Dissertation Research: Habitat Partitioning by Notonectids: Temporal Patterns and the Role of Spatial Complexity

[9902177gilbert]野生动物内部捕食者的共存，即相互掠食的潜在竞争对手，尽管经常发生，但却很少被模型预测到。减少冲突的一种机制是栖息地的空间划分。在一个小的浅池塘中观察到这样的分区，有四种不互相交配的物种——贪婪的昆虫捕食者，它们共享资源，随时以彼此为食。这种划分可能会减少冲突，但这些模式以可能严重危及或加强共存的方式表现出季节性和昼夜变化。在本论文的研究中，实地研究将定量地证实这里提出的初步观察结果。导致空间划分和时间变化的机制将在实验微观环境中进行研究。在季节中期，幼鱼的分布变化可能是对成年捕食者减少的一种反应，使幼鱼能够在资源丰富的栖息地完成发育。相反，物种分布的昼夜变化通过增加夜间重叠增加了冲突的可能性。利用电泳肠道含量分析，将野外采集的无尾虫的日间和夜间饮食进行比较，以确定夜间是否如预期的那样增加了野外捕食。此外，本文还提出了一种新的昼夜水平迁移假设：捕食者在夜间利用视觉和机械感知能力，逆转了空间复杂和开放栖息地的盈利能力。

9902177GilbertCoexistence of intraguild predators, potential competitors that are also mutually predaceous, is rarely predicted by models despite its commonplace occurrence. One mechanism by which conflict may be minimized is spatial partitioning of habitat. Such zonation has been observed in a small shallow pond with four notonectid species - voracious insect predators which share resources and readily feed on each other. Conflict may be reduced by this partitioning, but these patterns exhibit seasonal and diel shifts in ways that could substantially endanger or enhance coexistence. In this dissertation research, field study will quantitatively confirm the preliminary observations presented here. Mechanisms leading to spatial partitioning and temporal changes will be investigated in experimental microcosms. Mid-season distributional shifts of juveniles may be a response to a decline in adult predators, allowing juveniles to complete development in a high-resource habitat. Conversely, diel shifts in species distribution increase potential for conflict by increasing nocturnal overlap. Diurnal and nocturnal diet of field-collected notonectids will be compared, using electrophoretic gut content analysis, to determine whether intraguild predation increases at night as expected. In addition, a new hypothesis for diel horizontal migration is proposed: profitability of spatially complex and open habitat is reversed at night for predators using both vision and mechanoreception.