The truth behind species richness and growth

The truth behind species richness and growth

New Zealand researchers have overturned a widely accepted pattern in nature.

Dr Len Gillman from AUT University and Dr Shane Wright from the University of Auckland have demonstrated the predominant pattern in nature is continuing increases in species richness as productivity (growth rate) increases.

Their study, published this month in the science journal Ecology, contradicts the widely-held belief of the past two decades that plant species richness climbs to a peak as productivity increases, and then declines as productivity continues to increase.

To establish this Dr Gillman and Dr Wright carried out a meta-analysis of 131 published studies, carefully scrutinising their experimental design and analysis before including them in the analysis.

"Remarkably, only 38% of previously reported relationships were found to be robust tests of the productivity-species richness link," say the researchers.

"Many of the studies were rejected because they used rainfall as a surrogate for productivity, but failed to control for temperature which also influences productivity and can be negatively correlated with rainfall."

These results are consistent with a recently-published study in Proceedings of the National Academy of Sciences USA by the same authors. This showed the rate of molecular evolution is twice as fast in warm productive tropical forests as it is in less productive forests at higher latitudes.

ENDS

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