Is specialization an evolutionary dead end? Testing for differences in speciation, extinction and trait transition rates across diverse phylogenies of specialists and generalists
Is specialization an evolutionary dead end? Testing for differences in speciation, extinction and trait transition rates across diverse phylogenies of specialists and generalists
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DOI：
10.1111/jeb.12867
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发表时间：
2016-06-01
影响因子：
2.1
通讯作者：
Bromham, L.
中科院分区：
文献类型：
--
作者：
Day, E. H.;Hua, X.;Bromham, L.
专业化经常被认为是进化的死胡同，专业血统的持续或多样化能力降低。在一个系统发育的比较框架，一个进化的死胡同可能是从专家的系统发育分布检测，如果专家很少产生大的，不同的分支。以前的系统发育研究的专业化的影响，宏观进化过程中已经证明了一系列的模式，包括专家有更高和更低的多样化率比通才的例子，以及从通才到专家的进化过渡率更高，更低或等于从专家到通才的过渡的例子。在这里，我们想问这些不同的答案是由于不同分支的宏观进化过程的差异，还是部分由于方法的差异。我们分析了10个包含多个独立起源的专业化和量化的系统发育分布的专家通过应用一组通用的指标，所有的数据集。我们比较了专家的尖端分支长度通才，专家分支的大小所产生的每个进化起源的一个专门的特点，以及专家是否倾向于集群或分散的遗传。对于每一个这些措施，我们比较了观察值的期望下的零模型的性状进化和预期结果下的替代宏观进化的情况。我们发现，专业化有时是一个进化的死胡同：在两个十个案例研究（传粉特定的植物和主机特定的苍蝇），专业化与多样化或性状持久性的速度降低。然而，在大多数的研究中，我们不能区分观察到的系统发育分布的专家从空模型中的专业化没有影响多样化或性状持久性。
Specialization has often been claimed to be an evolutionary dead end, with specialist lineages having a reduced capacity to persist or diversify. In a phylogenetic comparative framework, an evolutionary dead end may be detectable from the phylogenetic distribution of specialists, if specialists rarely give rise to large, diverse clades. Previous phylogenetic studies of the influence of specialization on macroevolutionary processes have demonstrated a range of patterns, including examples where specialists have both higher and lower diversification rates than generalists, as well as examples where the rates of evolutionary transitions from generalists to specialists are higher, lower or equal to transitions from specialists to generalists. Here, we wish to ask whether these varied answers are due to the differences in macroevolutionary processes in different clades, or partly due to differences in methodology. We analysed ten phylogenies containing multiple independent origins of specialization and quantified the phylogenetic distribution of specialists by applying a common set of metrics to all datasets. We compared the tip branch lengths of specialists to generalists, the size of specialist clades arising from each evolutionary origin of a specialized trait and whether specialists tend to be clustered or scattered on phylogenies. For each of these measures, we compared the observed values to expectations under null models of trait evolution and expected outcomes under alternative macroevolutionary scenarios. We found that specialization is sometimes an evolutionary dead end: in two of the ten case studies (pollinator-specific plants and host-specific flies), specialization is associated with a reduced rate of diversification or trait persistence. However, in the majority of studies, we could not distinguish the observed phylogenetic distribution of specialists from null models in which specialization has no effect on diversification or trait persistence.