海南变色树蜥个体发育中形态和食性的变化

Ontogenetic Shifts of Morphology and Food Habits in the Oriental Garden Lizard,Calotes versicolor (Agamidae)

研究变色树蜥 (Calotesversicolor)头、尾大小和食性在个体发育过程中的变化 ,以及头、尾大小两性异形的个体发生。成体体长 (SVL)无显著的两性差异 ,两性异形主要表现为雄性个体有较大的头部 (头长和头宽 )和尾部。头、尾大小的两性异形在初生幼体就已存在 ,并随个体发育的进行变得更加显著。不同年龄组两性个体头长以及雌体头宽随SVL呈同速增长 ;雄性头宽随SVL呈异速增长 ,表现为雄性头宽的增长速率在个体发育过程中逐渐增大。头、尾部的相对大小在个体发育过程中有显著的变化 ,初生幼体头部相对较大、尾部相对较小 ,这种形态特征是胚胎优先保证生态学意义更为显著的部分 (如头部 )生长的结果 ,有利于初生幼体的早期生存和生长。不同性别和年龄组的变色树蜥摄入食物的种类及各种食物在摄入食物中所占的比例有一定程度的差别 ,因而食物生态位宽度和重叠度有一定程度的差别 ,然而没有直接的证据表明头部大小的两性异形能导致两性食物生态位的明显分离。

Males and females of the oriental garden lizard ( Calotes versicolor ) from a population in Tongshi,Hainan,southern China,differ in head size at hatchlings,with males having larger heads than females.This sexual dimorphism is slightly more pronounced in adults than in hatchlings.Embryos of C versicolor allocate relatively more resources to the growth of ecologically significant morphological characters than do characters less directly tied to early survival and growth of hatchlings.As a consequence of this allocation pattern,hatchlings have larger heads but shorter tails relative to snout vent length (SVL) than do juveniles and adults.Adults do not show a sexual dimorphism in SVL,but male adults attain longer tails than do female ones at the same SVL.An isometric growth pattern with SVL's increase is showed in the head length of both sexes and the head width of females during ontogeny.However,an allometric growth pattern with SVL's increase is showed in the head width of males,which the growth rate becomes increasingly fast with the ontogeny.The food niche width and overlap differ in the different age and sex groups to a certain extent.However,no direct evidence has been found to show a noticeable contribution of the divergence in head size to the food niche segregation between males and females.