Biogeographic Drivers of Evolutionary Radiations-猫眼课题宝

DOI：

10.3389/fevo.2021.644328

发表时间：

2021-08

期刊：

影响因子：

通讯作者：

中科院分区：

其他

文献类型：

作者：

Ran Tao;L. Sack;J. Rosindell

在殖民一个地区时，一些血统会散发出壮观的光芒，但另一些则不会。大辐射通常归因于物种对生态位的适应，或其他驱动因素，如生物地理学，包括扩散能力和景观的空间结构。在这里，我们的目标是解开决定辐射大小的因素，通过建模简化的场景，没有明确的生态位的复杂性。我们建立了一个空间结构的中性模型，没有生态位，并纳入了一种解释种群之间基因流动的长期物种形成形式。我们发现，在这个模型中，根据地理隔离和物种扩散能力的组合，可能有一个大范围的辐射大小。在斑块之间极低的分散率下，每个斑块保持着自己的特有物种。中等扩散率促进了更大的辐射，因为它们允许偶尔在斑块之间移动，同时充分限制了基因流动，以支持异域物种的进一步形成。随着扩散速率的进一步增加，达到一个临界点，在这个临界点上，由于罕见和随机的扩散事件，人口统计学上相同的谱系在辐射大小上可能会发生很大的变化。在扩散频率的临界点，一些谱系在相对较长的时间内保持单一物种，而其他具有相同特征的谱系则通过一种新的快速辐射机制产生最大的辐射，我们称之为“辐射级联”。假设一个单一物种覆盖了许多与基因流动相关的斑块，当随机扩散在一段时间内异常低时，就会触发辐射级联，导致初始物种形成事件。这种物种形成意味着每个物种的个体数量更少，从而进一步减少了同种物种之间的基因流动。减少的基因流动反过来又使进一步的物种形成更容易发生。在辐射级联过程中，个体在斑块之间的分散以与以前相同的速度继续进行，但由于多样性的增加，它主要引入了后来将形成物种的新物种，而不是增加现有物种的基因流。一旦辐射级联开始，它就会迅速持续下去，直到在物种形成和灭绝之间达到新的平衡。我们推测这种辐射级联可能更普遍地发生，而不仅仅存在于中性模式中。这一过程可能有助于解释快速辐射，以及某些祖先分散的谱系的极端辐射大小。虽然生态位无疑在群落聚集中发挥了作用，但我们的研究结果使我们质疑，生态位的多样化和适应有时是否是物种形成和快速辐射的结果，而不是其原因。

Some lineages radiate spectacularly when colonizing a region, but others do not. Large radiations are often attributed to species’ adaptation into niches, or to other drivers, such as biogeography including dispersal ability and spatial structure of the landscape. Here we aim to disentangle the factors determining radiation size, by modeling simplified scenarios without the complexity of explicit niches. We build a spatially structured neutral model free from niches and incorporating a form of protracted speciation that accounts for gene flow between populations. We find that a wide range of radiation sizes are possible in this model depending on the combination of geographic isolation and species’ dispersal ability. At extremely low rates of dispersal between patches, each patch maintains its own endemic species. Intermediate dispersal rates foster larger radiations as they allow occasional movement between patches whilst sufficiently restricting gene flow to support further speciation in allopatry. As dispersal rates increase further, a critical point is reached at which demographically identical lineages may vary greatly in radiation size due to rare and stochastic dispersal events. At the critical point in dispersal frequency, some lineages remain a single species for a comparatively long time, whilst others with identical characteristics produce the largest radiations of all via a new mechanism for rapid radiation that we term a ‘radiation cascade’. Given a single species covering many patches connected with gene flow, a radiation cascade is triggered when stochastic dispersal is unusually low for a period, leading to an initial speciation event. This speciation means there are fewer individuals per species and thus further reduced gene flow between conspecifics. Reduced gene flow in turn makes it easier for further speciation to occur. During a radiation cascade, dispersal of individuals between patches continues at the same rate as before, but due to the increasing diversity it primarily introduces novel species that will later speciate, rather than adding to gene flow of existing species. Once a radiation cascade begins, it continues rapidly until it is arrested by a new equilibrium between speciation and extinction. We speculate that such radiation cascades may occur more generally and are not only present in neutral models. This process may help to explain rapid radiation, and the extreme radiation sizes of certain lineages with dispersing ancestors. Whilst niches no doubt play a role in community assembly, our findings lead us to question whether diversification and adaptation into niches is sometimes an effect of speciation and rapid radiation, rather than its cause.

Biogeographic Drivers of Evolutionary Radiations

文献摘要

相似文献