腾格里荒漠沙蜥(PHRYNOCEPHALUS PRZEW ALSKII)年龄划分的研究

A STUDY OF THE IDENTIFYING AGE OF A SPECIES OF DESERT LIZARD (PHRYNOCEPHALUS PRZEWALSKⅡ) IN TENGGELI DESERT OF NORTHWEST CHINA

本文给出了两次标志重捕所获得的荒漠沙蜥体长的资料。由中国西北腾格里荒漠1985年标志重捕的182个个体体长与被捕时间的关系,我们发现不同体长的个体形成离散的体长区间,根据体长区间又可以推断各组对应的年龄。各年龄组的体长区间为:1—6月,一龄组无被捕个体,二龄组35—54毫米,三龄组55—65毫米,四龄组66—70毫米,五龄组大于70毫米;7—12月,一龄组小于42毫米,二龄组43—56毫米,三龄组57—67毫米,四和五龄组同前。我们用兰州大学校园内持续5年的第二次标志重捕资料验证了根据体长来划分荒漠沙蜥的年龄组是合理的。由低龄组到高龄组,各组体长日平均增长率逐渐降低且组间差异极显著(P<0.01)。以6月作为时间间隔,对第一次标志重捕资料用生命表方法分析的结果显示,年龄为0—6月的个体平均预期寿命是16.7月;存活曲线介于对角线型和长方形之间,该种群密度1985年后保持稳定。

Two sets of mark-recapture data on body length and recapture time of the desert lizared (Phrynocephalus Przewalskii) are presented. The first mark-recapture research in Tenggeli Desert of Northwest China covered the periods of time from April-September of 1985 when 182 lizards were marked and 78 of them recaptured. According to the capture or recapture time, the body length of 182 lizads can be divided into five discrete groups. The body length ranges in these groups are: during the period from January to June, none of lizard in Group Ⅰ was captured; in Group Ⅱ, between 35-54mm; in Group Ⅲ 55 -65mm; in Group Ⅳ 66-70mm and in Group V,longer than 70mm. During the period from July to December,in Group Ⅰ,the body length was less than 42mm;in Group Ⅱ 43-56mm; in Group Ⅲ,57 - 67mm; and in GroupⅣ and Ⅴ, the lizards had the same body length as the former. Few individuals appeared simultaneously in two groups. The body length of the desert lizards in the same group tended to increase at the same rate. However, increase in the shorter-body-length groups appeared at a higher rate than in the longer-body-length groups.We hypothesize that the individuals from the same groups must have been incubated during the same year so that they are at the same age and make up a cohort or an age group. And body length can be used as a criterion for identifying age of the desert lizards. Our experiment has five age groups corresponding to five body-length groups.The hypothesis was tested and verified by analyzing the second mark-recapture data on the desert lizards at the campus of lanzhou University. Twelve lizards were marked in August of 1962 and recaptured in each August of the following four years. Of 12 marked lizards, the body length of five in different years was completely within the above body length range. The result suggests that using body length range as a criterion for identifying the age of the desert lizards is reasonable. A statistical analysis on increase of body length in growth of the desert lizards shows that the standard deviation of the mean of body length in growth rate within an age group is less than 0. 06mm/day and the difference of the mean of body-length in growth rate between any two age groups is significant (P<0. 01).Furthermore,we worked out a stable-life table of the desert lizard population in Tenggeli Desert and it shows that the expectation of life span of the lizards at age 0-6 month is 16. 7 months. Its survival curve is between diagonal and rectangular mode and it suggests a quite slow rate of death increase during the first few months. An analysis on the number pyramid of the desert lizards proposes that the population density of it tends to be stable after 1985.