SICB Division of Ecology and Evolution (DEE)

DEE Researchers Database Entry

Alisha Shah

Determinants of elevation range limits in aquatic insects
I explore the role temperature plays in shaping the elevation range distributions of aquatic insects living in temperate and tropical mountain streams. To this end, I have measured a variety of thermal tolerance traits including thermal breadth, defined as the difference between critical thermal maximum and minimum temperatures. However, thermal breadth fails to accurately predict the true distributions of mayflies; their ranges are far narrower than predicted by thermal breadth. Here, we attempted to explain this discrepancy by investigating the synergistic effects of temperature and an important biotic interaction in streams predation. We predicted that if mayflies were "transplanted" to higher or lower elevation streams, they would experience reduced swimming performance due to the sub-optimal temperatures and become easy prey for stonefly predators. We found that indeed "transplanted" mayflies experienced greater mortality due to predation. Moreover, tropical mayflies experienced mortality due solely to temperature as well, suggesting that thermal stress amplifies vulnerability to predation in tropical species, and serves as a possible explanation for why mayfly range limits are narrower than predicted by thermal breadth alone.