The fitness of hybrid offspring between two different species is critical in determining the evolutionary trajectory of those species. Hybrids are typically assumed to be less fit than pure species, but hybrids may also be equal to, or even more fit, than pure species. For my graduate work, I conducted a series of experiments to look at the differences between hybrid offspring and pure species offspring of two species of spadefoot toad (Spea multiplicata and S. bombifrons). I found that hybrids actually grow faster than pure species as tadpoles, while pure and hybrid individuals showed no difference in fitness in terms of body condition or escape time as metamorphs. Determining lifetime fitness of hybrids will be a critical step in predicting the long-term outcome of hybridization between these two species.
Undergraduates Alyssa Stewart (above left), Alycia Lackey, and Elizabeth Alloway (measuring metamorphs above right) were an invaluable part of this research.