Rojas, Monica L.

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    Genetic population structure of two species of brittle stars with contrasting life histories
    (2010) Rojas, Monica L.; Schizas, Nikolaos V.; College of Arts and Sciences - Sciences; Yoshioka, Paul; Weil, Ernesto; Aponte, Nilda; Department of Marine Sciences; Ramirez, Lillian
    Echinoderms display a wide array of life histories, which can have a profound effect in the dispersal potential and population structure of species. The brittle stars Ophiocoma echinata and Amphipholis squamata are commonly found in the shallow waters of the Caribbean Sea. The two species exhibit differing modes of development: O. echinata is a spawning species having asynchronous breeding cycles and A. squamata is a brooding species, viviparous and selffertilizing hermaphrodite. Their overlapping geographic range offers the opportunity to compare their genetic population structure as brooders are expected to exhibit higher population subdivision than spawners. Mitochondrial (16S) and ribosomal nuclear DNA sequences (ITS-1) were recovered from 16 populations of O. echinata and five populations of A. squamata around the Caribbean and Western Atlantic. Results indicate that the spawning O. echinata harbors moderate levels of genetic variability in the 16S gene (163 specimens, 66 haplotypes). There is no significant population structure (16S; FST = 0.00236; P = 0.38319) in this wide geographic area. This pattern is further supported by the ITS-1 gene. A. squamata however, harbors high levels of genetic variability (63 specimens, 45 haplotypes) with two well supported lineages. One of these is a newly discovered lineage of A. squamata around the world. Significant population structure (16S; FST = 0.63867; P = 0.0000) was observed between Puerto Rico and Florida, a result supported by the ITS-1 data. At a finer geographic scale in southwestern Puerto Rico, population differentiation was observed in A. squamata (FST = 0.14845; p<0.01369). These data provide compelling evidence that life history traits influence the connectivity of geographically distant populations. The spawner O. echinata showed no population structure from samples as far as Bermuda, Curaçao, Panama and Belize whereas the brooder A. squamata is potentially a complex of at least 2 cryptic species with partially overlapping geographic distributions.