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Genetic differentiation and phylogeography of partially sympatric species complex Rhizophora mucronata Lam. and R. stylosa Griff. using SSR markers.

Wee AK, Takayama K, Chua JL, Asakawa T, Meenakshisundaram SH - BMC Evol. Biol. (2015)

Bottom Line: Our results demonstrated the general genetic distinctiveness of R. mucronata and R. stylosa, and potential hybridization or introgression between them.Our findings have important implications on the conservation of mangroves, especially relating to replanting efforts and the definition of evolutionary significant units in Rhizophora species.These results serve as the foundation for the conservation genetics of R. mucronata and R. stylosa and highlighted the need to recognize the genetic distinctiveness of closely-related species, determine their respective genetic structure, and avoid artificially promoting hybridization in mangrove restoration programmes.

View Article: PubMed Central - PubMed

Affiliation: Department of Biology, Graduate School of Science, Chiba University, 1-33 Yayoi-cho, Inage-ku, Chiba, 263-8522, Japan. alisonwks@xtbg.ac.cn.

ABSTRACT

Background: Mangrove forests are ecologically important but globally threatened intertidal plant communities. Effective mangrove conservation requires the determination of species identity, management units, and genetic structure. Here, we investigate the genetic distinctiveness and genetic structure of an iconic but yet taxonomically confusing species complex Rhizophora mucronata and R. stylosa across their distributional range, by employing a suite of 20 informative nuclear SSR markers.

Results: Our results demonstrated the general genetic distinctiveness of R. mucronata and R. stylosa, and potential hybridization or introgression between them. We investigated the population genetics of each species without the putative hybrids, and found strong genetic structure between oceanic regions in both R. mucronata and R. stylosa. In R. mucronata, a strong divergence was detected between populations from the Indian Ocean region (Indian Ocean and Andaman Sea) and the Pacific Ocean region (Malacca Strait, South China Sea and Northwest Pacific Ocean). In R. stylosa, the genetic break was located more eastward, between populations from South and East China Sea and populations from the Southwest Pacific Ocean. The location of these genetic breaks coincided with the boundaries of oceanic currents, thus suggesting that oceanic circulation patterns might have acted as a cryptic barrier to gene flow.

Conclusions: Our findings have important implications on the conservation of mangroves, especially relating to replanting efforts and the definition of evolutionary significant units in Rhizophora species. We outlined the genetic structure and identified geographical areas that require further investigations for both R. mucronata and R. stylosa. These results serve as the foundation for the conservation genetics of R. mucronata and R. stylosa and highlighted the need to recognize the genetic distinctiveness of closely-related species, determine their respective genetic structure, and avoid artificially promoting hybridization in mangrove restoration programmes.

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Neighbour-joining (NJ) tree showing the relationships among populations for (A)Rhizophora mucronataand (B)Rhizophora stylosa. The oceanic region of each population cluster is indicated in italics. Dotted ellipses outline the clusters as denoted by the STRUCTURE analysis.
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Fig6: Neighbour-joining (NJ) tree showing the relationships among populations for (A)Rhizophora mucronataand (B)Rhizophora stylosa. The oceanic region of each population cluster is indicated in italics. Dotted ellipses outline the clusters as denoted by the STRUCTURE analysis.

Mentions: STRUCTURE analysis with pure individuals (after removing both putative hybrids and possibly misidentified individuals) supported two genetic clusters (K = 2) for both R. mucronata and R. stylosa (Figure 5). In R. mucronata, the two genetic clusters were: (1) populations from West Indian Ocean, Arabian Sea, Bay of Bengal and Andaman Sea, and (2) populations from Malacca Strait, South China Sea, Bali Sea and West Pacific Ocean (Figure 6A). Low level of admixture was detected in R. mucronata populations from the Andaman Sea and Malacca Strait. Two genetic clusters were also detected in R. stylosa; the clustering pattern was more conspicuous than that of R. mucronata. A strong genetic break separated populations in the South China Sea and East China Sea from populations in the Southwest Pacific Ocean (Figure 6B). The genetic breaks were constantly supported with increasing number of clusters in STRUCTURE analyses. AMOVA analysis revealed that within each species, most of the genetic variation was partitioned among regions (40.48% and 45.82% for R. mucronata and R. stylosa, respectively) (Table 2).Figure 5


Genetic differentiation and phylogeography of partially sympatric species complex Rhizophora mucronata Lam. and R. stylosa Griff. using SSR markers.

