Does fluctuating asymmetry reflect the importance of traits in little brown bats (Myotis lucifugus)?

Abstract

Small random deviations from perfect bilateral symmetry define fluctuating asymmetry, and these deviations reflect an individual's inability to genetically control the development of a particular trait. Natural selection should act to minimize fluctuating asymmetry in traits that are most functionally important to an organism. Temperate-zone bats forage in flight and therefore symmetry of wing bones should be very important to fitness. Bats use their hind limbs only for hanging in roosts, therefore asymmetry in the main leg bone, the tibia, should not be as significant to a bat's fitness. We predicted that there would be less fluctuating asymmetry in the forearms than in the tibia. We measured the forearms and tibias of 119 little brown bats (Myotis lucifugus), and as predicted, forearm length did show less fluctuating asymmetry than tibia length. This result supports the hypothesis that traits can be ranked in order of functional importance according to the degree of fluctuating asymmetry found for each.