Riparian forest fragments in rice fields under different management: differences on hymenopteran parasitoids diversity

Abstract Hymenopteran parasitoids are important biological control agents in agroecosystems, and their diversity can be increased with habitat heterogeneity. Thus, the purpose of the study is to evaluate the influence of distance of rice-growing areas from natural fragment, type of crop management (organic and conventional) and crop stages (vegetative and reproductive stages) on parasitoids family diversity. The work took place in two irrigated rice crops, one with organic management (O.M.) and another one with conventional management (C.M.), in the municipality of Nova Santa Rita, RS, Brazil, during the 2013/2014 and 2014/2015 seasons. The parasitoids were collected with Malaise trap arranged at different distances in relation to the native vegetation surrounding the rice crop in both places. Specimens were collected twice a month from seeding until the rice harvest. Average abundance between management, distances and rice development were compared. The most abundant families were Platygastridae, Mymaridae, Encyrtidae, Eulophidae and Trichogrammatidae. Parasitoid average abundance was significantly higher on OM only in the second season. There was a negative correlation between distance from native vegetation and parasitoid abundance in C.M. areas. There were differences in the composition of the parasitoid assembly between the phenological stages of rice.

摘要：膜翅目寄生蜂（Hymenopteran parasitoids）是农田生态系统中重要的生物防治因子，生境异质性可提升其物种多样性。本研究旨在评估稻田与自然片段的距离、作物管理模式（有机与常规）以及作物生育阶段（营养生长期与生殖生长期）对寄生蜂科多样性的影响。试验于巴西南里奥格兰德州新圣丽塔市（Nova Santa Rita, RS, Brazil）的两块灌溉稻田开展，分别采用有机管理（O.M.）与常规管理（C.M.）模式，试验周期为2013/2014及2014/2015种植季。研究采用马氏诱捕器（Malaise trap）在两块稻田周边原生植被的不同距离梯度处布设，于播种至水稻收获期间每月采样两次。本研究比较了不同管理模式、距离梯度及水稻发育阶段下的寄生蜂平均丰度。采集到的优势寄生蜂科为广腹细蜂科（Platygastridae）、缨小蜂科（Mymaridae）、跳小蜂科（Encyrtidae）、姬小蜂科（Eulophidae）及赤眼蜂科（Trichogrammatidae）。仅在第二个试验季，有机管理稻田的寄生蜂平均丰度显著高于常规管理稻田。常规管理区域内，寄生蜂丰度与距原生植被的距离呈显著负相关。不同水稻物候期的寄生蜂群落组成存在显著差异。