The Evolution of the Argopecten Gibbus Stock (Mollusca: Bivalvia), with Emphasis on the Tertiary and Quaternary Species of Eastern North America
The Evolution of the Argopecten Gibbus Stock (Mollusca: Bivalvia), with Emphasis on the Tertiary and Quaternary Species of Eastern North America
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DOI：
10.1017/s0022336000062466
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发表时间：
1969-09
影响因子：
1.4
通讯作者：
T. Waller
中科院分区：
文献类型：
--
作者：
T. Waller
海湾扇贝（Argopecten gibbus）种群的现存成员包括海湾扇贝（Bay and calico scallops）、海湾扇贝（Argopecten irradians（Lamarck））和海湾扇贝（A. gibbus（Linné），两者都常见于西大西洋和墨西哥湾;核（Born）的加勒比海，墨西哥湾南部，安的列斯群岛，和东南部佛罗里达;和共同的A。circularis（Sowerby）和A.产于东太平洋的紫鳍金枪鱼（拉马克）。该种群的化石成员包括这些现存物种的祖先以及Argopecten eboreus（Conrad），后者是一个灭绝的物种或物种群，不是任何后来的分类群的祖先。本研究旨在通过从活体物种和亚种的形态和生态关系模型的化石记录来确定Argopecten gibbus股票内的进化关系。在生物学上，这项研究仅限于从种群样本中推断出的活类群的形态和生态学分析。在古生物学上，它仅限于分析从美国大西洋和海湾沿岸平原上暴露的上新生代地层（中新世中期至更新世的明矾海崖群）收集的化石种群样本之间的形态变化。根据最新公布的绝对时间尺度，调查的时间跨度约为1800万年。通过由70个测量值组成的形态测量数据和每个瓣膜的轮廓、韧带和肌肉组织的形状比，研究并评价了样本之间的差异。使用电子数字计算机，对数据进行单变量和双变量分析，并使用机器绘图、双变量散点图、简化主轴和其他图形技术对样本进行比较。来自右瓣和左瓣的数据被单独处理，除了在研究瓣间差异的特征时将它们重新组合，从而提供关于瓣间特征的新信息。假设的物种发生显示了一个鲜为人知的物种，海湾扇贝种B，在中新世早期（橡树格罗夫沙），这显然是非常接近的股票的起源。本种的系统演化是通过A. nicholsi（Gardner）和A. choctahatcheensis（曼斯菲尔德）的A. comparilis（Tuomey & Holmes）的上中新统（塔迈阿密组、Pinecrest组、Duplin组和约克镇组）。A. comparilis的适应范围广，分布范围广，生活在大西洋西部、墨西哥湾和加勒比海的海湾、海湾和开阔的沃茨，并可能通过航道延伸到太平洋，在那里它形成了A.环状的到了中新世末期，在美洲东部，这种变异的物种已经分裂，产生了一种原始的海湾扇贝，A。anemaplicostatus（曼斯菲尔德），像生活的海湾扇贝（它的谱系后代）一样，可能在生态上局限于海湾和海湾的半封闭沃茨，而另一个物种，A. vicenarius（Conrad），可能仅限于开放的海洋沃茨，如生活的印花扇贝。原始的海湾扇贝显然无法到达太平洋，但开放的海洋物种似乎已经引起了太平洋A。purpuratus和大西洋印花扇贝A. gibbus活着的太平洋A。circularis在形态上是原始的，因为它类似于中新世物种A。比美洲东部的任何后来的物种都要多，并且在生态上是原始的，因为它广泛适应并能够生活在海湾和海湾以及开放的海洋沃茨。在更新世，A. nucleus是从A. gibbus，并已成为形态收敛的真正海湾扇贝，A。波斯人A.在中新世和上新世，美洲东部的一种常见扇贝eboreus代表了一个高度可变但形态上持久的谱系，既没有分裂也没有产生其他物种的谱系，并在更新世早期灭绝。在某些形态学特征上，A. gibbus谱系收敛于A. Eboreus谱系，表明灭绝的物种也可能仅限于开放的海洋沃茨。根据迄今为止分析的材料，种群的进化（包括系属变化和分裂）在美洲大西洋一侧比在太平洋一侧更快，生活的太平洋物种类似于中新世晚期和上新世早期的大西洋物种。由于屏障岛屿似乎在种群内的物种形成中发挥了关键作用，因此，在近岸和近海扇贝种群之间的遗传差异出现之前，太平洋一侧的活跃沿海构造运动破坏了这些岛屿屏障，这可能导致了进化差异。在命名方面，Argopecten被证明是Plagioctenium的高级同义词;与Argopecten gibbus相关的美洲物种的属名Aequipecten被拒绝;并且得出结论，属名Chlamys，广义上，更好地应用于亚科Chlamydinae。Argopecten vicenarius（Conrad）的种名，自1898年起不再使用，现在被恢复为一个重要分类群的唯一可用名称，该分类群产于佛罗里达的Caloosahatchee泥灰岩和瓦卡莫组的Pakinas。
The living members of the Argopecten gibbus stock include the bay and calico scallops, Argopecten irradians (Lamarck) and A. gibbus (Linné), both common in the western Atlantic and Gulf of Mexico; the less common A. nucleus (Born) of the Caribbean, southern Gulf of Mexico, Antilles, and southeastern Florida; and the common A. circularis (Sowerby) and A. purpuratus (Lamarck) of the eastern Pacific. The fossil members of the stock include the ancestors of these living species together with Argopecten eboreus (Conrad), an extinct species or species-group not ancestral to any of the later taxa. This study seeks to determine evolutionary relationships within the Argopecten gibbus stock by working back through the fossil record from a model of the morphological and ecological relationships of living species and subspecies. Biologically, the study is limited to an analysis of the morphology and ecology of the living taxa deduced from population samples. Paleontologically, it is limited to an analysis of morphological variation among samples of fossil populations collected from upper Cenozoic strata (Alum Bluff Group of the middle Miocene through the Pleistocene) exposed on the Atlantic and Gulf Coastal Plains of the United States. The time span investigated is about 18 million years, according to the latest published scale of absolute time. Differences between samples were studied and evaluated by means of morphometric data consisting of 70 measurements and form ratios of the outline, ligamenture, and musculature of each valve. Using an electronic digital