Leaping lizards

Trade routes influence island biogeography According to the theory of island biogeography, the number of species (richness) is determined by how an island's area and isolation govern rates of colonization, extinction and speciation. There is a long history of human introduction of anole lizards to Caribbean islands, hitching a ride on on crops such as pineapple and recently on ornamental plants for hotel gardens. Matt Helmus et al. take advantage of this spread of exotic species to conduct a large-scale direct test of the theory of island biogeography. Their results confirm some theoretical predictions — geographic area remains a good positive predictor of species richness, for instance. But in a world dominated by humans, geographic isolation as a negative predictor of richness has been replaced by economic isolation. For example, shipping traffic among islands is unrelated to geographic isolation and is instead linked to trade policy — illustrated by the fact that the US embargo has reduced the number of exotic anoles established on Cuba.