common skink
It’s often thought that the most powerful driver in the creation of new species is geographical isolation. This is thought to be one of the main reasons for diversity in a tropical rain forest. A natural barrier such as a river or mountain range can lead, over time, to the separation of a single species into sub species that are clearly different from each other even though they come from a common ancestor. If there is no barrier then the chances of speciation decreases because of interbreeding. So species that live on the edge of the forest – where there are no barriers – should be much less likely to split.
That view is increasingly being challenged through research. Life on the forest edge can be as productive – in terms of species evolution – as life in the forest itself. Research has shown that ecotones ( a transitional area between one type of vegetation and another eg. forest edge) can be a driving force in evolution. This was first put forward by a team that studied ecotones of West African tropical forests. They discovered that biodiversity of the region was being feed from these forest edge habitats.
Further research on lizards in Australia has confirmed the earlier research findings. The same productivity of evolution has been seen in other species in other countries. In the case of the common skink in Australian forests researchers found that there was far greater diversity in the lizards that lived in the ecotone when compared to the lizards that lived in the forests themselves.
Lead author of the research Chris Schneider said, ”The differences in the shape, size and sexual maturity of skinks between the rain forest and adjacent open forest populations, but not between historically isolated populations, suggests that natural selection rather than isolation is promoting these physical differences,
“This stands in stark contrast to the prevailing view that geographic isolation alone is the key to population divergence and speciation.“
By understanding the roles that different habitats and ecotones play in diversity it becomes possible to adapt management plans to greatly improve conservation of species. the research shows that conservations of the forest themselves without taking into account the forest edges and surrounding lands may not be the correct strategy. to keep maximum diversity it will take more than protecting the core rain forest and the buffer zone of protection needs to extend beyond the forest habitat.
“The general belief is that if we preserve rainforests, we’re also preserving the processes that create biodiversity. But considering the role of ecotones, that may not be the case,” says Thomas B. Smith, an evolutionary biologist and director ofSFSU’s Center for Tropical Research (CTR).
