Transferrin polymorphism in a population of Nuttall's cottontail in central Oregon Public Deposited


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  • Temporal changes in gene frequencies and genotype frequencies, monthly densities, survival rates, growth rates, trap susceptibility and home ranges were evaluated from 291 Nuttall's cottontails (Sylvilagus nuttallii) captured 950 times by livetrapping and 53 cottontails collected by shooting. Electrophoretic analyses of sera revealed protein polymorphism at the transferrin locus in the Nuttall's cottontail population. The locus was characterized by three codominant alleles, Trf-A, Trf-B and Trf-C with relative mobilities of 1.04, 1.00 and 0.95, respectively. No significant relationship between transferrin genotypes of Nuttall's cottontails and their sex was observed (P > 0.05). The frequencies of the transferrin genotypes was not significantly different from expected values computed by Hardy-Weinberg equilibrium frequencies suggesting genetic inheritance at a single autosomal locus (P > 0. 05). During the summer of 1974 the occurrence of the Trf-BB genotype increased 13.3 percent between the samples of parental stock and their trappable progeny. In 1975, the Trf-BB genotype frequency decreased by 14.5 percent between parental stock and trappable progeny. Associated with the opposite trends in Trf-BB genotype frequencies between years were significant differences in the growth rates of juveniles in 1974 and 1975 (P < 0.05). Mean rate of growth for juveniles in a litter were computed by regression of weight at first capture against date of acquisition for all juveniles of a litter group. Computed rates of growth ranged from 1.51 to 3.70 grams per day for juveniles in litter groups in 1974 and from 4.28 to 5.98 grams per day in 1975. The differences in growth rates of juveniles between 1974 and 1975 were thought to be related to a 4-fold difference in precipitation falling from the time the first litter was weaned through August each year with 1.47 cm and 5.89 cm of rain, respectively. There was a significant difference in Trf-C gene frequencies between the 1974 and 1975 trappable progeny (P < 0. 05). Significant changes in the gene pool of the cottontail population were thought to have resulted from possible selection of juveniles best adapted to the prevailing environment. Apparently four litters of cottontails were produced during the 1974 and 1975 breeding seasons with an estimated total production of 305.6 and 354.1 young, respectively. Monthly estimates of population density ranged from 17.8 cottontails per 100-ha on 14 February 1974 to 241.8 cottontails per 100-ha on 31 July 1975. Estimates of cottontail density on 30 August 1974 and 1975 were 173.6 and 213.9 cottontails per 100-ha, respectively. The overall survival rate of juvenile cottontails from birth through 30 August was 42.1 and 44.4 percent, respectively, for 1974 and 1975. However, the minimum survival rate for cottontials in the trapped population was computed as 78.8 and 73.6 percent, respectively, for 1974 and 1975. Survival rates indicated a high rate of mortality for juveniles prior to their entrance into the trapped population. No differences were found in the size of home ranges or weights at first capture of cottontails of the various transferrin genotypes captured (P > 0. 05). Cottontails of the Trf-BC genotype were found to be significantly more difficult to capture than those of the Trf-BB in 1975 with 35.1 and 26.3 trapnights required per capture, respectively (P < 0. 05). Transferrin genotypes were determined for 51 of the 53 cottontails collected by shooting in September 1975. Analysis indicated no significant relationship between the transferrin genotype composition of the sample and the method of acquisition, with the comparison of cottontails livetrapped in August 1975 and those shot in September 1975 (P > 0. 05). No significant differences were found between the sex and age structure of the hunted sample of September 1975 and the trapped population of August 1975 (P > 0.05).
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