-
-
-
Bird Conservation International 01/2013; · 1.25 Impact Factor
-
[show abstract]
[hide abstract]
ABSTRACT: Spatial variation in the environment can lead to divergent selection between populations occupying different parts of a species' range, and ultimately lead to population divergence. The colonization of new areas can thus facilitate divergence in beneficial traits, yet with little differentiation at neutral genetic markers. We investigated genetic and phenotypic patterns of divergence between low- and high-altitude populations of cinnamon teal inhabiting normoxic and hypoxic regions in the Andes and adjacent lowlands of South America. Cinnamon teal showed strong divergence in body size (PC1; P(ST) = 0.56) and exhibited significant frequency differences in a single nonsynonymous α-hemoglobin amino acid polymorphism (Asn/Ser-α9; F(ST) = 0.60) between environmental extremes, despite considerable admixture of mtDNA and intron loci (F(ST) = 0.004-0.168). Inferences of strong population segregation were further supported by the observation of few mismatched individuals in either environmental extreme. Coalescent analyses indicated that the highlands were most likely colonized from lowland regions but following divergence, gene flow has been asymmetric from the highlands into the lowlands. Multiple selection pressures associated with high-altitude habitats, including cold and hypoxia, have likely shaped morphological and genetic divergence within South American cinnamon teal populations.
Evolution 01/2013; 67(1):170-84. · 5.15 Impact Factor
-
[show abstract]
[hide abstract]
ABSTRACT: Speciation is a process in which genetic drift and selection cause divergence over time. However, there is no rule dictating the time required for speciation, and even low levels of gene flow hinder divergence, so that taxa may be poised at the threshold of speciation for long periods of evolutionary time. We sequenced mitochondrial DNA (mtDNA) and eight nuclear introns (nuDNA) to estimate genomic levels of differentiation and gene flow between the Eurasian common teal (Anas crecca crecca) and the North American green-winged teal (Anas crecca carolinensis). These ducks come into contact in Beringia (north-eastern Asia and north-western North America) and have probably done so, perhaps cyclically, since the Pliocene-Pleistocene transition, ∼2.6 Ma, when they apparently began diverging. They have diagnosable differences in male plumage and are 6.9% divergent in the mtDNA control region, with only 1 of 58 crecca and 2 of 86 carolinensis having haplotypes grouping with the other. Two nuclear loci were likewise strongly structured between these teal (Φ(st) ≥ 0.35), but six loci were undifferentiated or only weakly structured (Φ(st) = 0.0-0.06). Gene flow between crecca and carolinensis was ∼1 individual per generation in both directions in mtDNA, but was asymmetrical in nuDNA, with ∼1 and ∼20 individuals per generation immigrating into crecca and carolinensis, respectively. This study illustrates that species delimitation using a single marker oversimplifies the complexity of the speciation process, and it suggests that even with divergent selection, moderate levels of gene flow may stall the speciation process short of completion.
Molecular Ecology 07/2012; 21(18):4563-4577. · 5.52 Impact Factor
-
[show abstract]
[hide abstract]
ABSTRACT: Inferring aspects of the population histories of species using coalescent analyses of non-coding nuclear DNA has grown in popularity. These inferences, such as divergence, gene flow, and changes in population size, assume that genetic data reflect simple population histories and neutral evolutionary processes. However, violating model assumptions can result in a poor fit between empirical data and the models. We sampled 22 nuclear intron sequences from at least 19 different chromosomes (a genomic transect) to test for deviations from selective neutrality in the gadwall (Anas strepera), a Holarctic duck. Nucleotide diversity among these loci varied by nearly two orders of magnitude (from 0.0004 to 0.029), and this heterogeneity could not be explained by differences in substitution rates alone. Using two different coalescent methods to infer models of population history and then simulating neutral genetic diversity under these models, we found that the observed among-locus heterogeneity in nucleotide diversity was significantly higher than expected for these simple models. Defining more complex models of population history demonstrated that a pre-divergence bottleneck was also unlikely to explain this heterogeneity. However, both selection and interspecific hybridization could account for the heterogeneity observed among loci. Regardless of the cause of the deviation, our results illustrate that violating key assumptions of coalescent models can mislead inferences of population history.
