Papaj D R, Alonso-Pimentel Henar
Department of Ecology & Evolutionary Biology and Center for Insect Science, Biological Sciences West 310, University of Arizona, Tucson, AZ 85721, USA fax: + 520-621-9190; e-mail:
Oecologia. 1996 Dec;109(1):166-174. doi: 10.1007/s004420050071.
This study evaluated a possible fitness advantage, specifically time savings, that might account for an unusual propensity in walnut flies (Rhagoletis spp.) to superparasitize their walnut hosts and to place eggs into existing egg-laying cavities. The first part of this study demonstrated that, in laboratory assays, females of two walnut fly species, R. boycei and R. juglandis, save time when cavities are reused and that in R. juglandis, where it was examined in detail with in vivo staining of eggs, time saving was not an artifact of differences in the size of clutches deposited at new versus existing sites. We further demonstrated that time savings reflected a reduction in the time required to generate the cavity itself. In the second part of the study, we evaluated the possibility that, in the field, time saved by reusing existing cavities is nullified by extra time spent mating associated with a previously described tendency for males to guard these cavities. Field observations of R. juglandis indicated that use of existing sites was, as expected, associated with increased mating. Yet, despite the added time spent mating, in observations of similar length females attempting to lay eggs at existing sites deposited clutches more often than females attempting to lay eggs at new sites. We discuss these results in the context of the more common pattern of superparasitism avoidance observed in host-specific insects.
本研究评估了一种可能的适应性优势，特别是节省时间，这可能解释了核桃实蝇（Rhagoletis spp.）在核桃寄主上进行多次寄生并将卵产入现有产卵孔的异常倾向。本研究的第一部分表明，在实验室试验中，两种核桃实蝇物种，即博伊斯核桃实蝇（R. boycei）和胡桃实蝇（R. juglandis）的雌性在重复利用产卵孔时节省了时间，并且在对胡桃实蝇进行详细研究时，通过对卵进行体内染色发现，节省时间并非是在新地点与现有地点所产一窝卵的大小差异造成的假象。我们进一步证明，节省时间反映了产生产卵孔本身所需时间的减少。在研究的第二部分中，我们评估了在野外，重复利用现有产卵孔节省的时间是否会因与之前描述的雄性守护这些产卵孔的倾向相关的额外交配时间而抵消。对胡桃实蝇的野外观察表明，正如预期的那样，利用现有地点与交配增加有关。然而，尽管交配时间增加了，但在长度相似的观察中，试图在现有地点产卵的雌性比试图在新地点产卵的雌性更频繁地产下卵块。我们在寄主特异性昆虫中更常见的避免多次寄生模式的背景下讨论了这些结果。
