Conclusion
In this study, we sought to more fully understand which factors
contribute to diversity in the Cyprinodon pupfish system. Our
data support the idea that phenotypic variation and covariation, or the
relationship between traits, is an additional and important axis of
variation that contributes to diversification in the pupfish system.
When investigating the factors driving diversification between pupfish
groups, we find that the lack of a flexible P matrix may impede the
ability to diversify. We also used F2 hybrid P-matrices to make
inferences about underlying mechanisms which produce variation in
craniofacial traits in the pupfish system. We found that many traits
adhere to the expectations of a simple additive genetic model. Yet, key
traits such as head depth, maxilla length, palatine height, lower jaw
length, and dentigerous arm width appear to be influences by nonadditive
genetic effects and produce large phenotypic changes in other traits.
Future work should examine whether this relationship between flexibility
and diversification is generalizable across many species or is specific
to Cyprinodon pupfish.