Rapid genetic divergence and mitonuclear discordance in the Taliang knobby newt ( Liangshantriton taliangensis, Salamandridae, Caudata) and their driving forces.

The Hengduan Mountains Region (HMR) is the largest "evolutionary frontier" of the northern temperate zone, and the origin and maintenance of species in this area is a research hotspot. Exploring species-specific responses to historical and contemporary environmental changes will improve our understanding of the role of this region in maintaining biodiversity. In this study, mitochondrial and microsatellite diversities were used to assess the contributions of paleogeological events, Pleistocene climatic oscillations, and contemporary landscape characteristics to the rapid intraspecific diversification of Liangshantriton taliangensis, a vulnerable amphibian species endemic to several sky-island mountains in the southeastern HMR. Divergence date estimations suggested that the East Asian monsoon, local uplifting events (Xigeda Formation strata), and Early-Middle Pleistocene transition (EMPT) promoted rapid divergence of L. taliangensis during the Pleistocene, yielding eight mitochondrial lineages and six nuclear genetic lineages. Moreover, population genetic structures were mainly fixed through isolation by resistance. Multiple in situ refugia were identified by ecological niche models and high genetic diversity, which played crucial roles in the persistence and divergence of L. taliangensis during glacial-interglacial cycles. Dramatic climatic fluctuations further promoted recurrent isolation and admixing of populations in scattered glacial refugia. The apparent mitonuclear discordance was likely the result of introgression by secondary contact and/or female-biased dispersal. Postglacial expansion generated two major secondary contact zones (Ganluo (GL) and Chuhongjue (CHJ)). Identification of conservation management units and dispersal corridors offers important recommendations for the conservation of this species.

[Effects of nitrapyrin-nitrogen (N) fertilizer application rates on N utilization and N2O emission in summer maize field.] / ä¸åŒæ°®è‚¥å–·æ¶‚å¡å•¶å¯¹å¤çŽ‰ç±³ç”°æ°®ç´ åˆ©ç”¨åŠåœŸå£¤N2O排放的影响.

To reduce the N2O emission from soil and enhance N utilization by crop, a field experiment was carried out to study the effects of nitrapyrin-N fertilizer application rates (0, 180, 270, 360 kg N·hm-2) on soil N2O emission and N apparent loss, grain yield and N utilization of summer maize. Results showed that the soil N2O emission under different N fertilizer treatments mainly occurred in periods from sowing to seedling, and from jointing to tasseling. Soil N2O emission peaks were observed after basal and top dressing events. Maize yield increased with N fertilizer rates but there was no significant difference between 270 and 360 kg N·hm-2, and the net income of these two treatments was 5209 and 5426 yuan·hm-2, respectively. Compared with no N fertilizer treatment, the N uptake in the N fertilizer treatments was increased by 109.6%-134.1%. The treatment of 270 kg N·hm-2 had the highest agronomic N efficiency and N use efficiency, but the N apparent loss was low. The treatment with nitrapyrin-N fertilization rate of 270 kg N·hm-2 appeared to be the optimal rate to obtain high maize yield and N use efficiency, and low soil N2O emission and N apparent loss.