Data from: Predator-prey trophic relationships in response to organic management practices

A broad range of environmental conditions likely regulate predator-prey population dynamics and impact the structure of these communities. Central to understanding the interplay between predator and prey populations and their importance is characterizing the corresponding trophic interactions. Here we use a well-documented molecular approach to examine the structure of the community of natural enemies preying upon the squash bug, Anasa tristis, a herbivorous cucurbit pest that severely hinders organic squash and pumpkin production in the United States. Primer pairs were designed to examine the effects of organic management practices on the strength of these trophic connections and link this metric to measures of the arthropod predator complex density and diversity within an experimental open-field context. Replicated plots of butternut squash were randomly assigned to three treatments and were sampled throughout a growing season. Row-covers treatments had significant negative effects on squash bug and predator communities. In total, 640 predators were tested for squash bug molecular gut-content, of which 11% were found to have preyed on squash bugs, but predation varied over the season between predator groups (coccinellids, geocorids, nabids, web-building spiders and hunting spiders). Through the linking of molecular gut-content analysis to changes in diversity and abundance, these data delineate the complexity of interaction pathways on a pest that limits the profitability of organic squash production.多种环境因素均可调控捕食者-猎物种群动态，并影响此类群落的结构。理解捕食者与猎种种群间的相互作用及其生态重要性的核心，在于表征对应的营养互作关系。本研究采用经充分验证的分子检测方法，针对以南瓜缘蝽（Anasa tristis）为猎物的天敌群落结构展开分析。南瓜缘蝽是一种植食性葫芦科害虫，严重制约美国境内有机西葫芦与南瓜的生产。研究设计了特异性引物对（primer pairs），以探究有机管理措施对上述营养联系强度的影响，并将该指标与试验大田环境下节肢动物天敌类群的密度及多样性测定结果相关联。试验将重复布置的胡桃南瓜样地随机分为三组处理，并在整个生长季内进行采样。行间覆盖处理对南瓜缘蝽及天敌群落具有显著的负调控效应。总计对640头天敌样本开展了南瓜缘蝽分子肠道内容物检测（molecular gut-content analysis），其中11%的样本呈南瓜缘蝽捕食阳性结果；但不同天敌类群（瓢虫科、长蝽科、姬蝽科、结网蜘蛛及游猎蜘蛛）的捕食率随生长季发生动态变化。通过将分子肠道内容物分析与天敌多样性及丰度变化相结合，本研究数据阐明了制约有机西葫芦生产经济效益的靶标害虫所面临的多重互作路径的复杂性。