Yoshioka T, Yano S
Laboratory of Ecological Information, Graduate School of Agriculture, Kyoto University, Sakyo-ku, Kyoto, 606-8502, Japan
Laboratory of Ecological Information, Graduate School of Agriculture, Kyoto University, Sakyo-ku, Kyoto, 606-8502, Japan.
J Exp Biol. 2014 Jul 1;217(Pt 13):2297-300. doi: 10.1242/jeb.098277. Epub 2014 Apr 15.
The two-spotted spider mite, Tetranychus urticae, usually lives in kin groups under common webs. Because only the first mating results in fertilisation in female T. urticae, adult males guard quiescent deutonymph females, those at the stage immediately before maturation, to ensure paternity. Therefore, the cost of precopulatory guarding time seems considerable for males. Moreover, the fitness indices of daughters from intra-population crosses were significantly lower than those of daughters from inter-population crosses, indicating that inbreeding depression exists in T. urticae. Therefore, we hypothesised that T. urticae males should be choosy in guarding familiar females to avoid inbreeding depression. Furthermore, webs should be a key element of the environment shared by familiar individuals. In this study, we demonstrated the inbreeding avoidance mechanism of T. urticae males in relation to webs produced by familiar females (known webs) or unfamiliar females (unknown webs). Regardless of surrounding webs (known or unknown), males preferred unfamiliar to familiar females. We further examined whether males detect unfamiliar females by their webs. When males had experienced a female's web without encountering that female, they subsequently preferred females that did not produce the surrounding webs in which the choice experiment was conducted. Results suggest that putative kin recognition for inbreeding avoidance in T. urticae males is based on the relationship between webs and females, and not on the discrimination of webs in shared environments.
二斑叶螨（Tetranychus urticae）通常生活在共同的蛛网上的亲属群体中。由于只有首次交配才能使雌性二斑叶螨受精，成年雄性会守护静止的若螨期雌性（即即将成熟阶段的雌性），以确保自己的父权。因此，对于雄性来说，交配前守护的时间成本似乎相当可观。此外，种群内杂交后代的适合度指标显著低于种群间杂交后代，这表明二斑叶螨存在近亲繁殖衰退现象。因此，我们推测二斑叶螨雄性在守护熟悉的雌性时应该会有所选择，以避免近亲繁殖衰退。此外，蛛网应该是熟悉个体共享环境的一个关键要素。在本研究中，我们展示了二斑叶螨雄性在面对熟悉雌性（已知蛛网）或陌生雌性（未知蛛网）所产生的蛛网时的近亲繁殖避免机制。无论周围的蛛网是已知还是未知，雄性都更喜欢陌生雌性而非熟悉雌性。我们进一步研究了雄性是否通过蛛网来识别陌生雌性。当雄性体验过雌性的蛛网但未遇到该雌性时，随后它们会更喜欢那些不产生用于选择实验的周围蛛网的雌性。结果表明，二斑叶螨雄性为避免近亲繁殖而进行的假定亲属识别是基于蛛网与雌性之间的关系，而非基于对共享环境中蛛网的辨别。
