Aretz et al_2011.pdf - ORBi - Université de Liège

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Kölner Forum Geol. Paläont., 19 (2011)
M. ARETZ, S. DELCULÉE, J. DENAYER & E. POTY (Eds.)
Abstracts, 11th Symposium on Fossil Cnidaria and Sponges, Liège, August 19-29, 2011
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The scleractinian corals: a perspective
Vassil N. ZLATARSKI 1 & Joel L. STAKE 2
1 131 Fales Rd., Bristol, RI 02809, U.S.A.; vzlatarski@yahoo.com
2 Department of Biology, Rivier College, 420 South Main Street, Nashua, NH 03060, U.S.A.;
jstake@rivier.edu
During the last three decades, new research approaches have exponentially increased our knowledge of
scleractinian corals. The existing paradigms have been challenged and the accumulated data are in need of
new interpretation. Events like the XI International Symposium on Fossil Cnidaria and Porifera offer a rare
possibility to analyze the existing knowledge and to formulate future directions of scientific research. This
task is not possible for single researchers and needs the competence of the entire collegium. So, this
presentation is a respectful appeal for discussion and suggestions that should find place in the Symposium
resolutions. A historical review of the scleractinian research is followed by an update of the current status
and issues facing scleractinain coral taxonomy and phylogeny and suggestions for some prospective
directions for future studies.
The history of the scleractinian research can be divided in three periods. During the first, the Plant
period (1576-1727), the scleractinians were considered plants and as such were figured by many botanists.
PEYSSONNEL was the first to declare scleractinians to be animals and marked the start of the second, Animal
period (1727-2007). The notion of the coral holobiont, the hologenome theory, the holistic species concept
and integrative taxonomy marked the beginning of the third, Holistic period (2007-present). A graphical
presentation of the progression of scleractinian knowledge reveals that it was not a gradual process. There
are three considerable impulses, reflecting new approaches for studying the Scleractinia: first, on the
boundary between the 19th and 20th centuries; second, originating in the 1950s; and third, starting in the
1980s. In the beginning, scarce material was found on the beaches or during fishing and was described
typologically. Later, the entrance into the natural habitat in the end of the 19th and early 20th centuries
brought to attention the exceptional coralla variability and led to usage of formae and transplantation
experiments. The microstructure of the skeleton became a focus of the studies during this time. Starting in
the middle of the last century, detailed studies were undertaken on multiple skeletal macro- and
micromorphological characters, microstructure, and on their variability in fossil and extant material.
Functional micromorphology became a new area of exploration. Scuba research in situ on a global scale also
made a considerable contribution to the field during the second half of the last century. Beginning in the
1980s, a series of fundamental discoveries in life history and molecular biology opened new horizons for
scleractinian understanding. Only less than two decades ago, the scleractinian classification was based
exclusively on skeletal characters. Then in a short period of time, there were rapidly accumulated data from
the new sources of knowledge, i.e. molecular biology, ecology, life history and new approaches in
paleobiology. The results of molecular biology did not fit for the existing systematics. The return to the
micromorphological and mictrostructural characters suggested a possible way to harmonize the skeletal
information with the coming data of molecular biology.
Presently, the taxonomy is an artifact of the insufficient sampling size resulting in a lack of knowledge
about morphological, geographic, bathymetric and genetic variability. There are no large recent
scleractinian collections, and the old collections are not always available. Fortunately, 83% (4,980
specimens) of the largest Atlantic scuba collections made four decades ago in Cuba are well preserved and
digitalized in a multimedia format. Molecular biological studies suggest that incomplete lineage sorting,
hybridization and morphological convergent evolution all present challenges to a morphologically based
taxonomy and phylogenetic analysis for the Scleractinia. Individual approaches, while providing
interesting and new evolutionary hypotheses, are still not presenting a unified system of classification.
Many molecular based studies ignore the implied taxonomic revision or relegate it to a future endeavor.
Although some researchers have embraced an integrative approach to studying the Scleractinia, the area is
ripe for more collaborative work across the disciplines. While the ecological interest has been
predominantly focused on shallow waters, the mesophotic zone and the deep sea are still terra incognita.