Friday, September 26, 2014

Saurians Set Sail

The theory of island biogeography posits that the amount of biodiversity - usually species richness - present on a landmass is positively correlated to the area of the landmass and negatively correlated to the distance the landmass lies from other landmasses.  In general, the larger a landmass, the lower the rate at which species tend to go extinct, but the further the landmass is from other source populations, the less likely will be replenishment via immigration.

In an elegant study on the island biogeography of Anolis lizards throughout the Caribbean, Helmus et al. suggest that economics, rather than natural processes, has become a dominant driver of biodiversity.  As they explain,
Economic isolation determines Caribbean biodiversity in the Anthropocene—both exotic and present-day (that is, native + exotic) anole richness were negative functions of economic isolation.
The authors identify commercial shipping as a major culprit for remixing the species complements of islands throughout the Caribbean.  These days, stowaway Anolis lizards seem to be island hopping less on logs or leaves than on massize metal container ships sailing from port to port.  Forget leaping lizards;  sailing lizards may be more accurate.