Phylogeny, morphology, and biogeography of Haplophyllum (Rutaceae), a species-rich genus of the Irano-Turanian floristic region

Haplophyllum A. Juss. is one of the most species-rich, but poorly-known genera of Rutaceae (citrus family), reaching maximum species diversity in Turkey, Iran, and Central Asia. Many of its species exhibit a narrow geographic range ("narrow endemics"), which makes them particularly vulnerable to extinction. Despite its importance for the characterization of the Irano-Turanian floristic region, the evolution of species diversity in Haplophyllum has never been examined in a phylogenetic and biogeographic context. We generated gene trees from DNA sequences of four regions of the chloroplast genome for 118 accessions, representing 66% of the species diversity of the genus. Additionally, Haplophyllum was examined morphologically. The phylogenetic analyses showed that several species of the genus do not form reciprocally monophyletic groups. Optimization of morphological characters on the chloroplast DNA phylogeny indicated that most of the species, in particular those with a widespread geographic distribution, can only be diagnosed by combinations of homoplasious character states. Homoplasy notwithstanding, the main morphological characters traditionally used to classify the genus are consistent with the molecular phylogeny ofHaplophyllum. Finally, the Mediterranean representatives ofHaplophyllum were found to be embedded within a clade that includes primarily Irano-Turanian species, suggesting multiple invasions of the Mediterranean basin from the east.