Sandra L. Talbot

Gene flow and genetic characterization of Northern Goshawks breeding in Utah

Abstract Adult movement and natal dispersal data demonstrate that Northern Goshawks (Accipiter gentilis) are able to travel over long distances, suggesting a large functional population. However, these data are unable to determine whether these movements contribute to gene flow among adjacent breeding areas. We used eight microsatellite DNA loci and mitochondrial DNA control-region sequence data to assess population structure of Northern Goshawks breeding in Utah. Goshawks had moderate levels of genetic variation at microsatellite loci (observed heterozygosity = 50%), similar to levels found in other medium-sized, highly mobile birds. Overall estimates of interpopulation variance in microsatellite alleles (FST = 0.011) and mtDNA haplotypes (ΦST = 0.126) were low and not significantly different from zero. Pairwise population comparisons using microsatellite markers revealed no differentiation among sampled sites, indicating that the functional population extends beyond Utah. However, pairwise population analyses of mtDNA uncovered a single case of differentiation between goshawks inhabiting Ashley National Forest, in northeastern Utah, and Dixie National Forest, in southwestern Utah. Low levels of population structuring observed in mtDNA between the two forests may be due to the smaller effective population size sampled by mtDNA, a cline of haplotypes across the West, or the presence of a contact zone between A. g. atricapillus and goshawks of southern Arizona and the Mexican Plateau. Flujo Genético y Caracterización Genética de Accipiter gentilis Reproduciéndose en Utah Resumen. Datos sobre el movimiento de los adultos de Accipter gentilis y la dispersión natal demuestran que A. gentilis es capaz de viajar largas distancias, lo que sugiere una gran población funcional. Sin embargo, dichos estudios no son capaces de determinar si estos movimientos contribuyen al flujo genético entre las áreas de reproducción. En este estudio se utilizaron ocho loci de microsatélites de ADN y secuencias de la región control del ADN mitocondrial para estimar la estructura poblacional de la unidad reproductiva de A. gentilis en Utah. Este halcón presentó niveles intermedios de variación genética en loci de microsatélites (heterocigosidad observada = 50%), similares a los niveles encontrados en otras aves de tamaño medio con gran dispersión. La estimación total inter-poblacional de la varianza en alelos de microsatélites (FST = 0.011) y haplotipos de ADNmt (ΦST = 0.126) resultaron ser bajas y no significativamente diferentes de cero. Las comparaciones entre pares de poblaciones utilizando marcadores de microsatélites no mostraron diferencias entre los sitios muestreados, indicando que la población funcional se extiende más allá de Utah. Sin embargo, el análisis con ADNmt entre pares de poblaciones mostró en un sólo caso una diferenciación entre la población de A. gentilis que habita en el Bosque Nacional Ashley al noreste de Utah y la población de A. gentilis del Bosque Nacional Dixie, al sureste de Utah. Los niveles bajos de estructura poblacional observados con ADNmt entre los dos bosques pueden deberse a un bajo tamaño poblacional efectivo muestreado con ADNmt, a una disminución de haplotipos hacia el oeste o a la presencia de una zona de contacto entre A. g. atricapillus y Accipiter gentilis del sureste de Arizona y la meseta Mexicana.

PHYLOGEOGRAPHY OF CANADA GEESE (BRANTA CANADENSIS) IN WESTERN NORTH AMERICA

Abstract Using molecular genetic markers that differ in mode of inheritance and rate of evolution, we examined levels and partitioning of genetic variation for seven nominal subspecies (11 breeding populations) of Canada Geese (Branta canadensis) in western North America. Gene trees constructed from mtDNA control region sequence data show that subspecies of Canada Geese do not have distinct mtDNA. Large and small-bodied forms of Canada Geese were highly diverged (0.077 average sequence divergence) and represent monophyletic groups. A majority (65%) of 20 haplotypes resolved were observed in single breeding locales. However, within both large and small-bodied forms certain haplotypes occurred across multiple subspecies. Population trees for both nuclear (microsatellites) and mitochondrial markers were generally concordant and provide resolution of population and subspecific relationships indicating incomplete lineage sorting. All populations and subspecies were genetically diverged, but to varying degrees. Analyses of molecular variance, nested-clade and coalescencebased analyses of mtDNA suggest that both historical (past fragmentation) and contemporary forces have been important in shaping current spatial genetic distributions. Gene flow appears to be ongoing though at different rates, even among currently recognized subspecies. The efficacy of current subspecific taxonomy is discussed in light of hypothesized historical vicariance and current demographic trends of management and conservation concern.

Epizootic of BEak DEformitiEs among WilD BirDs in alaska: an EmErging DisEasE in north amErica?

