Vermeij Geerat J
Department of Zoology, University of Maryland, College Park, MD, 20742.
Evolution. 1987 Sep;41(5):1046-1058. doi: 10.1111/j.1558-5646.1987.tb05875.x.
Stretches of deep ocean constitute barriers to the dispersal of many shallow-water marine species in the tropical Pacific. The purpose of this study was to assess the selectivity of these barriers with respect to the habitat characteristics, adult size, and predation-related shell architecture of gastropods, and to explore the implications of this selectivity for macroevolutionary patterns of extinction and speciation. The dispersal barrier between continental islands (represented in my collections by species from eastern Indonesia, the southern Philippines, and the north coast of New Guinea) and the nearby oceanic Palau Islands was studied by evaluating the percentage of each architectural and habitat category that is present on the continental islands but missing in Palau. The barrier is significantly more effective against sand-dwelling species than against rock-dwellers, and among rock-dwellers it is most effective against aperturally unarmored taxa. Barriers between Palau and Guam, Guam and the Hawaiian Islands, and the Line Islands and the tropical Eastern Pacific are generally unselective with respect to substratum type and architecture. The fact that narrow-apertured species are less affected by the barrier between the continental islands and Palau than are other rock-dwelling gastropods is consistent with the interpretation that this group has been unusually resistant to extinction and highly susceptible to founder speciation when oceanic circulation is altered. These patterns of susceptibility and geographical distribution may explain why armored gastropods have increased in numbers relative to unarmored ones in the tropical Pacific during the Cenozoic.
在热带太平洋，广阔的深海区域对许多浅水海洋物种的扩散构成了障碍。本研究的目的是评估这些障碍对于腹足纲动物的栖息地特征、成体大小以及与捕食相关的贝壳结构的选择性，并探讨这种选择性对灭绝和物种形成的宏观进化模式的影响。通过评估在大陆岛屿（在我的样本中以来自印度尼西亚东部、菲律宾南部和新几内亚北海岸的物种为代表）上存在但在帕劳群岛缺失的每种结构和栖息地类别的百分比，研究了大陆岛屿与附近的海洋性帕劳群岛之间的扩散障碍。该障碍对栖息在沙地的物种的阻碍作用明显大于对栖息在岩石上的物种，并且在栖息在岩石上的物种中，它对没有口部装甲的类群最为有效。帕劳与关岛、关岛与夏威夷群岛以及莱恩群岛与热带东太平洋之间的障碍，对于基质类型和结构通常没有选择性。与其他栖息在岩石上的腹足纲动物相比，口部狭窄的物种受大陆岛屿与帕劳之间障碍的影响较小，这一事实与以下解释一致：当海洋环流改变时，这一类群对灭绝具有异常的抵抗力，并且极易发生奠基者物种形成。这些易感性模式和地理分布可能解释了为什么在新生代期间，有装甲的腹足纲动物相对于无装甲的腹足纲动物在热带太平洋的数量有所增加。
