斑翅果蝇自然种群生命表的初步研究

【目的】为了探究在自然环境中影响斑翅果蝇Drosophila suzukii种群的关键因子。【方法】本研究于2015年7—9月,应用生命表技术,采用室内分段饲养和田间观察相结合的方法进行调查统计,组建了斑翅果蝇自然种群生命表。【结果】室外斑翅果蝇各发育阶段的历期为:卵期(22.50±2.78)h、1龄幼虫期(23.14±2.27)h、2龄幼虫期(48.86±4.14)h、3龄幼虫期(79.00±11.01)h、蛹期(99.00±6.00)h;斑翅果蝇为A型存活曲线;在果园,斑翅果蝇7月世代的关键虫期为卵期,8月、9月世代的关键虫期为1~2龄幼虫期;在杉树林,斑翅果蝇8月、9月世代的关键虫期均为卵期;卵期的关键致死因子为自然死亡,1~2龄幼虫的关键致死因子为竞争。【结论】影响斑翅果蝇自然种群的关键致死因子为自然死亡和竞争。其存活曲线为A型,不同的生态环境的关键致死因子不同,不同发育阶段的关键致死因子也不同。     

斑衣蜡蝉若虫寄生蜂地理种群遗传差异及早期快速检测

【目的】明确不同地理种群斑衣蜡蝉Lycorma delicatula若虫寄生蜂种群遗传差异,实现若虫被寄生早期的快速准确检测,以评估其对斑衣蜡蝉种群的控制作用。【方法】利用DNA条形码技术获得不同地理种群斑衣蜡蝉若虫寄生蜂COI和28S rDNA序列,利用K2P模型计算不同地理种群间的遗传距离,以邻接(neighbor-joining,NJ)法构建系统发育树;基于COI序列设计种特异性PCR(SS-PCR)引物,利用SS-PCR对斑衣蜡蝉若虫DNA进行扩增,测定其体内是否有中华螯蜂Dryinus sinicus寄生;利用目测法观察和PCR扩增测定寄生蜂对不同采样点斑衣蜡蝉若虫的寄生率。【结果】经鉴定,不同地理种群斑衣蜡蝉若虫寄生蜂为中华螯蜂,该寄生蜂COI序列共检测到16个单倍型,28S rDNA序列共检测到4个单倍型。不同地理种群间中华螯蜂遗传距离在0.00691~0.01310之间。邻接法构建的系统发育树显示不同地理种群中华螯蜂均聚于一枝。基于COI序列设计的SS-PCR引物对中华螯蜂成虫、幼虫均具有良好的扩增效果,最低检测阈值为0.000005 ng/μL DNA。利用SS-PCR测定中华螯蜂对各采样点斑衣蜡蝉若虫的寄生率为22.54%~60.00%,显著高于目测统计的结果(5.63%~36.98%)。【结论】不同中华螯蜂地理种群间遗传差异较小;SS-PCR引物可用于不同地区中华螯蜂对斑衣蜡蝉早期寄生率的快速检测。     

马铃薯甲虫自然种群生命表的组建及影响因子

应用作用因子生命表方法,组建了马铃薯2代马铃薯甲虫自然种群生命表,并采用排除分析法分析了作用因子对马铃薯甲虫种群数量的控制作用.结果表明:马铃薯甲虫卵期和1龄幼虫期的存活率分别为79.1％和69.3％,显著低于其他虫态的存活率,表明该阶段为马铃薯甲虫种群生存的脆弱阶段,是马铃薯甲虫防治的关键时期.“自然死亡”的排除作用控制指数最大(1.87);其次为“捕食及其他”,排除作用控制指数为1.51;寄生性天敌对马铃薯甲虫没有控制作用.如果排除所有天敢等因子的作用,马铃薯甲虫自然种群趋势指数将增长2.8倍.表明天敌等自然因子虽对马铃薯甲虫种群数量有一定的控制作用,但控制能力较弱.     

山东苹果园凹唇壁蜂种群的制约因子分析

【目的】凹唇壁蜂Osmia excavata Alflken是山东苹果园的主要授粉昆虫,明确影响凹唇壁蜂种群的自然因子,对于发挥其传粉生态服务功能有重要意义【方法】本文应用生命表方法,比较研究了山东省6个地点的壁蜂种群参数。【结果】各个地点的成茧率(7.64%~73.84%)和每管成茧数量(0.80~5.56)存在非常大的差异;6个地点的种群趋势指数大于1,变化范围为1.80~11.80;壁蜂种群的致死因子包括卵败育、螨寄生、蜂捕食和自然死亡,排除作用控制指数分别为1.07、1.10、1.03、2.53,各地所有致死因子的排除作用控制指数为1.19~5.50,如果没有寄生、自然死亡等因子,凹唇壁蜂种群将增加19%~450%。【结论】自然死亡是限制山东省果园凹唇壁蜂种群的主要因子,因此需要加强凹唇壁蜂饲养管理,减少其自然死亡率。     

