Jablonski David, Huang Shan, Roy Kaustuv, Valentine James W
Am Nat. 2017 Jan;189(1):1-12. doi: 10.1086/689739. Epub 2016 Dec 2.
An impediment to understanding the origin and dynamics of the latitudinal diversity gradient (LDG)-the most pervasive large-scale biotic pattern on Earth-has been the tendency to focus narrowly on a single causal factor when a more synthetic, integrative approach is needed. Using marine bivalves as a model system and drawing on other systems where possible, we review paleobiologic and biogeographic support for two supposedly opposing views, that the LDG is shaped primarily by (a) local environmental factors that determine the number of species and higher taxa at a given latitude (in situ hypotheses) or (b) the entry of lineages arising elsewhere into a focal region (spatial dynamics hypotheses). Support for in situ hypotheses includes the fit of present-day diversity trends in many clades to such environmental factors as temperature and the correlation of extinction intensities in Pliocene bivalve faunas with net regional temperature changes. Support for spatial dynamics hypotheses includes the age-frequency distribution of bivalve genera across latitudes, which is consistent with an out-of-the-tropics dynamic, as are the higher species diversities in temperate southeastern Australia and southeastern Japan than in the tropical Caribbean. Thus, both in situ and spatial dynamics processes must shape the bivalve LDG and are likely to operate in other groups as well. The relative strengths of the two processes may differ among groups showing similar LDGs, but dissecting their effects will require improved methods of integrating fossil data with molecular phylogenies. We highlight several potential research directions and argue that many of the most dramatic biotic patterns, past and present, are likely to have been generated by diverse, mutually reinforcing drivers.
理解纬度多样性梯度（LDG）——地球上最普遍的大规模生物格局——的起源和动态变化存在一个障碍，即在需要更综合、整体的方法时，人们往往倾向于狭隘地关注单一因果因素。我们以海洋双壳类为模型系统，并尽可能借鉴其他系统，回顾了古生物学和生物地理学对两种看似对立观点的支持，即LDG主要由以下因素塑造：（a）当地环境因素，这些因素决定了给定纬度上的物种和高级分类单元数量（原地假说）；或（b）起源于其他地方的谱系进入一个重点区域（空间动态假说）。对原地假说的支持包括许多类群中当前多样性趋势与温度等环境因素的契合，以及上新世双壳类动物群灭绝强度与区域净温度变化的相关性。对空间动态假说的支持包括双壳类属在纬度上的年龄频率分布，这与“走出热带”动态一致，澳大利亚东南部和日本东南部温带地区的物种多样性高于热带加勒比地区也是如此。因此，原地和空间动态过程都必定塑造了双壳类的LDG，并且可能在其他类群中也起作用。在显示相似LDG的类群中，这两个过程的相对强度可能不同，但剖析它们的影响将需要改进将化石数据与分子系统发育相结合的方法。我们强调了几个潜在的研究方向，并认为过去和现在许多最显著的生物格局可能是由多样且相互强化的驱动因素产生的。
