Ecologic Novelty in Taxonomic Diversification: Evolution of Photosymbiosis in Planktic Foraminifera

诺里斯9505836关于生态和形态多样化之间的关系目前存在很大争议。越来越多的工作表明，许多物种形成是在没有任何生态变化的情况下发生的。这一范式表明，大多数物种形成是通过被动地建立扩散障碍来进行的。相反，像“适应区”这样的概念意味着，当分类群进化出“关键创新”，使它们能够攀登空置的阳极峰时，就会发生许多物种形成。从这个角度来看，多样化是一个在生态战略变化的中介下的积极过程。研究重点将集中在球状有孔虫分支的系统发育和生态研究上，该分支是光共生有孔虫中现存的最大类群。这项拟议的研究将使用稳定同位素方法来推断已灭绝的有孔虫中光共生的发生，然后将这些生态信息映射到系统发育树上。如果结果表明共生是在球状辐射开始很久之前或之后获得的，或者如果光共生和非共生姐妹群具有相似的进化史，那么反驳关键创新假说应该很容易。此外，共生和分类多样化之间的任何联系可以通过比较新近纪球虫共生和非共生姐妹群的辐射模式与光共生的古新世莫氏虫的基本完整的数据集来检验。这些结果可能会为光共生在其他类群中的进化作用以及在软体动物和其他无脊椎动物中的化学共生提供见解。

Norris 9505836 The relationship between ecologica and morphological diversification is currently much in debate. There is an increasing body of work that suggests that much speciation occurs in the absence of any change in ecology. This paradigm suggests that most speciation takes place by the passive erection of barriers to dispersal. In contrast, concepts such as "adaptive zone" imply that much speciation occurs when taxa evolve "key innovations" that permit them to scale unoccupied adative peaks. From this perspective, diversification is an active process mediated by changes in ecological strategies. Research will focus on phylogenetic and ecologic study of the globigerinid clade--the largest exant group of photosymbiotic foraminifera. The proposed study will use stable isotope methods to deduce the occurrence of photosymbiosis in extinct foraminifera and then map this ecological information onto a phylogenetic tree. It should be easy to disprove the key-innovation hypothesis if the results demonstrate that symbiosis was acquired long before or after the globigerinid radiation began or if photosymbiotic and non-symbiotic sister groups have similar evolutionary histories. Moreover, any linkage between symbiosis and taxonomic diversification can be tested by comparing patterns of radiation in symbiotic and non-symbiotic sister groups in Neogene globigerinids with a mostly complete data set for the photosymbiotic Paleocene morozovellids. The results may provide insights on the evolutionary role of photosymbiosis in other groups as well as chemosymbiosis in mollusc and other invertebrates.