Sinsch Ulrich
Institut für Biologie, Universität Koblenz-Landau, Rheinau 1, D-56075 Koblenz, Germany Fax: ++49-261-9119 315; e-mail:
Oecologia. 1997 Sep;112(1):42-47. doi: 10.1007/s004420050281.
The migratory capacity of metamorphs and their later integration into local breeding populations was studied in a Bufo calamita metapopulation inhabiting the northern Rhineland, Germany (1991-1994). A new tagging method allowed unequivocal distinction among metamorphs (n = 1,709), which originated either from the spring-breeding cohort in 1991 and 1992 or from the summer-breeding cohort in 1991. The life history of batch-marked individuals was followed until adulthood, focusing on postmetamorphic dispersal, choice of breeding locality and timing of adult reproduction. Almost all metamorphs left the patches used for breeding within a few weeks after emergence. They were found at about the same density in all favourable microhabitats in a radius of up to 2 km around their native patch. This demonstrates that even small toadlets (6-11 mm snout-to-vent length) migrate distances of several hundred metres within a short time and that they significantly help prevent local extinction in sink populations (rescue effect). Recaptures of reproductive adults originating from tagged metamorphs were limited to males belonging to the 1997 spring and summer cohorts. The absence of recaptured females was probably due to their greater vagility and later sexual maturation. First-breeding males (2 years old) without exception joined the breeding cohort from which they originated: early breeders originated from spawn of the spring cohort, mid-summer breeders from spawn of the summer cohort. This result is in accordance with the hypothesis that the integration of first breeders to a specific breeding cohort is genetically controlled in central European natterjacks. The exchange of individuals between different cohorts in the same patch is considerably less than the migratory exchange between the same breeding cohorts among local populations, as predicted from the allozyme data.
在德国北莱茵兰的一个绿蟾蜍复合种群中（1991 - 1994年），研究了变态幼体的迁移能力及其随后融入当地繁殖种群的情况。一种新的标记方法能够明确区分变态幼体（n = 1709），它们要么来自1991年和1992年的春季繁殖群体，要么来自1991年的夏季繁殖群体。对批量标记个体的生活史进行追踪直至成年，重点关注变态后的扩散、繁殖地点的选择以及成年繁殖的时间。几乎所有变态幼体在出现后的几周内就离开了用于繁殖的斑块。在其原生斑块周围半径达2公里的所有适宜微生境中，它们的密度大致相同。这表明，即使是小蟾蜍幼体（吻肛长度6 - 11毫米）也能在短时间内迁移数百米，并且它们显著有助于防止汇种群的局部灭绝（救援效应）。对源自标记变态幼体的成年繁殖个体的重捕仅限于1997年春季和夏季群体的雄性。未重捕到雌性可能是由于它们更强的迁移能力和更晚的性成熟。首次繁殖的雄性（2岁）无一例外地加入了它们所源自的繁殖群体：早期繁殖者源自春季群体的卵，仲夏繁殖者源自夏季群体的卵。这一结果符合以下假设：在中欧绿蟾蜍中，首次繁殖者融入特定繁殖群体是由基因控制的。同一斑块内不同群体之间的个体交换远少于当地种群中相同繁殖群体之间的迁移交换，正如从等位酶数据所预测的那样。
