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Sunday, May 22, 2011

Species Reemergence After The Collapse



Species pairs that disappear through hybridization after human-induced changes to the environment can reemerge if the disturbance is removed, according to a new mathematical model that shows the conditions under which reemergence might happen.


By simulating environmental disturbances that reduce the ability of individuals to identify and select mates from their own species, the model explores the mechanisms that cause hybridization between closely-related species. Hybridization can lead to population decline and the loss of biodiversity. For instance, certain species of stickleback fish have collapsed into hybrid swarms as water clarity in their native lakes has changed, and certain species of tree frogs have collapsed as vegetation has been removed around their shared breeding ponds. Such hybrid swarms can replace the original species.


Triplicate Girl, Duo Damsel & The LSH © DC Comics
The reemergence of species pairs is more likely when the disturbances were strong than when they were weak, and most likely when disturbances were quickly corrected. However, even temporary bouts of hybridization often led to substantial homogenization of species pairs. This suggests that ecosystem managers may be able to refill ecological niches, but probably won't be able to resurrect lost species after species collapse.
Ref: Hybridization, species collapse, and species reemergence after disturbance to premating mechanisms of reproductive isolation. Evolution. R.T. Gilman and J.E. Behm, published online April 29.