Are species distributions constrained by biological timing mechanisms and the photic environment?
Biotic and abiotic factors determine species distributions, and organisms use abiotic cues, such as the diel and annual changes in available light, to synchronize their biology to the environment. Temperature is a dominant factor determining species distributions, and under global climate change, global temperature gradients are shifting polewards, away from the equator. In contrast, the photic environment is fixed by latitude and date, and is a dominant factor in determining ecological interactions and physiology. We, however, know little about whether these static photic cues determine species distributions. I aim to elucidate the relationship between species distributions and the photic environment by studying four species of migratory flycatchers (songbirds) breeding along a latitudinal gradient spanning from 56 degrees North latitude to above the northern polar circle (66.6 °N) in Sweden. Migratory flycatchers are excellent models to test hypotheses regarding the interaction between species distributions and the photic environment, because they use photic cues for determining breeding, migration, and compass bearings. The selected species also have different breeding and migratory ranges that span the polar circle and cross the equator, thus providing an excellent comparative system for understanding constraints on the northern and southern edges of their distributions. I will bring individuals into captivity to investigate experimentally how the photic environment associated with their breeding and wintering ranges affect their ability to track the diel and annual cycles. This project will provide novel insight into the interaction among species distributions and photic environment, insight required to predict properly whether species could successfully track their optimal thermal environment to new latitudes and photic environments. This new insight allows us to understand better the changes to biodiversity under global climate change.