Nishimura Kinya
Graduate School of Fisheries Sciences Hokkaido University Japan.
Ecol Evol. 2018 Jan 27;8(4):2305-2319. doi: 10.1002/ece3.3801. eCollection 2018 Feb.
Cannibalism is induced in larval-stage populations of the Hokkaido salamander, , under the control of a cannibalism reaction norm. Here, I examined phenotypic expression under the cannibalism reaction norm, and how the induction of a cannibalistic morph under the norm leads to populational morphological diversification. I conducted a set of experiments in which density was manipulated to be either low or high. In the high-density treatment, the populations become dimorphic with some individuals developing into the cannibal morph type. I performed an exploratory analysis based on geometric morphometrics and showed that shape characteristics differed between not only cannibal and noncannibal morph types in the high-density treatment but also between those morph types and the solitary morph type in the low-density treatment. Size and shape of cannibal and noncannibal individuals were found to be located at either end of a continuum of expression following a unique size-shape integration rule that was different from the rule governing the size and shape variations of the solitary morph type. This result implies that the high-density-driven inducible morphology of an individual is governed by a common integration rule during the development of dimorphism under the control of the cannibalism reaction norm. Phenotypic expression under the cannibalism reaction norm is driven not only by population density but also by social interactions among the members of a population: variation in the populational expression of dimorphism is associated with contingent social interaction events among population members. The induced cannibalistic morph thus reflects not only by contest-type exploitative competition but also interference competition.
在同类相食反应规范的控制下，北海道蝾螈幼体阶段的种群会出现同类相食现象。在此，我研究了同类相食反应规范下的表型表达，以及该规范下同类相食形态的诱导如何导致种群形态多样化。我进行了一组实验，将密度控制为低或高。在高密度处理中，种群出现二态性，一些个体发育成同类相食形态类型。我基于几何形态测量学进行了探索性分析，结果表明，不仅在高密度处理中同类相食形态类型和非同类相食形态类型之间的形状特征不同，而且在低密度处理中这些形态类型与独居形态类型之间的形状特征也不同。同类相食个体和非同类相食个体的大小和形状位于一个独特的大小 - 形状整合规则所决定的表达连续体的两端，该规则不同于控制独居形态类型大小和形状变化的规则。这一结果表明，在同类相食反应规范的控制下，高密度驱动的个体可诱导形态在二态性发育过程中受共同的整合规则支配。同类相食反应规范下的表型表达不仅受种群密度驱动，还受种群成员之间的社会互动驱动：二态性在种群中的表达变化与种群成员之间偶然的社会互动事件相关。因此，诱导产生的同类相食形态不仅反映了竞争型剥削竞争，还反映了干扰竞争。
