Constraints on host use by a parasitic plant
Constraints on host use by a parasitic plant
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寄生植物对寄主利用的限制
作者：
Emily S. Marquardt;S. Pennings
消费者并不总是使用所有合适的主机。要理解为什么寄生植物并不总是寄生在潜在的合适寄主上，就需要更好地理解限制寄生植物利用寄主的制约因素。在德克萨斯州的盐沼中，寄生植物Cuscuta indecora很少寄生在支持温室中旺盛生长的三个寄主身上。我们确定了C. indecora对宿主使用的三个限制。首先，木蠹物候特征与适宜寄主不匹配，导致木蠹生长最旺盛时寄主数量不足，未得到充分利用。其次，相对于矮生植物，indecora更倾向于寄生于高大植物，导致相对矮小的植物被利用不足。第三，在一些多年生寄主中越冬，但每年都要重新感染一年生寄主，导致不支持越冬的一年生和多年生寄主得不到充分利用。综上所述，这些限制反映了寄生植物相对于食草动物普遍缺乏移动性，从C. indecora的实际饮食中消除了一半的潜在寄主物种，因此可能是这种寄生虫成功的主要限制。类似的限制可能会限制许多寄生植物的宿主范围，并选择普遍的饮食偏好。
Consumers do not always utilize all suitable hosts. Understanding why parasitic plants do not always parasitize potentially suitable hosts requires a better understanding of the constraints that limit host use by parasitic plants. In Texas salt marshes, the parasitic plant Cuscuta indecora rarely parasitizes three hosts that support vigorous growth in the greenhouse. We identified three constraints on host use by C. indecora. First, a mismatch between the phenology of C. indecora and some suitable hosts meant that these hosts were not abundant when C. indecora was growing most vigorously, and therefore were underutilized. Second, C. indecora preferentially parasitized tall plants versus short ones, causing relatively short species to be underutilized. Third, C. indecora overwinters in some perennial hosts but has to reinfect annual hosts each year, causing annuals and perennials that do not support overwintering to be underutilized. In combination, these constraints, which reflect the general lack of mobility of parasitic plants relative to herbivores, remove half of the potential host species from the actual diet of C. indecora, and therefore likely represent a major limitation on the success of this parasite. Similar constraints are likely to limit the realized host range of many parasitic plants and select for generalized diet preferences.