Université de Pau et des Pays de l'Adour, Unité Mixte de Recherche 5254, Institut Pluridisciplinaire pour l'Environnement et les Matériaux, Equipe Environnement et Microbiologie, Centre National de la Recherche Scientifique, Pau, France.
PLoS One. 2011;6(9):e25374. doi: 10.1371/journal.pone.0025374. Epub 2011 Sep 30.
Understanding the ways in which human environmental modifications affect biodiversity is a key challenge in conservation planning, pest control and evolutionary ecology. Parasitoid communities, particularly those associated with agricultural pests, may be susceptible to such modifications. We document here changes in the larval parasitoid communities of Ostrinia nubilalis--the main pest of maize--and its sibling species O. scapulalis, based on two historical datasets, one collected from 1921-1928 and the other from 2001-2005. Each of these datasets encompasses several years and large geographical areas and was based on several thousands/millions of host larvae. The 80-year interval between the two datasets was marked by a decrease in O. nubilalis parasitism to about two thirds its initial level, mostly due to a decrease in the rate of parasitism by hymenopterans. However, a well balanced loss and gain of species ensured that species richness remained stable. Conversely, O. scapulalis displayed stable rates of parasitism over this period, with a decline in the species richness of its parasitoid community. Rates of parasitism and species richness in regions colonized by O. nubilalis during the 1950s were one half to one third those in regions displaying long-term colonisation by this pest. During the recent human activity-driven expansion of its range, O. nubilalis has neither captured native parasitoids nor triggered parasite spill back or spill over.
了解人类环境改变如何影响生物多样性是保护规划、害虫防治和进化生态学的一个关键挑战。寄生性昆虫群落，特别是与农业害虫相关的那些，可能容易受到这种改变的影响。我们在这里根据两个历史数据集记录了玉米主要害虫玉米螟及其近缘种 O. scapulalis 的幼虫寄生性昆虫群落的变化，其中一个数据集收集于 1921-1928 年，另一个数据集收集于 2001-2005 年。这两个数据集的每一个都涵盖了数年和大面积的范围，并基于数千/数百万个宿主幼虫。这两个数据集之间的 80 年间隔以玉米螟寄生率下降到初始水平的三分之二为标志，主要是由于膜翅目寄生率下降。然而，物种的得失平衡确保了物种丰富度保持稳定。相反，在这段时间里，O. scapulalis 的寄生率保持稳定，其寄生性昆虫群落的物种丰富度下降。在 20 世纪 50 年代 O. nubilalis 殖民的地区，寄生率和物种丰富度是那些长期被该害虫殖民的地区的一半到三分之一。在其范围最近因人类活动驱动而扩大期间，O. nubilalis 既没有捕获本地寄生性昆虫，也没有引发寄生虫反向溢出或溢出。
