My original interest in coral reef ecosystems was focussed on the
structure and dynamics of populations and communities of tropical reef
fishes. These interests centred on recruitment, predation,
disturbance, and habitat structure. Because reef populations and
communities are replenished, for the most part, by settlement from the
plankton, a debate had developed in the literature regarding the
importance of presettlement versus postsettlement processes in
tropical and temperate marine populations with open demographics. My
research indicated to me that, across geographic spatial scales, the
relative importance of these processes varied from place to place.
This observation, coupled with insights I gained from Prof. A.R.E.
Sinclair (University of British Columbia), and his research on
terrestrial population dynamics, stimulated the idea for a review of
the dynamics of demographically open marine populations. The group of
us that assembled to write this review brought expertise in temperate
and tropical systems, and from sessile invertebrates to fishes. By
applying to open marine systems population dynamics theory and
principles developed for closed terrestrial populations, we were able
to demonstrate that the debate about whether recruitment or some
postrecruitment process drives the dynamics of the open, marine
populations was unnecessary. In nearly every case, the dynamics of
these systems could be expected to result from a combination of
processes operating both before and after settlement to benthic
habitats. This review appears to have facilitated a shift away from
these polarized views of marine population dynamics toward a better
appreciation of the relative importance of these different processes
in generating observed patterns of abundance.
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“…understanding evolutionary processes in tropical marine systems is important in its own right, and the high diversity of these systems provide great opportunities to design new and powerful tests with the potential to shed new light on long-standing issues.”
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The integration of processes operating at large scales, both
spatial and temporal, and how they influence local patterns and
processes continues to dominate my research. At large spatial scales,
I have studied local-regional diversity relationships both in tropical
reef species and global patterns of biodiversity. My co-authors and I
have shown patterns of regional enrichment of local biodiversity,
which are remarkably consistent across major taxa (e.g., including
trees, freshwater fishes, terrestrial mammals, and birds) and
continents with vastly different histories (e.g., North America and
Australia). I have also investigated patterns of rarity in reef
fishes. While our understanding of rarity is well advanced for
terrestrial species, our understanding of rarity and commonness in
marine species is comparatively poor. Not only is it important to
understand these issues for marine taxa, marine taxa can provide
independent tests of theory developed with terrestrial taxa in mind.
In addition to the effects of regional processes on local ecology
being poorly understood in marine ecosystems, the roles of historical
processes in these systems have not been adequately researched. As
with rarity, understanding evolutionary processes in tropical marine
systems is important in its own right, and the high diversity of these
systems provide great opportunities to design new and powerful tests
with the potential to shed new light on long-standing issues. Three
examples from my recent research illustrate this point. 1) For more
than three decades, ecologists and evolutionary biologists have
sought, without success, evidence that the high performance of
resource specialists on a limited range of resources trades off
against lower average performance of generalists across a broader
resource-use spectrum. Using coral-dwelling gobies which display
interspecific variation in habitat specialization, we were able to
show that indeed the jack-of–all-trades-is-master-of-none by
transplanting gobies between coral species and estimating their growth
performance. 2) The evolution of a Batesian mimic to resemble its
model species has generally been thought to require a large initial
improvement in resemblance occurring in a large, single step, to
overcome costs of increased conspicuousness. Using a model-mimic pair
of tropical reef fish species, we were able to demonstrate that small
improvements in resemblance can instead be associated with increased
fitness suggesting that Batesian mimicry could evolve gradually. 3)
Since the late 1970s, allocation to reproduction was thought to be
optimised as a two-stage process: first total reproductive effort is
optimised, then offspring size is optimised and traded off against
fecundity (i.e., the Smith and Fretwell model). One implication of
this view is that reproductive effort and offspring size will evolve
independently. Theoretically at least, offspring size and total
reproductive effort might not evolve independently (e.g., the Winkler
and Wallin model). We were able to test this idea and show correlated
evolution of reproductive effort and offspring size using a
comparative analysis of copepod life histories that included 105
families of copepods.
My current research continues to range from population and
community dynamics through to macroecology and evolution of reef
species with a particular emphasis on the evolution of these organisms
in the face of climate change.
Julian Caley, Ph.D.
Australian Institute of Marine Science
Townsville, Queensland, Australia
n
the essay below, Dr. Julian Caley discusses his highly cited
work in coral reef ecology. According to our Special Topic on
this research area, Dr. Caley’s work ranks at #10, with 13
papers cited a total of 416 times. Dr. Caley’s most-cited
paper, "Recruitment and the local dynamics of open marine
populations," (Annual Review of Ecology and
Systematics, 27:477-500, 1996), ranks at #2 on our list of
highly cited papers over the past decade with 244 citations to
date. In the 
Web product, Dr. Caley’s work can be found in the
field of Environment/Ecology. Dr. Caley is the Group Leader of
the Conservation and Biodiversity Group at the Australian
Institute of Marine Science.