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Bridgette E Hagerty - One of the best experts on this subject based on the ideXlab platform.
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translocation relative to spatial genetic structure of the Mojave Desert tortoise gopherus agassizii
Chelonian Conservation and Biology, 2014Co-Authors: Roy C Averillmurray, Bridgette E HagertyAbstract:Abstract Mojave Desert tortoises (Gopherus agassizii) have been translocated for decades, and research-oriented translocations recently have been recommended as a tool to help recover this threatened species. However, avoiding negative genetic impacts from wildlife translocations has been widely cautioned. Populations of the Mojave Desert tortoise within a 200–276-km straight-line radius of each other (249–308 km measured around topographic barriers) tend to be genetically correlated and may be considered single genetic units for management purposes. When planning translocations among wild populations, releasing tortoises at recipient sites within a straight-line distance of 200 km from the source population would most conservatively maintain historic genetic population structure. However, the risk of causing outbreeding depression by inadvertently translocating Mojave Desert tortoises between more distant populations or those of unknown provenance is low.
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defining population structure for the Mojave Desert tortoise
Conservation Genetics, 2010Co-Authors: Bridgette E Hagerty, Richard C TracyAbstract:We used highly variable microsatellite markers to identify population structure, movement, and biological boundaries for populations of the Desert tortoise, Gopherus agassizii, in the Mojave and Colorado Deserts of the southwestern United States. The Mojave Desert tortoise (listed as “threatened” by the U.S. Fish and Wildlife Service) has a large geographic range, long generation time, low population densities, and little above-ground activity. Additionally, the dispersal patterns of individual tortoises are virtually unknown, making indirect methods to assess movement among populations valuable. Using Bayesian assignment tests, we detected hierarchical structuring within the Mojave Desert tortoise. Three basal groups were identified, and these corresponded to the mitochondrial DNA haplotypes reported in 1989. Additional population structure was evident within each basal unit, and this structure corresponds with major geographic barriers. Our analyses suggest that gene flow among populations was historically high because levels of population differentiation were low across the range. Geographic distance explained a large proportion of variation in genetic distance (68%), which pinpoints that dispersal is limited only on a regional scale. In light of these new analyses of the genetic population structure of the Mojave Desert tortoise, we make new recommendations for the number and locations of recovery units for conservation of this species.
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polymorphic microsatellite markers for the Mojave Desert tortoise gopherus agassizii
Molecular Ecology Resources, 2008Co-Authors: Bridgette E Hagerty, Veronica S. Kirchoff, Mary M Peacock, C R TracyAbstract:: We describe primers and polymerase chain reaction (PCR) conditions to amplify 14 tri- and tetranucleotide microsatellite loci for the Mojave Desert tortoise (Gopherus agassizii). Across three populations (87 individuals) located in the Mojave Desert, USA, the markers yielded a range of four to 33 alleles and an average observed heterozygosity of 0.733 (range 0.433 to 0.933). We neither detected linkage disequilibrium between any pair of loci nor did we find a consistent pattern of deviation from Hardy-Weinberg equilibrium. These microsatellites are designed for PCR multiplexing, and provide higher throughput capacity to aid in conservation genetics studies for this threatened species.
C R Tracy - One of the best experts on this subject based on the ideXlab platform.
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polymorphic microsatellite markers for the Mojave Desert tortoise gopherus agassizii
Molecular Ecology Resources, 2008Co-Authors: Bridgette E Hagerty, Veronica S. Kirchoff, Mary M Peacock, C R TracyAbstract:: We describe primers and polymerase chain reaction (PCR) conditions to amplify 14 tri- and tetranucleotide microsatellite loci for the Mojave Desert tortoise (Gopherus agassizii). Across three populations (87 individuals) located in the Mojave Desert, USA, the markers yielded a range of four to 33 alleles and an average observed heterozygosity of 0.733 (range 0.433 to 0.933). We neither detected linkage disequilibrium between any pair of loci nor did we find a consistent pattern of deviation from Hardy-Weinberg equilibrium. These microsatellites are designed for PCR multiplexing, and provide higher throughput capacity to aid in conservation genetics studies for this threatened species.
Christopher J. Travis - One of the best experts on this subject based on the ideXlab platform.
