Meeting Abstract

32.3  Friday, Jan. 4  Observing skeletal evolution in real time: preliminary results from an artificial selection experiment in laboratory mice. ROLIAN, C*; DOWHANIK, A; KRUEGER, C; HALLGRIMSSON, B; University of Calgary cprolian@ucalgary.ca

Vertebrates show tremendous diversity in the morphology of the postcranial skeleton. This diversity is the long-term result of evolutionary forces acting on population-level skeletal variation. However, this variation is not random or uniformly distributed across traits. Instead, the direction and magnitude of phenotypic variation across the skeleton is patterned by normal processes of organismal development, in turn affecting the evolvability of individual traits. Here, we report on the first few generations of an artificial selection experiment targeting increases in tibia length in the mouse. The experiment is designed to observe skeletal evolution in real time, and to document how the structure of (co)variation across the skeleton affects the evolvability of individual skeletal traits. The experiment comprises two Selected lines and one Control line of CD1 mice, each set up into 14 families. In the Selected lines, mice are tagged and x-rayed, and littermates with the longest tibiae relative to body mass are chosen as breeders for the following generation, and out-bred to top-ranked individuals from other litters. Control mice are paired randomly. After six generations, tibia length has increased 7.3% in Selected vs. Control mice, while the change in body mass is not significant. Other limb bones have increased significantly in length, though not to the same extent, leading to significant changes in limb proportions. These early results show that despite strong phenotypic covariation with other limb bones and overall body mass, targeted selection on a single quantitative skeletal trait can produce relatively independent evolutionary change in individual skeletal traits.