What can multiple phylogenies say about the latitudinal diversity gradient? A new look at the tropical conservatism, out-of-the-tropics, and diversification rate hypotheses

We reviewed published phylogenies and selected 111 phylogenetic studies representing mammals, birds, insects, and flowering plants. We then mapped the latitudinal range of all taxa to test the relative importance of the tropical conservatism, out of the tropics, and diversification rate hypotheses in generating latitudinal diversity gradients. Most clades originated in the tropics, with diversity peaking in the zone of origin. Transitions of lineages between latitudinal zones occurred at 16–22% of the tree nodes. The most common type of transition was range expansions of tropical lineages to encompass also temperate latitudes. Thus, adaptation to new climatic conditions may not represent a major obstacle for many clades. These results contradict predictions of the tropical conservatism hypothesis (i.e., few clades colonizing extratropical latitudes), but support the out-of-the-tropics model (i.e., tropical originations and subsequent latitudinal range expansions). Our results suggest no...我们检索并梳理已发表的系统发育（phylogeny）研究，最终筛选出涵盖哺乳类、鸟类、昆虫与显花植物的111项系统发育研究。随后我们绘制了所有分类单元（taxon）的纬度分布范围，以检验热带保守主义假说（tropical conservatism hypothesis）、走出热带模型（out of the tropics model）与多样化速率假说（diversification rate hypothesis）在塑造纬度多样性梯度过程中的相对重要性。结果显示，多数演化支（clade）起源于热带地区，其多样性峰值恰好位于起源区域。谱系在不同纬度带间的转换事件发生于16%~22%的系统发育树节点中。其中最常见的转换类型为热带谱系的分布范围扩张至温带纬度区域。由此可见，适应全新气候条件对多数演化支而言并非主要障碍。本研究结果与热带保守主义假说的预测相悖（该假说认为极少有演化支能够拓殖非热带纬度区域），但支持走出热带模型（该模型主张类群起源于热带并伴随后续的纬度分布范围扩张）。我们的研究结果表明……