Witt Jonathan D S, Blinn Dean W, Hebert Paul D N
Department of Zoology University of Guelph, Guelph, Ontario N1G 2W1, Canada.
Mol Ecol. 2003 Feb;12(2):405-13. doi: 10.1046/j.1365-294x.2003.01728.x.
Numerous molecular studies have identified morphologically cryptic, freshwater invertebrate species, but have not suggested possible mechanisms for their phenotypic stasis. The amphipod crustacean genus Hyalella contains numerous morphologically cryptic species in the H. azteca complex, as well as a small number of morphologically very divergent, narrowly endemic taxa. One such taxon, Hyalella montezuma, is the sole planktonic filter-feeder within the North American amphipod fauna, and is known only from Montezuma Well, a fishless travertine spring mound in Arizona, USA. In this study, we conduct a phylogenetic analysis of mtDNA sequence data using likelihood, Bayesian and cladistic approaches to determine both the relationship of H. montezuma to the H. 'azteca' species complex, and to ascertain if its morphological and ecological differentiation have been comparatively recent. The results show that H. montezuma has a very close phylogenetic affiliation with one lineage in the H. azteca complex, indicating that its origin has been recent. We present evidence suggesting that fish predation is an important ecological factor, which constrains morphological and ecological diversification within the genus Hyalella, and that Montezuma Well has provided a relaxation on this constraint.
众多分子研究已识别出形态上难以区分的淡水无脊椎动物物种，但尚未提出其表型停滞的可能机制。 双甲甲壳纲动物Hyalella属在阿兹特克透明虾（H. azteca）复合体中包含许多形态上难以区分的物种，以及少数形态差异很大、分布狭窄的特有分类群。 其中一个分类群，蒙特祖马透明虾（Hyalella montezuma），是北美双甲动物区系中唯一的浮游滤食性动物，仅在美国亚利桑那州一个没有鱼的石灰华泉丘蒙特祖马井被发现。 在本研究中，我们使用似然法、贝叶斯法和分支法对线粒体DNA序列数据进行系统发育分析，以确定蒙特祖马透明虾与“阿兹特克透明虾”物种复合体的关系，并确定其形态和生态分化是否相对较新。 结果表明，蒙特祖马透明虾与阿兹特克透明虾复合体中的一个谱系有非常密切的系统发育关系，表明其起源较近。 我们提供的证据表明，鱼类捕食是一个重要的生态因素，它限制了透明虾属内的形态和生态多样化，而蒙特祖马井则提供了对这种限制的缓解。