ABSTRACT. The sudden appearance of a large cluster of animals with gross abnormalities may signal a significant change in an ecosystem. We describe an unusual concentration of beak deformities that appear to have arisen rapidly within Alaska and now extend southward along the Pacific Coast. In Alaska we have documented 2,160 Black-capped Chickadees (Poecile atricapillus) and 435 individuals of 29 other species of birds, primarily during the past decade, with grossly overgrown and often crossed beaks. The annual prevalence of beak abnormalities among adult Black-capped Chickadees in south-central Alaska varied from 3.6% to 9.7% and averaged 6.5 ± 0.5% between 1999 and 2008. Only 0.05 ± 0.05% of nestlings and 0.3 ± 0.2% of juveniles <6 months old had abnormal beaks, which suggests that this is either a latent developmental or an acquired condition. We documented 80 cases in which a Black-capped Chickadee captured with an apparently normal beak was subsequently recaptured with a beak abnormality and 8 cases in which a beak deformity was no longer detectable upon recapture. Necropsy and histopathology of a sample of affected individuals provided no conclusive evidence of the etiology of this condition. Deformities appear to affect primarily the keratin layer of the beak and may result from abnormally rapid growth of the rhamphotheca. Some affected birds also exhibited lesions in other keratinized tissues of the skin, legs, feet, claws, and feathers, which may represent a systemic disorder or secondary conditions. Additional studies are currently underway to determine diagnostic signs and the underlying cause of this avian keratin disorder.

Limited genetic differentiation among breeding, molting, and wintering groups of the threatened Steller’s eider: the role of historic and contemporary factors

Due to declines in the Alaska breeding population, the Steller’s eider (Polysticta stelleri) was listed as threatened in North America in 1997. Periodic non-breeding in Russia and Alaska has hampered field-based assessments of behavioral patterns critical to recovery plans, such as levels of breeding site fidelity and movements among three regional populations: Atlantic-Russia, Pacific-Russia and Alaska. Therefore, we analyzed samples from across the species range with seven nuclear microsatellite DNA loci and cytochrome b mitochondrial (mt)DNA sequence data to infer levels of interchange among sampling areas and patterns of site fidelity. Results demonstrated low levels of population differentiation within Atlantic and Pacific nesting areas, with higher levels observed between these regions, but only for mtDNA. Bayesian analysis of microsatellite data from wintering and molting birds showed no signs of sub-population structure, even though band-recovery data suggests multiple breeding areas are present. We observed higher estimates of F-statistics for female mtDNA data versus male data, suggesting female-biased natal site fidelity. Summary statistics for mtDNA were consistent with models of historic population expansion. Lack of spatial structure in Steller’s eiders may result largely from insufficient time since historic population expansions for behaviors, such as natal site fidelity, to isolate breeding areas genetically. However, other behaviors such as the periodic non-breeding observed in Steller’s eiders may also play a more contemporary role in genetic homogeneity, especially for microsatellite loci.

DEMOGRAPHY, GENETICS, AND THE VALUE OF MIXED MESSAGES

Abstract Iverson et al. (2004) used estimates of the homing rate for molting adult Harlequin Ducks (Histrionicus histrionicus) in Alaska to draw inferences about population structure. Homing rates, defined as one minus the ratio of birds recaptured elsewhere to those recaptured at the original banding site, were high (0.95–1.00) for males and females. Iverson et al. (2004) concluded that these high rates of homing are indicative of demographic independence among molting groups separated by small distances (tens to hundreds of kilometers) and that conservation efforts should recognize this fine-scale population structure. We re-examined their use of the homing rate, because their assumption of equal detection probability across a wide sampling area could have led to an upward bias in their estimates of site fidelity. As a result, we are hesitant to agree with their conclusion of high adult homing to molting areas and that molt-site fidelity is evidence for demographic independence. Our hesitancy stems from the fact that little is known about juvenile and adult movements within and among years, breeding area origins, and the variation of demographic parameters (e.g., survival and productivity) among molting groups. Furthermore, population genetic data of these molting groups suggest gene flow at both nuclear and mitochondrial loci. Such mixed messages between demographic (i.e., banding) and genetic data are increasingly common in ornithological studies and offer unique opportunities to reassess predictions and make more robust inferences about population structure across broad temporal and spatial scales. Thus, we stress that it is this broader scale perspective, which combines both demography and genetics, that biologists should seek to quantify and conservation efforts should seek to recognize.

MOLECULAR GENETIC STATUS OF ALEUTIAN CANADA GEESE FROM BULDIR AND THE SEMIDI ISLANDS, ALASKA

Abstract We conducted genetic analyses of Aleutian Canada Geese (Branta canadensis leucopareia) from Buldir Island in the western Aleutians and the Semidi Islands in the eastern portion of their breeding range. We compared data from seven microsatellite DNA loci and 143 base pairs of the control region of mitochondrial DNA from the two populations of Aleutian Canada Geese and another small-bodied subspecies, the Cackling Canada Goose (B. c. minima) which nests in western Alaska. The widely separated island-nesting Aleutian geese were genetically more closely related to each other than to mainland-nesting small-bodied geese. The populations of Aleutian geese were genetically differentiated from one another in terms of mitochondrial DNA haplotype and microsatellite allele frequencies, suggesting limited contemporary gene flow and/or major shifts in gene frequency through genetic drift. The degree of population genetic differentiation suggests that Aleutian Canada Goose populations could be considered separate management units. There was some evidence of population bottlenecks, although we found no significant genetic evidence of non-random mating or inbreeding.

