Song‐based species discrimination in a rapid Neotropical radiation of grassland seedeaters

Abstract

Acoustic signals among newly diverged taxa have the potential to convey species identity, information that is key to reducing hybridization. Capuchino seedeaters constitute a remarkable example of recently radiated endemic species from the grasslands of South America. They are sexually dimorphic and show striking differences in male plumage coloration and song. Contrasting with this divergence in phenotype most species show extremely low neutral genetic differentiation and lack of reciprocal monophyly, which is interpreted to be a product of recent common ancestry and hybridization. Here we use field‐based playback experiments to test for the first time if males of two species, Sporophila hypoxantha and S. palustris, discriminate between conspecific and heterospecific song. Using various measures of behavior we find that both species react more strongly to their own songs. The response to playback from another southern capuchino cannot be differentiated from that of a control song from a more distantly related Sporophila species. Additionally, we did not find evidence for reinforcement as the response of S. hypoxantha did not differ between individuals that co‐occur with S. palustris and those that do not. Our finding suggests that song, a culturally inherited trait, may help maintain reproductive isolation between species in the rapid and explosive capuchino radiation.

The multiple applications of DNA barcodes in avian evolutionary studies

“…This group shows remarkably high plumage colour divergence among males, which also produce distinctive vocalizations, suggesting that species-level designations to them are correct (Campagna et al 2012a). There is also evidence that males from these species react more strongly to male conspecific vocalizations than to hetero-specific ones, indicating that the interspecific differences in vocalizations are in fact detected by the birds, supporting the notion that these are different species (Benites et al 2015). The first DNA barcode study to include six of these species (among others from Argentina) showed that this was one of the very few cases with low or null interspecific differentiation in COI.…”

Distinguishing noise from signal in patterns of genomic divergence in a highly polymorphic avian radiation

“…; Benites et al . ), they may not have yet accumulated differences in neutral markers. This lack of neutral differentiation may be a product of their recent origin and large ancestral effective population size (incomplete lineage sorting) and perhaps high levels of gene flow (although we do not find evidence of this, see below).…”

“…Playback experiments suggest male southern capuchinos are able to distinguish conspecific from heterospecific vocalizations, responding aggressively only to conspecifics (Benites et al . ). Southern capuchinos are sexually dimorphic: females are phenotypically similar among different species (mostly brown and olive), yet show some cryptic (to the human eye) plumage differences in the ultraviolet portion of the spectrum that birds are capable of seeing (Benites et al .…”

“…In contrast, the nine species differ conspicuously in male plumage and song (Campagna et al 2012), two sets of traits that are particularly important for generating reproductive isolation in birds more generally (Price 2008). Playback experiments suggest male southern capuchinos are able to distinguish conspecific from heterospecific vocalizations, responding aggressively only to conspecifics (Benites et al 2014). Southern capuchinos are sexually dimorphic: females are phenotypically similar among different species (mostly brown and olive), yet show some cryptic (to the human eye) plumage differences in the ultraviolet portion of the spectrum that birds are capable of seeing (Benites et al 2010).…”

Full Issue

“…Such studies can offer important insights into possible premating barriers, at least those based on vocalizations, even for allopatric groups. Although a finding of little or no response to song playback can be indicative of reproductive barriers (e.g., Benites et al 2014), equally aggressive responses are generally inconclusive (McKitrick and Zink 1988). In general, however, there has not been a broad application of playback studies, particularly between allopatric groups.…”