The genus Crataegus L. has approximately 200 species worldwide. However, the number of the species is increased to 1200 species by some taxonomists. Traditionally, the genus is placed in the subfamily Maloideae and it is closely related to the genera Pyracantha M.Roem., Mespilus L. and Hesperomeles Lindl. The latest phylogenetic analysis of the genus shows that it is closest to the genus Osteomeles Lind. Crataegus is divided into 40 sections by various taxonomists. The genetic diversity centre of the section Crataegus ranges from Turkey to Iran. According to field observations in Turkey, new diversity centres are proposed. The latest studies on Turkish Crataegus species show that there are more species than hitherto known. Hybridisation is common between the Crataegus species in Turkey and the biogeographic distributions of them and their parents are given. Some features of the genus, including leaf and pyrenes morphology, pyrenes number and fruit colours, are polymorphic. Polymorphism and hybridisation are the main reason for abundance of the synonyms of the Crataegus species.
DÖNMEZ, ALİ ARSLAN (2004) "The Genus Crataegus L. (Rosaceae) with Special Reference to Hybridisation and Biodiversity in Turkey," Turkish Journal of Botany: Vol. 28: No. 1, Article 4. Available at: https://journals.tubitak.gov.tr/botany/vol28/iss1/4