Elevation Related Variation in Climatic Harshness is Associated with Premating Mechanisms in Food-caching Mountain Chickadees (Poecile gambeli)

Abstract

Heterogeneous environments are often associated with differential selection pressures and montane habitats present a particularly interesting and useful case for the study of local adaption, as the environment changes rapidly and predictably along an elevation gradient. Higher elevations are characterized by predictably lower temperatures, more snowfall, and longer periods of winter conditions compared to lower elevations. Due to such environmental heterogeneity, individuals inhabiting higher elevations may experience stronger selection on various ecologically relevant traits compared to their lower elevation counterparts. These local adaptations may be enhanced by reduced movement between elevations and potentially maintained by assortative mating. Throughout my dissertation work, I aim to elucidate potential premating mechanisms involved in reproductive separation of mountain chickadees inhabiting differentially harsh environments along a montane gradient. These birds have previously been shown to different in several behavioral and neural traits important for survival at their respective elevations, thus making this system ideal for addressing the role of premating separation in a population postulated to be locally adapted. I have addressed this overarching question both indirectly, and directly, throughout the five chapters of my dissertation.