ABSTRACT

Dispersal flight is an essential component of the life history of bark and ambrosia beetles. Previous studies have shown considerable variation in flight distance between individual beetles; however, different factors drive this variation between species. Furthermore, when the ecological role of dispersal flight differs between sexes (i.e., males locate hosts and females follow), influencing factors might also vary. Here, we evaluated the factors driving variation in the dispersal flight distance of the ambrosia beetle Platypus quercivorus (Murayama) (Coleoptera: Curculionidae: Platypodinae), which is a vector insect of Raffaelea quercivora, the causal agent of the Japanese oak wilt, and we estimated sex-based differences for each influencing factor. A flight mill was used to measure flight distance, flight duration, and initial and terminal flight speed. Because flight speed was not constant during beetle flight, we estimated both initial and terminal flight speed, and assumed that initial flight speed represents a relative measure of energy allocated to flight. Flight distance was mainly determined by flight duration, with an average flight speed of 4.22 km/h for both sexes. Initial and terminal flight speed affected flight distance; however, these factors had contrasting effects between sexes. Specifically, a simultaneous increase in initial and terminal flight speed by males increased flight distance. In comparison, increased flight distance by females was mainly achieved by increasing the initial flight speed. These different patterns in increased flight speed likely reflect differences in the relative importance of flight in the life history of the two sexes.

摘要

分散飞行是树皮和失落甲虫生活史的重要组成部分。先前的研究表明，各个甲虫之间的飞行距离差异很大。但是，不同的因素导致物种之间的差异。此外，当分散飞行的生态作用在性别之间有所不同时（即，男性位于寄主而女性跟随），影响因素也可能不同。在这里，我们评估了在豚草甲虫的分散飞行距离驱动变化的因素鸭嘴兽quercivorus（村山）（鞘翅目：象甲科：Platypodinae），这是一个矢量昆虫Raffaelea quercivora，是日本橡树枯萎病的病因，我们估算了每种影响因素的性别差异。使用飞行磨机测量飞行距离，飞行持续时间以及初始和终端飞行速度。由于在甲虫飞行过程中飞行速度不是恒定的，因此我们估算了初始飞行速度和最终飞行速度，并假定初始飞行速度代表分配给飞行的能量的相对度量。飞行距离主要取决于飞行时间，男女平均飞行速度为4.22 km / h。初始和终端飞行速度会影响飞行距离；然而，这些因素在两性之间具有相反的影响。具体而言，男性同时提高初始和终末飞行速度会增加飞行距离。相比下，女性增加的飞行距离主要是通过提高初始飞行速度来实现的。飞行速度增加的这些不同模式可能反映出飞行在两性生活史中相对重要性的差异。