PARENT SESSION
Poster Session 35: Evolutionary Ecology
Thursday, August 11, 5:00 PM - 6:30 PM, Exhibit Hall 220 A-E, Level 2, Palais des congrès de Montréal
Divergent and convergent character suites and a new approach for investigating character displacement in bats.
Ingersoll, Thomas1, 1 University of Colorado, Institute of Arctic and Alpine Research, Boulder, Colorado, USA
ABSTRACT- We compared morphological traits of 2 closely related species of bats, using canonical discrimination to investigate the controls of character displacement. 62 specimens of Myotis lucifugus and 51 specimens of M. yumanensis from 22 locations in the southwest United States were examined. Comparisons of morphology were made between allopatric and sympatric populations and between species. We found that gross size measurements, such as forearm and tibia length, converge in sympatric populations. Individuals were smaller and the difference of mean size between species was significantly smaller in sympatric populations. This matches community models where the response to competition is reduction of individual size, allowing more population to pack onto a limiting habitat. Alternatively, traits associated with fine locomotary control and sensory systems, such as foot and ear size, were divergent in sympatric populations, consistent with communities that use resource partitioning to reduce competition. Investigating character displacement can be complicated by these opposite trends in the direction of adaptation. Certain character suites can converge with competition with while others diverge. Such opposite responses to competition can counteract class distinctions in combined variables. A new approach separates divergent and convergent traits. Each opposing suite of variables is treated separately, combined into complex variables using canonical discrimination. Differences in distribution with sympatry are then tested. Platykurtosis in convergent traits fits a model where competing species pack against each other laterally and against carrying capacity vertically, while skewed distributions in divergent traits are less bounded above. This suggests convergence along axes of intense competition, and radiation along axes where resources are less limiting.
Key words: divergent, convergent, character displacement, bats