Rare Species May be Some of the Most Important to an Ecology

A new study, published 28 May in the open access journal PLOS Biology, has revealed the potential importance of rare species in the functioning of highly diverse ecosystems. Using data from three very different ecosystems—coral reefs, tropical forests and alpine meadows—a team of researchers led by David Mouillot at the University of Montpellier 2, France, has shown that it is primarily the rare species, rather than the more common ones, that have distinct traits involved in unique ecological functions. As biodiversity declines, these unique features are therefore particularly vulnerable to extinction because rare species are likely to disappear first.

"These unique features are irreplaceable, as they could be important for the functioning of ecosystems if there is major environmental change," explained Dr Mouillot.

Biodiverse environments are characterized by a large number of rare species. These rare species contribute to the taxonomic richness of the area, but their functional importance in ecosystems is largely unknown. Represented by few individuals or distributed over narrow geographic areas, rare species are generally considered to have little influence on the functioning of an ecosystem compared with more common species. Indeed, it is often assumed that they fulfill the same ecological roles as those of common species but have less impact because of their low abundance; a phenomenon known as 'functional redundancy'. This redundancy suggests that rare species merely serve as an "insurance" policy for the ecosystem, in the event of an ecological loss.

Something to pay attention to, paleo folks.  Keystone species may not just be the most common.  Something to think abotu when reconstructing ecosystems in Deep Time and working with mass extinctions.  Its really not hard to imagine there was a keystone species (or three) whose loss caused the massive shift from the paleozoic marine ecosystems to the mesozoic style during the PT Extinction.