Meyer Axel
Museum of Vertebrate Zoology and Department of Zoology, University of California, Berkeley, CA, 94720.
Evolution. 1987 Nov;41(6):1357-1369. doi: 10.1111/j.1558-5646.1987.tb02473.x.
Cichlid fishes in African rift lakes have undergone rapid speciation, resulting in "species flocks" with more than 300 endemic species in some of the lakes. Most researchers assume that there is little phenotypic variation in cichlid fishes. I report here extensive phenotypic plasticity in a Neotropical cichlid species. I examined the influence of diet on trophic morphology during ontogeny in Cichlasoma managuense. Two groups of full siblings were fed two different diets for eight months after the onset of feeding; thereafter both groups were fed a common diet. Phenotypes that differed significantly at 8.5 months converged almost completely at 16.5 months. If feeding on two different diets is continued after 8.5 months, the phenotypes remain distinct. Differences in diet and possibly in feeding mode are believed to have caused these phenotypic changes. Phenotypic plasticity is described in terms of a qualitative model of heterochrony in which phenotypic change in morphology is explained as retardation of the normal developmental rate. If phenotypic expression of morphology is equally plastic in African cichlid species as it may be in the American cichlids, as exemplified by C. managuense, then taxonomic, ecological, and evolutionary analyses of "species flocks" may be in need of revision. However, Old World cichlids may be less phenotypically plastic than New World cichlids, and this may contribute to the observed differences in speciation rate and degree of endemism.
非洲裂谷湖中的丽鱼科鱼类经历了快速的物种形成，在一些湖泊中形成了拥有300多种特有物种的“物种集群”。大多数研究人员认为丽鱼科鱼类的表型变异很小。我在此报告一种新热带丽鱼科物种中广泛存在的表型可塑性。我研究了饮食对马那瓜丽体鱼个体发育过程中营养形态的影响。两组全同胞在开始摄食后八个月被投喂两种不同的食物；此后两组都被投喂相同的食物。在8.5个月时显著不同的表型在16.5个月时几乎完全趋同。如果在8.5个月后继续投喂两种不同的食物，表型仍然不同。饮食差异以及可能的摄食方式差异被认为导致了这些表型变化。表型可塑性是根据异时性的定性模型来描述的，在该模型中，形态学上的表型变化被解释为正常发育速率的延迟。如果非洲丽鱼科物种的形态学表型表达与美洲丽鱼（如马那瓜丽体鱼所示）一样具有可塑性，那么对“物种集群”的分类学、生态学和进化分析可能需要修订。然而，东半球的丽鱼科鱼类在表型上可能比西半球的丽鱼科鱼类可塑性小，这可能导致了观察到的物种形成速率和特有程度的差异。
