Research On Seed Dispersal Effectiveness To Different Plants And Parturition Timing In Cynopterus Sphinx

Fruit-eating bat is an important disperser in tropical and subtropical rainforest. By building diffuse mutualism with plants, their feeding behaviors influence seed germination and determine plant distribution in the future. Fruit bat not only maintain the diversity of native species but provide the possibility for exotic species invasion. However, exotic species often have negative impacts on native species, which reducing the diversity of native species. At present, researches on the contribution of fruit bats to different original plants are rare, especially under wild conditions, most investigations only focus on the efficiency of seed germination which are insufficient to explain the important and the affect mechanism that dispersers contribute to plant populations.Reproduction is a key stage of animal’s life history which relate to its survival and perish. Animal reproductive activities are constrained by trade-offs between different natural selection pressures and their physiological limitations. Many abiotic factors including the climate(such as temperature, photoperiod and rainfall), richness and availability of food resources, affect reproductive activities. To date, however, there are no researches about the relationship between the life history of Cynopterus sphinx and ecological condition in Xishuangbanna.Hence, we chosed the dominant species of C. sphinx and aimed at tackling the above questions by field observation and seed germination trials in the laboratory. So, we 1) studied the feeding preference and seed dispersal effectiveness(SDE) of bats to different original plants; 2) determined the reliablity of these two parameters in appraisal the contribution of bats to plants; 3) explain the reason for distinct seed dispersal effectiveness, which will benefit us to know the importance and mechanism of fruit bats in maintaining the diversity of rainforest ecosystem in Xishuangbanna; 4) researched the relationship between the parturition time of C. sphinx and precipitation, the degree of food availability; 5) revealed the effect of local ecological conditions on the parturition time of C. sphinx; 6) clarified the adaptable changes of bats parturition for adapting to local ecological conditions. The main results were as follows:1. In addition to naturally fall, C. sphinx was the most important seed disperser to the four plants. Bas dispersed 54.19 ± 18.64 % seeds for Syzygium fluviatile, 51.65 ± 2.16% for Ficus hispida, 27.29 ± 1.07% for Syzygium samarangense and 50.08 ±2.53% for Psidium guajava respectively. C. sphinx had no significant feeding preference to co-occuring native plant of F. hispida and exotic plant S. samarangense(sign test, P = 1.00).2. C. sphinx provided distinct SDE to different plants. F. hispida(1.25) > P. guajava(0.45) > S. fluviatile(0.02) > S. samarangense(0.00).There was no significant correlation between seed dispersal effectiveness and plants origin(Spearman correlation, r = 0.447, P = 0.145), but there was a significant relationship between SDE and C. sphinx treatment(Spearman correlation, r = 0.894, P = 0.00) and varied by plant species(Spearman correlation, r = 0.80, P = 0.002).3. Partial correlation analysis showed that after control the remaining four morphological parameters(fruit length: r =-0.017, fruit wet weight: r =-0.060, seed diameter: r = 0.011, and seed wet weight: r =-0.058; P > 0.05) only the number of seeds in each fruit was significantly correlated with SDE(r = 0.913, P < 0.01).4. The invasion process of P. guajava was postively correlate with SDE(Kendall’s B, r = 1.00, P = 0.00).5. C. sphinx often acted as seed gulpers or seed discarders during feeding activities that benefit to improve seed germination dynamic. C. sphinx had distinct effects on seed germination performance of four plant species. For S. fluviatile, germination percentage(GP), germination start(GS), minimum imbibitions time(Tmin) and time need for 50% seed germination(T50) were significantly improved. However, for F. hispida, GP, GS, Tmin and T50 were not affected. For S. samarangense, GS, Tmin and T50 were significantly improved. For P. Guajava, GP, GS and Tmin were significantly improved.6. The plant resources for C. sphinx(4-9 species) were increase along with the increase of precipitation(19.82-41.13 kg/m2). There were weak correlation between the degree of food availability and precipitation(Pearson correlation, r = 0.64, P = 0.18).7. The number of captured sub-adults was positively correlate with the degree of food availability significantly(Pearson correlation, r = 0.94, P = 0.01). Most of C. sphinx concentrates on March to May for parturition in Xishuangbanna. The timing of flying out and feeding activity of sub-adults are consistent with the peaking of food availability.