Woodruff D S, Mulvey M, Yipp M W
J Hered. 1985 Sep-Oct;76(5):355-60.
Since its introduction in the early 1970s Biomphalaria straminea (Gastropoda: Planorbidae) has spread rapidly and is locally the most abundant fresh water snail in Hong Kong. Studies of 19 electrophoretically detected loci in four populations show that the colonists retain high levels of variability (P = 0.26, H = 0.056 - 0.097), comparable with those found in autochthonous samples of related species. Genotype frequencies at the five polymorphic loci, and a comparison of maternal and progeny genotypes of individual field-collected snails, revealed no evidence for self-fertilization in these functional hermaphrodites. F statistics indicated minimal genetic structuring, presumably because of outcrossing and recency of origin of the populations. Geographic distribution of various alleles and their frequencies suggest that two southern populations were derived from the original colonists by dispersal but that a northern population represents a second introduction in about 1982. This interpretation (based on genetics) is consistent with the known history of the various populations. The Asian populations of this South American snail are interpreted as being in the "flush" phase of the colonization process. Finally, the probability of the secondary spread of this snail from Hong Kong, and the probability of its parasite, the human blood fluke Schistosoma mansoni, being introduced to Asia are discussed.
自20世纪70年代初被引入以来，淡黄巴蜗牛（腹足纲：扁卷螺科）迅速扩散，在香港当地成为最为常见的淡水螺。对四个种群中19个通过电泳检测的基因座的研究表明，这些外来种群保留了较高水平的变异性（P = 0.26，H = 0.056 - 0.097），与相关物种的本地样本中的变异性相当。五个多态性基因座的基因型频率，以及对野外采集的单个蜗牛的母本和子代基因型的比较，未发现这些功能性雌雄同体存在自体受精的证据。F统计量表明遗传结构最小，推测是由于异交和种群起源较近。各种等位基因的地理分布及其频率表明，两个南部种群是通过扩散从原始殖民者衍生而来，但一个北部种群代表了大约在1982年的第二次引入。这种基于遗传学的解释与各个种群的已知历史一致。这种南美蜗牛的亚洲种群被解释为处于殖民化过程的“繁荣”阶段。最后，讨论了这种蜗牛从香港二次扩散的可能性，以及其寄生虫——人类血吸虫曼氏血吸虫被引入亚洲的可能性。
