Moth J J, Barker J S F
Department of Animal Husbandry, University of Sydney, 2006, Sydney, N.S.W., Australia.
Oecologia. 1976 Jun;23(2):151-164. doi: 10.1007/BF00557853.
The number of eggs laid in aDrosophila culture and the survival of these eggs may depend on the number of larvae that are still inhabiting or that have already used the culture medium.A known average number ofD. simulans st larvae (designated original inhabitants) were introduced into culture vials by allowing adults to lay for 24 h (low density) or 48 h (high density). On each day for 14 days, adults of three competitor strains (D. melanogaster Or-R-C, D. melanogaster yw andD. simulans st) were added to different samples of these vials and allowed to lay for 24 h. The numbers of "effective eggs" (eggs expected to be laid less those withheld, cannibalised or buried) produced by competitor strains were estimated from adult emergences. Survival of original inhabitant larvae to the adult stage also was measured.At the lower density of original inhabitants, the mean proportions of effective eggs (number of effective eggs/number of eggs expected in an uninhabited culture) were not significantly different for the three competitor strains. The mean proportions were lower at the higher density (significantly so for the twoD. melanogaster competitors), and at this density, the mean proportion forD. melanogaster yw was significantly less than that forD. simulans st. These results are consistent with a simple egg destruction hypothesis, but suggest thatyw females were retaining more eggs at the higher density.Original inhabitants showed higher survival when at the higher density. Each of the three competitors caused a significantly different reduction in original inhabitant survival, which was directly related to competitor larval activity. Increasing larval activity probably reduced survival of original inhabitants by increasing pupal mortality due to drowning in the medium.Day of introduction of competitors influenced survival of original inhabitants and also the proportion of effective eggs from each competitor. The proportion of effective eggs decreased to the day 5 introduction. From day 5 to day 8, the proportion increased because the original inhabitants were pupating. After day 8, effective egg proportions again decreased, possibly due to inhibition of egg-laying or reduced survival of immature stages.
在果蝇培养物中所产的卵的数量以及这些卵的存活率可能取决于仍栖息在培养基中或已经利用过该培养基的幼虫数量。通过让成虫产卵24小时（低密度）或48小时（高密度），将已知平均数量的拟暗果蝇st幼虫（指定为原始栖息者）引入培养瓶中。在14天的每一天，将三种竞争品系（黑腹果蝇Or-R-C、黑腹果蝇yw和拟暗果蝇st）的成虫添加到这些培养瓶的不同样本中，并让它们产卵24小时。从成虫羽化情况估算竞争品系产生的“有效卵”（预期产下的卵减去被扣留、被同类相食或被掩埋的卵）数量。还测定了原始栖息者幼虫到成虫阶段的存活率。在原始栖息者密度较低时，三种竞争品系的有效卵平均比例（有效卵数量/在无栖息者培养物中预期的卵数量）没有显著差异。在较高密度时，平均比例较低（对于两种黑腹果蝇竞争者而言差异显著），且在此密度下，黑腹果蝇yw的平均比例显著低于拟暗果蝇st的平均比例。这些结果与一个简单的卵破坏假说是一致的，但表明yw雌蝇在较高密度时保留了更多的卵。原始栖息者在较高密度时显示出更高的存活率。三种竞争者中的每一种对原始栖息者存活率的降低都有显著差异，这与竞争幼虫的活动直接相关。幼虫活动的增加可能由于蛹在培养基中溺亡导致蛹死亡率增加而降低了原始栖息者的存活率。引入竞争者的日期影响原始栖息者的存活率以及每个竞争者的有效卵比例。有效卵比例在引入竞争者的第5天下降。从第5天到第8天，比例上升是因为原始栖息者正在化蛹。第8天之后，有效卵比例再次下降，可能是由于产卵受到抑制或未成熟阶段的存活率降低。
