Burg, Theresa

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https://opus.uleth.ca/handle/10133/4449

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Browsing Burg, Theresa by Subject "Black-capped chickadee"

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    Gene flow of a forest-dependent bird across a fragmented landscape
    (Public Library of Science, 2015) Adams, Rachael V.; Burg, Theresa M.
    Habitat loss and fragmentation can affect the persistence of populations by reducing connectivity and restricting the ability of individuals to disperse across landscapes. Dispersal corridors promote population connectivity and therefore play important roles in maintaining gene flow in natural populations inhabiting fragmented landscapes. In the prairies, forests are restricted to riparian areas along river systems which act as important dispersal corridors for forest dependent species across large expanses of unsuitable grassland habitat. However, natural and anthropogenic barriers within riparian systems have fragmented these forested habitats. In this study, we used microsatellite markers to assess the finescale genetic structure of a forest-dependent species, the black-capped chickadee (Poecile atricapillus), along 10 different river systems in Southern Alberta. Using a landscape genetic approach, landscape features (e.g., land cover) were found to have a significant effect on patterns of genetic differentiation. Populations are genetically structured as a result of natural breaks in continuous habitat at small spatial scales, but the artificial barriers we tested do not appear to restrict gene flow. Dispersal between rivers is impeded by grasslands, evident from isolation of nearby populations (~ 50 km apart), but also within river systems by large treeless canyons (>100 km). Significant population genetic differentiation within some rivers corresponded with zones of different cottonwood (riparian poplar) tree species and their hybrids. This study illustrates the importance of considering the impacts of habitat fragmentation at small spatial scales as well as other ecological processes to gain a better understanding of how organisms respond to their environmental connectivity. Here, even in a common and widespread songbird with high dispersal potential, small breaks in continuous habitats strongly influenced the spatial patterns of genetic variation.
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    Genetic evidence supports boreal chickadee (Poecile hudsonicus) x black-capped chickadee (Poecile atricapillus) hybridization in Atlantic Canada
    (Ottawa Field-Naturalists' Club, 2012) Lait, Linda Amy; Lauff, Randolph F.; Burg, Theresa M.
    Both morphological and genetic evidence support a hybridization event between a Boreal Chickadee (Poecile hudsonicus) and a Black-capped Chickadee (Poecile atricapillus) in Atlantic Canada. Plumage of the hybrid was intermediate to both parental species, with buffy sides and a dark brown cap on the head. Mitochondrial DNA control region showed the female lineage to be from a Boreal Chickadee, while Z-linked markers showed mixed Boreal Chickadee × Black-capped Chickadee heritage, likely representing an F1 hybrid. This is the first documented case of hybridization between these species in eastern North America, and it adds to the increasing evidence supporting intrageneric avian hybridization.
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    Influence of landscape features on the microgeographic genetic structure of a resident songbird
    (2016-08-08) Adams, Rachael V.; Lazerte, Stefanie E.; Burg, Theresa M.
    Variation in landscape features influence individual dispersal and as a result can affect both gene flow and genetic variation within and between populations. The landscape of British Columbia, Canada, is already highly heterogeneous due to natural ecological and geological transitions, but disturbance from human mediated processes has further fragmented continuous habitat, particularly in the central plateau region. In this study, we evaluated the effects of landscape heterogeneity on the genetic structure of a common resident songbird, the black-capped chickadee (Poecile atricapillus). Previous work revealed significant population structuring in British Columbia which could not be explained by physical barriers, so our aim was to assess the pattern of genetic structure at a microgeographic scale and determine the effect of different landscape features on genetic differentiation. A total of 399 individuals from 15 populations were genotyped for fourteen microsatellite loci revealing significant population structuring in this species. Individual and population based analyses revealed as many as nine genetic clusters with isolation in the north, the central plateau and the south. Moreover, a mixed modelling approach that accounted for non-independence of pairwise distance values revealed a significant effect of land cover and elevation resistance on genetic differentiation. These results suggest that barriers in the landscape influence dispersal which has led to the unexpectedly high levels of population isolation. Our study demonstrates theimportance of incorporating additional landscape features when interpreting patterns of population differentiation. Despite taking a microgeographic approach, our results have opened up additional questions concerning the processes influencing dispersal and gene flow at the local scale.
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    Pleistocene glacial cycles and physical barriers influence phylogeographic structure in Black-capped chickadees (Poecile atricapillus), a widespread North American passerine
    (Canadian Science Publishing, 2018) Hindley, J.; Graham, Brendan A.; Burg, Theresa M.
    The nonmigratory Black-capped Chickadee (Poecile atricapillus (Linnaeus, 1766)) has a continent-wide distribution extending across large parts of North America. To investigate the phylogeographic structure and verify possible refugia during the last glacial maximum, we sequenced a 678 bp region of the mitochondrial control region from 633 Black-capped Chickadees at 35 sites across North America and performed paleoecological distribution modeling. Two genetically distinct groups were found using multiple analyses: one in Newfoundland (Canada) and a widespread continental group, with additional substructure evident in western continental populations. While gene flow is low throughout the range, it is especially low in peripheral populations. The Newfoundland population has remained isolated from continental populations for at least 65 000 years and contains a number of fixed nucleotide differences. Within the continental populations, Black-capped Chickadees are subdivided into Pacific Coast, Alaska (USA), southeast Rockies, and main-northeast groups consistent with late Pleistocene vicariance events. Evidence of secondary contact was identified between Pacific and main-northeast populations in northwest British Columbia (Canada) and between southeast Rockies and main-northeast groups in Montana (USA). Paleoecological distribution modeling predicted suitable habitat in Alaska, off the coast of Newfoundland, and several locations across the southern United States during the last glacial maximum, whereas suitable habitat during the last interglacial was more similar to the contemporary distribution.