Song patterns support species status for some, but possibly not all, island populations of House Wren (Troglodytes spp.) in the Lesser Antilles

Abstract

Island populations are special for the study of evolutionary processes and can be a zone of incipient speciation. Recently, several island populations of House Wren in the Lesser Antilles (Dominica, St Lucia, St Vincent, and Grenada), formerly recognized as subspecies of the continental form, were reclassified as distinct species. However, much of the supporting data was fragmentary in its sampling of the different islands or equivocal in the patterns observed. Because song is a core element of mate recognition and choice, and can therefore be a key character in species identification, I report here the first detailed characterization and analysis of song for House Wren on all of the islands of the Lesser Antilles where they remain, including Trinidad and Tobago; and compare song patterns across the different islands as well as to several continental populations. Results show that song is broadly similar across all of the islands and to continental populations in high-level features of its structure, organization and delivery but is discriminably different among many of them in its more detailed features. The latter differences are consistent with the recent species splits, with the possible exception of Grenada. They also support retention of House Wren on Trinidad and Tobago as subspecies of the continental form. Results also point to the possibility of a central American origin for some of the islands and a south American origin for others, yielding a trait mosaic where islands that putatively share the same geographic origins, and are therefore presumably genetically closest, are not the most similar in patterns of song (or plumage). This pattern would therefore entail multiple intriguing instances of convergent evolutionary divergence among them that warrants further detailed study. Lay SummaryO_LII provide the first comprehensive analysis and comparison of song patterns of House Wrens for all of the islands of the Lesser Antilles where they remain, some of which are at risk of extirpation, or even extinction if they represent distinct species. C_LIO_LII use the patterns to interpret the recent taxonomic reclassification of many of these island populations as distinct species. C_LIO_LIIn their general structure, organization and delivery male song is similar across all of the islands and follows patterns common to contintental forms of House Wren distributed broadly across North, Central and South America. C_LIO_LISongs of the different islands are, however, discriminably different in their more detailed features and these differences are consistent with most, but possibly not all, of the recent species splits. C_LIO_LIFor the island populations recently reclassified as different species, the distinctiveness of male song is greatest in Dominica and St Vincent and to a lesser extent also St Lucia, and least distinctive in Grenada. Song in Trinidad and Tobago is not substantively different from populations in mainland South America which supports retaining these two island populations as subspecies of the closest continental forms. C_LIO_LISong patterns also point to different possible continental sources for some of the island populations: a source in Central America for Dominica and St Lucia; and a source in South America for the rest. If true, this creates multiple instances of convergent evolutionary divergence in trait patterns across the various islands which merits further study. C_LI