computer, data were subjected to univariate and bivariate analyses, and samples were compared using machine-plotted, bivariate scatter diagrams, reduced major axes, and other graphical techniques. Data from right and left valves were treated separately, except that they were recombined in the study of characters that differ between valves, thereby furnishing new information on intervalve features. The postulated phylogeny shows a poorly known species, Argopecten species b, in the early middle Miocene (Oak Grove Sand), that is apparently very near the origin of the stock. This species evolved phyletically through A. nicholsi (Gardner) of the Shoal River Formation and A. choctawhatcheensis (Mansfield) of the Arca Faunizone into A. comparilis (Tuomey & Holmes) of the upper Miocene (Tamiami, Pinecrest, Duplin, and Yorktown Formations). A. comparilis was apparently broadly adapted and widely distributed, living in bays, sounds, and open marine waters in the western Atlantic, Gulf of Mexico, and Caribbean and probably extending through seaway passages to the Pacific, where it gave rise phyletically to A. circularis. By the end of the Miocene, on the eastern side of the Americas, this variable species had split, giving rise to a primitive bay scallop, A. anteamplicostatus (Mansfield), that, like the living bay scallop (its phyletic descendant), was probably ecologically restricted to the semienclosed waters of bays and sounds, and to another species, A. vicenarius (Conrad), probably restricted to open marine waters like the living calico scallop. The primitive bay scallop was apparently unable to reach the Pacific, but the open-marine species seems to have given rise to both the Pacific A. purpuratus and the Atlantic calico scallop, A. gibbus. The living Pacific A. circularis is morphologically primitive in that it resembles the Miocene species A. comparilis more than it does any of the later species on the eastern side of the Americas and is ecologically primitive in that it is broadly adapted and able to live both in bays and sounds and in open marine waters. During the Pleistocene, A. nucleus, a tropical bay scallop, is inferred to have split from A. gibbus and to have become morphologically convergent on the true bay scallop, A. irradians. A. eboreus, a common scallop on the eastern side of the Americas in the Miocene and Pliocene, represents a highly variable yet morphologically persistent lineage that neither split nor gave rise phyletically to other species and that became extinct during the early Pleistocene. In certain features of morphology, the A. gibbus lineage is convergent on the A. eboreus lineage, indicating that the extinct species may also have been restricted to open marine waters. On the basis of the materials analyzed thus far, the evolution (both phyletic change and splitting) of the stock has been faster on the Atlantic side of the Americas than on the Pacific side, with the living Pacific species resembling late Miocene and early Pliocene Atlantic species. Because barrier islands seem to have played a key role in speciation within the stock, it would appear that evolutionary differences may have been caused by the active coastal tectonism of the Pacific side destroying such island barriers before genetic differences between inshore and offshore scallop populations could arise. With regard to nomenclature, the name Argopecten is shown to be a senior synonym of Plagioctenium; the generic name Aequipecten is rejected for American species related to Argopecten gibbus; and it is concluded that the generic name Chlamys, sensu lato, is better applied as the subfamily name Chlamydinae. The species name Argopecten vicenarius (Conrad), unused since 1898, is reinstated as the only available name for an important taxon occurring in the Caloosahatchee Marl of Florida and the Waccamaw Formation of the Carolinas.