Genetic structure among greater white‐fronted goose populations of the Pacific Flyway

Abstract

An understanding of the genetic structure of populations in the wild is essential for long‐term conservation and stewardship in the face of environmental change. Knowledge of the present‐day distribution of genetic lineages (phylogeography) of a species is especially important for organisms that are exploited or utilize habitats that may be jeopardized by human intervention, including climate change. Here, we describe mitochondrial (mtDNA) and nuclear genetic (microsatellite) diversity among three populations of a migratory bird, the greater white‐fronted goose (Anser albifrons), which breeds discontinuously in western and southwestern Alaska and winters in the Pacific Flyway of North America. Significant genetic structure was evident at both marker types. All three populations were differentiated for mtDNA, whereas microsatellite analysis only differentiated geese from the Cook Inlet Basin. In sexual reproducing species, nonrandom mate selection, when occurring in concert with fine‐scale resource partitioning, can lead to phenotypic and genetic divergence as we observed in our study. If mate selection does not occur at the time of reproduction, which is not uncommon in long‐lived organisms, then mechanisms influencing the true availability of potential mates may be obscured, and the degree of genetic and phenotypic diversity may appear incongruous with presumed patterns of gene flow. Previous investigations revealed population‐specific behavioral, temporal, and spatial mechanisms that likely influence the amount of gene flow measured among greater white‐fronted goose populations. The degree of observed genetic structuring aligns well with our current understanding of population differences pertaining to seasonal movements, social structure, pairing behavior, and resource partitioning.

Flyway structure in the circumpolar greater white‐fronted goose

“…Greater white‐fronted geese possess many behavioral and ecological characteristics that might restrict genetic interchange among populations, not only at the broad flyway (macrogeographic) scale but also on a more local (microgeographic) scale (see Ely et al., ). As seen in Pacific Flyway white‐fronted geese and other goose species, the timing of pairing can have pronounced implications on genetic structuring in geese (Ely & Scribner, ; Ely et al., ). Typically, in waterfowl, multiple populations from disparate locales utilize the same wintering site, thus providing an avenue for genetic exchange if pair formation occurs during this period of the annual cycle.…”

“…Further, North American greater white‐fronted goose populations are temporally segregated throughout much of the annual cycle despite having a high degree of spatial overlap during winter (Ely & Takekawa, ; Ely et al., ). This temporal and spatial segregation is more pronounced in the Pacific Flyway with segregation of site use observed at the population level (Ely et al., ), while the midcontinent population tends to be more temporally segregated by general breeding areas (Ely et al., ). In the midcontinent, Ely et al.…”

“…Geese occupying northern high latitudes exhibit life-history traits that may facilitate population structure and restrict interflyway genetic exchange, such as high philopatry in both sexes along with long-term pair bonds and familial associations and delayed reproduction (Ely & Scribner, 1994;Scribner et al, 2003;Ely, Wilson, & Talbot, 2017). In contrast to ducks, pair-bonding in some goose species is thought to occur primarily during the spring and summer when genetically similar individuals are segregated (Ely & Scribner, 1994;Leafloor, Moore, & Scribner, 2013;Weegman et al, 2015), and this would provide an additional mechanism to further limit gene flow among breeding areas.…”

“…Within the Pacific Flyway, for example, three morphologically distinct populations, including the largest and smallest forms, overlap in migratory pathways and winter distribution (Ely & Takekawa, 1996;Ely et al, 2005;Orthmeyer, Takekawa, Ely, Wege, & Newton, 1995). Several mechanisms have been proposed in the maintenance of reproductive isolation of sympatric wintering populations, such as microgeographic and behavioral barriers (see Ely et al, 2017). Furthermore, greater white-fronted goose populations, at least in North America, tend to be spatially and temporally segregated during migration (Ely, Neiman, Alisauskas, Schmutz, & Hines, 2013;Ely & Takekawa, 1996).…”

“…Previous population genetic studies on greater white-fronted geese have focused on either within flyway (Ely et al, 2017;Volkovsky, Fisenko, Gerasimov, & Zhuravlev, 2016;Volkovsky, Kulikova, Gerasimov, & Zhuravlev, 2013) or between Eurasia and Greenland populations (Eda, Shimada, Ushiyama, Mizota, & Koike, 2013). Here we present the most comprehensive population genetic assessment of the greater white-fronted goose to date across their entire breeding range, using genotypic data from eight autosomal microsatellite loci and sequence data from the mitochondrial DNA (mtDNA) control region, as well as contemporary observational data in the form of band recovery distribution through 2015.…”