Larval Survival, Growth And Development Of The Alpine Frog (Rana Kukunoris) And Associated Ecological Factors In Northwestern Sichuan,China

Climate warming and change in precipitation pattern are two major aspects of global climate change. Global surface temperature has increased by 0.85? from 1880 to 2012 and is predicted to increase by 2-6? by the end of the 21st century. The magnitude of temporal-spatial variation of precipitation has being increasing and extreme precipitation events will become more frequent in the future. Numerous studies have revealed that climate changes have affected the phenology, physiology and distribution of plants and animals worldwide. Nevertheless, more work is needed for a complete understanding about the responses (to climate change) of animal species such as amphibians with complex life history stages and traits.Amphibians such as frogs are often vulnerable to climate change because there is no a temperature regulation system for their body. In particular, the larval stage is very sensitive to disturbances. Accordingly, amphibians suffer the highest extinction risk than other animal taxa. Present research on amphibians focusing on the effects of climate change primarily concentrates either long-term, large spatial-scale investigations, or short-term experiments. However, there are few studies at a meso-scale.The Tibet Plateau is one of the most sensitive areas to climate change in the world. The average surface temperature of this plateau increased by about 0.4? per decade between 1982 and 2012 and is predicted to increase by 1.4-2.2? in the following 50 years. In addition, variation of precipitation amount is small among years but large among regions. Alpine frog (Rana kukunoris), a native species in this plateau, is one of the most abundant predators, displaying crucial functional roles in community structuring. Population size and distribution range of the frogs are declining as aconsequence of human activities and climate changes.Our study was conducted in an alpine meadow in Hongyuan County, Northwest of Sichuan province, China. We conducted a field investigation and a glasshouse experiment to clarify the effects of warming and precipitation change on population dynamics of R. kukunoris. In the field, we investigated the egg mass number, egg number per mass, hatching rate, larval survival rate and metamorphosising rate in each pond during the breeding period (from May to August) for 44 ponds belonging to five types (i.e. temporary pond,permanent pond, permanent marsh,ephemeral stream, disturbed pond). In the glasshouse, we conducted a factorial experiment (2 factors x 2 levels) involving predator presence vs. absence and warmed vs. ambient treatments in mescosms by using tadpoles and one of their fiercest predator species, a diving beetle (Agabus sp.) to test the effect of warming and predator on tadpole survival rate,growth and development. We also set an experiment including rainfall intensity and frequency to explore the influence of rainfall change on breeding and hatching. The major results are shown as follows:1. Hatching rate decreased, but metamorphosising rate increased with the increasing rainfall amount. Tadpole survival rate and metamorphosis number/egg number decreased with the increasing density of predator, both of which were not correlated with rainfall amount. Pond type had significant influence on hatching rate,survival rate and metamorphosis rate. Specifically, population survival was the lowest in the disturbed ponds. Importantly, the effect of rainfall and pond type depended on spawning time. In addition, increase of rainfall intensity and frequency significantly enhanced hatching rate.2. In predator-absence treatments, warming significantly increased body fresh weight, enhanced growth rate, reduced tadpole activity time, and increased metamorphosising size. However, warming decreased body fresh weight and metamorphosising size, advanced metamorphosising time when predators were absent.Predators strongly increased tadpole mortality rate regardless of warming or not.In conclusion, warming and predators are two important factors determining tadpole survival, growth and development; changes in precipitation pattern can affect spawning time,larval survival and growth of alpine frogs. Our results facilitate a complete understanding of the ecological mechanisms referring to the response and adaption of amphibian to climate change. Moreover, the results also provide a theoretical basis to biodiversity conservation in the alpine meadow ecosystem.