PARENT SESSION
Oral Session #47: Animal Population Ecology: Amphibians, reptiles, others. Presiding: K. Hatch.
Wednesday, August 8, 2001. 8:00 AM to 11:45 AM. Hall of Ideas J.
Of mice, mothers and mirror-images: fluctuating asymmetry in relation to fitness in deer mice.
LONG, TRISTAN1, FRYXELL, JOHN1, FALLS, J. BRUCE2, 1 2
ABSTRACT- Fluctuating asymmetries are subtle, random deviations from perfect bilateral symmetry that are the hypothesized consequence of an imperfect regulation of development. Recently, the monitoring of fluctuating asymmetry has been suggested as a tool for assessing the severity of environmental "stress" within and between populations, as well as over time. However, scientific debate exists over the validity of the theoretical relationship between this type of asymmetry and fitness. We used a long-term (1966-1987) collection of deer mice, Peromyscus maniculatus, whose population has undergone dramatic fluctuations, to test this relationship. Dentary bones from mated females were photographed, and landmarks identified on the sinistral and dextral structures. These data were used to quantify asymmetry at both the levels of the individual and of the population. MANOVA was used to determine whether individual asymmetry could explain variation in female fitness correlates (embryo/ placental scar counts), and revealed no significant relationship. However, at the population level, increased asymmetry was positively correlated with relative population growth. In years with poor environmental "quality", only the most symmetrical mice seem to be able to sustain the physiological condition necessary to breed, while in more favourable years, a greater fraction of the population could achieve this condition. These findings provide mixed support for the assertion that fluctuating asymmetry studies provide a reliable means of studying and predicting variation in fitness.
KEY WORDS: fluctuating asymmetry, fitness, population ecology, Peromyscus maniculatus