Evolution of Photosymbiosis in Oligocene-Miocene Planktic Foraminifera

渐新世-中新世浮游有孔虫光共生的演化

• 批准号: 9706394
• 负责人: Richard Norris
• 金额: $ 23万
• 依托单位: Woods Hole Oceanographic Institution
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 1997
• 资助国家: 美国
• 起止时间: 1997-08-01 至 2001-07-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=9706394&HistoricalAwards=false
• 关键词: Evolution; Photosymbiosis; Oligocene; Miocene; Planktic

9706394 Norris Symbioses are ubiquitous in the diversity of life and are often cited as a source of evolutionary novelty. I propose to test the role of photosymbiosis in the diversification of planktic foraminifera-a large group of pelagic protistans that have a complex and well preserved fossil record. Equally important for this study, planktic foraminifera preserve a clear isotopic signal of foraminiferal-algal symbiosis in their calcareous shells that permits the history and evolution of symbiosis to be studied in extinct species. My previous isotopic and phylogenetic work has established that a large clade of planktic foraminifera (the morozovellids) diversified simultaneously with their evolution of foraminiferal-algal symbiosis. Evidence from the ecology of living photosymbiotic foraminifera and changes in the taxonomic diversity of extinct groups strongly suggest that at least some clades radiated as soon as they acquired photosymbionts-perhaps because the photosymbiosis permitted the foraminifera to diversify into oligotrophic surface waters. It remains to study other clades of photosymbiotic foraminifera to determine whether these symbioses consistently initiate major diversifications of the host foraminifera. This proposal will examine two large clades: the Neogene globiginids (which may have harbored symbionts following the major extinction of photosymbiotic species in the middle Eocene). Data from both clades will be compared to a previously studied group: the Paleogene morozovellids. The globigerinids are almost exclusively photosymbiotic today as demonstrated both by observation of living foraminifera and isotopic analyses of their shells. Yet, a small number of isotopic analyses done as a pilot study for this project suggest the surprising conclusion that the globigerinids only recently acquired the photosymbiotic ecology. At least some of the early Miocene and Oligocene representatives of the group were apparently asymbiotic. Should this conclusion be supported by further cladistic and isotopic study, this will weaken the hypothesized link between the evolution of symbiosis and taxonomic radiation of the host group. Conversely, evidence for the recent evolution of photosymbiosis in both the globigerinids and globoquadrinids will provide strong evidence that symbioses are easily established in planktic foraminifera-a point also suggested by recent molecular phylogenetic data that find that the same symbiotic dinoflagellate species within diverse groups of globigerinid foraminifera. This study is significant because it compares isotopic and cladistic evidence from three major clades of planktic foraminifera that have independently evolved photosymbiosis to determine whether symbioses play an important evolutionary role in the diversification of these plankton. These analyses will result in a detailed history of the photosymbiotic strategy in planktic foraminifera for the last 65 million years. The history of photosymbiosis can then be compared with the oceanographic record to assess the paleoceanographic control on the evolution of photosymbiosis.

9706394诺里斯 共生体在生命的多样性中无处不在，经常被引用为进化新奇性的来源。 我建议测试光合作用在浮游有孔虫多样化中的作用--浮游有孔虫是一大群有着复杂而保存完好的化石记录的浮游原生生物。 对于这项研究同样重要的是，南极有孔虫在其钙质壳中保留了有孔虫-藻类共生的明确同位素信号，这使得可以在灭绝物种中研究共生的历史和进化。 我以前的同位素和系统发育的工作已经建立了一个大的分支的浮游有孔虫（morozovellids）多样化的同时，他们的进化有孔虫藻类共生。 来自现存的光共生有孔虫生态学和已灭绝类群的分类多样性变化的证据强烈表明，至少有一些分支在获得光共生体后立即辐射，这可能是因为光共生作用使有孔虫多样化，进入贫营养的表面沃茨。 它仍然需要研究其他分支的光共生有孔虫，以确定这些共生体是否始终启动主机有孔虫的主要多样化。 该建议将研究两个大的分支：新近纪球海胆（可能在始新世中期光共生物种大灭绝后拥有共生体）。 从这两个分支的数据将进行比较，以前研究组：古近纪morozovellids。 通过对有孔虫的观察和对它们外壳的同位素分析，证明了今天的球盖虫几乎完全是光共生的。 然而，作为该项目的试点研究，少量的同位素分析表明了一个令人惊讶的结论，即球海胆只是最近才获得了光共生生态。 至少有一些早中新世和渐新世的代表显然是非共生的。 如果这一结论得到进一步的分支和同位素研究的支持，这将削弱共生进化和宿主群的分类辐射之间的假设联系。 相反，最近的进化的光共生的globigerinids和globoquadrinids的证据将提供强有力的证据，共生很容易建立在浮游有孔虫-一个点也建议最近的分子系统发育数据，发现不同的globigerinid有孔虫群内的相同的共生甲藻物种。 这项研究是重要的，因为它比较了同位素和分支的证据，从三个主要分支的浮游有孔虫，独立发展的光共生，以确定共生是否发挥了重要的进化作用，这些浮游生物的多样化。 这些分析将导致过去6500万年来南极有孔虫光共生策略的详细历史。 光共生的历史可以与海洋学记录进行比较，以评估古海洋学对光共生演化的控制。