Wee AK, Takayama K, Chua JL, Asakawa T, Meenakshisundaram SH - BMC Evol. Biol. (2015)

Neighbour-joining (NJ) tree showing the relationships among populations for (A)Rhizophora mucronataand (B)Rhizophora stylosa. The oceanic region of each population cluster is indicated in italics. Dotted ellipses outline the clusters as denoted by the STRUCTURE analysis.
© Copyright Policy - open-access
Related In: Results  -  Collection

License 1 - License 2
Show All Figures
getmorefigures.php?uid=PMC4389924&req=5

Fig6: Neighbour-joining (NJ) tree showing the relationships among populations for (A)Rhizophora mucronataand (B)Rhizophora stylosa. The oceanic region of each population cluster is indicated in italics. Dotted ellipses outline the clusters as denoted by the STRUCTURE analysis.
Mentions: STRUCTURE analysis with pure individuals (after removing both putative hybrids and possibly misidentified individuals) supported two genetic clusters (K = 2) for both R. mucronata and R. stylosa (Figure 5). In R. mucronata, the two genetic clusters were: (1) populations from West Indian Ocean, Arabian Sea, Bay of Bengal and Andaman Sea, and (2) populations from Malacca Strait, South China Sea, Bali Sea and West Pacific Ocean (Figure 6A). Low level of admixture was detected in R. mucronata populations from the Andaman Sea and Malacca Strait. Two genetic clusters were also detected in R. stylosa; the clustering pattern was more conspicuous than that of R. mucronata. A strong genetic break separated populations in the South China Sea and East China Sea from populations in the Southwest Pacific Ocean (Figure 6B). The genetic breaks were constantly supported with increasing number of clusters in STRUCTURE analyses. AMOVA analysis revealed that within each species, most of the genetic variation was partitioned among regions (40.48% and 45.82% for R. mucronata and R. stylosa, respectively) (Table 2).Figure 5

Bottom Line: Our results demonstrated the general genetic distinctiveness of R. mucronata and R. stylosa, and potential hybridization or introgression between them.Our findings have important implications on the conservation of mangroves, especially relating to replanting efforts and the definition of evolutionary significant units in Rhizophora species.These results serve as the foundation for the conservation genetics of R. mucronata and R. stylosa and highlighted the need to recognize the genetic distinctiveness of closely-related species, determine their respective genetic structure, and avoid artificially promoting hybridization in mangrove restoration programmes.

View Article: PubMed Central - PubMed

Affiliation: Department of Biology, Graduate School of Science, Chiba University, 1-33 Yayoi-cho, Inage-ku, Chiba, 263-8522, Japan. alisonwks@xtbg.ac.cn.

ABSTRACT

Background: Mangrove forests are ecologically important but globally threatened intertidal plant communities. Effective mangrove conservation requires the determination of species identity, management units, and genetic structure. Here, we investigate the genetic distinctiveness and genetic structure of an iconic but yet taxonomically confusing species complex Rhizophora mucronata and R. stylosa across their distributional range, by employing a suite of 20 informative nuclear SSR markers.

Results: Our results demonstrated the general genetic distinctiveness of R. mucronata and R. stylosa, and potential hybridization or introgression between them. We investigated the population genetics of each species without the putative hybrids, and found strong genetic structure between oceanic regions in both R. mucronata and R. stylosa. In R. mucronata, a strong divergence was detected between populations from the Indian Ocean region (Indian Ocean and Andaman Sea) and the Pacific Ocean region (Malacca Strait, South China Sea and Northwest Pacific Ocean). In R. stylosa, the genetic break was located more eastward, between populations from South and East China Sea and populations from the Southwest Pacific Ocean. The location of these genetic breaks coincided with the boundaries of oceanic currents, thus suggesting that oceanic circulation patterns might have acted as a cryptic barrier to gene flow.

Conclusions: Our findings have important implications on the conservation of mangroves, especially relating to replanting efforts and the definition of evolutionary significant units in Rhizophora species. We outlined the genetic structure and identified geographical areas that require further investigations for both R. mucronata and R. stylosa. These results serve as the foundation for the conservation genetics of R. mucronata and R. stylosa and highlighted the need to recognize the genetic distinctiveness of closely-related species, determine their respective genetic structure, and avoid artificially promoting hybridization in mangrove restoration programmes.

Show MeSH