Biogeosciences, Queensland University of Technology, 2 George St., Brisbane 4001, Australia.
Mol Phylogenet Evol. 2011 May;59(2):458-68. doi: 10.1016/j.ympev.2011.03.003. Epub 2011 Mar 21.
Restrictions to effective dispersal and gene flow caused by the fragmentation of ancient supercontinents are considered to have driven diversification and speciation on disjunct landmasses globally. Investigating the role that these processes have played in the development of diversity within and among taxa is crucial to understanding the origins and evolution of regional biotas. Within the chironomid (non-biting midge) subfamily Orthocladiinae (Diptera: Chironomidae), a group of genera that are distributed across the austral continents (Australia, New Zealand, South America) have been proposed to represent a relict Gondwanan clade. We used a molecular approach to resolve relationships among taxa with the aim to determine the relative roles that vicariance and dispersal may have played in the evolution of this group. Continental biotas did not form monophyletic groups, in accordance with expectations given existing morphological evidence. Patterns of phylogenetic relationships among taxa did not accord with expected patterns based on the geological sequence of break-up of the Gondwanan supercontinent. Likewise, divergence time estimates, particularly for New Zealand taxa, largely post-dated continental fragmentation and implied instead that several transoceanic dispersal events may have occurred post-vicariance. Passive dispersal of gravid female chironomid adults is the most likely mechanism for transoceanic movement, potentially facilitated by West Wind Drift or anti-cyclone fronts. Estimated timings of divergence among Australian and South American Botryocladius, on the other hand, were congruent with the proposed ages of separation of the two continents from Antarctica. Taken together, these data suggest that a complex relationship between both vicariance and dispersal may explain the evolution of this group. The sampling regime we implemented here was the most intensive yet performed for austral members of the Orthocladiinae and unsurprisingly revealed several novel taxa that will require formal description.
古大陆碎裂导致有效扩散和基因流动受限，被认为在全球离散陆地上推动了多样化和物种形成。研究这些过程在分类群内部和之间的多样性发展中所起的作用，对于理解区域生物群的起源和进化至关重要。在摇蚊（非吸血蠓）亚科 Orthocladiinae（双翅目：摇蚊科）中，一组分布在澳大利亚大陆（澳大利亚、新西兰、南美洲）的属被认为代表了冈瓦纳大陆的一个残余分支。我们使用分子方法解决分类群之间的关系，旨在确定隔离和扩散在该组进化中的相对作用。大陆生物群没有形成单系群，这与现有形态学证据的预期一致。分类群之间的系统发育关系模式不符合基于冈瓦纳超大陆分裂的地质序列的预期模式。同样，特别是对于新西兰分类群的分歧时间估计，主要发生在大陆分裂之后，这意味着可能发生了多次跨洋扩散事件，发生在隔离之后。育性雌性摇蚊成虫的被动扩散是跨洋移动最可能的机制，西风漂流或反气旋锋面可能会促进这种移动。另一方面，澳大利亚和南美洲的 Botryocladius 之间的分歧时间估计与这两个大陆与南极洲分离的预期年龄一致。总的来说，这些数据表明隔离和扩散之间的复杂关系可能解释了该组的进化。我们在这里实施的采样方案是针对 Orthocladiinae 的澳大利亚成员进行的最密集的采样方案，令人惊讶的是，它揭示了几个需要正式描述的新分类群。
