Research challenges rainforest theory
St Louis - New research into the makeup of the earth's rainforests has posed a challenge to a currently popular ecological theory, concluding that "deterministic, not random" factors explain patterns of diversity around the world.
Robert Ricklefs, Curators' Professor of Biology at the University of Missouri-St Louis (UMSL), and Susanne Renner, Professor of Biology at Ludwig Maximilians University of Munich, reported in Science magazine a finding that they said now puts "a nail in the coffin" of the so-called neutral theory in ecology.
In remarks to the online paper UMSL Daily, the two researchers commented on US ecologist Stephen Hubbell's unified neutral theory of biodiversity and biogeography. This theory, according to Renner, "postulates that random fluctuations in population size and probabilities of species production and dispersal play the dominant role" in those tropical forests.
Renner, who is also ecological diversity director of the Botanic Garden and Herbaria in Munich, notes that Hubbell's theory had gained many "influential" backers over the past decade. However, the research by Ricklefs and Renner points to a different conclusion, that deterministic factors are at play in the process of biodiversity.
The two scientists analysed data from censuses of trees in species-rich rainforests of Africa, Asia, and Central and South America. They then compared those findings with fossils dating back 55 to 65 million years from similar forests of South America.
"[The] species' and individuals' particular evolutionary lineages are highly correlated on all three continents," Ricklefs told UMSL Daily.
"If a family of trees, such as the legumes, is abundant in Asia, then it is likely to be abundant in Africa and South America. If it is uncommon in one, then it is most likely uncommon in the others."
This observation, he said, leads to the conclusion that "there is a very definite process that leads to abundance and it is deterministic, not random".
"Diversity is a central issue in ecology. Neutral theory predicts that the relative abundance of evolutionary groups should be unpredictable across regions. Looking at large-scale patterns across millions of years of evolution and diversification clearly allows us to reject neutral interpretations," he added.