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    Homoploid Hybridization and Its Role in Emergence and Diversity of the Genus Origanum L. (Lamiaceae)
    (Nova Science Publisher Inc., 2020) Dirmenci T.; Arabacı T.; Özcan T.; Yazıcı T.; Martin E.; Çelenk S.; Açar M.
    Hybrid specimens can be occurred as same ploidy level (homoploidy) or not (polyploidy) with its parents. Homoploid hybrids are originated without any change in their ploidy level (2n) and polyploid hybrids are produced with the change in ploidy level (3n, 4n etc.). According to recent studies, the frequency of natural hybridization (homoploid and polyploid) has been estimated to 25% of all flowering plants. Recent studies show that the genus Origanum has homoploid hybrids. Hybridization is a common phenomenon among the species of Origanum in overlapping distribution habitats (natural or cultivated areas). Ietswaart suggested that the hybridization process is a significant factor in the speciation of Origanum, and Origanum is probably caused by the hybridization of the old tribe Saturejeae (now tribe Mentheae) genera. Based on the hypothesis of Ietswaart, we can discuss the emergence of the genus Origanum, its intrageneric speciation and its hybrids having the possibility for speciation via hybridization using morphological and cytological evidence. During the field studies, it was seen that many populations of wide-distributed species were overlapping, and some Origanum putative hybrid specimens were also observed in these overlapping areas with morphological differences from their parents. All studied Origanum species and hybrids have 2n = 30 chromosome numbers to define homoploidy. Palynological characters were revealed, and intermediate pollen structure (size, P/E ratio etc.) was seen in the hybrids between their parents. In addition, DNA extractions were done from all the hybrids and their parents. nrITS DNA was sequenced. Hybrid specimens have some heterozygous DNA loci in comparison to their parents. This study presents some evidence about homoploid the hybridization of the genus Origanum put forward by Ietswaart. If habitat, ecological and geographic isolations occur between the hybrids and their parents, these hybrids can be speciation via homoploid hybridization in the future. © 2020 by Nova Science Publishers, Inc. All rights reserved.
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    Taxonomy of origanum L. (Lamiaceae)
    (Nova Science Publishers, Inc., 2021) Dirmenci1 T.; Arabaci T.; Özcan1 T.; Drew B.; Yazici T.; Martin E.; Celep F.
    Origanum (Subfamily Nepetoideae, tribe Mentheae, subtribe Menthinae) contains several species commonly used as spices, tea, and for medicinal purposes, and is one of the most commercially important genera within the family Lamiaceae. Origanum is found exclusively in the Northern Hemisphere of the Old World, with 90% of the taxa occurring in the Mediterranean region. Although members of the genus are predominantly distributed in the Mediterranean region, there are also species (e.g., O. vulgare s.l.) distributed from the Azores to Taiwan and throughout much of Eurasia. Diploid chromosome numbers have been reported as 2n = 28, 30 and 32, with the basic number x = 15. Hybridization is quite common (~52% of species) within Origanum, and can occur between individuals belonging to the same or different generic sections. Homoploid hybridization appears to be the primary ploidy mechanism within the genus. Here, we define Origanum as having 42 species (49 taxa) and 22 hybrids, and provide an updated sectional delimitation of the genus. In addition to providing taxonomic clarification, information including gross morphological characters, photographs and drawings, distribution, ecology, and cytology of the genus are also provided. © 2022 Nova Science Publishers, Inc.