PLoS ONE 01/2012; 7(2):e31972. · 4.09 Impact Factor
-
[show abstract]
[hide abstract]
ABSTRACT: Utilizamos plumas de individuos adultos de la especie Falco rusticolus que habian sido mudadas en territorios de cría y muestras de sangre de pichones para documentar la fidelidad a los sitios de anidación y la dispersión de adultos reproductores y aves jóvenes en tres áreas separadas por 100–350 km en el Yukon Delta National Wildlife Refuge, Alaska, entre 2003 y 2007. Empleamos los genotipos de siete loci microsatélites polimórficos, que brindaron una probabilidad media de identidad de 0.91 × 10-5. Los individuos reproductores fueron altamente fieles a las áreas de estudio y a sus territorios. No documentamos movimientos entre areas de estudio y sóolo registramos un evento de dispersión entre territorios. Sin embargo, la fidelidad a los sitios de anidación fue baja. El 22% de las aves regresó al mismo sitio de anidación al año siguiente. La distancia promedio entre nidos alternos dentro de un territorio fue de 750 m y fue similar para ambos sexos. El tiempo medio de permanencia en un territorio fue de 2.8 años, fue similar entre sexos y se distribuyó bimodalmente, con picos en 1 y 4 años. La tasa media de recambio anual en el área de estudio de las colinas Ingakslugwat (volcanes) fue 20%. Detectamos tres aves jóvenes que establecieron territorios a distancias de 0 a 254 km de su territorio natal, lo que representa un reclutamiento aparente del 2.5%. Los individuos del area de estudio de las montañas Askinuk eran ligeramente pero significativamente diferentes genéticamente de aquellos de las áreas de estudio de los volcanes y de la montaña Kilbuck. Estos son los primeras datos publicados sobre la fidelidad a los sitios de anidación y sobre la dispersión de F. rusticolus en América del Norte. Además, demuestran la utilidad de los muestreos genéticos no invasivos para aumentar de forma considerable nuestro conocimiento sobre la dispersión de las aves y sus mecanismos subyacentes.
The Condor 12/2011; · 1.12 Impact Factor
-
[show abstract]
[hide abstract]
ABSTRACT: Hypoxia is a key factor determining survival, and haemoglobins are targets of selection in species native to high-altitude regions. We studied population genetic structure and evaluated evidence for local adaptation in the crested duck (Lophonetta specularioides). Differentiation, gene flow and time since divergence between highland and lowland populations were assessed for three haemoglobin genes (α(A) , α(D) , β(A) ) and compared to seven reference loci (six autosomal introns and mtDNA). Four derived amino acid replacements were found in the globin genes that had elevated Φ(ST) values between the Andean highlands and Patagonian lowlands. A single β(A) -globin polymorphism at a site known to influence O(2) affinity was fixed for different alleles in the two populations, whereas three α(A) - and α(D) -globin polymorphisms exhibited high heterozygosity in the highlands but not in the lowlands. Coalescent analyses supported restricted gene flow for haemoglobin alleles and mitochondrial DNA but nonzero gene flow for the introns. Simulating genetic data under a drift-migration model of selective neutrality, the β(A) -globin fell outside the 95% confidence limit of simulated data, suggesting that directional selection is maintaining different variants in the contrasting elevational environments, thereby restricting migration of β(A) -globin alleles. The α(A) - and α(D) -globins, by contrast, did not differ from the simulated values, suggesting that variants in these genes are either selectively neutral, or that the effects of selection could not be differentiated from background levels of population structure and linkage disequilibrium. This study illustrates the combined effects of selection and population history on inferring levels of population divergence for a species distributed across an altitudinal gradient in which selection for hypoxia resistance has likely played an important role.
