Another paper from the PNAS colloquium on biodiversity extinction. In this study, the authors (Sax & Gaines) present evidence that despite an explosion of naturalized/invasive plant species on islands across the world, there hasn’t been a commensurate decrease in native flora. In fact, they find an incredibly tight, 1:1 linear relationship between native and non-native species diversity. This, on the face of it, suggests that species invasions may increase the world’s biodiversity (as non-native plants on islands begin to experience allopatric speciation). The one major worry would be that the islands are in a state of “extinction debt” where many of these species still present are going to face extinction sometime in the future, we simply haven’t observed it yet. Needless to say, extinction debt is both an important concept in conservation but also a good way to hand-wave around the fact that we haven’t seen the level of extinctions that we’d expect — yet. Here’s a write-up on the article from Science Daily.

[edit: More from Corey on Extinction Debt]

Dov F. Sax and Steven D. Gaines. Species invasions and extinction: The future of native biodiversity on islands. PNAS, 105: 11490-11497. (doi: 10.1073/pnas.0802290105)