Diversity of elytra morphology: tradeoffs between anti-predation and flight efficiency

2023 Fiscal Year Final Research Report

• Project/Area Number: 20K15863
• Research Category: Grant-in-Aid for Early-Career Scientists
• Allocation Type: Multi-year Fund
• Review Section: Basic Section 45030:Biodiversity and systematics-related
• Research Institution: Yamaguchi University
• Principal Investigator: Kojima Wataru 山口大学, 大学院創成科学研究科, 講師 (70750462)
• Project Period (FY): 2020-04-01 – 2024-03-31
• Keywords: 甲虫 / 物理的防御 / 捕食

Outline of Final Research Achievements

We demonstrated the critical role of the robust beetle exoskeleton in protecting against avian predation. We found that flower chafers (Scarabaeidae, Cetoniinae) have more robust bodies than other scarab species. Laboratory experiments with naive Japanese quail Coturnix japonica revealed that some individuals of intact Cetoniinae survived attacks without serious injury, while all individuals of soft scarab species or elytra-removed Cetoniinae were consumed. The survival rate of intact Cetoniinae increased under complex environments because the combination of its stiffness and elliptical shape made it difficult for quail to handle the prey. Field experiments with wild starlings and Eurasian tree sparrows demonstrated that most individuals of Cetoniinae species were ignored before being attacked, while soft species were readily preyed upon. These results collectively provide evidence that the robust exoskeleton of beetles renders them unprofitable to attack for the predators.

Free Research Field

行動生態学

Academic Significance and Societal Importance of the Research Achievements

甲虫は最も成功した分類群と言われており、全動物種の25%をも占める。これまで、甲虫の硬い体は物理的防御として機能すると考えられてきたものの、クモやトカゲを捕食者のモデルとして用いた研究がいくつか存在するのみで、実証例は少なかった。本研究により、甲虫の硬さが鳥類からの捕食を回避する上で有効であることが示されたが、鳥類を用いた研究としてはおそらく初めてのものである。このような甲虫の天敵回避能力の高さが、このグループの驚くべき多様化につながった可能性がある。