Meeting Abstract

40.1  Tuesday, Jan. 5  Does the Red Queen control the evolution of fossorial rodents in the Miocene of the southern Columbia Plateau? CALEDE, Jonathan JM*; HOPKINS, Samantha SB; University of Oregon; University of Oregon jcalede@uoregon.edu

Several authors have proposed that the richness and species composition of the burrowing rodent guild was shaped by a series of competitive replacements. A test of this idea in the Miocene of the southern Columbia Plateau (encompassing parts of Oregon, Nevada and Idaho) includes fossorial rodents present there between the Barstovian and the Hemphillian (17 to 4.8 Ma) , members of the Aplodontidae, Geomyidae, Mylagaulidae, Palaeocastorinae, and Marmotini. Competitive replacement has been suggested to be a difficult process to demonstrate in the fossil record but some patterns and ecological parameters can be investigated to corroborate such biological interaction. Examination of relative diversity, body size, habitat use, and diet makes it possible to recognize patterns consistent with competitive replacement in these groups of rodents. Preliminary data suggest the possibility of competition between Barstovian mylagaulids and fossorial castorids. Moreover, a significant Hemphillian increase in diversity of geomyids corresponds with a significant decrease in that of the Mylagaulidae and might explain their extinction; this may also reflect changes in the environment favoring a change in the dominant group of burrowers. The diversity of Marmotini does not significantly vary through time suggesting that ground squirrels do not interact competitively with these other burrowing rodents. Finally, the lack of significant change in the diversity of aplodontids throughout most of the Miocene, remaining low compared to contemporaneous burrowers, is yet to be understood.