神农架地区4种啮齿类食性及脏器形态差异比较

生活在同一地域的物种,会因强烈的资源竞争而产生生态位重叠与分离,从而实现相互共存。以神农架地区啮齿动物为研究对象,比较分析不同啮齿类食性、脏器重量及消化道形态差异,探索其共存机制及其生理生态学上的适应策略。食性上,安氏白腹鼠(Niviventer andersoni)、社鼠(N.confucianus)、高山姬鼠(Apodemus chevrieri)、中华姬鼠(A.draco)均为杂食者,但各自喜食偏好不同,安氏白腹鼠的食物组成以植物枝叶和种子为主,社鼠、高山姬鼠和中华姬鼠的食物组成均以种子和动物性食物为主。与各自生态习性及其食性相适应,不同啮齿动物的脏器重量及消化道形态发生相应的变化。脏器重量上,不同啮齿动物心鲜重、肺鲜重、脾鲜重和干重无显著差异,其它指标差异显著。安氏白腹鼠的心干重、肺干重、肝鲜重和干重、肾鲜重和干重显著大于社鼠、高山姬鼠和中华姬鼠。消化道形态上,不同啮齿动物盲肠长、净鲜重和干重无显著差异,其它指标差异显著。其中,胃含内容物鲜重、净鲜重和干重,盲肠含内容物鲜重,大肠长、含内容物鲜重、净鲜重和干重均以安氏白腹鼠具较大值,但各自变化趋势不同;小肠长、含内容物鲜重、净鲜重和干重则以社鼠具较大值。且同属姬鼠属的高山姬鼠和中华姬鼠脏器重量及消化道形态各指标间均无显著差异。由于小泡巨鼠和猪尾鼠数量较少,未进行统计分析。以上结果显示:食物资源利用上的分化有利于安氏白腹鼠与其近缘物种社鼠及其他鼠类的同域共存,且为适应不同的食物资源利用模式,其脏器及消化道形态也发生了适应性的变化;同域分布的近缘物种高山姬鼠、中华姬鼠则有可能采取其它策略而非食物资源分化模式实现共存。

Variations in food habit and viscera organ morphology of four rodents in Shennongjia, central China

The separation of ecological niches in terms of food resource, activity pattern or space contributes to the coexistence of sympatric species. Spatiotemporal variations in resource availability affect foraging behavior, habitat selection and even the existence of species. To explore the coexistence mechanisms of sympatric rodents, variations in food habit, viscera organ and digestive tract morphology among different rodent species were investigated in Shennongjia, central China.Studied rodents were trapped by snap-trap in October 2010. Upon capture, all rodents were carried to laboratory. The species, gender, age, reproductive status, body mass and length were recorded. Then the heart, lung, liver, spleen, kidney and the entire digestive tract were removed from the body and the carcass mass was weighted. The connective tissue and lipid was stripped and the digestive tract was extended to its full length. Fresh weights of all organs and lengths of digestive tract were weighted. After removing digestive tract contents, fresh weights without contents and food items in the stomach were recorded. Dry weights of all organs were measured after drying in the oven.A total of 220 adult rodents, including 8 Niviventer andersonii, 167 N. confucianus, 5 Apodemus chevrieri, and 35 A. draco, 2 Leopoldamys edwardsi and 3 Typhlomys cinereus, were collected for analysis. L. edwardsi and T. cinereus were excluded for statistical tests due to insufficient samples. The analysis of food habit showed that N. andersoni, N. confucianus, A. chevrieri and A. draco were omnivorous but the Chi-square test detected significant variation in dietary biases. N. andersoni was primarily phyllophagous and seminivorous and the others were primarily seminivorous and carnivorous. The analysis of covariance of viscera organs showed that while fresh weights of heart, lung and spleen and dry weight of spleen did not differ between rodents, other indices did exhibit significant variation with the highest value found in N. andersoni. In the analysis of digestive tract morphology, while length, fresh and dry weight of caecum did not differ between rodents, fresh and dry weights of stomach and large intestine, fresh weights including stomach, caecum and large intestine contents, and length of large intestine did differ significantly with the highest value found in N. andersoni. Otherwise, the length, fresh and dry weight of small intestine, and fresh weight including small intestine contents also showed significant variations between species, with the highest value found in N. confucianus.Variations in viscera organ morphology of N. andersoni compared to other species indicate that the segregation of food resources contributes to this species coexistence with other rodents. In order to adapt to different availability of food resources, the viscera organ and digestive tract morphology of N. andersoni show adaptable phenotypic plasticity. However, A. chevrieri and A. draco, both belonging to the genus Apodemus, do not exhibit differences in food habit, viscera organ and digestive tract morphology, which implied that their coexistence may result from other strategies than resource allocation, such as habitat selection.