Dissertation Research: Phylogenetics of Derived Leptosporangiate Ferns: A Reassessment of the Polypodiaceae S. L.

0073036施密特，史密斯和克兰菲尔研究生雷蒙德克兰菲尔，在博士的指导下。Rudolf Schmid和Alan Smith建议通过使用分子序列数据和形态学来研究衍生的细孢子蕨类植物Polypodiales的进化史。水螅目蕨类植物包括大部分现存的蕨类植物，大约有8000 - 10000种。在湿润热带和亚热带以及一些温带生态系统中，它们几乎是每个生态系统中一个显著而多样的元素。虽然我们现在知道这个群体是单系的（也就是说，有一个假定的祖先），但我们对多足动物内部相互关系的理解是贫乏和不可靠的。对于最先进化的最不特化或最基础的群体来说尤其如此。水足动物的进化辐射可能发生在白垩纪很短的时间内，大约发生在1.4亿到6500万年前。由于在相对较远的地质时代，多样化显然是迅速的，我们需要检查叶绿体、线粒体和细胞核中的几种不同基因，以及形态学特征，以便确定这些蕨类植物之间的更深层次的关系。了解多足动物的明确进化关系是很重要的，原因有几个。(1)因为这是现存蕨类植物中最多样化的一组，对这些关系的理解有望揭示进化和结构生物学中一系列不同的和有趣的话题，从宏观进化过程到形态特征的进化转变。(2)对于对植物发育过程的遗传控制感兴趣的发育生物学家来说，对后者的新认识尤为重要。(3)该研究对我们理解现代陆地和附生（非陆地）生态系统的演化也具有重要意义。水螅类植物可能是与开花植物同时辐射的，也可能是对栖息地多样化的反应，开花植物辐射到各种各样的栖息地，并开始形成比以前更复杂的生态群落。类似的过程似乎正在形成类似的多样性模式。因此，我们从蕨类植物身上学到的东西可能对我们今天看到的植物群落的早期进化和发展有重要的帮助。

0073036Schmid, Smith, and Cranfill Graduate student Raymond Cranfill, under the direction of Drs. Rudolf Schmid and Alan Smith, proposes to study the evolutionary history of derived leptosporangiate ferns, the Polypodiales, through use of both molecular sequence data and morphology. The Polypodiales comprise most of the ferns living today and number about 8,000-10,000 species. They are a conspicuous and diverse element of almost every ecosystem in the wetter tropics and subtropics, as well as some temperate ecosystems. Although we now know that this group is monophyletic (that is, with a single presumed ancestry), our understanding of interrelationships within the Polypodiales is poor and unreliable. This is particularly true for the least specialized or basal groups that were the first to evolve. The evolutionary radiation of the Polypodiales probably occurred over a very short time in the Cretaceous Period, which occurred 140-65 million years ago. Because the diversification apparently was rapid at a relatively distant geological time, we will need to examine several different genes from the chloroplast, mitochondrion, and nucleus, as well as morphological features, in order to define the deeper relationships between these ferns. An understanding of the explicit evolutionary relationships of the Polypodiales is important for several reasons. (1) Because this is the most diverse group of extant ferns, an understanding of these relationships promises to shed light on a range of different and interesting topics in evolutionary and structural biology, from macroevolutionary processes to evolutionarytransformations in morphological characters. (2) A fresh understanding of the latter is particularly important to developmental biologists who are interested in the genetic control of developmental processes in plants. (3) This research is also important to our understanding of the evolution of modern terrestrial and epiphytic (non-terrestrial) ecosystems. It appears that the Polypodialesmay have radiated contemporaneously with the flowering plants and perhaps in response to habitat diversification that occurred as the flowering plants radiated into a wide variety of habitats and began to form communities of greater ecological complexity than may have existed before. Comparable processes appear to be shaping similar patterns of diversity. Therefore, what we learn from ferns may contribute significantly to an understanding of the early evolution and development of plant communities that we see today.