Comparative population structure of cavity-nesting sea ducks

ABSTRACT A growing collection of mtDNA genetic information from waterfowl species across North America suggests that larger-bodied cavity-nesting species exhibit greater levels of population differentiation than smaller-bodied congeners. Although little is known about nest-cavity availability for these species, one hypothesis to explain differences in population structure is reduced dispersal tendency of larger-bodied cavity-nesting species due to limited abundance of large cavities. To investigate this hypothesis, we examined population structure of three cavity-nesting waterfowl species distributed across much of North America: Barrows Goldeneye (Bucephala islandica), Common Goldeneye (B. clangula), and Bufflehead (B. albeola). We compared patterns of population structure using both variation in mtDNA control-region sequences and band-recovery data for the same species and geographic regions. Results were highly congruent between data types, showing structured population patterns for Barrows and Common Goldeneye but not for Bufflehead. Consistent with our prediction, the smallest cavity-nesting species, the Bufflehead, exhibited the lowest level of population differentiation due to increased dispersal and gene flow. Results provide evidence for discrete Old and New World populations of Common Goldeneye and for differentiation of regional groups of both goldeneye species in Alaska, the Pacific Northwest, and the eastern coast of North America. Results presented here will aid management objectives that require an understanding of population delineation and migratory connectivity between breeding and wintering areas. Comparative studies such as this one highlight factors that may drive patterns of genetic diversity and population trends.

Intraspecific evolutionary relationships among peregrine falcons in western North American high latitudes

Subspecies relationships within the peregrine falcon (Falco peregrinus) have been long debated because of the polytypic nature of melanin-based plumage characteristics used in subspecies designations and potential differentiation of local subpopulations due to philopatry. In North America, understanding the evolutionary relationships among subspecies may have been further complicated by the introduction of captive bred peregrines originating from non-native stock, as part of recovery efforts associated with mid 20th century population declines resulting from organochloride pollution. Alaska hosts all three nominal subspecies of North American peregrine falcons–F. p. tundrius, anatum, and pealei–for which distributions in Alaska are broadly associated with nesting locales within Arctic, boreal, and south coastal maritime habitats, respectively. Unlike elsewhere, populations of peregrine falcon in Alaska were not augmented by captive-bred birds during the late 20th century recovery efforts. Population genetic differentiation analyses of peregrine populations in Alaska, based on sequence data from the mitochondrial DNA control region and fragment data from microsatellite loci, failed to uncover genetic distinction between populations of peregrines occupying Arctic and boreal Alaskan locales. However, the maritime subspecies, pealei, was genetically differentiated from Arctic and boreal populations, and substructured into eastern and western populations. Levels of interpopulational gene flow between anatum and tundrius were generally higher than between pealei and either anatum or tundrius. Estimates based on both marker types revealed gene flow between augmented Canadian populations and unaugmented Alaskan populations. While we make no attempt at formal taxonomic revision, our data suggest that peregrine falcons occupying habitats in Alaska and the North Pacific coast of North America belong to two distinct regional groupings–a coastal grouping (pealei) and a boreal/Arctic grouping (currently anatum and tundrius)–each comprised of discrete populations that are variously intra-regionally connected.

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.

Phylogeography, Postglacial Gene Flow, and Population History of North American Northern Goshawks (Accipiter gentilis)

ABSTRACT. Climate cycling during the Quaternary played a critical role in the diversification of avian lineages in North America, greatly influencing the genetic characteristics of contemporary populations. To test the hypothesis that North American Northern Goshawks (Accipitergentilis) were historically isolated within multiple Late Pleistocene refugia, we assessed diversity and population genetic structure as well as migration rates and signatures of historical demography using mitochondrial control-region data. On the basis of sampling from 24 locales, we found that Northern Goshawks were genetically structured across a large portion of their North American range. Long-term population stability, combined with strong genetic differentiation, suggests that Northern Goshawks were historically isolated within at least three refugial populations representing two regions: the Pacific (CascadesSierra-Vancouver Island) and the Southwest (Colorado Plateau and Jemez Mountains). By contrast, populations experiencing significant growth were located in the Southeast Alaska-British Columbia, Arizona Sky Islands, Rocky Mountains, Great Lakes, and Appalachian bioregions. In the case of Southeast Alaska-British Columbia, Arizona Sky Islands, and Rocky Mountains, Northern Goshawks likely colonized these regions from surrounding refugia. The near fixation for several endemic haplotypes in the Arizona Sky Island Northern Goshawks (A. g apache) suggests long-term isolation subsequent to colonization. Likewise, Great Lakes and Appalachian Northern Goshawks differed significantly in haplotype frequencies from most Western Northern Goshawks, which suggests that they, too, experienced long-term isolation prior to a more recent recolonization of eastern U.S. forests.