The Mutual Adaption Between the Ovipositor of <italic>Epicephala eriocarpa</italic> and the Style of <italic>Glochidion eriocarpum</italic>.

Specialization of adaptive devices can reflect the coevolution of closely interactive relationship between partners in mutualism. <italic>Glochidion eriocarpum</italic> and <italic>Epicephala eriocarpa</italic> have formed a strict species-specific mutualism over a long term of evolution. Based on field observation and the anatomical study of adult specimens, we clarified the morphological and biological characteristics of <italic>E. eriocarpa</italic> and performed morphological analyses of the specialized female genitalia for the first time. <italic>Epicephala eriocarpa</italic> had four generations per year. Adaptive specialization in the mutualism was expressed by morphological variations in the relative length of the ovipositor and the flower style. The mean length of the apophyses posteriores, which constituted 38% of <italic>E. eriocarpa</italic> body size, was unique among known <italic>Epicephala</italic> species. The variations among partners suggested that the flower style might have selected an optimal ovipositor length in its pollinator. This indicated that highly specialized structures resulted from mutual specificity and reciprocal adaptation among interacting partners in “one-to-one” mutualism. The evolutionary characteristics of pollinators might be more sensitive to outside stimulation than their partners and could express the process of adaptive evolution better. Moreover, our analyses help to further understand the evolutionary mechanism and driving force of cospeciation in obligate pollination mutualism. [ABSTRACT FROM AUTHOR]