The Use of AroB and Agt1. Nuclear Markers in the Investigation of the Homoploid Hybrid Speciation Origin of Stewartia Ovata
Dr. Jianhua Li, Hope College
The homoploid hybrid speciation origin of Stewartia ovata was investigated using conserved ortholog set (COS) nuclear markers AroB and Agt1. Molecular data has been useful in identification of other homoploid hybrid species and COS markers were used because of the high number of parsimonious informative sites due to variation within introns. Maximum parsimony and maximum likelihood analysis using PAUP identified the formation of a clade containing both S. ovata and S. malacodendron, the other North-American species of Stewartia, that is sister to the clade containing other Asian species of Stewartia and is statistically well supported. This data conflicts with data based on chloroplast markers that identifies a clade containing S. ovata and Asian species of Stewartia that is sister to S. malacodendron. This then suggests that an ancestral population of S. malacodendron served as a pollen donor while an ancestral Asian species served as a maternal genetic donor since chloroplast and mitochondria DNA are inherited maternally. It may be concluded then that there is strong statistical support for the hypothesis that S. ovata resulted from a homoploid hybrid speciation mechanism since all species of Stewartia contain 2n = 30 chromosomes.
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