions via acoustic adaptation and cultural drift. However, males and females differ in the relationship between dispersal distance and song-sharing with parents (Graham et al, 2017a), the speed of cultural change, and the relationship between immigration rate and cultural diversity (Graham et al, 2021).…”