[Coral-List] Repeated loss of coloniality and symbiosis in corals

Marcos S. Barbeitos msbb at ku.edu
Sat Jun 19 23:34:06 EDT 2010

Dear listers,

I'd like to draw your attention to this paper, recently published in PNAS:

Repeated loss of coloniality and symbiosis in scleractinian corals
Marcos S. Barbeitos, Sandra L. Romano, and Howard R. Lasker


The combination of coloniality and symbiosis in Scleractinia is thought to
confer competitive advantage over other benthic invertebrates, and it is
likely the key factor for the dominance of corals in tropical reefs.
However, the extant Scleractinia are evenly split between zooxanthellate and
azooxanthellate species. Most azooxanthellate species are solitary and
nearly absent from reefs, but have much wider geographic and bathymetric
distributions than reef corals. Molecular phylogenetic analyses have
repeatedly recovered clades formed by colonial/zooxanthellate and
solitary/azooxanthellate taxa, suggesting that coloniality and symbiosis
were repeatedly acquired and/or lost throughout the history of the
Scleractinia. Using Bayesian ancestral state reconstruction, we found that
symbiosis was lost at least three times and coloniality lost at least six
times, and at least two instances in which both characters were lost. All of
the azooxanthellate lineages originated from ancestors that were
reconstructed as symbiotic, corroborating the onshore-offshore
diversification trend recorded in marine taxa. Symbiotic sister taxa of two
of these descendant lineages are extant in Caribbean reefs but disappeared
from the Mediterranean before the end of the Miocene, whereas extant
azooxanthellate lineages have trans-Atlantic distributions. Thus, the
phyletic link between reef and nonreef communities may have played an
important role in the dynamics of extinction and recovery that marks the
evolutionary history of scleractinians, and some reef lineages may have
escaped local extinction by diversifying into offshore environments.
However, this macroevolutionary mechanism offers no hope of mitigating the
effects of climate change on coral reefs in the next century.


The paper is open access. 


Marcos S. Barbeitos

Post-Doc Fellow
The University of Kansas
Department of Ecology and Evolutionary Biology
2041 Haworth Hall
1200 Sunnyside Avenue
Lawrence, Kansas 66045
p: 785.864.5887
f: 785.864.5860

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