Molecular Ecology 12/2011; 21(2):350-68. · 5.52 Impact Factor
-
[show abstract]
[hide abstract]
ABSTRACT: Aim Glacial refugia during the Pleistocene had major impacts on the levels and spatial apportionment of genetic diversity of species in northern latitude ecosystems. We characterized patterns of population subdivision, and tested hypotheses associated with locations of potential Pleistocene refugia and the relative contribution of these refugia to the post-glacial colonization of North America and Scandinavia by common eiders (Somateria mollissima). Specifically, we evaluated localities hypothesized as ice-free areas or glacial refugia for other Arctic vertebrates, including Beringia, the High Arctic Canadian Archipelago, Newfoundland Bank, Spitsbergen Bank and north-west Norway.Location Alaska, Canada, Norway and Sweden.Methods Molecular data from 12 microsatellite loci, the mitochondrial DNA (mtDNA) control region, and two nuclear introns were collected and analysed for 15 populations of common eiders (n = 716) breeding throughout North America and Scandinavia. Population genetic structure, historical population fluctuations and gene flow were inferred using F-statistics, analyses of molecular variance, and multilocus coalescent analyses.Results Significant inter-population variation in allelic and haplotypic frequencies were observed (nuclear DNA FST = 0.004–0.290; mtDNA ΦST = 0.051–0.927). Whereas spatial differentiation in nuclear genes was concordant with subspecific designations, geographic proximity was more predictive of inter-population variance in mitochondrial DNA haplotype frequency. Inferences of historical population demography were consistent with restriction of common eiders to four geographic areas during the Last Glacial Maximum: Belcher Islands, Newfoundland Bank, northern Alaska and Svalbard. Three of these areas coincide with previously identified glacial refugia: Newfoundland Bank, Beringia and Spitsbergen Bank. Gene-flow and clustering analyses indicated that the Beringian refugium contributed little to common eider post-glacial colonization of North America, whereas Canadian, Scandinavian and southern Alaskan post-glacial colonization is likely to have occurred in a stepwise fashion from the same glacial refugium.Main conclusions Concordance of proposed glacial refugia used by common eiders and other Arctic species indicates that Arctic and subarctic refugia were important reservoirs of genetic diversity during the Pleistocene. Furthermore, suture zones identified at MacKenzie River, western Alaska/Aleutians and Scandinavia coincide with those identified for other Arctic vertebrates, suggesting that these regions were strong geographic barriers limiting dispersal from Pleistocene refugia.
Journal of Biogeography 06/2011; 38(7):1368 - 1380. · 4.54 Impact Factor
-
[show abstract]
[hide abstract]
ABSTRACT: Interspecific hybridization is common in plants and animals, particularly in waterfowl (Anatidae). One factor shown to contribute to hybridization is restricted mate choice, which can occur when two species occur in sympatry but one is rare. The Hubbs principle, or "desperation hypothesis," states that under such circumstances the rarer species is more likely to mate with heterospecifics. Here we report interspecific hybridization between two waterfowl species that coexist in broad sympatry and mixed flocks throughout southern South America. Speckled teal (Anas flavirostris) and yellow-billed pintails (Anas georgica) are abundant in continental South America, but in the Falkland Islands speckled teal outnumber yellow-billed pintails approximately ten to one. Using eight genetic loci (mtDNA and 7 nuclear introns) coupled with Bayesian assignment tests and relatedness analysis, we identified a speckled teal x yellow-billed pintail F(1) hybrid female and her duckling sired by a male speckled teal. Although our sample in the Falkland Islands was small, we failed to identify unequivocal evidence of hybridization or introgression in a much larger sample from Argentina using a three-population "isolation with migration" coalescent analysis. While additional data are needed to determine if this event in the Falkland Islands was a rare singular occurrence, our results provide further support for the "desperation hypothesis," which states that scarcity in one population and abundance of another will often lead to hybridization.
