Microhabitat conditions influence mesohabitat associations and distribution of larval salamanders in headwater streams

Abstract

Distribution patterns of stream biota are the result of complex interactions between individuals and their surrounding environment. Determining the spatial scale by which an organism is most influenced is paramount to understanding distribution patterns. Using a multi-scale approach, we investigated factors influencing habitat associations of larval Ambystoma barbouri (streamside salamander) and Eurycea cirrigera (southern two-lined salamander) in three Kentucky headwater streams. We used likelihood ratio G tests to identify associations between species and mesohabitat (i.e., runs, riffles, and pools), and we used microhabitat variables to predict the presence and abundance of salamanders via a priori multiple regression modeling. Ambystoma barbouri presence and abundance were influenced by conditions at micro-scales, which in turn dictated mesohabitat associations. Eurycea cirrigera were also influenced by microhabitat variables, but displayed associations to A. barbouri presence in late spring. Associations of larval salamanders to mesohabitat and microhabitat parameters shifted from early to late spring, likely in response to changes in developmental stage. The multi-scale approach of our study improved our understanding of complex relationships between larval salamanders and their surrounding environment in headwaters, and underscored the importance of (1) research investigating multiple spatial and temporal scales and (2) heterogeneous in-stream habitat to headwater biota.