Taxonomy and reproduction of Microtus canicaudus Public Deposited

http://ir.library.oregonstate.edu/concern/graduate_thesis_or_dissertations/r781wj752

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  • The taxonomic status of Microtus canicaudus was compared with that of a morphologically similar vole, Microtus montanus. Four means of comparison were utilized: hybridization experiments, comparative karyology, growth distinctions (total length and body weight), and qualitative behavioral observations. The hybridization experiments indicated that, while the incidence of pregnancy of M. montanus x M. canicaudus was similar to one of the control groups (M. montanus x M. montanus) and was even greater than the other control group (M. canicaudus x M. canicaudus), the litter size and survival of hybrid offspring until weaning was significantly less than both control groups. Therefore, reduced reproductive compatibility between the two species is indicated. The karyotypes of the two species (M. canicaudus from Benton County, Oregon; M. montanus from Moran, Wyoming, Red Butte Canyon - near Salt Lake City, Utah, and the Columbia River Gorge, Oregon) showed consistent interspecific differences. Karyotypes of male and female hybrids exhibited chromosome "mis-matching". Growth comparisons between Benton County M. canicaudus and Red Butte M. montanus demonstrated that M. canicaudus was significantly shorter and weighed less. Behavioral interactions between a group of seven individuals of each species housed in a network of interconnected cages revealed that 77% of the agonistic interactions noted were interspecific, These results lend support to the hypothesis that M. canicaudus deserves species status. In addition to the taxonomic study, the breeding records of M. canicaudus yielded information concerning its gestation period and trends in sizes of consecutive litters. The most common gestation interval was 21 days. Temporal patterning of successive litters led to speculation on the presence of a 21 day pseudopregnancy. Evidence was presented which suggests that the sizes of first litters were relatively smaller than the mean size of litters two through four.
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