影响开花植物物种多样化速率变化的因素探讨

Discussion on factors affecting diversification rates of flowering plants

关键词:  物种多样化速率, 开花植物, 多倍化, 性状, 地理环境

Key words:  diversification rate, flowering plant, polyploidization, trait, geographical factor

摘要:

开花植物(被子植物)是目前最为繁荣兴盛的陆地植物,是地球上种类最多、分布最广、适应性最强的优势植物类群。然而,物种多样性在开花植物的谱系中极端不均匀,同时其物种并非匀速增加,而是集中在某些时期快速扩张。这种现象暗示了开花植物的多样性受到某些因素的调控,而揭示影响开花植物多样化速率的机制便是这数十年来植物学家孜孜不倦努力的目标。该文介绍了当前的研究进展。研究显示,那些与类群分类相关的关键性状大多与多样化无关,而早期被视为决定因素的花性状,目前被认为影响较低或是需要多性状联合才产生实际影响。多倍化是一个受到高度关注的候选因素,被认为能提供物种扩张所需的遗传物质,在适当的情况或其他因素的参与下促成物种多样化。然而,许多研究也呈现各类的争议,这些悖论或许代表了多倍化不是决定因素,而是扮演着间接的角色。另外,环境的变异(温度、湿度、空间)也能提高多样性的发生。整体而言,影响开花植物多样化速率的原因,很可能是一种综合因素共同促成的结果,而每个植物类群多样化速率提升的原因亦可能不尽相同。因此,先分别对植物类群进行探讨,再进行整合,或许更能提供一个确实且普遍的模型。

Abstract:

Flowering plants(angiosperms)constitute the most prosperous group of land plants. They are the dominant plant group with the highest diversity and the widest distribution. However, species richness across lineages of flowering plants is extremely uneven, and species expansion is not smooth, but concentrated in certain lineages during particular periods. This implies that the distribution of biodiversity of flowering plants is influenced by some factors, and revealing the underlying mechanism is the goal of botanists' unremitting efforts for decades. In this review, we try to review the progress of current researches related to this scientific question. Previous studies showed that most of the synapomorphies used by systematists to define the major clades of flowering plants do not drive higher rates of diversification. Flower traits, which were considered as determinants in the first place, were currently considered to have low impact to diversification, while a combination of multiple traits seemed more influential than a single character. As a popular candidate, polyploidy has been widely studied with debates. These paradoxes imply that instead of a determinant factor, polyploidy may act indirectly by providing the genetic materials for and thus promoting species diversification under appropriate circumstances with the participation of other factors. Environmental variation(such as temperature, humidity, and space)seems to associated with improved biodiversity, too. Overall, what affects the biodiversity of flowering plants is likely the result of a combination of factors and may not be the same for different lineages. Therefore, exploring potential factors in different plant groups and integrating the information may provide a solid conclusion than considering one particular factor across the whole flowering plants.