Onshore-offshore patterns of faunal change occurred at many taxonomic scales during the Paleozoic Era, ranging from replacement of the Cambrian evolutionary fauna by the Paleozoic fauna to the environmental expansion of many orders and classes. A simple mathematical model is constructed to investigate such change. The environmental gradient across the marine shelf-slope is treated as a linear array of discrete habitats, each of which holds a set number of species, as observed in the fossil record. During any interval of time, some portion of the species in each habitat becomes extinct by background processes, with rates of extinction varying among both clades and habitats, as also observed in the record. After extinction, species are replaced from within the habitat and from immediately adjacent habitats, with proportions dependent on surviving species. This model leads to the prediction that extinction-resistant clades will always diversify at the expense of extinction-prone clades. But if extinction intensity is highest in nearshore habitats, extinction-resistant clades will expand preferentially in the onshore direction, build up diversity there, and then diversify outward toward the offshore. Thus, onshore-offshore patterns of diversification may be the expectation for faunal change quite independently of whether or not clades originate onshore. When the model is parameterized for Paleozoic trilobites and brachiopods, numerical solutions exhibit both a pattern of faunal change and a time span for diversification similar to that seen in the fossil record. They also generate structure similar to that seen in global diversification, including logistic patterns of growth, declining origination but constant extinction within clades through time, and declining overall extinction across clades through time.

中文翻译：

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动物群多样性的陆上 - 近海变化模型

在古生代，陆上-近海的动物群变化模式发生在许多分类尺度上，从古生代动物群取代寒武纪进化动物群到许多目和类的环境扩张。构建了一个简单的数学模型来研究这种变化。海洋陆架斜坡上的环境梯度被视为离散栖息地的线性阵列，如化石记录中所观察到的，每个栖息地都拥有一定数量的物种。在任何时间间隔内，每个栖息地中的某些物种都会因背景过程而灭绝，灭绝率在进化枝和栖息地之间有所不同，正如记录中所观察到的那样。灭绝后，物种从栖息地内和紧邻的栖息地被替换，比例取决于幸存的物种。这个模型导致了这样的预测，即抗灭绝的进化枝总是会以牺牲易灭绝的进化枝为代价而多样化。但是，如果近岸栖息地的灭绝强度最高，那么抗灭绝的进化枝将优先向陆上方向扩展，在那里建立多样性，然后向外向近海多样化。因此，陆上 - 海上多样化模式可能是对动物群变化的预期，这与进化枝是否起源于陆上无关。当模型为古生代三叶虫和腕足动物参数化时，数值解既表现出动物群变化的模式，也表现出类似于化石记录中的多样化的时间跨度。它们还产生类似于全球多样化的结构，