Analysis from avian visual perspective reveals plumage colour differences among females of capuchino seedeaters (Sporophila)

Abstract

Females of the closely related capuchino seedeaters are difficult to distinguish from one another based on human visual perception of colouration and morphology. We examined plumage colour differences among females of four species, the tawny‐bellied seedeater Sporophila hypoxantha, the dark‐throated seedeater S. ruficollis, the rufous‐rumped seedeater S. hypochroma, and the chesnut‐bellied seedeater S. cinnamomea. Reflectance values were measured on museum skins, and interspecific differences were analyzed using the Vorobyev‐Osorio avian colour discrimination model. Interspecific distances in the colour space calculated by the model were considerably higher than the threshold for colour discrimination, indicating the presence of colour differences among species that should be detectable by birds. Colour differences between S. hypoxantha and the other three species were the largest. A Discriminant Function Analysis showed that UV‐wavelength was particularly important in species separation. Our results indicate that female plumage of these four species is considerably divergent in colour; these differences being imperceptible to the human eye, thus representing previously unknown morphological evolution in these species.

Rapid phenotypic evolution during incipient speciation in a continental avian radiation

“…This is further substantiated by cryptic plumage differences found between females in the group [21]. Playback experiments are required to test if the observed phenotypic differences result in assortative mating.…”

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

“…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). The combination of their recent origin, divergent phenotypes and overall apparent lack of neutral genetic differentiation prompted us to use the southern capuchino radiation to test predictions of the model of speciation with gene flow.…”

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

“…These taxa are diagnosed through male song and reproductive color patterns since they are otherwise extremely similar in size and shape; capuchinos can also show eclipse plumage and gather in mixed flocks when not breeding (Rising et al ). Spectrophotometric analysis of female plumage has identified previously undetected differences among some capuchino females in the UV‐portion of the spectrum (Benites et al ). Eight of the capuchinos appear to have radiated rapidly during the Pleistocene and are predominantly sympatric and often syntopic, endemic species to central and southern South America (hereafter southern capuchinos, Lijtmaer et al , Campagna et al , , ).…”

“…Recent detailed analyses of these traits have led to the discovery of alternative color morphs within some species (Repenning et al , Areta and Repenning , Areta et al ), the merger of previously recognized taxa (Areta ), and helped identify the sister species to the core southern capuchino radiation (Machado and Silveira , , Campagna et al ). The southern capuchino species that are currently recognized show statistically significant differences in their songs and plumage attributes, which are maintained in sympatry (Benites et al , Campagna et al ). Nevertheless, the biological relevance of these differences remains untested.…”