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Speciation is widely accepted to be a complex and continuous process. Due to complicated evolutionary histories, desert plants are ideal model systems to understand the process of speciation along a continuum. Here, we elucidate the evolutionary history of Reaumuria soongarica (Pall.) Maxim., a typical desert plant that is wildly distributed across arid central Asia. Based on variation patterns present at nine nuclear loci in 325 individuals (representing 41 populations), we examined the demographic history, patterns of gene flow, and degree of ecological differentiation among wild R. soongarica. Our findings indicate that genetic divergence between the ancient western and eastern lineages of R. soongarica occurred approximately 0.714 Mya, probably due to the Kunlun–Yellow River tectonic movement and the Naynayxungla glaciation. Later, multiple hybridization events between the western and eastern lineages that took place between 0.287 and 0.543 Mya, and which might have been triggered by the asynchronous historical expansion of the western and eastern deserts, contributed to the formation of a hybrid northern lineage. Moreover, despite continuing gene flow into this population from its progenitors, the northern lineage maintained its genetic boundary by ecological differentiation. The northern lineage could be an incipient species, and provides an opportunity to study the continuous process of speciation. This study suggests that two opposite evolutionary forces, divergence and hybridization, coexisting in the continuous speciation of the desert plant R. soongarica in a short time. Moreover, we provide evidence that this continuous speciation process is affected by geological events, climatic change, and ecological differentiation. [ABSTRACT FROM AUTHOR]

Mafic–intermediate igneous rocks can provide important insights into the geodynamic evolution of orogenic belts. Here, we investigate the petrogenesis of mafic–intermediate intrusive igneous rocks in the East Kunlun Orogenic Belt (EKOB) to constrain regional geodynamic and magmatic evolution. These intrusive rocks are all located in the Permian-Triassic magmatic arc and parallel to the Paleo-Tethys ophiolite belt. Zircon U Pb dating results indicate that these various igneous rocks crystallized during the Triassic. The 250–248 Ma appinites display low SiO 2 contents, high MgO contents, and marked enrichments in large-ion lithophile elements and depletions in high-field-strength elements; combined with their enriched ε Hf (t) values, these appinites were considered to be derived from lithospheric mantle modified by subducted slab-derived fluids. The Harizha host granodiorites and MMEs have indistinguishable crystallization ages of 235 Ma but distinct SiO 2 contents and δ18O SMOW values, which, together with enriched Sr–Nd–Hf–Pb isotopes, suggest that their primary magmas were derived from the Mesoproterozoic lower crust (MLC) and subduction-modified lithospheric mantle (SMLM), respectively. The 241 Ma Baidungou quartz diorite and the 218 Ma Huanglonggou diorite porphyry show characteristics of medium SiO 2 contents, moderate Mg# and ε Hf (t) values relative to contemporaneous mafic and granitic rocks; therefore they probably represent the mixing products of MLC-derived felsic and SMLM-derived mafic magmas. Different from the Baidungou diorite and Harizha granodiorite, the Huanglonggou diorite porphyries have adakitic characteristics, which suggests crustal thickening during the Late Triassic. A synthesis of these new data with previous researches shows that the EKOB undergone three magmatic peaks corresponding to three extension events (slab-rollback, slab-breakoff, and delamination) during the Triassic evolution. • Subdution-modified lithospheric mantle (SMLM) derived mafic dikes and MMEs. • Mixing of melts derived from SMLM and Mesoproterozoic lower crust. • Three magmatic peak periods correspond to three extensional events. • Slab rollback, slab breakoff, delamination. [ABSTRACT FROM AUTHOR]