Genic data from two chromosomal races of Geomys bursarius from a contact zone in central Texas indicated that the two races possessed distinct gene pools which would define them as separate species. Data from proteins encoded from 21 loci in this study substantiated this hypothesis. A pattern of alternately fixed alleles at the ADH-l, MDH-2, LDH-l, and IDH-1 loci with no apparent gene flow in zones of contact strongly suggested that these two races should be designated as separate species. Levels of heterozygosity and high FST values indicate that genomic structuring within Geomys is most heavily influenced by high levels of inbreeding and low migration rates. Fossorial rodents were suggested to undergo speciation primarily through parapatric means.

Baird's pocket gopher (Geomys breviceps) is found in eastern Texas, eastern Oklahoma, central and western Arkansas, and western Louisiana. The cytochrome-b gene was sequenced and analyzed for 16 pocket gophers from throughout the range of the species. Similar phylogenetic trees were obtained using maximum-parsimony, maximum-likelihood, neighbor-joining, and Bayesian analyses. Two major clades were formed with northern individuals belonging to clade I and southern individuals belonging to clade II. G. b. sagittalis was paraphyletic in relation to G. b. breviceps in all analyses. Based on inconsistencies between the taxonomic classification and systematic relationships within Baird's pocket gopher, a taxonomic restructuring appears warranted.

Genetic variation was analyzed for populations of seven taxa comprising four cytotypes of the Geomys bursarius chromosome complex, including G. b. major, G. b. knoxjonesi, and the Edwards Plateau taxa, G. b. llanensis and G. b. texensis. Genetic relationships of the Edwards Plateau gophers with other taxa and between themselves were examined. Genetic similarity, number of fixed allelic differences, and ectoparasite distribution indicate the Edwards Plateau gophers are a distinct gene pool. Isolation of the Edwards Plateau taxa precludes contact zone analysis. However, genetic differentiation is typical of that between other species of Geomys, and the Edwards Plateau taxa should be recognized as G. texensis. Distributions of allelic frequencies indicate little justification in retaining the subspecific status of the Edwards Plateau forms.

The Baird’s pocket gopher (Geomys breviceps) is a solitary, fossorial rodent found throughout areas of Texas, Arkansas, Oklahoma, and Louisiana. Research focusing on the population genetics of pocket gophers and other species with limited vagility and isolated populations is lacking. Through the use of mitochondrial and microsatellite data, a series of population genetic analyses were completed to better understand the population structure and gene flow among a series of G. breviceps localities. Pocket gophers were captured from five localities in the Brazos Valley and used in this study. Due to the lack of microsatellite loci available for G. breviceps, 10 loci were created for use in this study. Overall estimates from the population genetic analyses showed high levels of gene flow amongst nearby localities with decreasing levels as distance between localities increased. Findings suggest that 2-3 localities located within 2 km of each other function as one genetic cluster thus showing 3-4 total genetic clusters total in this study. Results also suggest that the Baird’s pocket gopher is capable of moving at least 2 km, but further analyses should be completed to better understand dispersal distance.

This study was initiated to investigate the distribution patterns of two species of pocket gophers, Thomomys umbrinus albicaudatus Hall and T. talpoides wasatchensis Durrant whose ranges come together in the Hobble Creek area, Utah. The effect of certain ecological factors upon their distribution was determined. The ecological factors included: vegetation and land use, soil, moisture and exposure, hybridization and interspecific competition. From morphological examination no interbreeding was detected even though the breeding seasons of the two species correspond. A limited area was found where the ranges of the two species are in contact. A lack of available moisture was determined to be a major factor inhibiting the distribution or talpoides in non-irrigated soils. Umbrinus is very versatile toward moisture and does not appear to be affected. Both species show a preference for sandy or gravelly-loam soils. Interspecific competition apparently inhibits the distribution of both species where the ranges come together. It is supposed that where only one species occurs that ranges will continue to be extended with talpoides being limited to the more moist areas. The other ecological factors are of no apparent significance to the distribution of either species except as they relate to the amount of available moisture.

The purpose of this study was to compare the morphology of the hind limb of the pocket gopher with that of the kangaroo rat and to determine their differences. This was accomplished by first, obtaining the specimens; second, preparation of the specimens for preservation and dissection; third, photographing and tracing the muscles; fourth, noting the origin and insertion of each muscle and their general morphology; and fifth, preparation and photographing of the bones. Comparative volumetric measurements were made of the muscles of the two animals to determine the differences between them. These two families, Geomyidae and Heteromyidae, are closely related but show great morphological differences which are adaptive due to their different environments and habits. The volumetric measurements of the two animals showed the shank of the kangaroo rat to be twice the size of that of the pocket gopher. The muscles used by the kangaroo rat in jumping are longer and larger as indicated by the volumetric displacement and linear measurements. Also, linear measurements were made of the various muscles and bones, These measurements also showed the variation in lenth and width, with those muscles of the kangaroo rat baing longer and wider. In the study of the bones, the general outlines of the two forms were vastly different. The location of tuberosities, size of the tuberosities for muscle attachment, bone length and width made up these differences. Origins, insertion, actions and description of the muscles are given for each animal.

Anhydrous ammonia (NH3) was tested as a potential replacement for residual, non specific toxicants as an effective control agent. It was postulated that NH3 would effectively control northern pocket gophers (Thomomys talpoides) and also act as a fertilizer for rangeland vegetation. Compound 1080 was selected as a standard for comparison of gopher control efficiency. Over 700 burrow systems were treated or monitored. Results showed compound 1080 to be 81 percent and NH3 45 percent efficient in controlling gophers. Although fertilizing effects of NH3 were positive, the low control efficiency and high application costs make NH3 an unlikely replacement for the now restricted residual toxicants.

This item was digitized as part of the Million Books Project led by Carnegie Mellon University and supported by grants from the National Science Foundation (NSF). Cornell University coordinated the participation of land-grant and agricultural libraries in providing historical agricultural information for the digitization project; the University of Arizona Libraries, the College of Agriculture and Life Sciences, and the Office of Arid Lands Studies collaborated in the selection and provision of material for the digitization project.