Systematics/Phytogeography / Taxonomie/ Section
Takayama, Koji , Tamura, Mariko , Tateishi, Yoichi , Kajita, Tadashi .
Remarkable genetic structure of mangrove genus Rhizophora (Rhizophoraceae) in the Atlantic-East Pacific.
To examine the importance of sea-dispersal for the speciation of mangrove species in the Atlantic-East Pacific, phylogenetic relationships and the spatial genetic structure of Rhizophora mangle and R. racemosa were investigated using molecular markers. Rhizophora samoensis from South Pacific Islands was also included, as the species was morphologically so similar with R. mangle that its taxonomic status was in question. In the phylogenetic analysis using c. 4,000 bp of cpDNA sequences, R. mangle and R. racemosa were basically well differentiated but shared several identical haplotypes, which indicates interspecific gene flow between these species. Clear genetic diversifications between the Pacific and Atlantic haplotypes were observed in both R. mangle and R. racemosa. The differentiation pattern was also confirmed by population analysis of cpDNA performed on more than 500 samples from 20 populations. This result suggests that the American continent is a clear geographic barrier that prevents gene flow by sea-dispersal for Rhizophora species. On the other hand, an identical haplotype was found among the Atlantic populations of the New World and West Africa, and another identical haplotype among the Pacific populations of R. mangle and R. samoensis. These results suggest that recent events of transoceanic long distance seed dispersal, which would be responsible for the integration of the wide distribution range of R. mangle. In microsatellite analysis, genetically differentiated populations of R. mangle were detected in the South Atlantic. Although there are no known land barriers, the bifurcating South Equatorial Current at the northeastern horn of Brazil could be a potential barrier to gene flow and may promote the genetic differentiation of these populations.
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1 - Chiba University, Graduate School of Science, Depertment of Biology, 1-33 Yayoi-cho, Inage-ku, Chiba, 263-8522, Japan
2 - University of the Ryukyus, Faculty of Education, 1 Senbaru, Okinawa, 903-0129, Japan
long distance dispersal
Presentation Type: Poster:Posters for Sections
Location: Ball Room & Party Room/SUB
Date: Monday, July 28th, 2008
Time: 12:30 PM