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Ancient tropical extinctions at high latitudes contributed to the latitudinal diversity gradient
Evolution ( IF 3.1 ) Pub Date : 2020-04-18 , DOI: 10.1111/evo.13967
Andrea S Meseguer 1, 2, 3 , Fabien L Condamine 2
Affiliation  

Global biodiversity currently peaks at the equator and decreases toward the poles. Growing fossil evidence suggest this hump‐shaped latitudinal diversity gradient (LDG) has not been persistent through time, with similar diversity across latitudes flattening out the LDG during past greenhouse periods. However, when and how diversity declined at high latitudes to generate the modern LDG remains an open question. Although diversity‐loss scenarios have been proposed, they remain mostly undemonstrated. We outline the “asymmetric gradient of extinction and dispersal” framework that contextualizes previous ideas behind the LDG under a time‐variable scenario. Using phylogenies and fossils of Testudines, Crocodilia, and Lepidosauria, we find that the hump‐shaped LDG could be explained by (1) disproportionate extinctions of high‐latitude tropical‐adapted clades when climate transitioned from greenhouse to icehouse, and (2) equator‐ward biotic dispersals tracking their climatic preferences when tropical biomes became restricted to the equator. Conversely, equivalent diversification rates across latitudes can account for the formation of an ancient flat LDG. The inclusion of fossils in macroevolutionary studies allows revealing time‐dependent extinction rates hardly detectable from phylogenies only. This study underscores that the prevailing evolutionary processes generating the LDG during greenhouses differed from those operating during icehouses.

中文翻译:

高纬度古代热带灭绝导致纬度多样性梯度

全球生物多样性目前在赤道达到顶峰,向两极减少。越来越多的化石证据表明,这种驼峰状纬度多样性梯度 (LDG) 并没有随着时间的推移而持续存在,在过去的温室期间,跨纬度的相似多样性使 LDG 变得平坦。然而,多样性何时以及如何在高纬度下降以产生现代 LDG 仍然是一个悬而未决的问题。尽管已经提出了多样性损失方案,但它们大多仍未得到证实。我们概述了“灭绝和扩散的不对称梯度”框架,该框架在时变情景下将 LDG 背后的先前思想背景化。利用 Testudines、Crocodilia 和 Lepidosauria 的系统发育和化石,我们发现,驼峰状的 LDG 可以通过以下方式来解释:(1)当气候从温室转变为冰库时,高纬度热带适应进化枝的不成比例灭绝,以及(2)当热带生物群落成为热带生物群落时,赤道区生物扩散追踪了它们的气候偏好。仅限于赤道。相反,跨纬度的等效多样化率可以解释古老的平坦 LDG 的形成。在宏观进化研究中包含化石可以揭示仅从系统发育中难以检测到的时间依赖性灭绝率。这项研究强调,在温室期间产生 LDG 的主要进化过程与在冰库期间运行的过程不同。(2) 当热带生物群落仅限于赤道时,赤道区的生物扩散会追踪其气候偏好。相反,跨纬度的等效多样化率可以解释古老的平坦 LDG 的形成。在宏观进化研究中包含化石可以揭示仅从系统发育中难以检测到的时间依赖性灭绝率。这项研究强调,在温室期间产生 LDG 的主要进化过程与在冰库期间运行的过程不同。(2) 当热带生物群落仅限于赤道时,赤道区的生物扩散会追踪其气候偏好。相反,跨纬度的等效多样化率可以解释古老的平坦 LDG 的形成。在宏观进化研究中包含化石可以揭示仅从系统发育中难以检测到的时间依赖性灭绝率。这项研究强调,在温室期间产生 LDG 的主要进化过程与在冰库期间运行的过程不同。
更新日期:2020-04-18
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