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Late Cenozoic strike-slip faulting in the Mojave Desert, California
Tectonics, 1990Co-Authors: Roy K. Dokka, Christopher J. TravisAbstract:Recent tectonic models for southern California treat the entire Mojave Desert Block as the site of distributed simple shear during late Cenozoic time. These models consider that much of the region is composed of a series of narrow blocks, bounded by active NW striking, right-slip faults that have facilitated the distortion and rotation of the region about vertical axes during translations. As much as 100 km of cumulative right slip is predicted for these faults by some of these models. These kinematic models require that the faults of the Mojave Desert Block merge with the Garlock fault, which is viewed as the intact northern boundary that served to accommodate the distortion of the Mojave Desert Block by simple shear. Map-scale structural relations are used to test explicit and implicit features of kinematic models proposed for the region. These relationships indicate that late Cenozoic NW striking, right-slip faults of the Mojave Desert Block possess the following characteristics: (1) the faults are discontinuous, with only the Calico-Blackwater fault spanning the entire Mojave Desert; (2) the faults terminate before reaching the Garlock fault; (3) faults south of an irregular line extending from near Barstow eastward to Ludlow and to Soda Lake are continuous and well developed and have a cumulative net slip of >40 km, whereas faults to the north are discontinuous and display
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late cenozoic strike slip faulting in the Mojave Desert california
Tectonics, 1990Co-Authors: Roy K. Dokka, Christopher J. TravisAbstract:Recent tectonic models for southern California treat the entire Mojave Desert Block as the site of distributed simple shear during late Cenozoic time. These models consider that much of the region is composed of a series of narrow blocks, bounded by active NW striking, right-slip faults that have facilitated the distortion and rotation of the region about vertical axes during translations. As much as 100 km of cumulative right slip is predicted for these faults by some of these models. These kinematic models require that the faults of the Mojave Desert Block merge with the Garlock fault, which is viewed as the intact northern boundary that served to accommodate the distortion of the Mojave Desert Block by simple shear. Map-scale structural relations are used to test explicit and implicit features of kinematic models proposed for the region. These relationships indicate that late Cenozoic NW striking, right-slip faults of the Mojave Desert Block possess the following characteristics: (1) the faults are discontinuous, with only the Calico-Blackwater fault spanning the entire Mojave Desert; (2) the faults terminate before reaching the Garlock fault; (3) faults south of an irregular line extending from near Barstow eastward to Ludlow and to Soda Lake are continuous and well developed and have a cumulative net slip of >40 km, whereas faults to the north are discontinuous and display <12 km of right slip; and (4) there is a northwestward decrease in net slip along most of the faults. A new kinematic model is proposed to reconcile these new observations with existing data. We assert that integrated strain within the province since middle Miocene time is not regionally homogeneous as predicted by simple shear models but is instead partitioned into six major domains. The domains probably have deformed and rotated about vertical axes independently of each other and are separated by zones of shortening or extension or by strike-slip faults. Strike-slip faults and folding have likely accommodated internal deformation and rotation of some of the domains. The model predicts that the Mojave Desert has been the site of ∼65 km of right shear since middle Miocene time. The broad network of faults of the Mojave Desert Block along with similar strike-slip faults of the Death Valley region constitute a regional zone of right shear, named here, the Eastern California shear zone. Because of its probable physical connection to the San Andreas fault system, the Eastern California shear zone may have accommodated a significant portion of Pacific-North American transform motion. The Eastern California shear zone accounts for 9–14% of the total shear, predicted from plate tectonic reconstructions, along the Pacific-North American transform boundary since ∼10.6 Ma. The kinematic connection of the normal faults of the Death Valley region, with the San Andreas fault system via the faults of the Mojave Desert accords with the deduction of Atwater (1970) that late Cenozoic extension in portions of the Basin and Range province is related to Pacific-North American transform shear. Finally, the present arcuate trace of the Garlock fault is ascribed to oroclinal folding within the broad zone of distributed shear of the Eastern California shear zone.
Richard C Tracy - One of the best experts on this subject based on the ideXlab platform.
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defining population structure for the Mojave Desert tortoise
Conservation Genetics, 2010Co-Authors: Bridgette E Hagerty, Richard C TracyAbstract:We used highly variable microsatellite markers to identify population structure, movement, and biological boundaries for populations of the Desert tortoise, Gopherus agassizii, in the Mojave and Colorado Deserts of the southwestern United States. The Mojave Desert tortoise (listed as “threatened” by the U.S. Fish and Wildlife Service) has a large geographic range, long generation time, low population densities, and little above-ground activity. Additionally, the dispersal patterns of individual tortoises are virtually unknown, making indirect methods to assess movement among populations valuable. Using Bayesian assignment tests, we detected hierarchical structuring within the Mojave Desert tortoise. Three basal groups were identified, and these corresponded to the mitochondrial DNA haplotypes reported in 1989. Additional population structure was evident within each basal unit, and this structure corresponds with major geographic barriers. Our analyses suggest that gene flow among populations was historically high because levels of population differentiation were low across the range. Geographic distance explained a large proportion of variation in genetic distance (68%), which pinpoints that dispersal is limited only on a regional scale. In light of these new analyses of the genetic population structure of the Mojave Desert tortoise, we make new recommendations for the number and locations of recovery units for conservation of this species.