PLoS ONE 01/2011; 6(8):e23173. · 4.09 Impact Factor
-
[show abstract]
[hide abstract]
ABSTRACT: Two species of waterfowl living at high altitude provide a prominent example of parallel adaptation at the molecular level. The bar-headed goose (Anser indicus) breeds at high elevations in central Asia and migrates across the Himalayas, where the partial pressure of oxygen (O(2)) is one-third of sea level. In South America, the distantly related Andean goose (Chloephaga melanoptera) is endemic to the high Andes. Both species exhibit increased blood-O(2) affinity, which has been attributed to the effects of single amino acid substitutions in the major hemoglobin. Here we present phylogenetic analyses of the swans and geese (Anserinae) and South American sheldgeese (Anatinae) using the three genes that encode the major (HbA) and minor (HbD) hemoglobin isoforms. We sought to determine whether two amino acid substitutions that have been the focus of extensive biochemical analysis (Ala-alpha(A)119 and Ser-beta(A)55) are uniquely derived in bar-headed goose and Andean goose, respectively, and to examine evidence of molecular adaptation at other positions in hemoglobin genes by comparing these two high-altitude taxa to their closest relatives. Bayesian analysis of the alpha(A)-, alpha(D)-, and beta(A)-subunit genes produced well-resolved phylogenies, with high posterior probabilities and bootstrap values for most genera. The bar-headed goose is likely sister to all other Anser species. Andean goose, the sole highland representative of the South American sheldgeese is either sister to the other Chloephaga species or sister to Neochen. In the bar-headed goose, four derived substitutions were observed in HbA (alpha(A)12, 18, 63, 119) and two in HbD (alpha(D)2, 47). Four derived substitutions in Andean goose include three in HbA (alpha(A)8, 77; beta(A)86) and two in HbD (alpha(D)9; beta(A)86). Considering both highland species, four substitutions (Ala-alpha(A)8, Ala-alpha(A)12, Ser-alpha(A)18, Leu-alpha(D)9) were located at adjacent positions on the A helix (or AB corner) of the alpha-chains, three others (Thr-alpha(A)77, Ser-beta(A)86, Ser-alpha(D)2) were in close proximity to inositolpentaphosphate (IP(5)) binding sites, and Ala-alpha(A)119 occurred at an alphabeta intersubunit contact. Ser-beta(A)55, which is involved in the same alphabeta intersubunit contact and was previously shown to increase Hb-O(2) affinity, is not unique to Andean goose, but is a synapomorphy of the South American sheldgeese, a clade of predominantly lowland waterfowl. Our findings illustrate the importance of understanding phylogenetic relationships and polarity of character-state changes when making inferences about adaptive evolution.
Molecular Phylogenetics and Evolution 08/2010; 56(2):649-58. · 3.61 Impact Factor
-
[show abstract]
[hide abstract]
ABSTRACT: We studied the phylogenetic relationships of four duck genera endemic to South America: Brazilian teal Amazonetta brasiliensis, spectacled duck Speculanas specularis, crested duck Lophonetta specularioides, and four species of steamer ducks Tachyerespatachonicus, T. leucocephalus, T. pteneres, T. brachypterus. Genetic divergence within and among species was compared using population-level sampling of the mitochondrial DNA (mtDNA) control region, supplemented with three additional mtDNA genes and six independent nuclear loci from one individual of each species and a variety of outgroup taxa. The monophyly of these four morphologically divergent South American genera was strongly supported. Within this clade, Amazonetta and Speculanas were supported as sister species in all analyses, but different gene regions yielded conflicting or ambiguous results for Lophonetta and Tachyeres. This lack of resolution resulted from little informative variation in nuclear loci and high levels of homoplasy in the mtDNA control region. Control region sequences from the four Tachyeres species fell into two distinct clades. In one clade, T. patachonicus and T. leucocephalus share a set of closely related haplotypes (≤0.6% sequence divergence); while no identical haplotypes were shared between species, the control region phylogeny was insufficiently resolved to either support or reject reciprocal monophyly. The second clade, ~1.7% divergent from the first, comprised haplotypes of the Falkland Islands species T. brachypterus and a captive individual of T. pteneres. These distinctive South American ducks likely experienced two bouts of rapid diversification, thus making analysis of their phylogenetic relationships difficult. Incomplete lineage sorting, founder effects, and perhaps introgression likely have contributed to obscuring the relationships among steamer ducks.
Journal of Avian Biology 02/2010; 41(2):186 - 199. · 2.28 Impact Factor
-
[show abstract]
[hide abstract]
ABSTRACT: We investigated local genetic associations among female Pacific common eiders (Somateria mollissima v-nigrum) nesting in a stochastic Arctic environment within two groups of barrier islands (Simpson Lagoon and Mikkelsen Bay) in the Beaufort Sea, Alaska. Nonrandom genetic associations were observed among nesting females using regional spatial autocorrelation analyses for distance classes up to 1000 m in Simpson Lagoon. Nearest-neighbour analyses identified clusters of genetically related females with positive lr values observed for 0-13% and 0-7% of the comparisons in Simpson Lagoon and Mikkelsen Bay, respectively, across years. These results indicate that a proportion of females are nesting in close proximity to more genetically related individuals, albeit at low frequency. Such kin groupings may form through active association between relatives or through natal philopatry and breeding site fidelity. Eiders nest in close association with driftwood, which is redistributed annually by seasonal storms. Yet, genetic associations were still observed. Microgeographic structure may thus be more attributable to kin association than natal philopatry and site fidelity. However, habitat availability may also influence the level of structure observed. Regional structure was present only within Simpson Lagoon and this island group includes at least three islands with sufficient driftwood for colonies, whereas only one island at Mikkelsen Bay has these features. A long-term demographic study is needed to understand more fully the mechanisms that lead to fine-scale genetic structure observed in common eiders breeding in the Beaufort Sea.
