Title:
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The consequences of extinction in experimental aquatic communities
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Predicting the consequences of extinction is an important goal in ecology, due to the
accelerating rate of global and local species loss. Cascading extinction~ the extinction
of one species as a consequence of the extinction of another, has been demonstrated
in several natural ecosystems and is widely predicted by theoretical studies.
Extinction may also affect the functioning of ecosystems, as functionally important
species may be lost from communities and positive interactions between species may
be disrupted.
Investigating the consequences of extinction in natural ecosystems is difficult, as
removing a species from an area of habitat is often problematic. Also, because
indirect effects may take many generations to be revealed, experimental
manipulations in natural ecosystems often need to last for several years. Experimental
aquatic microcosms provide a new opportunity for conducting removal experiments
in small, tractable, communities containing rapidly reproducing species. Here, I
present the results of four experiments conducted in such microcosms that
. investigated the consequences of the removal ofa species and the effect of
temperature and energy on patterns ofextinction.
In general, local diversity was robust to the removal of a species. No cascading
extinction was observed and some positive effects of extinction for diversity were
revealed. Species loss had a positive, negative or no effect on ecosystem functioning,
depending upon community composition. Small changes to the identity of the species
present in communities had large effects; the consequences of extinction for
. .
ecosystem functioning was very context-dependent and rare species were important.
Temperature and chemical energy interacted to determine species diversity and
extinction determinism, making it difficult to predict the consequences of changes to
either temperature or chemical energy for extinction without knowledge of the other.
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