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Open Access Highly Accessed Research article

Comparative genetic structure of two mangrove species in Caribbean and Pacific estuaries of Panama

Ivania Cerón-Souza12*, Eldredge Bermingham1, William Owen McMillan1 and Frank Andrew Jones13

Author Affiliations

1 Smithsonian Tropical Research Institute, Apartado, 0843-03092, Panama

2 University of Puerto Rico, Rio Piedras Campus, PO BOX 23360, San Juan, 00931-3360, Puerto Rico

3 Department of Botany and Plant Pathology, Oregon State University, 2070 Cordley Hall, Corvallis, OR, 97331, USA

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BMC Evolutionary Biology 2012, 12:205  doi:10.1186/1471-2148-12-205

Published: 18 October 2012

Abstract

Background

Mangroves are ecologically important and highly threatened forest communities. Observational and genetic evidence has confirmed the long distance dispersal capacity of water-dispersed mangrove seeds, but less is known about the relative importance of pollen vs. seed gene flow in connecting populations. We analyzed 980 Avicennia germinans for 11 microsatellite loci and 940 Rhizophora mangle for six microsatellite loci and subsampled two non-coding cpDNA regions in order to understand population structure, and gene flow within and among four major estuaries on the Caribbean and Pacific coasts of Panama.

Results

Both species showed similar rates of outcrossing (t= 0.7 in A. germinans and 0.8 in R. mangle) and strong patterns of spatial genetic structure within estuaries, although A. germinans had greater genetic structure in nuclear and cpDNA markers (7 demes > 4 demes and Sp= 0.02 > 0.002), and much greater cpDNA diversity (Hd= 0.8 > 0.2) than R. mangle. The Central American Isthmus serves as an exceptionally strong barrier to gene flow, with high levels nuclear (FST= 0.3-0.5) and plastid (FST= 0.5-0.8) genetic differentiation observed within each species between coasts and no shared cpDNA haplotypes between species on each coast. Finally, evidence of low ratios of pollen to seed dispersal (r = −0.6 in A. germinans and 7.7 in R. mangle), coupled with the strong observed structure in nuclear and plastid DNA among most estuaries, suggests low levels of gene flow in these mangrove species.

Conclusions

We conclude that gene dispersal in mangroves is usually limited within estuaries and that coastal geomorphology and rare long distance dispersal events could also influence levels of structure.

Keywords:
Rhizophora mangle; Avicennia germinans; Pollen dispersal; Seed dispersal; Spatial genetic structure