Lalonde R G, Roitberg B D
Behavioural Ecology Research Group, Department of Biological Sciences, Simon Fraser University, V5A 1S6, Burnaby, B.C., Canada.
Oecologia. 1992 Jul;90(4):534-539. doi: 10.1007/BF01875447.
Female Canada thistle seed flies (Orellia ruficauda) preferentially oviposit into seed heads which are a single day from opening. When flies are forced to oviposit into flower heads at other stages of development, offspring typically do slightly poorer: they attain a mature mass of about 15% less than do larvae derived from preferred hosts. Larval mass correlates strongly with reproductive success: heavy larvae develop into adults that produce eggs at a faster rate than do those developing from small larvae. After laying a clutch of eggs, flies circumscribe the rim of the flowerhead with their extended ovipositor and deposit a clear fluid. Flies reject previously-attacked hosts, bearing this apparent marking pheromone, significantly more often than they reject unattacked hosts. Costs of superparasitism in this system are relatively small, inasmuch as there is only a weak relationship between clutch size and larval success at the densities measured in this study. We speculate that flies are highly selective, when the apparent costs of making a mistake are rather low, because the information provided by phenological cues and by the putative marking pheromone is highly reliable, and low fecundity and time costs allow sufficient time to express a high level of discrimination.
雌性加拿大飞廉种子蝇（Orellia ruficauda）优先将卵产在距开放仅一天的种子头中。当苍蝇被迫在发育的其他阶段将卵产在花头中时，后代通常表现稍差：它们达到的成熟体重比来自首选宿主的幼虫轻约15%。幼虫体重与繁殖成功率密切相关：重幼虫发育成的成虫产卵速度比小幼虫发育成的成虫快。在产下一窝卵后，苍蝇用其伸展的产卵器在花头边缘划圈并分泌一种清澈的液体。携带这种明显标记信息素的苍蝇比拒绝未受攻击的宿主更频繁地拒绝先前受到攻击的宿主。在这个系统中，超级寄生的代价相对较小，因为在本研究测量的密度下，窝卵数与幼虫成功率之间只有微弱的关系。我们推测，当犯错的明显代价相当低时，苍蝇具有高度选择性，因为物候线索和假定的标记信息素提供的信息非常可靠，而且低繁殖力和时间成本允许有足够的时间表现出高度的辨别力。