Roy K. Dokka - One of the best experts on this subject based on the ideXlab platform.
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Late Cenozoic strike-slip faulting in the Mojave Desert, California
Tectonics, 1990Co-Authors: Roy K. Dokka, Christopher J. TravisAbstract:Recent tectonic models for southern California treat the entire Mojave Desert Block as the site of distributed simple shear during late Cenozoic time. These models consider that much of the region is composed of a series of narrow blocks, bounded by active NW striking, right-slip faults that have facilitated the distortion and rotation of the region about vertical axes during translations. As much as 100 km of cumulative right slip is predicted for these faults by some of these models. These kinematic models require that the faults of the Mojave Desert Block merge with the Garlock fault, which is viewed as the intact northern boundary that served to accommodate the distortion of the Mojave Desert Block by simple shear. Map-scale structural relations are used to test explicit and implicit features of kinematic models proposed for the region. These relationships indicate that late Cenozoic NW striking, right-slip faults of the Mojave Desert Block possess the following characteristics: (1) the faults are discontinuous, with only the Calico-Blackwater fault spanning the entire Mojave Desert; (2) the faults terminate before reaching the Garlock fault; (3) faults south of an irregular line extending from near Barstow eastward to Ludlow and to Soda Lake are continuous and well developed and have a cumulative net slip of >40 km, whereas faults to the north are discontinuous and display
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late cenozoic strike slip faulting in the Mojave Desert california
Tectonics, 1990Co-Authors: Roy K. Dokka, Christopher J. TravisAbstract:Recent tectonic models for southern California treat the entire Mojave Desert Block as the site of distributed simple shear during late Cenozoic time. These models consider that much of the region is composed of a series of narrow blocks, bounded by active NW striking, right-slip faults that have facilitated the distortion and rotation of the region about vertical axes during translations. As much as 100 km of cumulative right slip is predicted for these faults by some of these models. These kinematic models require that the faults of the Mojave Desert Block merge with the Garlock fault, which is viewed as the intact northern boundary that served to accommodate the distortion of the Mojave Desert Block by simple shear. Map-scale structural relations are used to test explicit and implicit features of kinematic models proposed for the region. These relationships indicate that late Cenozoic NW striking, right-slip faults of the Mojave Desert Block possess the following characteristics: (1) the faults are discontinuous, with only the Calico-Blackwater fault spanning the entire Mojave Desert; (2) the faults terminate before reaching the Garlock fault; (3) faults south of an irregular line extending from near Barstow eastward to Ludlow and to Soda Lake are continuous and well developed and have a cumulative net slip of >40 km, whereas faults to the north are discontinuous and display <12 km of right slip; and (4) there is a northwestward decrease in net slip along most of the faults. A new kinematic model is proposed to reconcile these new observations with existing data. We assert that integrated strain within the province since middle Miocene time is not regionally homogeneous as predicted by simple shear models but is instead partitioned into six major domains. The domains probably have deformed and rotated about vertical axes independently of each other and are separated by zones of shortening or extension or by strike-slip faults. Strike-slip faults and folding have likely accommodated internal deformation and rotation of some of the domains. The model predicts that the Mojave Desert has been the site of ∼65 km of right shear since middle Miocene time. The broad network of faults of the Mojave Desert Block along with similar strike-slip faults of the Death Valley region constitute a regional zone of right shear, named here, the Eastern California shear zone. Because of its probable physical connection to the San Andreas fault system, the Eastern California shear zone may have accommodated a significant portion of Pacific-North American transform motion. The Eastern California shear zone accounts for 9–14% of the total shear, predicted from plate tectonic reconstructions, along the Pacific-North American transform boundary since ∼10.6 Ma. The kinematic connection of the normal faults of the Death Valley region, with the San Andreas fault system via the faults of the Mojave Desert accords with the deduction of Atwater (1970) that late Cenozoic extension in portions of the Basin and Range province is related to Pacific-North American transform shear. Finally, the present arcuate trace of the Garlock fault is ascribed to oroclinal folding within the broad zone of distributed shear of the Eastern California shear zone.