Origin and early diversification of vascular plants: integrating evidence from the plant megafossil and dispersed spore fossil records

在地球历史的大部分时间里，大陆基本上是贫瘠的。即使在寒武纪爆发之后，当海洋开始充满复杂的动物生命时，地球表面也没有任何生物。最终，大约4.6亿年前，第一批陆地植物进化出来。光合作用植物第一次生长在陆地表面。这是地球生命史上的重大事件，主要有三个原因：-(I)它代表了多细胞生命的第三个王国的进化(植物加入了真菌和动物)。(2)它为其他生物入侵陆地铺平了道路，包括蠕虫、昆虫，最后是我们的直系祖先(最早的两栖动物)。(Iii)它对地球环境产生了巨大的影响，改变了大气成分和气候、土壤形成的模式、侵蚀、风化、沉积等。它将专注于石松子。这些是现存植物中最原始的一类，包括一些常见的植物，如石松和卷柏。石龙子有着丰富的化石记录，可以追溯到4亿多年前。这些化石要么以整株植物(巨型化石)的形式出现，要么以植物在生命过程中释放的孢子(散布的孢子)的形式出现。巨型化石很罕见，很难解释它们的化石记录。然而，幸运的是，植物一生中会产生和释放数十万个微小的孢子。这些孢子被风吹散，然后降落在潮湿肥沃的土壤上，长成新的植物，或者更常见的是，被沉积在湖泊、河流或海洋中。后者被合并到沉积物中，很容易变成化石。因此，我们可以溶解古老的湖泊、河流和海洋沉积物，并回收古代植物产生的孢子。这个项目的目的是整合石蒜、巨型化石和分散的孢子化石记录，以揭示植物入侵陆地的情况。将对新发现的仍含有孢子(原位孢子)的石蒜属巨化石进行研究，以确定石蒜属孢子的性质(这将与对活体石蒜属孢子特征的研究相结合)。然后，我们将研究丰富的分散孢子记录，以确定第一批石松属植物何时进化，它们是如何(通过进化)多样化并传播到大陆的。这也将提供一个空间/时间模板，用于理解随着早期植被的进化和传播而发生的复杂环境变化，有望揭示与当前全球变化有关的问题。

For most of earth history the continents were essentially barren. Even following the Cambrian explosion, when the oceans began to teem with complex animal life, nothing lived on the planet surface. Eventually, some 460 million years ago, the first land plants evolved. For the first time photosynthesizing plants grew on the land surface. This was a monumental event in the history of life on earth for three main reasons:- (i) It represented the evolution of the third kingdom of multicellular life (plants joined the fungi and animals). (ii) It paved the way for other organisms to invade the land, including the worms, insects and finally, our direct ancestors (the first amphibians). (iii) It had a dramatic effect on the environment of planet earth, altering atmospheric composition and climate, patterns of soil formation, erosion, weathering, sedimentation etc. The aim of this research project is to shed light on the invasion of the land by plants through the study of fossil plants. It will concentrate on lycopsids. These are the most primitive group of living plants, and include some familiar plants such as Lycopodium (clubmosses) and Selaginella. The lycopsids have a rich fossil record stretching back more than 400 million years. The fossils occur either as whole plants (megafossils) or spores that were released by the plants during life (dispersed spores). Megafossils are rare and interpreting their fossil record is difficult. Fortunately, however, plants produce and release hundreds of thousands of minute spores during a lifetime. These spores are widely dispersed by the wind before either landing on damp,fertile soil and growing into a new plant, or more commonly, being deposited in lakes, rivers or the sea. The later become incorporated into sediments and are easily fossilized. Thus we can dissolve up ancient lake, river and marine deposits and recover the spores produced by ancient plants. The aim of this project is to integrate the lycopsids megafossil and dispersed spore fossil records to shed light on the invasion of the land by plants. Newly discovered lycopsid megafossils that still contain spores (in situ spores) will be studied to characterise the nature of lycopsid spores (this will be done in conjunction with a study of spore characters in living lycopsids). We will then examine the rich dispersed spore record to ascertain when the first lycopsids evolved, how they diversified (through evolution) and spread across the continents. This will also supply a spatial/temporal template for understanding the complex environmental changes that occurred as the early vegetation evolved and spread, hopefully shedding light on issues concerned with current global change.