Vrijenhoek Robert C, Pfeiler Edward
Center for Theoretical and Applied Genetics, Rutgers University, New Brunswick, New Jersey, 08903-0231.
Departamento de Ciencias Marinas, Instituto Tecnológico y de Estudios Superiores de Monterrey, Guaymas, Sonora, 85400, Mexico.
Evolution. 1997 Oct;51(5):1593-1600. doi: 10.1111/j.1558-5646.1997.tb01482.x.
According to the Frozen Niche-Variation model, coexisting clones of an asexual species can freeze and faithfully replicate ecologically relevant genetic variability that segregates in the sexual ancestors. The present experiments with fish of the genus Poeciliopsis provide further evidence in support of this model. Sexual and clonal forms of Poeciliopsis live in the desert streams of Sonora, Mexico, and are exposed to environmental extremes ranging from flash floods to hot, desiccating, residual pools. We examined coexisting members of the monacha complex to see whether the fish types differed with respect to survival during stress and swimming endurance in an artificial flume. The two coexisting clones of the triploid gynogenetic fish P. 2 monacha-lucida differed dramatically: clone MML/II had the best survival during heat and cold stress and the worst survival during hypoxic stress, whereas clone MML/I had the best survival during hypoxic stress and the worst during heat stress. Poeciliopsis monacha, the sexual species with which these clones coexist, had intermediate survival during heat and hypoxic stress and very poor swimming endurance in the flume. The physiological differences seen in this study are consistent with the Frozen Niche-Variation model and provide some insights into environmental factors that affect the distribution and abundance of these fish.
根据“冻结生态位 - 变异”模型，无性繁殖物种中同时存在的克隆体能够冻结并忠实地复制在有性生殖祖先中分离的与生态相关的遗传变异性。目前对食蚊鱼属鱼类的实验为支持该模型提供了进一步的证据。食蚊鱼的有性和克隆形式生活在墨西哥索诺拉州的沙漠溪流中，面临着从山洪暴发至炎热、干燥的残留水塘等极端环境。我们研究了莫纳查复合体中同时存在的成员，以观察在人工水槽中，不同鱼类在应激期间的生存能力和游泳耐力是否存在差异。三倍体雌核发育鱼类墨西哥食蚊鱼的两个共存克隆体表现出显著差异：克隆体MML/II在热应激和冷应激期间的生存能力最佳，而在低氧应激期间最差；克隆体MML/I在低氧应激期间生存能力最佳，在热应激期间最差。与这些克隆体共存的有性物种墨西哥食蚊鱼，在热应激和低氧应激期间的生存能力处于中等水平，在水槽中的游泳耐力则非常差。本研究中观察到的生理差异与“冻结生态位 - 变异”模型相符，并为影响这些鱼类分布和数量的环境因素提供了一些见解。
