Acoustic Divergence with Gene Flow in a Lekking Hummingbird with Complex Songs

Abstract

Hummingbirds have developed a remarkable diversity of learned vocalizations, from single-note songs to phonologically and syntactically complex songs. In this study we evaluated if geographic song variation of wedge-tailed sabrewings (Campylopterus curvipennis) is correlated with genetic divergence, and examined processes that explain best the origin of intraspecific song variation. We contrasted estimates of genetic differentiation, genetic structure, and gene flow across leks from microsatellite loci of wedge-tailed sabrewings with measures for acoustic signals involved in mating derived from recordings of males singing at leks throughout eastern Mexico. We found a strong acoustic structure across leks and geography, where lek members had an exclusive assemblage of syllable types, differed in spectral and temporal measurements of song, and song sharing decreased with geographic distance. However, neutral genetic and song divergence were not correlated, and measures of genetic differentiation and migration estimates indicated gene flow across leks. The persistence of acoustic structuring in wedge-tailed sabrewings may thus best be explained by stochastic processes across leks, in which intraspecific vocal variation is maintained in the absence of genetic differentiation by postdispersal learning and social conditions, and by geographical isolation due to the accumulation of small differences, producing most dramatic changes between populations further apart.

Molecular and iridescent feather reflectance data reveal recent genetic diversification and phenotypic differentiation in a cloud forest hummingbird

“…(). If so, weakly divergent selection pressures on hummingbird individuals with structurally iridescent colors likely associated with mate choice and competition would suffice to a relatively fast differentiation, even in the presence of gene flow (Parra ; González and Ornelas ), compared to those lacking ornamental iridescent coloration that would require longer periods of geographic isolation.…”

“…With allopatry induced by the physical isolation of populations interrupting gene flow between allopatric sister populations isolated by geographic barriers, genetic divergence accrues as a result of adaptation to the prevailing environmental conditions and by means of genetic drift (Coyne and Orr 2004) and the allopatric sister populations will differentiate phenotypically given sufficient time or selection pressures (Coyne and Orr 2004;Nosil 2008a;Price 2008;Winger and Bates 2015). Migration and gene flow may occur between populations if geographical barriers are permeable (e.g., Rodr ıguez-G omez et al 2013;Rodr ıguez-G omez and Ornelas 2015), but despite high levels of gene flow, phenotypic plasticity and/or selection may be strong enough to the maintenance of phenotypic divergence (Jordan et al 2005;Niemiller et al 2008;Nosil 2008a;Mil a et al 2009;Gonz alez and Ornelas 2014). In the 'divergence with gene flow' model (Endler 1977), the physical barrier to gene flow is absent or the continuous divergence process leading to speciation is incomplete (Nosil 2008b).…”

“…Thus, a coalescent-based analysis is needed to distinguish the effects of time of isolation and gene flow on levels of genetic divergence using the 'isolation with migration' model (Hey 2006). Although geographical isolation leading to genetic divergence is traditionally considered fundamental to phenotypic divergence (Mayr 1963), empirical work suggests that strong selection can still lead to both genetic and phenotypic divergence in spite of high levels of gene flow (e.g., Smith et al 1997;Jordan et al 2005;Parra 2010;Gonz alez and Ornelas 2014).…”

Behavioural response to song and genetic divergence in two subspecies of white‐crowned sparrows (Zonotrichia leucophrys)

“…Payne & Westneat 1988;Lougheed & Handford 1992;Soha et al 2004;Ruegg et al 2006;Leader et al 2008;Ortiz-Ram ırez et al 2016), nor for nonoscines in which vocal learning evolved independently (e.g. Wright & Wilkinson 2001;Saranathan et al 2007;Gonzalez & Ornelas 2014). Thus, although there is abundant evidence that song acts as an isolating mechanism between bird species, when and how intraspecific song variation facilitates reproductive divergence is less clear (Slabbekoorn & Smith 2002;Lachlan & Servedio 2004).…”

High levels of gene flow among song dialect populations of the Puget Sound white‐crowned sparrow

“…A summary of further statistical analyses of each study can be found in Appendix Table S2. References: 1 Baker (1982); 2 Baker et al (1982); 3 Balaban (1988); 4 González and Ornelas (2014); 5 Hafner and Petersen (1985); 6 Handford and Nottebohm (1976); 7 Table 3. b F ST calculated as x ± SD of six of 60 pairwise F ST values that were significantly different from zero.…”