title: Genomic markers reveal introgressive hybridization in the Indo-West Pacific mangroves: a case study.
abstract: Biodiversity of mangrove ecosystems is difficult to assess, at least partly due to lack of genetic verification of morphology-based documentation of species. Natural hybridization, on the one hand, plays an important role in evolution as a source of novel gene combinations and a mechanism of speciation. However, on the other hand, recurrent introgression allows gene flow between species and could reverse the process of genetic differentiation among populations required for speciation. To understand the dynamic evolutionary consequences of hybridization, this study examines genomic structure of hybrids and parental species at the population level. In the Indo-West Pacific, Bruguiera is one of the dominant mangrove genera and species ranges overlap extensively with one another. Morphological intermediates between sympatric Bruguiera gymnorrhiza and Bruguiera sexangula have been reported as a variety of B. sexangula or a new hybrid species, B. × rhynchopetala. However, the direction of hybridization and extent of introgression are unclear. A large number of species-specific inter-simple sequence repeat (ISSR) markers were found in B. gymnorrhiza and B. sexangula, and the additive ISSR profiling of B. × rhynchopetala ascertained its hybrid status and identified its parental origin. The varying degree of scatterness among hybrid individuals in Principal Coordinate Analysis and results from NewHybrids analysis indicate that B. × rhynchopetala comprises different generations of introgressants in addition to F(1)s. High genetic relatedness between B. × rhynchopetala and B. gymnorrhiza based on nuclear and chloroplast sequences suggests preferential hybrid backcrosses to B. gymnorrhiza. We conclude that B. × rhynchopetala has not evolved into an incipient hybrid species, and its persistence can be explained by recurrent hybridization and introgression. Genomic data provide insights into the hybridization dynamics of mangrove plants. Such information can assist in biodiversity assessment by helping detect novel taxa and/or define species boundaries.
authors: Department of Organismic and Evolutionary Biology, Harvard University, Cambridge, Massachusetts, United States of America. meisun@oeb.harvard.edu
authors: Mei
authors: M
authors: Sun
authors: Eugenia Y Y
authors: EY
authors: Lo
references: Syst Biol. 2008 Oct;57(5):758-71
references: 18853362
references: Am J Bot. 2004 Sep;91(9):1333-44
references: 21652366
references: New Phytol. 2005 Feb;165(2):411-23
references: 15720652
references: BMC Evol Biol. 2008 May 16;8:149
references: 18485207
references: Genetics. 1992 Oct;132(2):619-33
references: 1385266
references: Evolution. 1990 Sep;44(6):1498-1511
references: 28564296
references: Bioinformatics. 2003 Aug 12;19(12):1572-4
references: 12912839
references: Heredity (Edinb). 2009 May;102(5):442-52
references: 19240752
references: Curr Opin Genet Dev. 2007 Dec;17(6):513-8
references: 17933508
references: Nucleic Acids Res. 1994 Nov 11;22(22):4673-80
references: 7984417
references: Philos Trans R Soc Lond B Biol Sci. 2008 Sep 12;363(1505):2841-50
references: 18508754
references: Proc Natl Acad Sci U S A. 2000 Jun 20;97(13):7043-50
references: 10860969
references: Bioinformatics. 2001 Aug;17(8):754-5
references: 11524383
references: J Evol Biol. 2010 Oct;23(10):2249-61
references: 20796134
references: Bioinformatics. 1998;14(9):817-8
references: 9918953
references: Mol Ecol. 2008 Mar;17(6):1552-63
references: 18321255
references: Trends Ecol Evol. 1992 Dec;7(12):401-5
references: 21236080
references: Proc Natl Acad Sci U S A. 1998 Apr 28;95(9):5112-5
references: 9560237
references: Am J Bot. 2004 Oct;91:1700-1708
references: 18677414
references: Bioinformatics. 2005 Feb 15;21(4):456-63
references: 15608047
references: Mol Phylogenet Evol. 2006 Mar;38(3):667-76
references: 16129628
references: Am J Bot. 2003 Dec;90(12):1708-19
references: 21653347
references: Mol Ecol. 2000 Oct;9(10):1657-9
references: 11050560