Browsing by Subject "Rodent"
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Item Ecology of a Rodent-Tick-Pathogen Community in East-Central Texas(2014-09-01) Rodriguez Jr., Jaime EleazarRodent species worldwide are critical to the maintenance of tick-borne disease systems because they serve as hosts for ticks and reservoirs for zoonotic pathogens. To learn more about native fauna that may be involved in enzootic transmission of pathogens that can cause tick-borne diseases (TBDs), a mark-recapture study of rodents was conducted in Brazos County in east-central Texas. My objectives were to: (i) describe the species richness and seasonal activity of rodents; (ii) characterize rodent infestation with ticks over time; and (iii) determine the infection prevalence of rodents and ticks with selected zoonotic tick-borne pathogens. For nineteen months, small mammals were live-trapped two nights per month and subjected to blood and ear biopsy collections. All captured mammals were checked for the presence of ticks, which were removed for diagnostic testing. Additionally, drag sampling was conducted to collect ticks from the vegetation. Five rodent species (Sigmodon hispidus, Reithrodontomys fulvescens, Peromyscus leucopus, P. gossypinus, and Baiomys taylori) were captured over the course of the study. A large increase in S. hispidus capture success was seen in fall 2013, reflecting the characteristic population booms exhibited by this species. Two tick species - Amblyomma maculatum and Ixodes scapularis - were found infesting the rodents at low levels (2.33%). No ticks were found in over 14,500 meters of drag sampling the vegetation. In an analysis of 698 ear biopsies, 3.2% of the specimens were positive for Borrelia miyamotoi, a spirochete that has recently been shown to cause relapsing fever in humans. One specimen (0.1%) was found to be infected with B. lonestari. No ticks were found to be infected with Borrelia. However, 4.3% of the larval A. maculatum pools were positive for a rickettsial endosymbiont. One larval A. maculatum pool and one I. scapularis nymph were found to be infected with Rickettsia monacensis, the causative agent for a Mediterranean spotted fever-like illness in Europe and North Africa. This study identifies novel TBDs in the southern United States and exposes the need for further study of TBD ecology, especially in understudied areas.Item Landmark morphometric assessment of the genus Baiomys (Mammalia: Rodentia): Geographic variation, secondary sexual dimorphism, and character displacement in sister species(2006-05) Abuzeineh, Alisa A.; Owen, Robert D.; McIntyre, Nancy E.; Bradley, Robert D.The purpose of this research was to evaluate geographic variation and secondary sexual dimorphism within the two recognized species of Baiomys (Rodentia: Muridae), and to determine whether (and to what extent) character displacement occurs within either or both of these species where they are found in sympatry. The genus Baiomys is composed of two extant species, B. taylori and B. musculus, which are quite similar in appearance. The two species are distinguishable by a limited number of cranial features (occipitonasal length, zygomatic breadth, and curvature of rostrum), hyoid, and baculum. Landmark point coordinates were collected from dorsal and ventral views of the crania and mandibles of 513 specimens representing the geographic distribution of both species. Geometric morphometric techniques were used to examine sexual dimorphism and geographic variation within each species, and to determine whether character displacement was present within the area of sympatry. A discriminant function analysis of Baiomys taylori showed a significant difference between the two sexes (p=0.03), whereas B. musculus did not (p=0.15). Additionally, a discriminant analysis showed significant differences (p=0.05) among four pre-designated groups (B. taylori allopatric and sympatric, and B. musculus allopatric and sympatric). The only significant pair-wise difference occurred between B. taylori sympatric and allopatric populations, whereas the sympatric B. taylori and B. musculus populations were quite similar to each other. A correlation coefficient (r) of 0.45 between morphometric variation and latitude was found for both species and sexes combined, and the slopes of the two species were not significantly different from each other (p=0.46). Furthermore, it was discovered that interpoint distances (¡Ö size) in the cranium and mandible increased in lower latitudes in both species, so that the largest B. taylori and smallest B. musculus were found in the zone of sympatry. This high correlation between morphological score and latitude across both species, together with the results of the discriminant analysis, indicate that character displacement does not occur in cranial and mandibular characters in Baiomys species. These findings are contrary to early speculations that character displacement was present in the genus.Item Landmark morphometric assessment of the genus Baiomys (Mammalia: Rodentia): geographic variation, secondary sexual dimorphism, and character displacement in sister species(Texas Tech University, 2006-05) Abuzeineh, Alisa A.; Owen, Robert D.; McIntyre, Nancy E.; Bradley, Robert D.The purpose of this research was to evaluate geographic variation and secondary sexual dimorphism within the two recognized species of Baiomys (Rodentia: Muridae), and to determine whether (and to what extent) character displacement occurs within either or both of these species where they are found in sympatry. The genus Baiomys is composed of two extant species, B. taylori and B. musculus, which are quite similar in appearance. The two species are distinguishable by a limited number of cranial features (occipitonasal length, zygomatic breadth, and curvature of rostrum), hyoid, and baculum. Landmark point coordinates were collected from dorsal and ventral views of the crania and mandibles of 513 specimens representing the geographic distribution of both species. Geometric morphometric techniques were used to examine sexual dimorphism and geographic variation within each species, and to determine whether character displacement was present within the area of sympatry. A discriminant function analysis of Baiomys taylori showed a significant difference between the two sexes (p=0.03), whereas B. musculus did not (p=0.15). Additionally, a discriminant analysis showed significant differences (p=0.05) among four pre-designated groups (B. taylori allopatric and sympatric, and B. musculus allopatric and sympatric). The only significant pair-wise difference occurred between B. taylori sympatric and allopatric populations, whereas the sympatric B. taylori and B. musculus populations were quite similar to each other. A correlation coefficient (r) of 0.45 between morphometric variation and latitude was found for both species and sexes combined, and the slopes of the two species were not significantly different from each other (p=0.46). Furthermore, it was discovered that interpoint distances (¡Ö size) in the cranium and mandible increased in lower latitudes in both species, so that the largest B. taylori and smallest B. musculus were found in the zone of sympatry. This high correlation between morphological score and latitude across both species, together with the results of the discriminant analysis, indicate that character displacement does not occur in cranial and mandibular characters in Baiomys species. These findings are contrary to early speculations that character displacement was present in the genus.