Sato Yukuto, Tsurui-Sato Kaori, Katoh Mitsuho, Kimura Ryosuke, Tatsuta Haruki, Tsuji Kazuki
Center for Strategic Research Project University of the Ryukyus Okinawa Japan.
Department of Agro-Environmental Sciences Faculty of Agriculture University of the Ryukyus Okinawa Japan.
Ecol Evol. 2020 Dec 24;11(2):872-886. doi: 10.1002/ece3.7092. eCollection 2021 Jan.
Batesian mimicry is a striking example of Darwinian evolution, in which a mimetic species resembles toxic or unpalatable model species, thereby receiving protection from predators. In some species exhibiting Batesian mimicry, nonmimetic individuals coexist as polymorphism in the same population despite the benefits of mimicry. In a previous study, we proposed that the abundance of mimics is limited by that of the models, leading to polymorphic Batesian mimicry in the swallowtail butterfly, on the Ryukyu Islands in Japan. We found that their mimic ratios (MRs), which varied among the Islands, were explained by the model abundance of each habitat, rather than isolation by distance or phylogenetic constraint based on the mitochondrial DNA (mtDNA) analysis. In the present study, this possibility was reexamined based on hundreds of nuclear single nucleotide polymorphisms (SNPs) of 93 individuals from five Islands of the Ryukyus. We found that the population genetic and phylogenetic structures of largely corresponded to the geographic arrangement of the habitat Islands, and the genetic distances among island populations show significant correlation with the geographic distances, which was not evident by the mtDNA-based analysis. A partial Mantel test controlling for the present SNP-based genetic distances revealed that the MRs of were strongly correlated with the model abundance of each island, implying that negative frequency-dependent selection interacting with model species shaped and maintained the mimetic polymorphism. Taken together, our results support the possibility that predation pressure, not isolation by distance or other neutral factors, is a major driving force of evolution of the Batesian mimicry in from the Ryukyus.
贝氏拟态是达尔文进化论的一个显著例子，其中拟态物种类似于有毒或难吃的模式物种，从而获得免受捕食者侵害的保护。在一些表现出贝氏拟态的物种中，尽管拟态有诸多益处，但非拟态个体作为多态性在同一群体中共存。在之前的一项研究中，我们提出拟态者的数量受模式物种数量的限制，这导致了日本琉球群岛上燕尾蝶的多态贝氏拟态现象。我们发现，它们的拟态比率（MRs）在各岛屿间存在差异，这可以通过每个栖息地的模式物种数量来解释，而非基于线粒体DNA（mtDNA）分析的距离隔离或系统发育限制。在本研究中，基于来自琉球群岛五个岛屿的93个个体的数百个核单核苷酸多态性（SNPs），重新审视了这种可能性。我们发现，群体遗传结构和系统发育结构在很大程度上与栖息地岛屿的地理布局相对应，岛屿种群之间的遗传距离与地理距离呈现出显著的相关性，而基于mtDNA的分析并未体现出这一点。控制当前基于SNP的遗传距离的部分曼特尔检验表明，燕尾蝶的拟态比率与每个岛屿的模式物种数量密切相关，这意味着与模式物种相互作用的负频率依赖选择塑造并维持了拟态多态性。综上所述，我们的结果支持了这样一种可能性，即捕食压力而非距离隔离或其他中性因素，是琉球群岛燕尾蝶贝氏拟态进化的主要驱动力。