Molecular Ecology 02/2010; 19(4):647-57. · 5.52 Impact Factor
-
Kevin G McCracken,
Christopher P Barger,
Mariana Bulgarella,
Kevin P Johnson,
Mary K Kuhner,
Andrew V Moore,
Jeffrey L Peters,
Jorge Trucco,
Thomas H Valqui,
Kevin Winker,
Robert E Wilson
[show abstract]
[hide abstract]
ABSTRACT: Hypoxia is one of the most important factors affecting survival at high altitude, and the major hemoglobin protein is a likely target of selection. We compared population genetic structure in the alphaA and betaA hemoglobin subunits (HBA2 and HBB) of five paired lowland and highland populations of Andean dabbling ducks to unlinked reference loci. In the hemoglobin genes, parallel amino acid replacements were overrepresented in highland lineages, and one to five derived substitutions occurred at external solvent-accessible positions on the alpha and beta subunits, at alpha(1)beta(1) intersubunit contacts, or in close proximity to inositolpentaphosphate (IPP) binding sites. Coalescent analyses incorporating the stochasticity of drift and mutation indicated that hemoglobin alleles were less likely to be transferred between highland and lowland populations than unlinked alleles at five other loci. Amino acid replacements that were overrepresented in the highlands were rarely found within lowland populations, suggesting that alleles segregating at high frequency in the highlands may be maladaptive in the lowlands and vice versa. Most highland populations are probably nonmigratory and locally adapted to the Altiplano, but gene flow for several species may be sufficiently high to retard divergence at unlinked loci. Heterozygosity was elevated in the alphaA or betaA subunits of highland populations exhibiting high gene flow between the southern lowlands and the highlands and in highland species that disperse seasonally downslope to midelevation environments from the central Andean plateau. However, elevated heterozygosity occurred more frequently in the alphaA subunit but not simultaneously in both subunits, suggesting that selection may be more constrained by epistasis in the betaA subunit. Concordant patterns among multiple species with different evolutionary histories and depths of historical divergence and gene flow suggest that the major hemoglobin genes of these five dabbling duck species have evolved adaptively in response to high-altitude hypoxia in the Andes.
The American Naturalist 11/2009; 174(5):631-50. · 4.72 Impact Factor
-
[show abstract]
[hide abstract]
ABSTRACT: Population genetic variation in Mallards (Anas platyrhynchos; n = 152) from Western Russia, North Asia, the Aleutian Islands, and mainland Alaska was investigated using 667 base pairs of the 5′-end of the mitochondrial DNA (mtDNA) control region. DNA sequencing revealed two clades that correspond to Avise et al.’s (1990) group A and B mtDNA haplotypes. Group A haplotypes (80.3%) were wide- spread in all localities from Western Russia to Alaska. Group B haplotypes (19.7%), by contrast, were found primarily in mainland Alaska, where they occurred at high frequency (77.4%), but they also occurred at low frequencies (declining east to west) in the Aleutian Islands (11.8%) and the Primorye region of North Asia (4.4%). Group B haplotypes were not observed in Western Russia or elsewhere in North Asia outside Primorye. Consequently, Mallards exhibited substantial genetic structure between Old World and New World (ΦST = 0.4112–0.4956) but possessed little genetic structure within the Old World continental area (ΦST = 0.0018). Nonetheless, when only group A haplotypes were included in the analysis, Mallards from the Aleutian Islands differed (albeit with low levels of divergence) from each of the other three sampled regions in the Old World and New World (ΦST = 0.0728–0.1461, P < 0.05). Mallards inhabit the Aleutian Islands year-round, so these insular populations may be isolated from Asian and North American populations that occur in the Aleutian Islands only during migration. Overall weak phylogeographic structure and low genetic differentiation within Asia, and between Asia and North America when only group A haplotypes were evaluated, is probably explained by large long-term population sizes and significant intra-continental dispersal. The coexistence and nonrandom distribution of two divergent mtDNA haplotype lineages in Alaska, the Aleutian Islands, and the Primorye region of North Asia, but not in Western Russia or elsewhere in North Asia, is consistent with historical and contemporary hybridization and incomplete sorting of A and B mtDNA haplotype lineages in Mallards and closely related species inhabiting the Old World and New World.
