The vulnerability to extinction by isolated populations also occurs because of lack of suitable habitat, environmental pressures (e.g., development, predation, climate change), and/or stochastic perturbations (i.e., survival and reproductive success, habitat variation, genetic drift, catastrophes) (Callaghan, 1997 Fahrig, 2013 Naranjo & Ávila, 2003 Shaffer, 1981 Soulé & Mills, 1998). In addition, patchy habitats often harbor small populations with low genetic diversity, which may reduce the effectiveness of selection and contribute to high rates of local extinction (Charlesworth, 2010 Hartl & Clark, 2007). Among types of species, habitat specialists are particularly prone to increased levels of population structure as a result of isolation on patchy habitats (Kawecki & Ebert, 2004 Kawecki et al., 2012 Nei, 2013 Orr, 2005). As populations subdivide through time, variation in the rate of genetic drift and gene flow, as well as selective pressures, will define the genetic diversity, divergence, or extinction of each species (Bowler & Benton, 2005 Frankham, 2005 Hey, 2010 Lenormand, 2002 Ma et al., 2015 Shaffer, 1981 Slatkin, 1987).
#EARTH FINAL CONFLICT SEASON 5 TORRENT TORRENT#
We suggest that the South American Arid Diagonal was preexisting and remains a current phylogeographic barrier between the ranges of the two torrent duck subspecies, and the adult territoriality and breeding site fidelity to the rivers define their population structure.Įstablishing how populations are structured is fundamental for understanding evolutionary processes (Hartl & Clark, 2007 Hey & Machaco, 2003 Ma, Ji, & Zhang, 2015 Wright, 1969). The populations were well-differentiated in Argentina but moderately differentiated in Peru, with low unidirectional gene flow in each country.
Demographic parameters estimated for mtDNA using IM and IMa2 analyses, and for autosomal markers using ∂a∂i (isolation-with-migration model), supported an old divergence (mtDNA = 600,000 years before present (ybp), 95% HPD range = 1.2 Mya to 200,000 ybp and autosomal ∂a∂i = 782,490 ybp), between the two subspecies, characteristic of deeply diverged lineages. Peruvian and Argentine subspecies showed concordant species-level differences (Φ ST mtDNA = 0.82 Φ ST autosomal = 0.30 Φ ST Z chromosome = 0.45), including no shared mtDNA haplotypes. Haplotype and nucleotide diversities were higher in Peru than Argentina across all markers.
Additionally, to test for differences between subspecies, and across genetic markers with distinct inheritance patterns, a subset of individuals (Peru, n = 10 and Argentina, n = 9) was subjected to partial genome resequencing, obtaining 4,027 autosomal and 189 Z-linked double-digest restriction-associated DNA sequences.
We sampled 156 individuals in Peru ( M. a. leucogenis Chillón River, n = 57 and Pachachaca River, n = 49) and Argentina ( M. a. armata Arroyo Grande River, n = 33 and Malargüe River, n = 17), and sequenced the mitochondrial DNA (mtDNA) control region to conduct coarse and fine-scale demographic analyses of population structure. Two subspecies of torrent duck ( Merganetta armata). To investigate the structure and rate of gene flow among populations of habitat-specialized species to understand the ecological and evolutionary processes underpinning their population dynamics and historical demography, including speciation and extinction.
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