The Meishan section, South China is the Global Stratotype Section and Point (GSSP) for the Permian-Triassic boundary (PTB), and also is well known for the best record demonstrating the Permian-Triassic mass extinction (PTME) all over the world. This section has also been studied using multidisciplinary approaches to reveal the possible causes for the greatest Phanerozoic biocrisis of life on Earth; many important scenarios interpreting the great dying have been proposed on the basis of data from Meishan. Nevertheless, debates on biotic extinction patterns and possible killers still continue. This paper reviews all fossil and sedimentary records from the Permo-Triassic (P-Tr) transition, based on previously published data and our newly obtained data from Meishan, and assesses ecologically the PTME and its aftermath to determine the biotic response to climatic and environmental extremes associated with the biocrisis. Eight updated conodont zones: C. yini, C. meishanensis, H. changxingensis, C. taylorae, H. parvus, I. staeschei, I. isarcica, and C. planate Zones are proposed for the PTB beds at Meishan.

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Human activities have caused worldwide loss and fragmentation of natural habitats, resulting in the decline and isolation of wild populations, consequently increasing their risks of extinctions. We investigated the genetic consequences of anthropogenic effects on the Sichuan snub-nosed monkeys (Rhinopithecus roxellana) in the Shennongjia Nature Reserve (SNR), which is a small and isolated distribution of R. roxellana in China and would continue to be threatened by habitat degradation and loss, using extensive sampling and 16 microsatellite loci. High level of genetic variation was observed from 202 individuals collected from three R. roxellana populations (SNR population, Sichuan-Gansu population and Shaanxi population). However, R. roxellana in SNR showed the lowest genetic diversity. The likelihood analysis of migration/drift equilibrium indicated that the SNR population suffered much stronger effect of drift than the other two populations, indicating that small populations are prone to be affected by drift. The STRUCTURE analysis identified two clusters, separating the SNR population from the other two populations, suggesting an increasing drift-induced differentiation between SNR and the other two populations. Bottleneck tests revealed that R. roxellana in SNR experienced a severe population decline (37-fold) during the past 500 years as a consequence of human population expansion. The current effective population size (Ne) in SNR is less than 100 and the ratio of Ne to the census population size is approximately 0.08. Based on our findings, we suggest that the SNR population should be monitored systematically and considered as an important conservation and management unit.

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