Investigation of Evolutionary Processes in Planktonic Foraminifera Using Stable Isotopic Analysis

本研究是用稳定同位素分析方法研究浮游有孔虫的演化过程。在没有明显的基因流动障碍的情况下，例如陆地块(例如巴拿马的地峡)或主要的海洋边界(例如极地前沿和塔斯曼前沿)，在基因流动很容易在很远的距离上保持的大流行人群中，进化如何进行？时间种是如何在一个传记省份内逐渐进化的？大多数模型预测，深水浮游有孔虫的进化变化是在深度分层发育时期通过水柱内的分离发生的。在更广泛的意义上，球状形态被认为是随着适应不断增加的水深而迭代进化的。然而，几乎还没有产生任何数据来检验这些假设。我们将在西南太平洋形成子午线断面的沉积序列中，对晚中新世的形态计量学定义的Globoratalia(Globoconella)分支的新物种进行同位素分析。将采用时间序列战略，重点关注祖先和后代物种范围重叠的地层区间。我们将解决的一些问题包括：祖先和后代物种在同位素值上是否表现出一致的差异，表明水柱中存在垂直或季节性隔离？在这个分支中是否有同位素趋势，表明无论是垂直还是季节上，更凉爽或更温暖的水域都在不断地居住？同位素趋势是否与古海洋学变化有关？同位素趋势是否与特定的形态特征有关？生活在不同水团中的祖先和后代物种，有些在支系的主要生物地理范围内，有些在主要生物地理范围的外围，是否在同位素值上表现出类似的差异，以及类似的古海洋学和形态联系？来自Globorotalia(Globoconella)分支的稳定同位素结果与另一个浮游有孔虫分支的稳定同位素结果相比如何：-Globorotalia(Truncorotalia)分支具有相似的形态特征？

This study is an investigation of processes of evolution in planktonic foraminifera using stable isotopic analysis. In the absence of obvious barriers to gene flow such as land masses (e.g. Isthmus of Panama) or major oceanographic boundaries (e.g. Polar Front and Tasman Front), how does evolution proceed in large pandemic populations in which gene flow is readily maintained over great distances? How do chronospecies gradually evolve within one biographic province? Most models predict that evolutionary change in the deep-dwelling planktonic foraminifera occurs through segregation within the water column during times of well developed depth stratification. In broader terms, the globorotalid morphology is believed to have evolved iteratively in association with adaptation to increasing water depths. However, almost no data have been have been generated to test such hypotheses. We will isotopically analyze morphometrically-defined Late Miocene to Recent species of the Globoratalia (Globoconella) clade in sedimentary sequences that form a meridional transect in the southwest Pacific. A time-series strategy will be employed focusing upon those stratigraphic intervals in which there is overlap in the ranges of ancestor and descendant species. Some of the questions we will address include: Do ancestor and descendant species exhibit consistent differences in isotopic values, suggesting vertical or seasonal segregation in the water column? Are there isotopic trends within this clade, suggesting progressive habitation of cooler or warmer waters, either vertically or seasonally? Are the isotopic trends associated with paleoceanographic changes? Are the isotopic trends associated with specific morphological characters? Do ancestor and descendant species living in different water masses, some within and some peripheral to the main biogeographic range of the clade, exhibit similar differences in isotopic values and similar paleoceanographic and morphological associations? How do the stable isotopic results from the Globorotalia (Globoconella) clade compare with those from another deep-dwelling planktonic foraminiferal clade that, in part, exhibits similar morphologic characteristics: - the Globorotalia (Truncorotalia) clade?