The Auk 01/2009; · 2.16 Impact Factor
-
[show abstract]
[hide abstract]
ABSTRACT: The Eastern Spot-billed Duck (Anas zonorhyncha) historically was rare in the southern Russian Far East. However, during the last 60–70 years, its breeding range in East Asia has expanded northwest; Eastern Spot-billed Ducks are breeding increasingly within the range of Mallards (A. platyrhynchos). We collected 120 Eastern Spot-billed Ducks and Mallards from Primorye, Russia, and sequenced 666–667 base pairs (bp) of the maternally inherited mitochondrial DNA (mtDNA) control region and 255 bp of the ornithine decarboxylase intron six (ODC6). Control region and ODC-6 allele sequences revealed two divergent groups of haplotypes and alleles that differ by 1.5% and 2.0%, respectively, and correspond to Avise et al.'s (1990) group A and B mtDNA haplotypes. Group A mtDNA haplotypes occurred in 22 Eastern Spot-billed Ducks and 78 Asian Mallards, and group B haplotypes occurred in 14 Eastern Spot-billed Ducks and 4 Asian Mallards. Moreover, the group B haplotypes that we observed predominantly in Eastern Spot-billed Ducks (i.e. group SB) were monophyletic and diverged by 2–16 substitutions from group B haplotypes previously sequenced from 241 Mottled (A. fulvigula), American Black (A. rubripes), and Mexican ducks (A. diazi), and from North American Mallards. In contrast, type 1 and 2 ODC-6 allele frequencies for Eastern Spot-billed Ducks and Mallards did not differ, but heterozygosity for the former was greater than expected under Hardy-Weinberg equilibrium. Our analysis is the first to document the existence of two divergent haplotype and allele lineages (group A and B, type 1 and 2) in Asian mallard species and suggests that Eastern Spot-billed Ducks are more closely related to North America's Mottled, American Black, and Mexican ducks than they are to Mallards, which occur sympatrically in East Asia. Our data are consistent with the hypothesis that Eastern Spot-billed Ducks and Mallards have hybridized extensively in the Russian Far East. If so, apparent differences in group A and B mtDNA haplotype ratios, effective populations sizes, and migration rates indicate that many more male Eastern Spot-billed Ducks mated with female Mallards and more Eastern Spot-billed Ducks received ODC-6 alleles from Mallards than vice versa. We hypothesize that those differences reflect strong female natal-site fidelity and high levels of male dispersal, and that Mallards significantly outnumber Eastern Spotbilled Ducks in Primorye. Excess heterozygosity in Eastern Spot-billed Ducks (and in Mallards to a lesser extent) is probably maintained by ongoing emigration of Eastern Spot-billed Ducks and Mallards from areas of allopatry outside the Primorye region, where Eastern Spot-billed Ducks and Mallards are predicted to possesses genotypic frequencies historically diagnostic of each species.
The Auk 01/2009; · 2.16 Impact Factor
-
[show abstract]
[hide abstract]
ABSTRACT: When populations become locally adapted to contrasting environments, alleles that have high fitness in only one environment may be quickly eliminated in populations adapted to other environments, such that gene flow is partly restricted. The stronger the selection, the more rapidly immigrant alleles of lower fitness will be eliminated from the population. However, gene flow may continue to occur at unlinked loci, and adaptive divergence can proceed in the face of countervailing gene flow if selection is strong relative to migration (s > m). We studied the population genetics of the major hemoglobin genes in yellow-billed pintails (Anas georgica) experiencing contrasting partial pressures of oxygen in the Andes of South America. High gene flow and weak population subdivision were evident at seven putatively neutral loci in different chromosomal linkage groups. In contrast, amino acid replacements (Ser-beta13, Ser-beta116, and Met-beta133) in the betaA hemoglobin subunit segregated by elevation between lowland and highland populations with significantly elevated F(ST). Migration rates for the betaA subunit alleles were approximately 17-24 times smaller than for five unlinked reference loci, the alphaA hemoglobin subunit (which lacks amino acid replacements) and the mitochondrial DNA control region. The betaA subunit alleles of yellow-billed pintails were half as likely to be transferred downslope, from the highlands to the lowlands, than in the opposite direction upslope. We hypothesize that migration between the lowlands and highlands is restricted by local adaptation, and the betaA hemoglobin subunit is a likely target of selection related to high-altitude hypoxia; however, gene flow may be sufficiently high to retard divergence at most unlinked loci. Individuals homozygous for lowland alleles may have relatively little difficulty dispersing to the highlands initially but may experience long-term fitness reduction. Individuals homozygous for highland genotypes, in contrast, would be predicted to have difficulty dispersing to the lowlands if their hemoglobin alleles confer high oxygen affinity, predicted to result in chronic erythrocytosis at low elevation. Heterozygous individuals may have a dispersal advantage if their hemoglobin has a wider range of function due to the presence of multiple protein isoforms with a mixture of different oxygen affinities.
