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Jonathan J. M. Calede - One of the best experts on this subject based on the ideXlab platform.
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geometric morphometric analyses of worn cheek teeth help identify extant and extinct Gophers rodentia geomyidae
Palaeontology, 2017Co-Authors: Jonathan J. M. Calede, Jennifer W GlusmanAbstract:Studies of the biostratigraphy and palaeoecology of fossil vertebrate assemblages require large samples of accurately identified specimens. Such analyses can be hampered by the inability to assign isolated and worn remains to specific taxa. Entoptychine Gophers are a diverse group of burrowing rodents found in Oligo-Miocene deposits of the western United States. In both entoptychines and their extant relatives the geomyines, diagnostic characters of the occlusal surface of the teeth are modified with wear, making difficult the identification of many isolated fossil teeth. We use geometric morphometrics to test the hypothesis that tooth shape informs taxonomic affinities and expected levels of morphological variation across Gopher taxa. We also incorporate data from microcomputer tomography to investigate changes in occlusal surface shape through wear within individuals. Our analyses demonstrate the usefulness of our approach in identifying extant geomyines to the genus, subgenus and species levels, and fossil entoptychines to the genus and, in some cases, the species level. Our results cast doubt on the validity of some species within Entoptychus and suggest future revisions to entoptychine taxonomy. The amounts of morphological divergence observed among fossil and extant genera are similar. Fossil species do not differ greatly from extant ones in that regard either. Further work evaluating the morphological variation within and across entoptychine species, including unworn teeth and osteological material, will allow revised analyses of the biostratigraphy and palaeoecology of important Oligo-Miocene mammalian assemblages of the western United States and help to infer the phylogenetic relationships and evolution of Gophers.
James L Patton - One of the best experts on this subject based on the ideXlab platform.
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morphological adaptations for digging and climate impacted soil properties define pocket Gopher thomomys spp distributions
PLOS ONE, 2013Co-Authors: Ariel E Marcy, Scott Fendorf, James L Patton, Elizabeth A HadlyAbstract:Species ranges are mediated by physiology, environmental factors, and competition with other organisms. The allopatric distribution of five species of northern Californian pocket Gophers (Thomomys spp.) is hypothesized to result from competitive exclusion. The five species in this environmentally heterogeneous region separate into two subgenera, Thomomys or Megascapheus, which have divergent digging styles. While all pocket Gophers dig with their claws, the tooth-digging adaptations of subgenus Megascapheus allow access to harder soils and climate-protected depths. In a Northern Californian locality, replacement of subgenus Thomomys with subgenus Megascapheus occurred gradually during the Pleistocene-Holocene transition. Concurrent climate change over this transition suggests that environmental factors – in addition to soil – define pocket Gopher distributional limits. Here we show 1) that all pocket Gophers occupy the subset of less energetically costly soils and 2) that subgenera sort by percent soil clay, bulk density, and shrink-swell capacity (a mineralogical attribute). While clay and bulk density (without major perturbations) stay constant over decades to millennia, low precipitation and high temperatures can cause shrink-swell clays to crack and harden within days. The strong yet underappreciated interaction between soil and moisture on the distribution of vertebrates is rarely considered when projecting species responses to climatic change. Furthermore, increased precipitation alters the weathering processes that create shrink-swell minerals. Two projected outcomes of ongoing climate change—higher temperatures and precipitation—will dramatically impact hardness of soil with shrink-swell minerals. Current climate models do not include factors controlling soil hardness, despite its impact on all organisms that depend on a stable soil structure.
