Speciation in the Millepora Complex: What Constitutes a Species?

April 29th, 2008

Fire coral from the genus Millepora are ubiquitous in tropical western Atlantic reefs. Two distinct morphologies of Millepora, currently classified as separate species, exist off the coast of the Bahamas. M. complanata have broad, smooth blades and prefer shallow waters whereas M. alcicornis have knobby branches and prefer deeper waters. After an intermediate morphology was discovered, the question arose as to whether these different morphologies represent different species or whether the differences result from ecophenotypic plasticity. Reef survey analyses have revealed the appearance of both the branching and blade morphs at the same depth at some reef locations. The occurrence of these two forms in mutual proximity supports the contention that morphologic variation of this genus is not primarily a response of a single species to environmental differences and suggests that they possess distinct genetic differences. uantitative analysis of coral colony microstructure suggests that it is possible to differentiate the forms.
DNA was collected from all morphs and the internal transcribed spacer regions (ITS) of rDNA were examined. All PCR amplification products of the rDNA ITS regions contained DNA fragments at approximately 824 bp regardless of species or reef location. DNA sequence analysis showed specific differences in nucleotide sequence between Milleporid specimens at five identical nucleotide positions at for all samples. These single nucleotide polymorphisms (SNPs) fit into two separate groups or clades. Each clade is independent of depth, reef location or morphology. This suggests that Milleporids may be reproductively isolated cryptic species, and that traditional features used for classification may be of little value.

Peter Lehr, ’08 West Des Moines, IA
Major: Biochemistry and Molecular Biology
Pavla Brachova, ’09 Ames, IA
Major: Biology
Dana Friend, ’09 Centennial, CO
Major: Geology
Benjamin Greenstein, Ph.D.
Cornell College
Robert Black, Ph.D.
Cornell College
Craig Tepper, Ph.D.
Cornell College

Sponsor: Craig Tepper

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