Divergent Sympatric Lineages Of The Atlantic And Indian Ocean Crinoid Tropiometra Carinata

The shallow water comatulid crinoid Tropiometra carinata is native to both the Atlantic and Indian Oceans, a distribution anomalous among shallow water crinoids and many other broadcast spawning species. Given this species\u27 short pelagic larval duration, the findings of previous work that suggest that the Benguela upwelling is a significant barrier to gene flow in broadcast spawning species, and T. carinata\u27s unexpected geographic distribution, we predicted that the crinoids presently recognized as T. carinata consisted of a species complex. To test this prediction, we sequenced a portion of the mitochondrial cytochrome oxidase 1 gene from 30 individuals of T. carinata collected from Brazil, the Mozambique Channel, Madagascar, and Reunion Island. We found that nucleotide divergence ranged 0.02-3.10% among haplotypes. Moreover, while a Bayesian phylogenetic tree indicated that there were two substantially divergent genetic lineages, there was no evidence to support that T. carinata is comprised of a species complex due to isolation-by-distance. Surprisingly, both lineages were found in sympatry in both the Atlantic and Indian Oceans. Likewise, a 95% parsimony haplotype network revealed that identical haplotypes are found in both oceans, suggesting that a species complex may indeed exist, just not one caused by geographic isolation. We discuss possible explanations for this unexpected genetic structure, such as natural dispersal or human-mediated movement, and how the genetic structure found here is relevant to other marine organisms and to cryptic speciation. © 2012, The American Microscopical Society, Inc