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geographic genetic architecture of pocket Gopher thomomys bottae populations in baja california mexico
Molecular Ecology, 2004Co-Authors: Sergio Ticul Alvarezcastaneda, James L PattonAbstract:Phylogenetic analyses of complete mitochondrial cytochrome b sequences support the monophyly of pocket Gopher ( Thomomys bottae ) populations from the 1000 km length of the Baja California peninsula of Mexico, relative to other geographical segments of the species range in western North America. The Baja California peninsula is an area that encompasses considerable ecomorphological and infraspecific diversity within this pocket Gopher species. However, detailed population analyses encompassing 35 localities distributed over the southern half of the peninsula reveal only trivial phylogeographical structure. Rather, most of the 72 unique 500-base pair haplotypes examined from 142 individuals is restricted to single populations, although a few haplotypes are shared broadly across geography. Individual populations are typically comprised of haplotype sets from different branches in a network of relationships. Analysis of molecular variance ( AMOVA ) indicates that approximately half of the total pool of variation is contained among individuals within local populations, and that only about 25% can be explained by the regional subdivisions of current subspecies distributions or physiographic realms. A hypothesized historical vicariant event that has been causally linked to the phylogeographical structure of other, codistributed species has had little influence on these pocket Gopher populations, explaining only 13% of the total variation. The temporal depth, estimated by coalescence parameters, of the haplotype lineage in Baja California is relatively recent, approximately 300 000 generations; both the mismatch distribution of pairwise comparisons and a significantly positive exponential growth estimate support a recent history of expanding populations; but current, or recent past, migration estimates have remained small, are largely unidirectional from north to south, and weak isolation by distance is present. All data suggest that pocket Gophers have relatively recently invaded the southern half of peninsular Baja California, with the genetic signature of expansion still evident but with sufficient time having lapsed to result in a weak isolation by distance pattern. The geographical assemblage of sampled populations thus appears as a meta-population, with limited gene flow contrasting with random haplotype loss due to drift in small, localized populations.
John H Young - One of the best experts on this subject based on the ideXlab platform.
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demonstration of ground penetrating radar as a useful tool for assessing pocket Gopher burrows
Wildlife Society Bulletin, 2013Co-Authors: Jorge D Cortez, Scott E Henke, Eric Redeker, Tim E Fulbright, Richard Riddle, John H YoungAbstract:Ground-penetrating radar (GPR) is an innovative and non-invasive method that uses radar to penetrate the ground and develop three-dimensional digital images of the top several meters of the earth. Ground-penetrating radar has been used extensively in the fields of engineering, military science, forensic science, archaeology, and environmental remediation, but has received little attention by wildlife professionals. We demonstrated a possible application of GPR for wildlife studies for mapping burrow systems using maritime pocket Gophers (Geomys personatus maritimus), a subspecies of concern as listed by the U.S. Fish and Wildlife Service. Ground-penetrating radar surveys were conducted at Naval Air Station—Corpus Christi on five 15-m × 15-m areas with >200 above-ground Gopher mounds/ha during July 2007. Survey areas were scanned with a Geophysical Survey Systems Inc. SIR-3000, GPR digital control unit and a 900-MHz ground-coupled antenna. Within the 5 areas, we located 8 Gophers and mapped 267 m of tunnels that had an average depth of 0.6 m. We were able to differentiate deteriorating or abandoned tunnels from active tunnels, detect an underground pipeline, and distinguish changes in soil texture using GPR. Ground-penetrating radar is a non-destructive and non-invasive method to gain knowledge of fossorial animal movements and potential destabilization of soil integrity. © 2013 The Wildlife Society.
Gary W. Witmer - One of the best experts on this subject based on the ideXlab platform.