Molecular Biology and Evolution 01/2009; 26(4):815-27. · 5.55 Impact Factor
-
[show abstract]
[hide abstract]
ABSTRACT: Moose (Alces alces) are highly mobile mammals that occur across arboreal regions of North America, Europe, and Asia. Alaskan moose (Alces alces gigas) range across much of Alaska and are primary herbivore consumers, exerting a prominent influence on ecosystem structure and functioning. Increased knowledge gained from population genetics provides insights into their population dynamics, history, and dispersal of these unique large herbivores and can aid in conservation efforts. We examined the genetic diversity and population structure of moose (n = 141) with 8 polymorphic microsatellites from 6 regions spanning much of Alaska. Expected heterozygosity was moderate (H(E) = 0.483-0.612), and private alleles ranged from 0 to 6. Both F(ST) and R(ST) indicated significant population structure (P < 0.001) with F(ST) < 0.109 and R(ST) < 0.125. Results of analyses from STRUCTURE indicated 2 prominent population groups, a mix of moose from the Yakutat and Tetlin regions versus all other moose, with slight substructure observed among the second population. Estimates of dispersal differed between analytical approaches, indicating a high level of historical or current gene flow. Mantel tests indicated that isolation-by-distance partially explained observed structure among moose populations (R(2) = 0.45, P < 0.01). Finally, there was no evidence of bottlenecks either at the population level or overall. We conclude that weak population structure occurs among moose in Alaska with population expansion from interior Alaska westward toward the coast.
The Journal of heredity 10/2008; 100(2):170-80. · 2.05 Impact Factor
-
Kevin Winker, Kevin G McCracken,
Daniel D Gibson,
Christin L Pruett,
Rose Meier,
Falk Huettmann,
Michael Wege,
Irina V Kulikova,
Yuri N Zhuravlev,
Michael L Perdue,
Erica Spackman,
David L Suarez,
David E Swayne
[show abstract]
[hide abstract]
ABSTRACT: Asian-origin avian influenza (AI) viruses are spread in part by migratory birds. In Alaska, diverse avian hosts from Asia and the Americas overlap in a region of intercontinental avifaunal mixing. This region is hypothesized to be a zone of Asia-to-America virus transfer because birds there can mingle in waters contaminated by wild-bird-origin AI viruses. Our 7 years of AI virus surveillance among waterfowl and shorebirds in this region (1998-2004; 8,254 samples) showed remarkably low infection rates (0.06%). Our findings suggest an Arctic effect on viral ecology, caused perhaps by low ecosystem productivity and low host densities relative to available water. Combined with a synthesis of avian diversity and abundance, intercontinental host movements, and genetic analyses, our results suggest that the risk and probably the frequency of intercontinental virus transfer in this region are relatively low.
Emerging infectious diseases 05/2007; 13(4):547-52. · 6.17 Impact Factor
-
[show abstract]
[hide abstract]
ABSTRACT: Apart from an outbreak in commercial poultry in Chile in 2002, there have been few reports of avian influenza in South America. However, surveillance in free-flying birds has been limited. An avian influenza virus was isolated from a Cinnamon Teal (Anas cyanoptera) in Bolivia in 2001 from samples collected for an avian influenza virus and avian paramyxovirus surveillance study. This isolate was determined to be an H7N3 virus by gene sequencing. Analysis of all eight genes revealed that five genes were most closely related to the H7N3 in Chile in 2002. Two genes were most closely related to North American wild aquatic bird virus lineages and one gene was most closely related to an equine influenza virus from South America.
Avian Diseases 04/2007; 51(1 Suppl):273-4. · 1.46 Impact Factor
