Marine biodiversity

A new model based on network theory explains why marine biodiversity has grown at a different pace from continental biodiversity.

BIODIVERSITY on land has been expanding exponentially, from a few species at the beginning of the Phanerozoic to some million species today. But the growth dynamics of marine life has been very different: According to fossil records, about 500 million years ago the number of marine species began growing exponentially and then levelled off for 200 million years before exploding again. A team of researchers from Germany and Switzerland has now constructed a model of species dependence that could explain this observation whose description appears in the latest issue of Physical Review Letters. The authors’ analysis, based on network dynamics, shows that a biodiversity stagnation can occur when species at the top of the ecological pyramid are dependent on only a few species at the bottom, whose extinctions can thus wipe out the whole ecosystem. Applying their model in combination with paleontological datasets, the authors argue this situation explains the observed slowdown of marine biodiversity.

R. Ramachandran