Ask any biologist or student of the natural sciences and they’ll agree: Madagascar is a peculiar menagerie of unique creatures, many of which live there and nowhere else on the planet. And according to a group of scientists, there’s no one reason or “one-size-fits-all” model to explain the biodiversity on Madagascar.
There’s a whole area of biological scholarship devoted to the study of natural anomalies called ‘biodiversity hotspots’. By definition, a biodiversity hotspot is “a biogeographic region with significant diversity that is at risk from humans.”
Scientists have sought to understand how Madagascar, which comprises a mere 0.5% of the Earth’s total landmass, could be home to so many distinct and unusual species, many of which exist nowhere else, given its near complete geographic isolation for millions and millions of years. In fact, the present study is part of a larger body of work that seeks to identify factors of climate, geography and other environmental features that not only allow for the development of new plant and animal species, but also sustain them and allow them to flourish.
No Single Cause for Biodiversity
Duke University biologist Anne Yoder and her colleagues looked at the geographic distributions of 325 species of amphibians and 420 species of reptiles that live on Madagascar today. They compared that data with historical and present-day estimates of local attributes like amount of rainfall and local topography among other variables across the island. They noted the steep tropical regions and the flat, desert-like areas and analyzed three key measures in biodiversity: number of species, proportion of unique species, and similarity of species composition from one site to another.
“Not surprisingly, we found that different groups of species have diversified for different reasons,” Yoder said. “For example, changes in elevation–due to the mountains, rivers and other features that shape the land–best predicted which parts of the island had high proportions of unique tree frog species. But the biggest influence on why some areas had higher proportions of unique leaf chameleons was climate stability through time.”
One of the greatest benefits to the findings of this study is that we better understand how the species in areas of great biological diversity respond to environmental fluctuations, which will help in identifying the groups most vulnerable to global warming and deforestation. Other studies have shown that some of Madagascar’s reptiles and amphibians are relocating to higher elevations because of climate change, and due to the effects of logging and farming on forest habitats roughly 40% of reptile species are threatened with extinction.