Western Kentucky University
Testing Hypotheses of Hybridization in Mentha spicata and M. canadensis Using Molecular Data
Institution
Western Kentucky University
Faculty Advisor/ Mentor
Lawrence A. Alice
Abstract
Due to frequent hybridization and polyploidy in Mentha, an understanding of the evolutionary histories of M. canadensis and M. spicata (spearmint) has been difficult to ascertain. The goal of this study was to test hypotheses regarding the allopolyploid origins of these two species. DNA sequences of two non-coding chloroplast regions, the nuclear ribosomal internal transcribed spacer (ITS) region and the granule-bound starch synthase (GBSSI) gene were analyzed. ITS data show that some of the M. canadensis 171 clones cluster with one of its putative parents, M. longifolia; the others form a clade with M. arvensis. However, M. canadensis ITS clones from three other individuals cluster exclusively with M. arvensis. GBSSI data support the ITS results as M. canadensis clones group with clones of M. arvensis, also a putative allopolyploid. Chloroplast data imply that M. arvensis is the maternal ancestor of M. canadensis. ITS clones of three M. spicata samples form a clade with both of its putative parents, M. longifolia and M. suaveolens, whereas GBSSI data place M. spicata with M. longifolia. Chloroplast data indicate that M. longifolia is the maternal parent of M. spicata.
Testing Hypotheses of Hybridization in Mentha spicata and M. canadensis Using Molecular Data
Due to frequent hybridization and polyploidy in Mentha, an understanding of the evolutionary histories of M. canadensis and M. spicata (spearmint) has been difficult to ascertain. The goal of this study was to test hypotheses regarding the allopolyploid origins of these two species. DNA sequences of two non-coding chloroplast regions, the nuclear ribosomal internal transcribed spacer (ITS) region and the granule-bound starch synthase (GBSSI) gene were analyzed. ITS data show that some of the M. canadensis 171 clones cluster with one of its putative parents, M. longifolia; the others form a clade with M. arvensis. However, M. canadensis ITS clones from three other individuals cluster exclusively with M. arvensis. GBSSI data support the ITS results as M. canadensis clones group with clones of M. arvensis, also a putative allopolyploid. Chloroplast data imply that M. arvensis is the maternal ancestor of M. canadensis. ITS clones of three M. spicata samples form a clade with both of its putative parents, M. longifolia and M. suaveolens, whereas GBSSI data place M. spicata with M. longifolia. Chloroplast data indicate that M. longifolia is the maternal parent of M. spicata.