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novel and current rodenticides for pocket Gopher thomomys spp management in vineyards what works
Pest Management Science, 2017Co-Authors: Roger A Baldwin, Ryan Meinerz, Gary W. WitmerAbstract:Background Rodenticides are often included as part of an integrated pest management approach for managing pocket Gophers (Thomomys spp.) given that they are relatively quick and inexpensive to apply. Strychnine has historically been the most effective toxicant for pocket Gophers, but its use is currently limited in the United States; alternative registered toxicants have not proven effective. Recent research with baits containing cholecalciferol plus anticoagulant toxicants proved effective against pocket Gophers in a lab setting. Therefore, we established a field study to compare cholecalciferol plus anticoagulant combinations [0.03% cholecalciferol plus 0.005% diphacinone (C + D), 0.015% cholecalciferol plus 0.0025% brodifacoum (C + B1), 0.03% cholecalciferol plus 0.0025% brodifacoum (C + B2)] with strychnine (0.5%) for pocket Gopher management. Results Strychnine treatments resulted in 100% efficacy after two treatment periods. Both C + D and C + B2 resulted in efficacy significantly greater than 70% after two treatment periods (83 and 75% respectively). Efficacy from C + B1 (85%) was not significantly greater than 70%, but did yield high overall efficacy as well. Conclusion Although strychnine remains the most effective rodenticide for pocket Gopher control, the cholecalciferol plus anticoagulant baits tested would be a good alternative when strychnine is unavailable. C + D may be the best option given that it uses a first-generation anticoagulant as the synergist. © 2016 Society of Chemical Industry.
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Field tests of denatonium benzoate to reduce seedling damage by pocket Gophers (Thomomys talpoides Rich.)
Crop Protection, 1998Co-Authors: Gary W. Witmer, Michael J. Pipas, John C. BucherAbstract:Abstract The repellency of a bitter compound, denatonium benzoate, to reduce pocket Gopher damage to conifer seedlings was tested in two independent field trials in Oregon and Idaho. In the Oregon trial (1992 to 1993), treatments included a denatonium benzoate tablet placed in-ground with the seedling roots; a tablet plus denatonium benzoate foliar spray applied to both roots and foliage; and no chemical application (i.e. control). No significant difference between treatments was noted for ponderosa pine (Pinus ponderosa Dougl.) or Douglas fir (Pseudotsuga menziesii (Mirbel) Franco) seedlings suffering Gopher-related mortality. Non-animal mortality (58.2% of all seedlings) accounted for a greater loss of seedlings than Gophers (38.2%). Composite foliage and composite soil samples collected from the treatment plots were all negative for the presence of denatonium benzoate. In the Idaho trial (1993 to 1994), similar treatments (but with an additional spray-only treatment) were used on ponderosa pine seedlings. There was no significant difference in Gopher-related mortality levels between treatments. A large portion (72.5%) of all seedlings was destroyed by Gophers. It appears that the bitter compound, denatonium benzoate, as evaluated in these trials, is not an effective Gopher repellent.
Jennifer W Glusman - One of the best experts on this subject based on the ideXlab platform.
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geometric morphometric analyses of worn cheek teeth help identify extant and extinct Gophers rodentia geomyidae
Palaeontology, 2017Co-Authors: Jonathan J. M. Calede, Jennifer W GlusmanAbstract:Studies of the biostratigraphy and palaeoecology of fossil vertebrate assemblages require large samples of accurately identified specimens. Such analyses can be hampered by the inability to assign isolated and worn remains to specific taxa. Entoptychine Gophers are a diverse group of burrowing rodents found in Oligo-Miocene deposits of the western United States. In both entoptychines and their extant relatives the geomyines, diagnostic characters of the occlusal surface of the teeth are modified with wear, making difficult the identification of many isolated fossil teeth. We use geometric morphometrics to test the hypothesis that tooth shape informs taxonomic affinities and expected levels of morphological variation across Gopher taxa. We also incorporate data from microcomputer tomography to investigate changes in occlusal surface shape through wear within individuals. Our analyses demonstrate the usefulness of our approach in identifying extant geomyines to the genus, subgenus and species levels, and fossil entoptychines to the genus and, in some cases, the species level. Our results cast doubt on the validity of some species within Entoptychus and suggest future revisions to entoptychine taxonomy. The amounts of morphological divergence observed among fossil and extant genera are similar. Fossil species do not differ greatly from extant ones in that regard either. Further work evaluating the morphological variation within and across entoptychine species, including unworn teeth and osteological material, will allow revised analyses of the biostratigraphy and palaeoecology of important Oligo-Miocene mammalian assemblages of the western United States and help to infer the phylogenetic relationships and evolution of Gophers.
