The causes of species hyperdiversity in tropical ecosystems - from reef
to rainforest.
Abstract
The tropics are renowned for extraordinary species richness across the
marine and terrestrial realms, holding more than three quarters of all
species [1]. Within the tropics, certain ‘hyperdiverse’ regions host
truly exceptional numbers of species at the local community level. For
example, a single hectare (100m x 100m) of coral reef in the
Indo-Pacific Coral Triangle hosts twice as many coral species as the
entire Atlantic ocean [2], and a hectare of the Ecuadorian Amazon
holds more tree species than the entirety of Europe [3,4]. Causes of
such outstanding species richness in hyperdiverse regions are varied,
and in some cases enigmatic, but in many ways the forces structuring
such high local-scale diversity have parallels across land and sea.
These range from the heightened accumulation of species due to quirks of
biogeography, climate and geology at evolutionary timescales, through to
the pressures of living at close quarters with many competitors and
natural enemies at ecological timescales. Comparing processes that
assemble hyperdiverse tropical communities across the marine and
terrestrial realms may allow future research to draw generalities about
the evolution of hyperdiverse regions as a whole, and may illuminate
ways in which they can be conserved.