Patterns of size change in late Neogene pocket gophers from the Meade Basin of Kansas and Oklahoma |
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Authors: | Robert A Martin Pablo Peláez-Campomanes Christopher Mecklin |
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Institution: | 1. Department of Biological Sciences , Murray State University , Murray , KY , 42071 , USA robert.martin@murraystate.edu;3. Department of Paleobiology , National Museum of Natural History, C.S.I.C. , Jose Guttierez Abascal 2, Madrid , 28006 , Spain;4. Department of Mathematics and Statistics , Murray State University , Murray , KY , 42071 , USA |
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Abstract: | A dense late Neogene history of pocket gophers from the Meade Basin of south-western Kansas and north-western Oklahoma preserves a detailed record of size change, as indicated by mean length of the lower fourth premolar. A ‘time for space substitution’ interpretation results in the tentative recognition of a pattern analogous to character displacement, in which the small to medium-sized Pliogeomys buisi, P. louderbachi, Geomys minor and G. floralindae are considered ecological analogues and treated as a single ecological entity, Avatar A. The larger G. jacobi and G. quinni are combined as Avatar B. Statistical analyses confirm that populations of Avatar A are of equal size when allochronic from Avatar B, and significantly smaller when synchronic (and sympatric) with Avatar B. However, this pattern is complicated by the observation that Avatar A began dwarfing before the appearance of Avatar B. This historical perspective suggests that static size patterns among modern taxa may have a complex history. Occasional diminutive geomyid transients (G. adamsi, Thomomys cf talpoides) are always paired with significantly larger, medium-sized Geomys. Although a random walk explanation for the pattern of size changes is unlikely, we are currently unable to distinguish between environmental change and competition as the likely forcing mechanisms. |
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Keywords: | character displacement Geomyidae Geomys pocket gophers Neogene Meade Basin |
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