Print PageVariation in ecology has been linked to mating system strategies; however the underlying mechanisms controlling changes in these strategies are largely unknown. It has been proposed that ecological variation could influence the expression of neuroanatomical structures controlling for social behavior. In mammals, social pair-bonding appears to be mediated by two neuropeptides: oxytocin and vasopressin. Socially monogamous species (Microtus ochrogaster) have high concentrations of these neuropeptide receptors in the reward and reinforcement regions of the brain. In contrast, non-monogamous species (M. pennsylvanicus) lack oxytocin and vasopressin receptors (OTR, VPR) in these regions. By using viral-vector gene transfer, a causal link between receptor expression and mating behavior has been determined. These observations suggest that ecological variation influences receptor distribution in the brain, thereby influencing intraspecific variation in mating systems. I will assess the impact of ecological variation on the social mating systems and neuroanatomy of the Taiwan vole (Microtus kikuchii). This species is endemic to Taiwan with populations in high elevation alpine meadows and surrounding evergreen forests. Data from four Chinese theses suggest the Taiwan vole is socially monogamous in the meadow similar to M. ochrogaster, indicating possible convergence of phenotypes.
Results/Conclusions
In order to assess if there are differences in behavior between habitat types, I live-trapped voles in both meadow and forest sites on Hehuan mountain in central Taiwan. Preliminary data collected in 2009 indicate that in the meadow, females occupy similarly sized home ranges as males (238.0±271.6m2 and 188.1±178.6m2, respectively) with extensive overlap between male-female pairs. In the forest, males and females also occupy similarly sized home ranges (765.0±963.5m2 and 616.0±624.7m2, respectively; t-test: df =20, p=0.67); however, there is less spatial overlap between males and females in the forest than in the meadow. Together, these data support a monogamous, but flexible mating system; however, no significant conclusions can be drawn until 2010 data are analyzed. Brain tissue samples (28 total) were also collected from individuals in both sites in 2009 and 2010. In spring 2011, audioradiography will be used to determine the distribution and concentrations of OTR and VPR in crucial reward regions of the brain, both within and between sites. If current trends persist, higher concentrations of OTR and VPR are expected in meadow populations than forest populations, where home range overlap is more exclusive. This research would benefit from genetic analyses to determine if intraspecific variation in mating system is the result of genetic divergence or phenotypic plasticity.
