Morphological distinctions between sugar maples and black maples are not consistently evident, and molecular assessment of genetic diversity is lacking for these taxa. We examined restriction-site polymorphisms in the ndhA intron of the chloroplast DNA (cpDNA) in populations of sugar maples and black maples representing their zones of allopatry and sympatry in eastern North America. Restriction-site analysis of the ndhA intron after digestion with HinfI and Sau3AI yielded no polymorphisms. Restriction digestion of the ndhA intron with TaqI revealed two cpDNA haplotypes that were neither geographically localized nor taxon specific. Although testing additional accessions of sugar maples and black maples for cpDNA variation will further elucidate patterns of genetic variation, our initial results suggest that the taxa are either exchanging genes or share an ancestral cpDNA polymorphism.
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