Geographic variation and the evolution of song in Mesoamerican rufous‐naped wrensCampylorhynchus rufinucha

Abstract

Speciation may be influenced by geographic variation in animal signals, particularly when those signals are important in reproductive decisions. Here, we describe patterns of geographic variation in the song of rufous-naped wrens Campylorhynchus rufinucha. This species complex is a morphologically variable taxon confined to tropical dry forest areas from Mexico to northwestern Costa Rica. Morphological and genetic analyses suggest that there are at least three partially isolated groups within the complex, including a secondary-contact zone in coastal western Chiapas between the subspecies C. r. humilus and C. r. nigricaudatus. Based on recordings throughout their geographic range, we investigate the effects of historical isolation on song structure and analyze whether genetic differences or climatic conditions explain observed patterns of variation. Our findings, based on a culturally-transmitted and sexually-selected trait, support the hypothesis that three evolutionary units exist within this taxon. Our results suggest that song differences between genetic groups were influenced by historical isolation. We report a strong relationship between vocal dissimilarity and genetic distance, suggesting that differences in vocal characteristics are probably affected by the same factors that drive genetic divergence. We argue that the evolution of song in this taxon is influenced by vicariant events, followed by accumulation of changes in song structure due to several possible factors: cultural drift in song structure; genetic drift in features related to song production; or natural selection acting on features that influence songs, such as body and beak size.

Divergence in mating signals correlates with genetic distance and behavioural responses to playback

“…Our results, however, show that divergence in learned signals may not occur as rapidly as is sometimes thought (discussed in Price & Lanyon, ). Our results are in line with other studies that show a parallel divergence between songs and genetics in other oscine bird species (Price & Lanyon, ; Farnsworth & Lovette, ; Irwin et al ., ; Cadena & Cuervo, ; Sosa‐López et al ., ), suggesting a bias for learning the song of the parental population and perhaps a partially genetically controlled sound production system (Remsen, ).…”

“…Many investigations have revealed that variation in acoustic signals parallels phylogenetic relationships (e.g. Ryan & Rand, 1999;Johnson et al, 2000;de Kort & ten Cate, 2001;Price & Lanyon, 2002;Ord & Martins, 2006;Percy et al, 2006;Farnsworth & Lovette, 2008;Irwin et al, 2008;Sosa-L opez et al, 2013; but see Price et al, 2007), suggesting that acoustic signals have phylogenetically conserved components. However, the evolutionary processes that drive animal perception of phylogenetically conserved components of acoustic signals are not well studied (Irwin & Price, 1999;Grether, 2011).…”

Geographic variation and divergence of songs in the Olive Sparrow species complex

“…Specifically, we found significant acoustic differences among three allopatric populations in the superciliosus group (Pacific, Chiapas, and Central America). Divergence in acoustic traits has been found to occur widely among allopatric populations (e.g., Toews and Irwin , Cadena and Cuervo , Chaves et al , Sosa‐López et al , Sosa‐López and Mennill , Ortiz‐Ramírez et al , Sandoval et al ). For example, geographic isolation of Wedge‐tailed Sabrewings ( Campylopterus curvipennis ) driven by paleoclimatic historical events might explain the vocal, genetic, and morphological differentiation exhibited by allopatric populations (González et al ).…”

“…Divergence in learned songs could have evolved due to selective (e.g., cultural selection, natural selection, or through selection on song as a social and sexual signal) and/or non‐selective factors (e.g., cultural drift and genetic drift; Wilkins et al ). Variation in learned songs is also influenced by the evolutionary history of a species, with a number of studies providing evidence of corresponding variation between song and genetic divergence, e.g., Pacific Wren ( Troglodytes pacificus ) vs. Winter Wren ( T. hiemalis ; Toews and Irwin ), Rufous‐naped Wren ( Campylorhynchus rufinucha ; Vázquez‐Miranda et al , Sosa‐López et al ), White‐browed Brush‐finch ( Arremon torquatus ; Cadena and Cuervo ), Wedge‐tailed Sabrewing ( Campylopterus curvipennis ; González et al ), White‐crowned Sparrow ( Zonotrichia leucophrys ; Lipshutz et al ), and Timberline Wren ( Thryorchilus browni ; Camacho‐Alpízar et al ), and concordance between vocal traits and phylogenetic relationships (e.g., McCracken and Sheldon , Price and Lanyon ).…”

“…Generally, studies showing variation in vocal traits congruent with genetic and/or morphological variation across geography involve species with isolated populations (Cadena and Cuervo , Sosa‐López et al , Sosa‐López and Mennill , Sandoval et al ). For example, Sandoval et al () evaluated phenotypic variation between isolated populations of White‐eared Ground‐sparrows ( Melozone leucotis ) in Central America and found differences in voice, plumage, and morphological traits.…”