The Preliminary Analysis Of Sexual Dimorphism And Feeding Habits Of The Main Anurans In Zhongxiang And Tianmen Of Jianghan Plain

From June to September 2010,through collecting of the main pond frogs in farmland ecosystem in Zhongxiang and Tianmen of Jianghan plain (Fejervarya multistriata,Pelophylax hubeiensis,Pelophylax nigromaculatus),the preliminary analysis of sexual dimorphism and feeding habits of them was made.243 frogs were collected in Zhongxiang and Tianmen.Among them,there were 77 F.multistriata,91 P.hubeiensis and 75 P.nigromaculatus.There were 39 F.multistriata,45 P.hubeiensis and 41 P.nigromaculatus which collected in Zhongxiang.38 F.multistriata,46 P. hubeiensis and 34 P.nigromaculatus were collected in Tianmen. Investigation results were as follows:The research on sexual dimorphism:The sexual dimorphism index of F.multistriata was 0.1045. Female SVL (weight) was significantly larger than male. In its analysis of local traits, only 4 traits were significantly different between the sexes.By analyzing the relationship between its local traits and the SVL with regression analysis,we found that the relationship between all the local traits and the SVL of different sexes was not consistent.The sexual dimorphism index of P. hubeiensis was 0.2947. Female SVL (weight) was significantly larger than male, only 3 of 8 local traits was significantly different between the sexes. By analyzing the relationship between its local traits and the SVL with regression analysis,we found that the growth rate of head length was similar to body length in female,.The male growth rate of head length was less than its growth rate of body length. Moreover,the growth rate of other local traits were less than body length.The sexual dimorphism index of P.nigromaculatus was 0.0204.Of 8 local traits, only head width was significantly different between the sexes.By analyzing the relationship between its local traits and the SVL with regression analysis,we found that all the local traits were positively correlated with its body length.The research on feeding habits:The feeding rate of F.multistriata was 83.12%, Its average food intakes were 2.23 suits.The total number of its food intakes was 172 suits belonging to 4 Phylums,7 Classes,16 Orders.Its beneficial coefficient was 41.86%. The overlap of trophic ecological niche between the sexes was similar to the separation of trophic ecological niche, indicating that the differences of its feeding habits was not significant.The feeding rate of P. hubeiensis was 94.51%, Its average food intakes were 2.4 suits.The total number of its food intakes was 220 suits belonging to 4 Phylums,9 Classes,17 Orders.Its beneficial coefficient was 41.36%.Gastropoda, Arachneida and Diptera were its favourite preys.The overlap of trophic ecological niche was larger and the separation of trophic ecological niche was smaller, indicating that the differences of its feeding habits between the sexes was great.The feeding rate of P.nigromaculatus was 89.33%. Its average food intakes were 2.6 suits.The total number of its food intakes was 195 suits belonging to 4 Phylums,9 Classes,18 Orders.Its beneficial coefficient was 60.00%.Lepidoptera Larvae and Coleoptera were its favourite preys.The overlap of trophic ecological niche between the sexes was similar to the separation of trophic ecological niche, indicating that the differences of its feeding habits was not significant.The overlap of trophic ecological niche was larger than the separation of trophic ecological niche amoung these three frogs,indicating that there was part of diet overlap amoung them,So there was a limited competition in feeding habits among F.multistriata, P. hubeiensis and P.nigromaculatus which distributed sympatriclly.Through the differentiation of their feeding habits, the feeding competition was buffered which maintained the basic stability of the community.