Scientists have released
ground-breaking findings that dismiss the 'Neutral Theory of Biodiversity'. The
theory has dominated biodiversity research for the past decade, and been
advocated as a tool for conservation and management efforts. The study, the
largest of its kind, covers a broad range of marine ecosystems on Earth and has
important implications for how marine conservation areas are managed.
Researchers
have today released ground-breaking findings that dismiss the 'Neutral Theory of
Biodiversity'. The theory has dominated biodiversity research for the past
decade, and been advocated as a tool for conservation and management efforts.
Professor Sean Connolly from the ARC Centre of Excellence
for Coral Reef Studies (Coral CoE) at James Cook University (JCU) is the lead
author of the international study, which he says overturns the long-used theory
by employing a novel mathematical method. It is the largest study of its kind,
covering a broad range of marine ecosystems on Earth.
"The study has important implications for how marine
conservation areas are managed," Professor Connolly says.
"The aim of neutral theory is to explain diversity and
the relative abundances of species within ecosystems. However, the theory has
an important flaw: it fails to capture how important the highly abundant
species that dominate marine communities are."
Professor Connolly explains that it's often the really
abundant species that deliver substantial ecosystem services like providing
habitat for fishes, or keeping reefs clear of seaweeds. "These species
have unique features that allow them to be so abundant, and to play those key
roles," he says.
But when neutral theory underpins marine conservation,
species are treated as swappable. "So the theory implies that, if you lose
a really abundant species, then another can simply increase in abundance to
take its place."
Using neutral theory, species become common or rare as a
consequence of random processes: chance variation in who a predator happens to
eat, or whose dispersing offspring happen to land on a vacant bit of real
estate on the seafloor. This study shows that these random processes are not
strong enough to explain the large differences between common and rare species.
Professor Connolly points to Caribbean coral reefs as an
example of why this problem with neutral theory can be important. "Until
the 1970s, these reefs were dominated by two species that were close relatives
of the branching corals that dominate the reefs of the Great Barrier Reef. When
these species were nearly lost as a consequence of overfishing and other forms
of reef degradation, no other coral species increased to fill the gap," he
says.
"Those species had particular traits that made them so
abundant, and therefore critical to a functioning healthy reef system,"
continues Dr Julian Caley a co-author of the study from the Australian
Institute of Marine Studies (AIMS).
"Both biodiversity theory and conservation managers need
to be alert to these characteristics, because it is often the common species,
not the rare ones, that are most important to healthy ecosystems," Dr
Caley explains.
"The results of this study are also unprecedented in
their remarkable consistency across a very large set of vastly different
ecological systems throughout the world's oceans," he adds.
The study looks at 14 different marine ecosystems sampled at
1185 locations across the globe. The datasets range from the polar to tropical
regions, from deep-sea to shallow coral reef environments and intertidal zones.
It includes vertebrates as well as invertebrates, from plankton, to clams, to
coral reef fishes.
To overturn neutral theory, the study used a novel
mathematical method that identified common predictions of the different models
that form the theory. These predictions were then tested against this wide
array of marine ecosystems.
Source:ARC Centre of Excellence in Coral Reef Studies & Science Daily
