中国水域江豚颅后骨骼的地理变异

GEOGRAPHICAL VARIATIONS OF POSTCRANIAL SKELETON AMONG THE POPULATIONS OF NEOPHOCAENA IN CHINESE WATERS

本文根据１４２号各年龄段的江豚颅后骨骼标本（其中长江种群标本３８号，黄海种群标本５９号，南海种群标本４５号），选用４２项颅后骨骼变量，应用ｔ－检验、协方差分析和判别分析研究了颅后骨骼在各地理种群之间的变异。结果表明，（１）中国水域江豚不同种群之间在颅后骨骼上的差异是明显的，而且表现在包括初生幼体在内的所有年龄段的标本中。（２）南海种群的颅后骨骼最发达，长江种群次之，黄海种群的最不发达．（３）黄海种群与长江种群的差异较小，与南海种群的差异较大；南海种群与长江种群的差异相对最大。（４）颅骨发生的适应性变化比其外形的变化要慢，而颅后骨骼的变化比颅骨的变化还要慢。

Geographical variations of postcranial skeleton among the Yangtze,Yellow Sea and South China Sea populations of the finless porpoise,Neophocaena phocaenoides,in CHi-nese waters were studied with t-test,covariance analysis(Table 2)and stepwise dis-criminant analysis(Tabie 3,Fig. 2)using 42 measurements based on 142 specimens ofall ages(38 from the Yangtze population,59 from the Yellow Sea population and 45from the South China Sea population)collected in 1974 to 1991 by the Cetacean Re-search Laboratory, Nanjing Normal University. The results showed that:(1 )Geo-graphical variations in the postcranial skeleton among the three Chinese populationswere demonstrated in all the ages even for the neonates(Table 2,Fig. 2).But the dif-ferences were interpreted by a group of variances. No single difference could be used asdiagnostic character for subspecies identification.(2)Summary of the results of thecomparison among the populations(Table 2 and 4)demonstrated that,the postcranialskeleton in the South China Sea population was the most developed,that of the Yangtzepopulation was the next,and that of the Yellow Sea population was the lowest.(3)Dif-ferences between the South China Sea and Yangtze populations were larger than that be-tween the South China Sea and Yellow Sea populations, and therefore wete the largest(Table 2 , Fig. 2).This is in agree with the result determined by external and skullmeasurements,(4)The degree of the difference and overlap in the measurements amongdifferent geographical populations implies that the adaptationary changes of the skulltook place slower than those of the external morphology during the evolution of the fin-less porpoise populations,and those of the postcranial skeleton,in turn,slower thanthose of the skull.