Foraging specialization and the evolution of life histories in Argyrodes spider.

本研究的目的是阐明寄生蜘蛛的觅食特化和生活史特征的进化。为此，我研究了1)取食方式和寄主范围，2)取食方式的可塑性，3)生活史特征，4)分子系统发育树的构建。1)寄主取食和猎物/蚕丝取食是银鱼的两种主要取食方式。以捕食为主要觅食方式的蜘蛛种类，除裂腹蜘蛛外，其余均为聚居的球网蜘蛛。这可能与留在球网上的大量小猎物有关。2)a.在猎物丰富的时候，黄姑鱼只偷猎物，而在其他季节它经常吃丝质。在食物供应不足的情况下，吃丝绸似乎是另一种觅食方式。以往的研究表明，寄主捕食是生活在三维网络中的物种的替代策略。3)寄主食性动物和食性天牛的生活史是单峰型的，而偷食猎物和蚕丝的小物种则表现出多峰性的生活史。这可能与猎物的可获得性有关。4)我们测定了六种银鱼和两种无尾轮虫的线粒体DNA序列，并构建了系统发育树。沙棘和毛羽形成一个支系，表明捕食寄主和窃取猎物/丝是独立进化的。通过将觅食方式从捕食寄主转变为窃取猎物，Argyrodes发展了多变的生活史。

The objective of this study is to clarify foraging specialization and the evolution of life history traits in kleptoparasitic Argyrodes spiders. To achieve this, I examined 1) foraging mode and host range, 2) plasticity in foraging mode, 3) life history traits, 4) construction of molecular phylogenetic tree.1) Host eating and prey / silk eating were the two major foraging modes in Argyrodes. Species whose main foraging mode was prey stealing inhabited orb-web spiders, except for A. fissifrons. This may be related to the abundant small prey left on orb-webs.2) A. flavescens exclusively steal prey when prey were abundant, while it often eat silk in other seasons. Silk eating appears to be the alternative foraging mode under poor food availability. Previous studies suggested that host eating was the alternative tactics in species living in three-dimensional webs.3) Host eaters and A. fissifrons had a univoltine life cycle, while small species stealing prey and silk showed a multivoltine life cycle. Probably this is related to the prey availability.4) We determined the sequence of mitochondrial DNA for six species of Argyrodes and two species of Achaearanea and constructed the phylogenetic tree. A. saganus and A. fur formed a clade, suggesting that host eating and prey / silk stealing evolved independently.It appears that Argyrodes developed multivoltine life cycle by changing its foraging mode from host eating to prey stealing.