# Biogeography and Hybridization

Hybridizing species typically co-occur only in intermediate environments. For example, if one species is better adapted to colder climates while a related species is found in hotter climates, then hybrids between these two species would most commonly occur in warm environments. In this study, I integrated field work with GIS tools to build a map of where two related spadefoot toad species occur alone (i.e., allopatry) and together (i.e. sympatry). I then looked at the patterns of these distributions in physical (i.e. on the map) and environmental (i.e. climate) space. Contrary to my predictions, I found that species were most likely to co-occur in hotter, drier environments, rather than in intermediate climate conditions. This work provides a basis for several new experiments that will test how climate mediates species co-existence, while having implications for how climate change might affect the evolutionary trajectory of these species.