Data from: Island biogeography and competition drive rapid venom complexity evolution across rattlesnakes

Understanding how human-mediated environmental change affects biodiversity
and the timescale of an evolutionary response is key for conserving
evolvability. Islands are proxies for fragmented landscapes and allow us
to use historical changes in biodiversity under Island Biogeography Theory
(IBT) to predict the consequences of immediate anthropogenic impacts on
trait evolution. Rattlesnake venoms are molecular phenotypes that mediate
interactions with prey, and diet and venom complexity are positively
correlated. Consequently, rattlesnake venoms allow us to investigate how
functional traits co-vary with changes in biodiversity according to IBT.
We collected venom from 83 rattlesnakes across multiple species and 11
islands in the Gulf of California and estimated venom complexity using the
Shannon Diversity Index. Using a mixed effects modeling approach, we found
that the number of congeneric competitors, island isolation, and island
area best predicted variation in venom complexity. All variables exhibited
a negative relationship with venom complexity, contrary to predictions for
island area under IBT. Larger islands with more congeneric competitors
exhibited reduced trait complexity, likely reflecting niche partitioning
and venom specialization driven by interspecific competition and/or
increases in habitat heterogeneity. Ultimately, we used a synthetic
eco-evolutionary framework to predict functional trait evolution across
fragmented and isolated habitats.