| Bufo minshanicus is the endemic species of Tibetan plateau, they distribute mainly arable land, forests and grassland region in high altitude. In addition to the Qinghai, they also distribute in the northwest of Sichuan, the southern of Gansu, and the distribution area of elevation ranges from 1700 m to 3700 m. Recently, the studies on Minshan toad have mainly focused on the morphology and geographic distribution. However, we know little about the basic life cycle, ecological and biological characteristics, and more in-depth quantitative research is very rare. The aim of this study was to examine elevational variation in life history characteristics of Minshan toad and assess the influence of elevation on the reproductive and population ecology of Minshan toad. Furthermore, we studied 5 populations on the life history and behavioural ecology of B. minshanicus in detail. In this study, we explored the adaptation mechanisms for the severe environmental conditions on the Tibetan plateau.In this study, the field study was collected from 2013 to 2015, and combined original data from 2008-2012. Finally, all the data from 2008-2015 were analyzed. In this study, we chose 9 study sites, and combined field investigation and laboratory work method to obtain the basic life history parameters of Minshan toad. Elevational variation in life history traits of B. minshanicus mainly included two aspects:(1) Elevation variation of mating system:our results showed that there was a male-biased sex ratio and a female-skewed size dimorphism at each site. We collected the data of matching system from 9 populations, and found that the mating patterns were varied during populations, and the same population has varied in different years. Our study shows that 4 populations’males which were in amplexus with females were larger than non-amplectant males (P< 0.05), which showed a large male advantage. In addition to body length, forearm length, leg length and weight with paired male may be greater than male with unpaired in some populations (P< 0.05). We also found that a strong positive association between SVL or body weight of the amplectant males and females at the 5 of 9 study populations (P< 0.05). Therefore, based on the previous sexual selection experiment, we suggested that size-assortative mating resulted in males mate choice and male-male competition. In addition, nonrandom matching model has a relationship with the population density, sex ratio, the length of the breeding time and rainfall.(2) Elevational variation in female reproductive investment:The life history theory predicts that increasing environmental stress not only leads to a shift in reproduction from the number of offspring to mass distribution, but also a greater trade-off between the size of the egg and clutch size. To test this prediction, we investigated the different life history characteristics (body size, clutch size, egg size and total reproductive investment) from 8 populations in Minshan toad. We found them were different in each population (P< 0.01). Clutch size and female reproductive output changed with the change of female’s SVL. When the SVL is controlled, clutch size increased with increasing altitude in 6 population from Gansu province (P< 0.01), it is the opposite of the temperature; 2 in Qinghai Province clutch size decreased with increasing altitude, but not significant. However, there were significantly different relationships between female size and egg size, but a tendency to increase with increasing altitude, but not significant. Similarly, the trade-off between egg size and clutch size was not significant among all populations. Our study showed that B. minshanicus from high altitude regions invest in large clutch size rather than large eggs because of the environmental constraints, which is contrary to the prediction of life history theory. |
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