Tuesday, September 26, 2006

 

Size doesn't matter: Island mammals 'dwarfed' by lack of competitors and predators ('Island Rule')

Elephas falconeri Sicily Miniaturization Gigantism Ungulates (Evolution Research: John Latter / Jorolat)The evolution of miniature or 'dwarf' versions of animals like elephants and hippos on islands is caused by lack of competition for food and the absence of predators, and not just because they are too large for their habitats, new research claims today.

The study, published in this month's issue of Evolution journal, examines the phenomenon of the 'Island Rule' which states that large mammals on islands evolve to be significantly smaller than their counterparts living on large continental land masses.

The researchers examined the fossilised remains of small elephants and other miniaturised mammals living on various sized Mediterranean islands in the Pleistocene and Holocene epochs, between 1.8 million and 4,500 years ago. Their findings suggest that this evolutionary tendency is caused by the specific way that predators, prey, and competitors for food interact in island eco-systems. They also found evidence that miniaturisation occurs for distinctly different reasons in carnivores and herbivores, and that herbivores are more dramatically affected by the phenomenon.

The team's findings show that for miniature herbivores such as hippos to evolve, there needs to be little competition for food on the island, and very few predators. [Palaeontology, Epoch, Fossilized]
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Based on "The Island Rule In Large Mammals: Paleontology Meets Ecology" (Abstract)

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