Portland State University. Department of Biology
Luis A. Ruedas
Term of Graduation
Date of Publication
Master of Science (M.S.) in Biology
Akodon siberiae -- Classification, Akodon -- Research -- Bolivia -- Yungas, Skull, Cytochrome b
1 online resource (viii, 62 pages)
The Cochabamba Grass Mouse, Akodon siberiae, is a small mouse (mean head+body length: 103 mm, N = 22) that occurs in a spatially restricted range in the Bolivian Yungas forests, the cloud forest transition zone between lowland Amazonia and the Andean Altiplano. Like many species in the genus, their appearance is very similar to that of other species in the genus: they are difficult to distinguish from their congeners, and are challenging to identify. In the absence of molecular data, A. siberiae specimens require a thorough and careful analysis of external and cranial features for identification. Furthermore, Akodon mimus, A. dayi, and A. varius, resemble A. siberiae and overlap its range. In this study, a detailed morphological comparison was carried out of external and cranial features between the sympatric A. siberiae and A. mimus. A principal component analysis was carried out on cranial measurements of A. siberiae and the three sympatric Akodon species that it most closely resembles. Two phylogenetic trees were constructed based on molecular data from the mitochondrial cytochrome b gene using 37 of the 39 Akodon species to further assess species relationships and the evolutionary relationships of A. siberiae. One tree was constructed with all Akodon specimens from Genbank and including specimens from this study. Another tree was constructed with one specimen per species for clarity. The morphological comparison revealed a number of key differences between A. siberiae and A. mimus. From the dentition, I infer that A. siberiae has an insect dominated omnivorous diet, in contrast to A. mimus, which has a vegetation dominated omnivorous diet. The ecological niche model revealed that even under ideal circumstances, A. siberiae only has a small geographical area that it could successfully inhabit. Habitat loss by anthropogenic development is a major threat to A. siberiae. The evolution and biology of A. siberiae appears to be tied to its particular habitat and small range in the Bolivian Yungas. Continued and enforced protection of those habitats is necessary to maintain stable populations of A. siberiae.
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Dunn, James George, "Morphology, Taxonomy, and Ecological Niche Modeling of the Cochabamba Grass Mouse, Akodon siberiae Myers & Patton, 1989" (2020). Dissertations and Theses. Paper 5597.