Aim The Irano-Turanian (IT) floristic region is characterized by high levels of endemicity. Despite its potential role as a cradle of xerophytic taxa for neighbouring areas, its biogeographical history remains poorly studied. Haplophyllum, a diagnostic element of the IT region, was used as a model to discriminate between alternative biogeographical scenarios for the evolution of the region and, more specifically, to investigate whether it served as a source of xerophytes for the colonization of the Mediterranean Basin.Location Irano-Turanian floristic region (Central Asia and West Asiatic areas) and Mediterranean floristic region (western and eastern parts of the Mediterranean Basin).Methods Three chloroplast DNA regions were sequenced in 77 accessions of Haplophyllum and 37 accessions from other subfamilies of Rutaceae. To elucidate the temporal and spatial evolution of Haplophyllum in the IT and Mediterranean regions, we performed Bayesian molecular dating analyses with four fossil constraints and ancestral range reconstructions, respectively. ResultsOur molecular dating and ancestral area reconstruction analyses suggest that Haplophyllum originated in the Central Asian part of the IT region during the early Eocene and started to diversify in situ during the early Oligocene, soon after the vanishing of the Tethys Ocean. Our results further imply that Haplophyllum later invaded the eastern Mediterranean Basin in the middle-to-late Miocene, concomitantly with the Paratethys Salinity Crisis and rapid palaeobiogeographical changes in the proto-Mediterranean. Finally, Haplophyllum diversified in the western Mediterranean in the early Pliocene at the end of the Messinian Salinity Crisis. Main conclusionsThe IT floristic region can serve as a 'donor' of xerophytic taxa to 'recipient' neighbouring regions, including the Mediterranean floristic region. The climatic/geological processes during the Miocene-Pliocene, by increasing aridity and topographic heterogeneity, facilitated range shifts and allopatric speciation in the region.

Ever since the 19th century, the immense arid lands of the Orient, now called the Irano-Turanian (IT) floristic region, attracted the interest of European naturalists with their tremendous plant biodiversity. Covering approximately 30% of the surface of Eurasia (16000000 km ), the IT region is one of the largest floristic regions of the world. The IT region represents one of the hotspots of evolutionary and biological diversity in the Old World, and serves as a source of xerophytic taxa for neighbouring regions. Moreover, it is the cradle of the numerous species domesticated in the Fertile Crescent. Over the last 200 years, naturalists outlined different borders for the IT region. Yet, the delimitation and evolutionary history of this area remain one of the least well-understood fields of global biogeography, even though it is crucial to explaining the distribution of life in Eurasia. No comprehensive review of the biogeographical delimitations nor of the role of geological and climatic changes in the evolution of the IT region is currently available. After considering the key role of floristic regions in biogeography, we review the history of evolving concepts about the borders and composition of the IT region over the past 200 years and outline a tentative circumscription for it. We also summarise current knowledge on the geological and climatic history of the IT region. We then use this knowledge to generate specific evolutionary hypotheses to explain how different geological, palaeoclimatic, and ecological factors contributed to range expansion and contraction, thus shaping patterns of speciation in the IT region over time and space. Both historical and ecological biogeography should be applied to understand better the floristic diversification of the region. This will ultimately require evolutionary comparative analyses based on integrative phylogenetic, geological, climatic, ecological, and species distribution studies on the region. Furthermore, an understanding of evolutionary and ecological processes will play a major role in regional planning for protecting biodiversity of the IT region in facing climatic change. With this review, we aim to introduce the IT floristic region to a broader audience of evolutionary, ecological and systematic biologists, thus promoting cutting-edge research on this area and raising awareness of this vast and diverse, yet understudied, part of the world.

Endemism is one of the most important concepts in biogeography and is of high relevance for conservation biology. Nevertheless, our understanding of patterns of endemism is still limited in many regions of high biodiversity. This is also the case for Iran, which is rich in biodiversity and endemism, but there is no up-to-date account of diversity and distribution of its endemic species. In this study, a comprehensive list of all endemic vascular plant species of Iran, their taxonomic composition and their geographical distribution are presented. To this end, a total of 2,597 (sub)endemic vascular plant species of Iran were documented and their distribution in three phytogeographical regions, two biodiversity hotspots and five areas of endemism were analysed. The Irano-Turanian phytogeographical region harbours 88% of the Iranian endemics, the majority of which are restricted to the Irano-Anatolian biodiversity hotspot (84%). Nearly three quarters of the endemic species are restricted to mountain ranges. The rate of endemism increases along an elevational gradient, causing the alpine zone to harbour a disproportionally high number of endemics. With increasing pastoralism, urbanization, road construction and ongoing climate change, the risk of biodiversity loss in the Iranian mountains is very high, and these habitats need to be more effectively protected.

Summary Flowers have been hypothesized to contain either modules of attraction and reproduction, functional modules (pollination‐effecting parts) or developmental modules (organ‐specific). Do pollination specialization and syndromes influence floral modularity? In order to test these hypotheses and answer this question, we focused on the genus Erica: we gathered 3D data from flowers of 19 species with diverse syndromes via computed tomography, and for the first time tested the above‐mentioned hypotheses via 3D geometric morphometrics. To provide an evolutionary framework for our results, we tested the evolutionary mode of floral shape, size and integration under the syndromes regime, and – for the first time – reconstructed the high‐dimensional floral shape of their most recent common ancestor. We demonstrate that the modularity of the 3D shape of generalist flowers depends on development and that of specialists is linked to function: modules of pollen deposition and receipt in bird syndrome, and access‐restriction to the floral reward in long‐proboscid fly syndrome. Only size and shape principal component 1 showed multiple‐optima selection, suggesting that they were co‐opted during evolution to adapt flowers to novel pollinators. Whole floral shape followed an Ornstein–Uhlenbeck (selection‐driven) evolutionary model, and differentiated relatively late. Flower shape modularity thus crucially depends on pollinator specialization and syndrome.

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 of Haplophyllum. Finally, the Mediterranean representatives of Haplophyllum were found to be embedded within a clade that includes primarily Irano‐Turanian species, suggesting multiple invasions of the Mediterranean basin from the east.