Surviving mass extinction by bridging the benthic/planktic divide
Surviving mass extinction by bridging the benthic/planktic divide
复制标题
DOI：
10.1073/pnas.0902827106
复制
发表时间：
2009-08-04
影响因子：
11.1
通讯作者：
Wade, Christopher M.
中科院分区：
文献类型：
--
作者：
Darling, Kate F.;Thomas, Ellen;Wade, Christopher M.
人们普遍认为，浮游生物从底栖祖先的进化代表着向新生态领域的单向扩张，每个进化枝可能只有一次。对于有孔虫来说，这种进化扩张发生在早中侏罗世，所有现存和灭绝的浮游有孔虫都被归入一个进化枝，即球形亚目。随后侏罗纪和白垩纪浮游有孔虫的辐射导致了高度多样化的组合，这些组合在白垩纪末遭受了大规模灭绝，留下了以微孔三列和二列形式为主的贫乏组合。少数幸存者物种在新生代再次辐射形成多样化的组合。然而，长期以来人们对浮游有孔虫的单系起源存有疑问。我们提出了令人惊讶但确凿的遗传证据，表明近期双列浮游链球菌与底栖玻利维亚多变球菌属于同一生物物种，并且地球化学证据表明，这种生态灵活的物种在公海表层水域中活跃生长，从而占据浮游和底栖领域。这种生活方式（tychopelagic）尚未被认为是有孔虫所适应的。中上层生物具有巨大的生态优势，能够使底栖生物快速重新殖民到易灭绝的中上层区域。我们认为，在解决有孔虫系统发育时必须考虑这种形式的存在。
Evolution of planktic organisms from benthic ancestors is commonly thought to represent unidirectional expansion into new ecological domains, possibly only once per clade. For foraminifera, this evolutionary expansion occurred in the Early-Middle Jurassic, and all living and extinct planktic foraminifera have been placed within 1 clade, the Suborder Globigerinina. The subsequent radiation of planktic foraminifera in the Jurassic and Cretaceous resulted in highly diverse assemblages, which suffered mass extinction at the end of the Cretaceous, leaving an impoverished assemblage dominated by microperforate triserial and biserial forms. The few survivor species radiated to form diverse assemblages once again in the Cenozoic. There have, however, long been doubts regarding the monophyletic origin of planktic foraminifera. We present surprising but conclusive genetic evidence that the Recent biserial planktic Streptochilus globigerus belongs to the same biological species as the benthic Bolivina variabilis, and geochemical evidence that this ecologically flexible species actively grows within the open-ocean surface waters, thus occupying both planktic and benthic domains. Such a lifestyle (tychopelagic) had not been recognized as adapted by foraminifera. Tychopelagic are endowed with great ecological advantage, enabling rapid recolonization of the extinction-susceptible pelagic domain from the benthos. We argue that the existence of such forms must be considered in resolving foraminiferal phylogeny.