Meeting Abstract
An ongoing selection experiment for increased voluntary wheel running resulted in four replicate high runner (HR) lines that run ~3-fold more revolutions per day than do four non-selected control lines. A previous study showed that the 4 HR lines, and both sexes within lines, differed in the rate as well as the total amount of response to uniform selection, and in the number of generations to reach selection limits (V. Careau, et al. 2013. Evolution 67:3102-3119), which suggests that somewhat different genetic (and behavioral or physiological) factors underlie wheel running for the two sexes and in replicate lines, i.e., multiple solutions have evolved. A study on thermoregulatory behavior in mice showed that selection limits in replicate lines for nest building could be overcome with continued selection on hybrid lines for 10 generations (A. Bult and C. B. Lynch. 2000. Behav. Genet. 30:193-206). Therefore, in an attempt to break the wheel-running selection limit in the HR lines, we crossed two HR lines and continued selection on this hybrid line concurrent with the parental lines. As in a previous line-cross study (R. M. Hannon, et al. 2011. Behav. Genet. 41:615-624), male hybrids, but not female hybrids, showed heterosis in the F1. With continued selection for 6 generations, there is no clear indication that the hybrid line will break the selection limit, but more generations are forthcoming. Interestingly, both male and female hybrids ran faster than the pure parental lines in every generation, but running duration was intermediate or reduced in the hybrid line, suggesting a possible trade-off in running duration versus average speed. Further analyses will incorporate estimates of heritability and genetic correlations from an “animal model,” accounting for the full pedigree of the three lines.
