研究揭示四肢動物起源時如何獲得陸地運動能力
作者：
小柯機器人發布時間：2020/11/27 13:10:48
美國哈佛大學Stephanie E. Pierce、Blake V. Dickson研究組的最新研究揭示，功能性適應性景觀預測了四肢動物起源時的陸地能力。這一研究成果在線發表於2020年11月25日的《自然》。
在本研究中，研究人員分析了從鰭到四肢過渡過程中40個絕種四足動物的三維保存肱骨，並使用功能上有根據的生態適應景觀重建了陸地運動的演變。研究表明，肱骨形狀的進化變化是由生態和系統發育驅動的，並且與運動有關功能的折衷相關。針對水生魚類和陸地皇冠四足動物恢復了兩種不同的適應性景觀，每種景觀都由功能特異的不同組合定義。肱骨四足動物具有一套獨特的功能適應性，但不符合它們自己的預測適應峰。
取而代之的是，肱骨四足動物位於陸地皇冠四足動物進化的底部，表明陸地運動能力隨四肢的起源而發生。該研究結果表明，肱骨四足動物在陸地探索的初始階段可能已經使用了過渡步態，這些步態由於其兩棲習性的相對選擇性壓力而穩定。直到皇冠四足動物失去了其祖先「L形」肱骨，才出現了有效的基於肢體的運動，這為陸地四足動物的多樣化和建立現代生態位奠定了基礎。
據了解，在四足動物進化過程中，以肢體為基礎陸地運動能力的獲取一直是一個有爭論的問題。目前對從水生到陸地運動過渡的理解主要基於一些典型的化石，例如提塔利克魚、棘螈、魚石螈和彼得普斯螈。但是，孤立的骨元素可能會揭示隱藏的功能多樣性，從而提供更全面的進化觀點。
附：英文原文
Title: Functional adaptive landscapes predict terrestrial capacity at the origin of limbs
Author: Blake V. Dickson, Jennifer A. Clack, Timothy R. Smithson, Stephanie E. Pierce
Issue&Volume: 2020-11-25
Abstract: The acquisition of terrestrial, limb-based locomotion during tetrapod evolution has remained a subject of debate for more than a century1,2. Our current understanding of the locomotor transition from water to land is largely based on a few exemplar fossils such as Tiktaalik3, Acanthostega4, Ichthyostega5 and Pederpes6. However, isolated bony elements may reveal hidden functional diversity, providing a more comprehensive evolutionary perspective7. Here we analyse 40 three-dimensionally preserved humeri from extinct tetrapodomorphs that span the fin-to-limb transition and use functionally informed ecological adaptive landscapes8,9,10 to reconstruct the evolution of terrestrial locomotion. We show that evolutionary changes in the shape of the humerus are driven by ecology and phylogeny and are associated with functional trade-offs related to locomotor performance. Two divergent adaptive landscapes are recovered for aquatic fishes and terrestrial crown tetrapods, each of which is defined by a different combination of functional specializations. Humeri of stem tetrapods share a unique suite of functional adaptations, but do not conform to their own predicted adaptive peak. Instead, humeri of stem tetrapods fall at the base of the crown tetrapod landscape, indicating that the capacity for terrestrial locomotion occurred with the origin of limbs. Our results suggest that stem tetrapods may have used transitional gaits5,11 during the initial stages of land exploration, stabilized by the opposing selective pressures of their amphibious habits. Effective limb-based locomotion did not arise until loss of the ancestral 『L-shaped』 humerus in the crown group, setting the stage for the diversification of terrestrial tetrapods and the establishment of modern ecological niches12,13.
DOI: 10.1038/s41586-020-2974-5
Source: https://www.nature.com/articles/s41586-020-2974-5