Trait evolution is reversible, repeatable, and decoupled in the soldier caste of turtle ants
Trait evolution is reversible, repeatable, and decoupled in the soldier caste of turtle ants
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在龟蚁的士兵种姓中，性状进化是可逆的、可重复的、解耦的
DOI：
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发表时间：
2020
影响因子：
11.1
通讯作者：
D. Kronauer
中科院分区：
文献类型：
--
作者：
S. Powell;S. Price;D. Kronauer
意义专门化种姓被视为群居昆虫生态和进化成功所必需的表型创新。然而，种姓如何随着世系填充生态空间而适应性地演变仍未得到解决。最近对海龟蚂蚁的研究表明，在标志性的士兵种姓中，头的形状和大小决定了筑巢生态的两个关键方面。在这里，物种水平的比较分析表明，头部形状和大小的进化是广泛可逆的、可重复的，并且在士兵种姓内和相对于女王种姓而言是分离的，这支撑了血统的多样化筑巢生态。这些发现重塑了我们对种姓进化的理解，摒弃了稳定的、定向的过程，转而支持表型和环境之间的动态适应过程。一个谱系内适应性表型变化的范围是由功能性状的进化决定的。种姓定义了复杂昆虫群落中适应性表型变化的功能特征，种姓进化预计在广泛的系统发育尺度上是系统发育保守和发育受限的。然而，种姓是如何在物种层面上进化的，在很大程度上仍然没有得到解决。种姓专业化的标志性例子--海龟蚂蚁士兵(Cephalotes属)用精心装甲的头部作为活的路障来保卫蚁穴的入口处。在物种之间，士兵的形态类型决定了入口的专门化和防御策略，而头部大小决定了防御入口的具体大小。我们对形态类型和头部大小进化的物种水平的比较分析表明，这些关键的生态形态特征在士兵内部以及士兵和女王种姓之间具有广泛的可逆性、可重复性和解偶性。通过多项分析一致地重建了四种形态的重复进化得失。此外，形态类型不能预测三种最常见的形态类型的平均头部大小，而且头部大小分布在所有形态类型中都有很大的重叠。一致的是，多个模型拟合方法表明，士兵头部大小的演变可以用发散的变化脉冲过程来最好地解释。最后，虽然士兵和女王的头部大小在物种之间广泛耦合，但不同种姓之间的头部大小差异的水平与女王头部大小和士兵的形态类型是分离的。这些发现表明，种姓进化在物种水平上可以是高度动态的，重塑了我们对复杂社会谱系中适应性形态变化的理解。
Significance Specialized castes are seen as phenotypic innovations necessary for ecological and evolutionary success in social insects. Nevertheless, how castes evolve adaptively as a lineage fills ecological space has remained unaddressed. Recent work with turtle ants has established that head shape and size in the iconic soldier caste, specialized for nest entrance defense, determine two key aspects of nesting ecology. Here species-level comparative analyses reveal that the evolution of head shape and size is extensively reversible, repeatable, and decoupled within the soldier caste and relative to the queen caste, underpinning the lineage’s diverse nesting ecology. These findings reshape our understanding of caste evolution, rejecting a stable, directional process in favor of a dynamic process of adaptive fitting between phenotype and environment. The scope of adaptive phenotypic change within a lineage is shaped by how functional traits evolve. Castes are defining functional traits of adaptive phenotypic change in complex insect societies, and caste evolution is expected to be phylogenetically conserved and developmentally constrained at broad phylogenetic scales. Yet how castes evolve at the species level has remained largely unaddressed. Turtle ant soldiers (genus Cephalotes), an iconic example of caste specialization, defend nest entrances by using their elaborately armored heads as living barricades. Across species, soldier morphotype determines entrance specialization and defensive strategy, while head size sets the specific size of defended entrances. Our species-level comparative analyses of morphotype and head size evolution reveal that these key ecomorphological traits are extensively reversible, repeatable, and decoupled within soldiers and between soldier and queen castes. Repeated evolutionary gains and losses of the four morphotypes were reconstructed consistently across multiple analyses. In addition, morphotype did not predict mean head size across the three most common morphotypes, and head size distributions overlapped broadly across all morphotypes. Concordantly, multiple model-fitting approaches suggested that soldier head size evolution is best explained by a process of divergent pulses of change. Finally, while soldier and queen head size were broadly coupled across species, the level of head size disparity between castes was decoupled from both queen head size and soldier morphotype. These findings demonstrate that caste evolution can be highly dynamic at the species level, reshaping our understanding of adaptive morphological change in complex social lineages.
影响因子：
8.8
作者：
Poisot T;Bever JD;Nemri A;Thrall PH;Hochberg ME
通讯作者：
Hochberg ME