Search

Quaternary climate fluctuations have profoundly affected the current distribution patterns and genetic structures of many plant and animal species in the Qinghai-Tibetan Plateau (QTP) and adjacent mountain ranges, e.g. Tianshan (TSR), Altay, etc. In this greater area disjunct distributions are prominent but have nevertheless received little attention with respect to the historical processes involved. Here, we focus on Pedicularis kansuensis to test whether the current QTP and TSR disjunction is the result of a recent Holocene range expansion involving dispersal across arid land bridge(s) or a Pleistocene range fragmentation involving persistence in refugia. Two chloroplast DNA spacers were sequenced for 319 individuals from 34 populations covering the entire distribution range of this species in China. We found a total of 17 haplotypes of which all occurred in the QTP, and only five in the TSR. Overall genetic diversity was high (HT = 0.882, HS = 0.559) and higher in the QTP than in the TSR. Genetic differentiation among regions and populations was relatively low (GST = 0.366) and little evidence for a phylogeographic pattern emerged. The divergence times for the four main lineages could be dated to the early Pleistocene. Surprisingly, the two ubiquitous haplotypes diverged just before or around the Last Glacial Maximum (LGM) and were found in different phylogenetic lineages. The Species Distribution Model suggested a disappearance of P. kansuensis from the TSR during the LGM in contrast to a relatively constant potential distribution in the QTP. We conclude that P. kansuensis colonized the TSR after the LGM. The improbable long-distance dispersal by wind or water across arid land seed flow may well have had birds or men as vector. [ABSTRACT FROM AUTHOR]

Granitoids, as a major component of the Earth's crust, have large K isotopic variations (δ41K = −1.0‰ to 0.4‰), but K isotope fractionation during granite differentiation is poorly constrained. Here, we examined K isotopic compositions of a suite of well-characterized crustal igneous rocks (quartz diorite, granodiorite and monzogranite) from the Tagong pluton, northeastern Tibetan Plateau. The rocks display increasing δ41K in the following order: quartz diorite (δ41K = −0.798‰ to −0.538‰) < granodiorite (δ41K = −0.520‰ to −0.378‰) < monzonite granite (δ41K = −0.439‰ and − 0.436‰). The δ41K values are positively correlated with SiO 2 and K 2 O contents and negatively with MgO and Al 2 O 3 contents, indicating up to ∼0.42‰ fractionation during magmatic differentiation. Taking into account mineral assemblage, fractional crystallization of K-rich phases (mica and K-feldspar) likely plays a dominant role in K isotopic variation. In addition, mafic microgranular enclaves (MMEs) commonly occurring in granitoid rocks show comparable δ41K values (−0.489‰ to −0.416‰) to their corresponding host rocks, implying their schlieren origin. These features demonstrate that K isotope heterogeneity of the crust could have been induced by magma differentiation in addition to source control. • K isotope fractionation during granite differentiation. • Fractional crystallization probably controlled fractionation of K isotopes. • Schlieren origin of mafic microgranular enclaves from perspective of K isotopes. • Contribution of magma differentiation to K isotopic heterogeneity of the crust. [ABSTRACT FROM AUTHOR]