Effect of Sub-Canopy on Habitat Selection in the Blue-spotted Salamander (Ambystoma laterale-jeffersonianum unisexual complex)

Abstract

Elucidating the mechanisms that influence spatial distribution patterns is vital to understanding how populations persist. We examined distribution in one of the most common salamanders in southeastern Michigan, the Blue-spotted Salamander (Ambystoma laterale-jeffersonianum unisexual complex). Three major tree species dominate the sub-canopy in the study site and form monospecific patches, which may have an effect on the distribution of terrestrial phases of local amphibian species. To examine this, we tested whether adult salamanders are significantly associated negatively or positively with patches of particular tree species. We then examined two potential causal factors: habitat quality, using leaf litter macroinvertebrate biomass as a proxy, and behavioral site choice in the Blue-spotted Salamander. We found that this species is positively associated with patches of red maple and negatively associated with patches of black cherry. We also found that, when presented with a choice, salamanders choose red maple leaf litter over black cherry leaf litter. In the absence of differences in physical leaf litter characteristics between patches of red maple and black cherry, we suggest that the Blue-spotted Salamander may be utilizing chemical cues to select habitat. Our findings imply that salamander populations may be affected not only by habitat loss, but also by changes in forest composition. These results provide evidence for a more complex model than the traditional amphibian metapopulation concept, where even fully forested habitat may form a matrix of optimal and sub-optimal, or even intolerable, patches.