Ecological Mechanisms of Diversification in Hyalella Amphipods

Hyalella 片足类动物多样化的生态机制

• 批准号: 9815059
• 负责人: Gary Wellborn
• 金额: $ 30万
• 依托单位: University of Oklahoma Norman Campus
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 1999
• 资助国家: 美国
• 起止时间: 1999-05-01 至 2004-04-30
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=9815059&HistoricalAwards=false
• 关键词: Ecological; Mechanisms; Diversification; Hyalella; Amphipods

9815059Wellborn Research by Dr. Gary Wellborn at the University of Oklahoma will examine the ecological and behavioral bases of evolutionary diversification within the freshwater amphipod Hyallela azteca complex, to determine the role of adaptation to predators and the mechanism of collateral evolution of reproductive isolation. Hyallela is a widespread, phenotypically variable, and taxonomically problematic group of freshwater crustaceans, that exhibits substantial ecotypic variation in morphology and in life history across New World habitats. A salient pattern in Hyallela is that small-bodied, early-reproducing ecotypes occur in habitats that contain size-selective predatory fish, and large-bodied, late-reproducing ecotypes occur in habitats lacking predatory fish. These phenotypic differences are genetic, and the body size and life history differences among natural populations are consistent with the hypothesis of adaptation to habitat-specific predation regimes. In preliminary studies on interfertility, individuals of the different ecotypes were found to be reproductively isolated. Genetic diversity, however, as revealed in preliminary allozyme analyses, did not correlate with ecotypic differences; still, genetic diversity appears to be moderate to high overall in populations of this species complex. The hypothesis under test is that the amphipods have diversified into large and small ecotypes repeatedly, and that reproductive isolation (hence, speciation) has evolved collaterally with ecotypic divergence. Predation-related selection on body size or on age-to-maturation may induce, as an accidental or collateral effect, differences in mating behaviors that reinforce reproductive isolation, and hence speciation. Observational work in North America and laboratory experiments will test various genetic, behavioral, and life-history aspects of the hypothesis. This diversification mode, termed replicate adaptive radiation or parallel speciation, may be common in freshwater taxa, although little appreciated until now.

俄克拉何马大学的Gary Wellborn博士将研究淡水片足类动物Hyallela azteca复群中进化多样化的生态和行为基础，以确定适应捕食者的作用以及生殖隔离的附带进化机制。透明藻是一种分布广泛、表型多变、分类有问题的淡水甲壳类动物，在新大陆栖息地的形态和生活史上表现出大量的生态型变化。小藻的一个显著模式是，小体、繁殖早的生态型出现在有大小选择性食肉鱼类的栖息地，而大体、繁殖晚的生态型出现在没有食肉鱼类的栖息地。这些表型差异是遗传的，自然种群之间的体型和生活史差异与适应栖息地特定捕食制度的假设是一致的。在杂种性的初步研究中，发现不同生态型的个体是生殖隔离的。然而，根据初步的同工酶分析，遗传多样性与生态型差异无关；尽管如此，在这个物种复合体的种群中，遗传多样性似乎总体上是中等到高的。该假说认为，片脚类动物已反复分化为大生态型和小生态型，而生殖隔离（因此，物种形成）是伴随着生态型分化而进化的。与捕食相关的体型或年龄到成熟的选择，作为意外或附带效应，可能导致交配行为的差异，从而加强生殖隔离，从而形成物种。在北美的观察工作和实验室实验将测试该假设的各种遗传、行为和生活史方面。这种多样化模式，被称为复制适应性辐射或平行物种形成，可能在淡水分类群中很常见，尽管直到现在还很少被认识到。