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版纳植物园古生态组:青藏高原带刺植物

已有 970 次阅读 2022-7-6 18:23 |系统分类:论文交流

Rapid Eocene diversification of spiny plants in subtropical woodlands of central Tibet

Eocene(始新世): The Eocene Epoch is a geological epoch that lasted from about 56 to 33.9 million years ago (mya). It is the second epoch of the Paleogene Period (古近纪) in the modern Cenozoic Era(新生代).

宙(Eon)代(Era)纪(Period)世(Epoch)期

Spinescence is an important functional trait possessed by many plant species for physical defence against mammalian herbivores. 

植物长刺是对植食动物的防御。

The development of spinescence must have been closely associated with both biotic and abiotic factors in the geological past, 

刺是怎么形成的呢?除了植食动物可能还跟地质事件有关吧。

but knowledge of spinescence evolution suffers from a dearth of fossil records, with most studies focusing on spatial patterns and spinescence-herbivore interactions in modern ecosystems. 

目前的研究主要还是关于现生的带刺植物,缺乏化石证据。

Numerous well-preserved Eocene (~39 Ma) plant fossils exhibiting seven different spine morphologies discovered recently in the central Tibetan Plateau, 

青藏高原中部(Figure 1) 发现很多始新世时期的带刺植物化石(本文共涉及44份),根据刺的形态可以分为7个大类(Figure 2)。

combined with molecular phylogenetic character reconstruction,

这个phylogenetic character reconstruction是什么呢?发现文章里面这个phrase再也没有出现了。会不会是molecular phylogeny reconstruction and character phylogeny reconstruction呢?看看methods吧。

Phylogenetic analyses. To investigate the emergence and early diversification of spiny eudicots, we reconstructed the evolutionary history of spines across species of woody eudicots represented on the mega-phylogeny of plants from Zanne et al.88 using the make.simmap function in phytools89 and the ape90 and Geiger91 R-libraries (Supplementary Code 1). We coded, as a binary trait, for the presence of spines in plants found in Eurasia (n = 1590 species) mostly using scans from https://plants.jstor.org/. We excluded species when the origin appeared ambiguous between more than one continent. To control for the relatively recent origin and diversification of spines, we allowed rates to vary through time (parameter Δ = 9), and constrained evolutionary transitions to preclude reversals from the spiny to non-spiny state, reflecting the rarity of this evolutionary event, and avoiding potential bias due to the over-representation of non-spiny lineages among woody taxa92.

看上去input是1. 1590个现生木本真双子叶植物的系统发育树 2. 他们是否有刺。output: 刺在欧亚大陆的进化历史。注意:模型不允许从有刺到无刺的进化事件。那我大概理解为:molecular phylogenetic character reconstruction 的重点是character reconstruction,即是否有刺这个trait在molecular phylogeny上的evolutionary history reconstruction.

point not only to the presence of a diversity of spiny plants in Eocene central Tibet 

发现西藏中部在始新世有大量的带刺植物的存在(这个应该是根据本句第一部分Numerous well-preserved Eocene (~39 Ma) plant fossils exhibiting seven different spine morphologies discovered recently in the central Tibetan Plateau得出的)

but a rapid diversification of spiny plants in Eurasia around that time. 

而且(刚才那个phylogenetic character reconstruction表明)这个时期有刺植物在欧亚大陆快速分化(暗示出现很多不同类型)。

These spiny plants occupied an open woodland landscape, 

这些带刺植物当时处于开阔林地,

indicated by numerous megafossils and grass phytoliths found in the same deposits, 

因为在同一个化石点还发现了大量的草本植物的化石和植硅体(化石化了的植物组织颗粒),Figure 4,

as well as numerical climate and vegetation modelling. 

同时对当时气候(下一句提到的局部干旱)和植被的模拟也支持开阔林地这一结论。

Our study shows that regional aridification and expansion of herbivorous mammals may have driven the diversification of functional spinescence in central Tibetan woodlands,

研究表明,局部气候的干旱(有刺植物跟干旱有强烈相关性)以及食草动物的扩张(Figure 3蓝线)或是促使西藏中部林地的带刺植物多样化的原因,

 ~24 million years earlier than similar transformations in Africa.

类似的事件(气候变化和食草动物导致带刺植物的大量出现)在非洲也发生过,但是比西藏晚了近24个百万年。(越早越novel!)

原文见:https://www.nature.com/articles/s41467-022-31512-z

最后恭喜苏涛老师及其团队!



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