Biology Reference
In-Depth Information
7
.
Some detailed examples at the
population/metapopulation
level
In the following chapters, I discuss some examples of equilibrium and
nonequilibrium conditions in populations and communities in greater
detail. Some studies deal with both populations and communities. Those
with emphasis on populations are discussed in this chapter, those with
emphasis on communities in Chapter
8
.
Reef fishes: density dependence and equilibrium
in populations?
Coral reefs are among the most diverse ecological systems on Earth. Species
include not only a great range of fishes but numerous invertebrates
and plants. For example, Heron Island, at the southern end of the Great
Barrier Reef is a small coral cay (island) 900
300m in size, with a reef
about 16 km long by a few km wide around it. Nobody has ever counted
the number of invertebrate species, most of which probably have not
been described, but more than 900 species of fishes have been recorded
there. Knowledge of how such diverse systems function is of paramount
importance, and, indeed, a very large number of studies on the behavior
and ecology of reef fishes in the Indo-Pacific and Atlantic Oceans have
been conducted using a variety of methods. Nevertheless, agreement on
some important aspects of reef fish ecology has not been reached, largely
due to the great range of habitats and species, and partly due to confusion
about concepts and theoretical interpretations of the findings. I will
discuss some studies to show the often contradictory findings and
interpretations.
Many but not all reef fishes live in open systems, producing numerous
dispersal larvae with high mortality. Many species are non-territorial,
juveniles of others settle and become strictly territorial.
Sale and others, in a number of important papers, investigated reef fish
assemblages on the Great Barrier Reef (and later in other regions), using
experiments and long-term monitoring. Populations studied were often
