Comparative mitochondrial genetics of North American and Eurasian mergansers with an emphasis on the endangered scaly-sided merganser (Mergus squamatus)

Abstract

The scaly-sided merganser, Mergus squamatus, is considered one of the most threatened sea duck species in the Palearctic with limited breeding and wintering distribution in China and Russia. To provide information for future conservation efforts, we sequenced a portion of the mitochondrial (mt) DNA control region in four species of mergansers and three additional sea duck taxa to characterize the evolutionary history of the scaly-sided merganser, infer population trends that may have led to its limited geographic distribution, and to compare indices of genetic diversity among species of mergansers. Scaly-sided mergansers exhibit substantially lower levels of mtDNA genetic diversity (h = 0.292, p = 0.0007) than other closely related sea ducks and many other avian taxa. The four haplotypes observed differed by a single base pair suggesting that the species has not experienced a recent population decline but has instead been at a low population level for some time. A phylogenetic analysis placed the scaly-sided merganser basal to North American and European forms of the common merganser, M. merganser. Our inclusion of a small number of male samples doubled the number of mtDNA haplotypes observed, suggesting that additional genetic variation likely exists within the global population if there is immigration of males from unsampled breeding areas.

Museum collections reveal that Buff-breasted Sandpipers (Calidris subruficollis) maintained mtDNA variability despite large population declines during the past 135 years

“…We expected a decrease in mitochondrial DNA variation and effective population size of females following patterns found in other birds of conservation concern (Martinez-Cruz et al 2007;Solovyeva and Pearce 2011;Draheim et al 2012). Unexpectedly, we found little evidence of change in genetic variation when we compared several measures of mtDNA variation, N ef , and haplotype distributions over a 135 year time period that coincided with a series of reductions in population size.…”

“…We chose not to use nuclear markers such as microsatellites due to the age of specimens and quality and quantity of DNA, which can result in high genotyping error rates and underestimates (due to allelic dropout) or, less frequently, overestimates (due to false alleles) of historic allelic variation (Wandeler et al 2007;Millar et al 2008). Previous studies have successfully used mitochondrial markers in hDNA samples to reveal declines in genetic diversity over time in several species of birds (Martinez-Cruz et al 2007;Solovyeva and Pearce 2011;Draheim et al 2012). We sought to evaluate changes in mtDNA variation and female effective population size (N ef ), as well as the possible extirpation of unique matrilineal units.…”

Use of geolocators reveals previously unknown Chinese and Korean scaly-sided merganser wintering sites

“…If this were the case for scaly-sided mergansers, this would seem to provide a mechanism to maintain genetic heterogeneity in this species by encouraging females to pair with males originating from a different breeding provenance to their own. Four haplotypes were found in scaly-sided merganser males trapped in the Kievka catchment, but only 2 of these were found in females from the same catchment (Solovyeva & Pearce 2011). There is evidence for female philopatry and male dispersal in the genetically related and ecologically similar M. merganser (e.g.…”

Ancient mitogenomes reveal evidence for the late Miocene dispersal of mergansers to the Southern Hemisphere

“…Our phylogenetic analysis was generally well-resolved and broadly concordant with previous studies of Mergini, taking into account the absence of previously un-sequenced taxa that may change some evolutionary relationships (Livezey, 1995; Gonzalez et al . 2009; Solovyeva & Pearce, 2011; Liu et al . 2012; Sun et al .…”