Evolutionary prospection is the study of morphological evolution and speciation in calcareous plankton from selected time-slices and key sites in the world oceans. In this context, the Neogene menardiform globorotalids serve as study objects for morphological speciation in planktic foraminifera. A downcore investigation of test morphology of the lineage of G. menardii-limbata-multicamerata during the past 8 million years was carried out in the western tropical Atlantic ODP Hole 925B. A total of 4669 specimens were measured and analyzed from 38 stratigraphic levels and compared to previous studies from DSDP Sites 502 and 503. Collection of digital images and morphometric measurements from digitized outlines were achieved using a microfossil orientation and imaging robot called AMOR and software, which was especially developed for this purpose. Most attention was given to the evolution of spiral height versus axial length of tests in keel view, but other parameters were investigated as well. The variability of morphological parameters in G. menardii, G. limbata, and G. multicamerata through time are visualized by volume density diagrams. At Hole 925B results show gradual test size increase in G. menardii until about 3.2 Ma. The combination of taxonomic determination in the light microscope with morphometric investigations shows strong morphological overlap and evolutionary continuity from ancestral to extant G. menardii (4–6 chambers in the final whorl) to the descendent but extinct G. limbata (seven chambers in the final whorl) and to G. multicamerata (≥8 chambers in the final whorl). In the morphospace defined by spiral height (δX) and axial length (δY) Globorotalia limbata and G. multicamerata strongly overlap with G. menardii. Distinction of G. limbata from G. menardii is only possible by slight differences in the number of chambers of the final whorl, nuances in spiral convexity, upper keel angles, radii of osculating circles, or by differences in reflectance of their tests. Globorotalia multicamerata can be distinguished from the other two forms by more than eight chambers in the final whorl. It appeared as two stratigraphically separate clusters during the Pliocene. Between 2.88 and 2.3 Ma G. menardii was severely restricted in size and abundance. Thereafter, it showed a rapid and prominent expansion of the upper test size extremes between 2.3 and 1.95 Ma persisting until present. The size-frequency distributions at Hole 925B are surprisingly similar to trends of menardiform globorotalids from Caribbean DSDP Site 502. There, the observations were explained as an adaptation to changes in the upper water column due to the emergence of the Isthmus of Panama. In light of more recent paleontological and geological investigations about the completion of the permanent land connection between North and South America since about 3 Ma the present study gives reason to suspect the sudden test size increase of G. menardii to reflect immigration of extra-large G. menardii from the Indian Ocean or the Pacific. It is hypothesized that during the Late Pliocene dispersal of large G. menardii into the southern to tropical Atlantic occurred during an intermittent episode of intense Agulhas Current leakage around the Cape of Good Hope and from there via warm eddy transport to the tropical Atlantic (Agulhas dispersal hypothesis).

中文翻译：

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从ODP孔925B（塞纳河上升带，热带西部大西洋）获得的新近纪板状有孔虫Globorotalia menardii及其相关形式的进化前景：长距离扩散叠加了逐步进化的证据吗？

演化前景是从世界海洋中选定的时间片和关键地点研究钙质浮游生物的形态演化和形态。在这种情况下，新基因的menardiform globorotalids用作浮游有孔虫的形态形态学的研究对象。在过去的八百万年间，在西部热带大西洋ODP孔925B中对menardii-limbata-multicamerata血统的测试形态进行了下层调查。从38个地层水平总共测量和分析了4669个标本，并将其与DSDP 502和503号站点以前的研究进行了比较。使用称为AMOR的微化石定向和成像机器人和软件，可以从数字化轮廓中收集数字图像和形态测量值。是专门为此目的而开发的。在龙骨视图中，最受关注的是螺旋高度相对于测试轴向长度的演变，但是还研究了其他参数。通过体积密度图可视化了美纳德氏菌，唇缘氏菌和多花变形菌的形态学参数随时间的变化。在孔925B处，结果显示梅纳德斯氏菌的试验尺寸逐渐增加，直到约3.2 Ma。光学显微镜中的分类学确定与形态学研究相结合，显示出强烈的形态学重叠和从祖先到现存的美纳德氏菌（最终螺纹中有4-6个腔室）到后代但已灭绝的灵芝（最终的七个腔室）中的进化连续性螺纹）和G. multicamerata（最终螺纹中的≥8个小室）。在由螺旋高度（δX）和轴向长度（δY）定义的形态空间中，Globoratalia limbata和G. multicamerata与G.menardii强烈重叠。只有通过最终轮生的室数，螺旋凸度的细微差别，上龙骨角，密合圆的半径或它们的测试反射率的差异，才能使唇缘线虫与Menardii区分。最终轮生中有八个以上的室可将多球藻与其他两种形式区分开。在上新世期间，它表现为两个地层分开的星团。在2.88到2.3之间，M。menardii的大小和丰度受到严格限制。此后，它显示出上限测试值极限在2.3至1.95 Ma之间迅速且显着扩展，一直持续到现在。925B孔的尺寸-频率分布令人惊讶地类似于加勒比DSDP站点502的月季状球叶拟南芥的趋势。那里的观测结果被解释为由于巴拿马地峡的出现而适应了上层水柱的变化。鉴于最近有关北美洲和南美洲之间永久土地连接完成的古生物学和地质调查，自大约3 Ma以来，本研究提供了理由怀疑美纳德氏菌的试验面积突然增加以反映超大G的迁移来自印度洋或太平洋的美纳德氏菌。据推测，在上新世晚期，大的美纳德氏菌向南大西洋到热带大西洋的扩散发生在间歇性强Agulhas间歇事件中，在好望角附近泄漏，并通过温暖的涡流从那里泄漏到热带大西洋（Agulhas扩散）。假设）。由于巴拿马地峡的出现，这些观测结果被解释为对上层水柱变化的适应。鉴于最近有关北美洲和南美洲之间永久土地连接完成的古生物学和地质调查，自大约3 Ma以来，本研究提供了理由怀疑美纳德氏菌的试验面积突然增加以反映超大G的迁移来自印度洋或太平洋的美纳德氏菌。据推测，在上新世晚期，大的美纳德氏菌向南大西洋到热带大西洋的扩散发生在间歇性强Agulhas间歇事件中，在好望角附近泄漏，并通过温暖的涡流从那里泄漏到热带大西洋（Agulhas扩散）。假设）。由于巴拿马地峡的出现，这些观测结果被解释为对上层水柱变化的适应。鉴于最近有关北美洲和南美洲之间永久土地连接完成的古生物学和地质调查，自大约3 Ma以来，本研究提供了理由怀疑美纳德氏菌的试验面积突然增加以反映超大G的迁移来自印度洋或太平洋的美纳德氏菌。据推测，在上新世晚期，大的美纳德氏菌向南大西洋到热带大西洋的扩散发生在间歇性强Agulhas间歇事件中，在好望角附近泄漏，并通过温暖的涡流从那里泄漏到热带大西洋（Agulhas扩散）。假设）。