Behavior, brain, and morphology in a complex insect society: trait integration and social evolution in the exceptionally polymorphic ant Pheidole rhea
Behavior, brain, and morphology in a complex insect society: trait integration and social evolution in the exceptionally polymorphic ant Pheidole rhea
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DOI：
10.1007/s00265-017-2396-z
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发表时间：
2017-11-01
影响因子：
2.3
通讯作者：
Traniello, James F. A.
中科院分区：
文献类型：
--
作者：
Gordon, Darcy G.;Ilies, Iulian;Traniello, James F. A.
群居昆虫中的多表型现象源于灵活的发育机制，这些机制可能产生行为和形态上专业化的工蜂。Pheidole蚁属的典型特征是小型工蚁和大型蚁兵亚种，但在一些物种中也进化出了更大的超级蚁兵，包括异常多态的Pheidole rhea。为了研究这种社会复杂的蚂蚁的工蚁表型进化，我们测试了行为、大脑结构和形态在工蚁大小类别中由于特殊社会角色的选择而整合在一起的假设，并且这些特征在这些群体中已经离散化。我们的分析显示，在小工人和两种士兵体型之间，大脑结构和体型存在显著差异。未成年人、士兵和超级士兵的行为表相似，但未成年人执行重要任务的频率高于士兵和超级士兵。士兵和超级士兵群体在行为方面的广泛重叠与共同的神经解剖和形态特征相关。尽管头和身体的大小在不同的大小类别中有异速变化，但尺度分析显示脑亚结构的异速变化很小。不同士兵体型之间的行为和大脑组织的共变表明，他们的功能可能是由于任务执行率或效率的差异，而不是任务曲目。P. rhea在Pheidole系统发育中的早期分支位置和工蚁表型可塑性模式表明，该物种表现出社会生物学和神经生物学组织的祖先状态，这是该生态优势蚁属多样化的基础计划。对不同社会角色的选择可能会影响个体内部和特殊群体之间的行为、神经解剖和形态表型整合的程度。在高度多样化的蚁属Pheidole的早期分支分支中，具有强烈多态性的P. rhea的行为技能、神经解剖学和工蚁身体形状似乎与工蚁头身大小的整合程度相对较低。体型较大的士兵群体在行为、大脑缩放关系和体型上无法区分，这一假定的祖先和发育可塑性条件表明，工人头身异速的优势可能来自行为表现的定量方面的变化，而不是专注于不同的定性任务。这似乎对该属的社会进化具有重要意义。
Polyphenisms in social insects arise from flexible developmental mechanisms that may produce behaviorally and morphologically specialized workers. The ant genus Pheidole is typically characterized by small minor worker and large soldier subcastes, but larger supersoldiers have evolved in several species, including the exceptionally polymorphic Pheidole rhea. To examine worker phenotype evolution in this socially complex ant, we tested the hypotheses that behavior, brain structure, and morphology are integrated within worker size classes due to selection for specialized social roles and that traits have been discretized among these groups. Our analyses revealed significant differences in brain structure and body shape between minor workers and the two soldier size classes. Behavioral repertoires of minors, soldiers, and supersoldiers were similar, but minors performed important tasks at higher frequencies than soldiers and supersoldiers. The extensive overlap in behavioral repertoire between soldier and supersoldier groups correlated with shared neuroanatomical and morphological traits. Although head and body size vary allometrically among P. rhea size classes, scaling analyses revealed little allometry in brain substructure. The covariation of behavior and brain organization between soldier size classes suggests that their functionality may be due to differences in task performance rate or efficiency rather than task repertoire. The early branching position of P. rhea in the phylogeny of Pheidole and patterns of worker phenotypic plasticity suggest this species exhibits an ancestral state of sociobiological and neurobiological organization that served as a ground plan for diversification in this ecologically dominant ant genus. Selection for divergent social roles may impact the degree to which behavioral, neuroanatomical, and morphological phenotypes are integrated within individuals and between specialized groups. Behavioral repertoire, neuroanatomy, and worker body shape in the strongly polymorphic P. rhea, a species of the hyperdiverse ant genus Pheidole that branched early in the phylogeny of the clade appear to show a relatively low degree of integration with worker head-body size. The putatively ancestral and developmentally plastic condition in which larger-bodied soldier groups are not distinguishable in behavior, brain scaling relationships, and body shape suggests the advantage of worker head-body allometry may derive from variation in quantitative aspects of behavioral performance rather than specialization on qualitatively different tasks. This appears to be significant to social evolution in the genus.