Dirmenci, Tuncay; Arabacı, Turan; Özcan, Taner; Yazıcı, Türker; Martin, Esra; Çelenk, Sevcan; Açar, Mikail; Üzel, Devrim

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.

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Dirmenci, Tuncay; Özcan, Taner; Açar, Mikail; Arabacı, Turan; Yazıcı, Türker; Martin, Esra

Origanum munzurense Kit Tan & Sorger (Sect. Brevifilamentum Ietsw.) was described by Kit Tan & Sorger in 1984, and it is an accepted species related to O. acutidens (Hand.-Mazz.) Ietsw. belonging to sect. Brevifilamentum. It is morphologically intermediate between O. acutidens and O. vulgare L. subsp. gracile (K.Koch) Ietsw., and its type locality lies in the overlap zone between the geographic distributions of these two taxa. We hypothesized that O. munzurense is in fact a hybrid between the two aforementioned taxa and we tested this hypothesis with the general morphology, chromosome features, and nuclear (ITS1–ITS2) and chloroplast (rpl32) DNA sequences of specimens of O. munzurense and its putative parental species, O. vulgare subsp. gracile and O. acutidens. The somatic chromosome number of O. munzurense, O. vulgare subsp. gracile and O. acutidens were counted as 2n = 30. Origanum munzurense presented polymorphic sites in the nuclear ITS region, but the chloroplast markers did not allow us to identify the putative maternal of O. munzurense. Our results suggest that O. munzurense is indeed a hybrid, and its rearrangement as a new homoploid hybrid (O. ×munzurense) would be more accurate. These present results support previous reports for the speciation of Origanum members via hybridization.

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