Testing competing hypotheses about the behavior of floral visitors in mixed-flower stands.

Plants occur in mixed stands and flower simultaneously. Most hypotheses about how flowers affect the visitation rates of conspecific or heterospecific neighbors involve attractiveness. Attractive flowers are thought to monopolize visitors, but also to act as magnets increasing visits to unattractive neighbors. Attractiveness may be density-dependent: visitors could profit from focusing on abundant species, sometimes forming search images that make rare flowers less detectable. Four hypotheses was tested using data on visitation rates by honeybees (Apis melifera) and bee flies (Bombyliidae) to 1072 stands comprising six plant species in different densities. Hypotheses were compared through multi-model inference using the disk equation (a functional-response model) modified for co-flowering species and density-dependent attractiveness.植物以混生群落形式存在，且同步开花。关于花朵如何影响同种或异种邻株的访花率的多数假说，均围绕吸引性展开。具有吸引性的花朵被认为既能独占传粉者，也可充当"磁源"，提升对缺乏吸引性邻株的访花频次。吸引性可能具有密度依赖性：传粉者可通过专注于丰富物种获益，有时会形成搜索图像，使得稀有花朵更难被识别。本研究针对1072个包含6种不同密度植物的群落，利用蜜蜂（Apis melifera）和蜂虻（Bombyliidae）的访花率数据，对四条假说进行了检验。通过针对共开花物种与密度依赖型吸引性修正的圆盘方程（disk equation，一种功能响应模型）开展多模型推断，对各假说进行比较。