Intraspecific variability and timing in ancestral ecology reconstruction: A test case from the Cape flora
Intraspecific variability and timing in ancestral ecology reconstruction: A test case from the Cape flora
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DOI：
10.1080/10635150590923317
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发表时间：
2005-04-01
影响因子：
6.5
通讯作者：
Linder, HP
中科院分区：
文献类型：
--
作者：
Hardy, CR;Linder, HP
Thamnochortus（约 32 种）是生态多样化的 Restionaceae 属。 Restionaceae是南部非洲开普植物区系的主要组成部分，其中生态多样化可能对于高水平物种丰富度的产生非常重要。在尝试重建 Thamnochortus 的宏观生态历史时，发现性格状态优化的标准程序做出了两个不适当的假设。第一个是祖先是单态的（即生态一致），第二个是生态多样化跟随谱系多样化，或者比谱系多样化更慢。我们演示了多种可以避免单态假设的编码方案。对于无序离散生态特征，存在编码和广义频率编码（GFC）不是最优的，因为它们偶尔会产生不合逻辑的无状态分配给祖先。多态性编码或程序 DIVA 的使用在这方面是优选的，但仅适用于简约性。对于连续的生态特征（例如，降雨梯度，其中单个物种出现在范围内），GFC 和 MaxMin 编码提供了同样有效的解决方案，以简约的方式优化范围。然而，MaxMin 可以扩展到似然方法，因此更可取。就速率和时间而言，目前用于祖先生态重建的所有算法都偏向于相对于谱系多样化而言生态多样化的缓慢速率。 DIVA 提供了这种偏见的替代方案，它倾向于加快生态多样化的速度，从而推论生态驱动的物种形成。我们看不到在这些偏见之间做出选择的方法。然而，系统发生学家应该意识到它们。将这些方法应用于 Thamnochortus，我们发现该分支的历史生态在细节上存在重要差异，但总体上是一致的。我们推断 Thamnochortus 最近的共同祖先是一种火后再发芽物种，分布在中低海拔、年降雨量适中（主要是冬季）的地区的岩石、排水良好、源自砂岩的土壤上。该物种的栖息地与今天开普省西南山区的栖息地非常相似。主要的生态趋势包括向较低降雨量的转变以及从砂岩向低海拔石灰岩衍生的碱性土壤的转变。
Thamnochortus ( ca. 32 species) is an ecologically diverse genus of Restionaceae. Restionaceae comprise a major component of the southern African Cape flora, wherein eco-diversification might have been important in the generation of high levels of species richness. In an attempt to reconstruct the macroecological history of Thamnochortus, it was found that standard procedures for character state optimization make two inappropriate assumptions. The first is that ancestors are monomorphic (i.e., ecologically uniform) and the second is that eco-diversification follows, or is slower than, lineage diversification. We demonstrate a variety of coding schemes with which the assumption of monomorphy can be avoided. For unordered discrete ecological characters, presence coding and generalized frequency coding (GFC) are suboptimal because they occasionally yield illogical assignments of no state to ancestors. Polymorphism coding or use of the program DIVA are preferable in this respect but are applicable only with parsimony. For continuous eco-characters ( e. g., a rainfall gradient, where individual species occur in ranges), GFC and MaxMin coding provide equally valid solutions to optimizing ranges with parsimony. However, MaxMin can be extended to likelihood approaches and is therefore preferable. With respect to rates and timing, all algorithms currently employed for ancestral ecology reconstruction bias toward slow rates of eco-diversification relative to lineage diversification. An alternative to this bias is provided by DIVA, which biases toward accelerated rates of eco-diversification and thus inferences of ecology-driven speciation. We see no way of choosing between these biases; however, phylogeneticists should be aware of them. Applying these methods to Thamnochortus, we find there to be important differences in details, yet general congruence, regarding the historical ecology of this clade. We infer the most recent common ancestor of Thamnochortus to have been a post-fire resprouting species distributed on rocky, well-drained, sandstone-derived soils at lower-middle elevations, in regions of moderate levels of yearly ( primarily winter) rainfall. This species would have been distributed in habitats much like those of the southwestern Cape mountains today. Major ecological trends include shifts to lower rainfall regimes and shifts from sandstone to limestone-derived alkaline soils at lower altitudes.