白颌大角蟾三个种群分化的研究

STUDIES ON THE DIVERSITY OF THREE POPULATIONS OF Megophrys lateralis

白颌大角蟾（Megophrys lateralis）广布东南亚一些国家和地区。现选择分布在中国云南境内的白颌大角蟾的3个彼此隔离种群,选用它们稳定而可量的性状进行了聚类分析,以检查3个种群的相似和趋异程度,借以评估是否达到亚种或种级水平。结果表明:3个种群分化尚未达到种级水平。估计这3个种群实现隔离和性状趋异的时间可能在横断山抬升的中期以后,即第四纪的上新世末至更新世初,山脉抬升至某一高度后,环境分异渐趋显著,种群适应环境变化,性状从微小变异的积累,分化才趋于明显。研究中发现,这些种群性状变异仍然是小的和连续的,甚至是不稳定的,没有出现间断性的鉴别性状,故尚未达到种级水平。3个种群中,以云南西北贡山县独龙江河谷的种群分异更明显,即使如此,如要作为一个亚种对待,亦感性状分异之不足。相似率表示出,腾冲、景东2种群相似程度最大,可相聚一起,只能作白颌大角蟾的不同地理隔离种群。费粱等（1990,1992）将景东种群描述为“腺角蟾Megophpys glandulosa”。作者所运用前耳骨（prootica）入眶、额顶骨（fronto-parietal）与鳞骨（squamosal）分开或彼此相接两种状态作为种的主要划分依据。事实上,白颌大角蟾的3个种群的任何一个都存在这两种状态,可见是不稳定的;加之,把体侧疣粒和颞褶后端膨大状?

A population of one same species could adapt changing environmental facts of its own, including food sources, breeding sites, microclimate of habitat, which will undoubtedly cause transformation of behavior, habits, external and internal characteristics, until form diversified population. Some of these populations would arise to a subdivision into subspecies or even independent species.Megophrys lateralis was widely distributed in many countries in southeastern Asia. Certainly, there are a lot of the isolates of this species in Indo-Malaya region. In the course of the origin, of course, must relate to the similarity between populations. As indicated by the dim clustering analysis, we found the transformation of characters are continuous, in three populations of M. lateralis, none of the characteristic reached subspecies level. However, M. glandulosa which is not a valid species. Because of using unstable characters, such as fronto-parietal separated from squamosal by prootica, unmeasurable characteristics, for example, swelling of posterior of temporal fold and tubercles in size etc. We propose that all of utilize unmeasured characters should determine in size and to calculate ratio with a length of part of body, In such case , one can avoid the fault result.The similarity between populations of M. lateralis show that the population of Jingdong is similar to that of Tengchun, both are a little different from that of Gongshan. Even though there are some little transformations, yet these disparities are not a sign for a level of species, such as the tubercles and posterior of temporal fold in size, which increase accompanying with body size.