Juliano S A, Stoffregen T L
Department of Biological Sciences, Ecology Group, Illinois State University, 61790-4120, Normal, IL, USA.
Oecologia. 1994 Apr;97(3):369-376. doi: 10.1007/BF00317327.
Models of complex life cycles predict that greater mortality of immature stages should induce earlier metamorphosis at smaller sizes. We tested for effects of one source of mortality, habitat drying, on size at and time to metamorphosis of the tree hole mosquito Aedes triseriatus. In a laboratory experiment, we manipulated two variables associated with drying, volume of water and solute concentration, and recorded mean mass at and median days to eclosion for males and females in replicate cohorts. We also tested for treatment effects on the correlation of mass at and time to eclosion. For females, decreasing volume consistently induced metamorphosis at smaller sizes than did constant volume. Decreasing volume also led to earlier metamorphosis of females than did constant volume, but only in one of two experimental runs. For both sexes, increasing concentration led to greater size at metamorphosis and, for males, earlier metamorphosis than did constant volume, but again only in one of two experimental runs. Correlations of size at and time to metamorphosis tended to be positive for females and negative for males, and this difference was significant. For both sexes, decreasing volume led to larger (more positive) correlations than did constant volume, but only in one of two experimental runs. The effects of decreasing volume on females are consistent with the predictions of models of complex life cycles, and suggest that A. triseriatus can perceive volume changes and modify metamorphosis to escape a deteriorating habitat. The effects of increasing concentration are opposite to those predicted, and are consistent with enhanced growth rates, possibly due to enhanced microbial growth, as solutes become concentrated due to drying. The responses of these mosquitoes to habitat drying are complex, and we suggest that habitat drying increases both mortality and growth rates, yielding no simple predictions of how habitat drying will affect these mosquitoes in natural tree holes.
复杂生命周期模型预测，未成熟阶段更高的死亡率应会导致在更小的体型时更早发生变态。我们测试了一种死亡来源——栖息地干涸，对树洞蚊三带喙库蚊变态时的体型大小和变态时间的影响。在一项实验室实验中，我们操控了与干涸相关的两个变量，即水量和溶质浓度，并记录了重复样本中雄性和雌性羽化时的平均质量以及羽化的中位天数。我们还测试了处理对羽化时质量和羽化时间之间相关性的影响。对于雌性而言，与恒定水量相比，水量减少始终会导致在更小的体型时发生变态。水量减少还导致雌性比恒定水量时更早发生变态，但仅在两次实验中的一次出现这种情况。对于两性来说，与恒定水量相比，浓度增加会导致变态时体型更大，并且对于雄性而言，会更早发生变态，但同样仅在两次实验中的一次出现这种情况。变态时的体型大小和变态时间之间的相关性对于雌性往往是正相关，对于雄性往往是负相关，且这种差异是显著的。对于两性来说，与恒定水量相比，水量减少会导致相关性更大（更正），但同样仅在两次实验中的一次出现这种情况。水量减少对雌性的影响与复杂生命周期模型的预测一致，表明三带喙库蚊能够感知水量变化并改变变态以逃离恶化的栖息地。浓度增加的影响与预测相反，这与生长速率增强一致，这可能是由于随着干涸溶质浓缩，微生物生长增强所致。这些蚊子对栖息地干涸的反应很复杂，我们认为栖息地干涸会同时增加死亡率和生长速率，从而无法简单预测栖息地干涸将如何影响天然树洞中这些蚊子。
