Molecular and morphological differentiation among Torrent Duck (Merganetta armata) populations in the Andes

Abstract

Birds living in riverine environments may show weak population structure because high dispersal abilities required to track habitat dynamics can result in gene flow over broad spatial scales. Alternatively, the configuration of river networks may result in restricted dispersal within river courses or basins, leading to high genetic structure. Although several bird species are riverine specialists in the Andes, no study has extensively evaluated the population genetic structure of any of them. We examined evidence from genetic and morphological data to address questions about the biogeography and taxonomy of the Torrent Duck (Merganetta armata), a riverine specialist bird with a broad distribution in Andean riverine habitats which certainly comprises different subspecies and may comprise more than one species. We found deep subdivisions of Torrent Duck populations from the northern, central and southern portions of the Andes. These lineages, which partly coincide with subspecies described based on plumage variation and body size, do not share mtDNA haplotypes, have private nuclear alleles and exhibit marked differences in morphometric traits. Some geographic barriers presumably restricting gene flow between groups partially coincide with those associated with major genetic breaks in forest species with similar distributions along the Andes, suggesting that bird assemblages including species occupying different habitats were likely affected by common biogeographical events. The three groups of Torrent Ducks may be considered different species under some species definitions and are distinct evolutionary lineages to be conserved and managed separately.

Unmasking hidden genetic, vocal, and size variation in the Masked Flowerpiercer along the Andes supports two species separated by Northern Peruvian Low

“…For instance, marked phenotypic differences exist between recently diverged, almost genetically indistinguishable populations of Coeligena hummingbirds (Palacios et al 2019). On the other hand, phenotypically indistinguishable populations with deep genetic divergences are found in several Andean bird complexes, including ducks (Gutiérrez-Pinto et al 2019), hummingbirds (Chaves et al 2011, Benham et al 2015), suboscines (Valderrama et al 2014, Cadena et al 2020, Chesser et al 2020), and oscines (Gutiérrez-Pinto et al 2012, Prieto-Torres et al 2018, Cadena et al 2019). That is, true diversity may be frequently overlooked because characterizations based on genetic or phenotypic traits alone are often insufficient.…”

Genetic, vocal, and body size divergence across the Northern Peruvian Low supports two species within the Masked Flowerpiercer (Diglossa cyanea)

“…For instance, marked phenotypic differences exist between recently diverged, almost genetically indistinguishable populations of Coeligena hummingbirds (Palacios et al 2019). On the other hand, phenotypically indistinguishable populations with deep genetic divergences are found in several Andean bird complexes, including ducks (Gutiérrez-Pinto et al 2019), hummingbirds (Chaves et al 2011; Benham et al 2014), suboscines (Valderrama et al 2014; Cadena et al 2020), and oscines (Gutiérrez-Pinto et al 2012; Prieto-Torres et al 2018; Cadena et al 2019). That is, true diversity may be frequently overlooked because characterizations based on genetic or phenotypic traits alone are often insufficient.…”