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Common species are most important in ecosystems

By JW Dowey - 27 May 2014 10:13:0 GMT
Common species are most important in ecosystems

To the NW of West Papua, south of the Philippines are these healthy coral reefs in Raja Ampat. The violet soft coral, Dendronephthya sp. illustrates the differences between many coral types and their community of fish and fellow-invertebrates; Coral image; Credit: © Shutterstock

Biodiversity theories state that abundance results from chance variations rather than individual traits. This test of theory finds that abundance of species varies so much that the species' traits drive the structure of a community. This seems an acceptable result, s a massive 1185 animal species were included from 14 marine ecosystems, leading to this modification of biodiversity theory in which crucial ecological differences among species are central.

Maintaining diversity in a community could be difficult. In a community, the abundant species are often critical in providing habitat for others or maintaining the status quo by removing excess plants. The neutral biodiversity theory indicates that species can be replaced with others. If the niche is given more priority, then replacement would be very difficult. Dr Julian Caley of the Australian Institute of Marine Science states, "those species had particular traits that made them so abundant, and therefore critical to a functioning healthy reef system."

He was one of several authors, led by Professor Sean Connolly of Australia's James Cook University, alongside researchers from the Universities of Pisa, Western Australia, Calcutta, and many other North American and European institutions. This august assemblage used mathematical tools to probe the likelihood of various aspects of biodiversity theory. The effects on our treatment of conservation issues will be profound.

The richness of species in marine communities has prevented a species by species approach previously, as the mathematical parameters increase to an infinite number. With many of the species very rare, their level of interaction is almost impossible to assess. Here, the researchers used Dr Salvador Pueyo's method to analyse the dynamics mathematically. The result is an explanation as to why 2 species of Acropora (elkhorn and staghorn) dominated Caribbean reefs until the 1970s. No coral has since been able to fill the niche of those corals. Their special characteristics or traits developed to suit that Caribbean niche and make them abundant.

All the analyses provide remarkably consistent evidence that very different ecosystems from the depths to the shore are similar. They all depend on abundant species to maintain aspects of their diversity, and the niches of others. The fact that these key species remain common over measurable timescales is also relevant to the argument. Now all we have to do is identify the traits that make them so abundant and keep them at the top. A lot of effort has been put in to investigate rare species, but it seems the common species are worth investigating more.

The whole paper from Sean Connolly et al can be viewed as, "Commonness and rarity in the marine biosphere," in - PNAS.