毒死蜱亚致死剂量对二斑叶螨实验种群动态的影响

【目的】为探讨毒死蜱(Chlorpyrifos)对二斑叶螨Tetranychus urticae Koch种群动态的影响,室内研究了毒死蜱亚致死剂量对二斑叶螨实验种群成螨和若螨的生长发育、存活和繁殖情况的影响。【方法】用浸虫法进行测定,生命表方法分析亚致死效应。【结果】结果表明毒死蜱亚致死剂量LC25处理成螨后,雌成螨寿命、总产卵量、子代孵化率、性比与对照组无显著差异,其净增值率、内禀增长率、周限增长率以及种群加倍时间显著低于对照组。毒死蜱亚致死剂量LC25处理若螨后,总产卵量、净增值率、世代平均周期显著低于对照组,内禀增长率、周限增长率以及种群加倍时间与对照组无显著差异。扩散试验证明毒死蜱对二斑叶螨有较强的刺激扩散作用。【结论】以上结果说明毒死蜱亚致死剂量对不同发育阶段的二斑叶螨发育和繁殖的影响不同,毒死蜱对二斑叶螨的刺激扩散作用可能是引起二斑叶螨再猖獗的原因之一。     

基于特定时间调查数据组建的白蜡窄吉丁种群生命表

为了探明影响白蜡窄吉丁Agrilus planipennis Fairmaire自然种群变化的关键因子, 本研究于2010-2011年采用当年秋季和翌年春季两个特定时间调查取样的方法, 组建了天津、 北京和辽宁3个地区白蜡窄吉丁的自然种群生命表。结果显示, 这3个地区白蜡窄吉丁的自然种群数量在今后几年均将呈增长趋势, 但不同地区的增长速率存在较大差异。北京地区白蜡窄吉丁的种群数量增长速率最快（种群趋势指数I=12.9997）, 其次是天津地区（I=12.4388）, 这两个地区的寄主植物相同, 均为绒毛白蜡。增长最慢的是辽宁地区（I=3.6394）, 其寄主植物为水曲柳。另外, 通过3个地区白蜡窄吉丁生命表和排除控制指数可以看出, 天津地区白蜡窄吉丁最主要的致死因子是白蜡吉丁柄腹茧蜂Spathius agrili Yang（种群数量排除控制指数EIPC=1.5382）, 对种群数量变动的贡献最大; 北京地区的是啄木鸟（EIPC=1.4515）, 而辽宁地区白蜡窄吉丁最主要的致死因子是白蜡吉丁卵跳小蜂Oobius agrili Zhang et Huang的寄生作用（EIPC=1.4701）。这些研究结果表明, 寄主植物的差异是影响白蜡窄吉丁自然种群数量变动的主要因素, 同时寄生性天敌白蜡吉丁柄腹茧蜂对种群数量的影响作用也比较大。因此, 实际应用中可以通过培育抗性树种和人工繁育优势天敌等方法对该虫进行有效防治。     

基于广义可加模型分析温湿度因子对斑翅果蝇田间种群动态的影响

探究温湿度因子对田间斑翅果蝇Drosophila suzukii Matsumura种群发生动态的影响,为进一步开展环境胁迫下斑翅果蝇适应性机制研究提供前期基础和参考.本文监测统计了 2016-2017年田间斑翅果蝇成虫种群动态数据,并利用广义可加模型(Generalized Additive Models,GAM)分析温湿度因子对成虫种群发生动态的影响.结果表明,通过模型检验和广义交叉验证值(Generalized Cross-Validation,GCV)对比,得出温湿度因子显著影响了2016-2017年斑翅果蝇田间成虫种群发生动态(P＜0.05),斑翅果蝇雌成虫、雄成虫、总种群数量的GAM模型参数α分别为2.21346、2.55606和3.08316;雌成虫、雄成虫、总种群数量与温湿度因子关联的GCV值分别为0.57299、0.74501、0.64611,因此雌成虫种群数量与温湿度因子拟合的模型最优;结合温湿度预测曲线分析,斑翅果蝇成虫种群发生动态与温湿度因子之间呈非线性相关,其中温度在23℃以下呈局部负相关,在23℃以上呈局部正相关;与湿度呈正相关,但影响程度较低,因此温度是影响斑翅果蝇成虫种群数量动态的关键生态因子.本文通过探究环境因子对田间斑翅果蝇种群消长规律的影响,为斑翅果蝇的种群发生机制提供了生态学理论基础.     

烟草和香芋上斜纹夜蛾的自然种群生命表

应用作用因子生命表方法,组建烟草和香芋上第2、3代斜纹夜蛾Spodoptera litura（Fabricius）自然种群生命表,分析作用因子对斜纹夜蛾种群数量的控制作用。结果表明,2005和2006年烟草和香芋上第2、3代斜纹夜蛾种群的增长倍数均以香芋高于烟草。无论烟草还是香芋上第2、3代斜纹夜蛾,均以“捕食及其它”的排除作用控制指数最大。如排除所有天敌等作用因子的作用,2005年烟草上第2、3代斜纹夜蛾自然种群趋势指数将分别增长31．2029和50．0371倍,香芋上第2、3代斜纹夜蛾自然种群趋势指数将分别增长29．3492和41．2873倍;2006年烟草上第2、3代斜纹夜蛾自然种群趋势指数将分别增长33．1421和75．4167倍,香芋上第2、3代斜纹夜蛾自然种群趋势指数将分别增长31．5357和70．5355倍。说明天敌等自然作用因子对斜纹夜蛾种群数量有较为明显的控制作用,而烟草上的自然作用因子的作用要强于香芋上的自然作用因子。     

斜纹夜蛾天敌作用的评价

通过组建斜纹夜蛾第4代和第8代自然种群生命表,运用排除作用控制指数分析了生物因子对斜纹夜蛾种群的自然控制作用。结果表明,低龄(1～3龄)幼虫的捕食性天敌是影响斜纹夜蛾种群数量动态的重要因子。对第4代和第8代种群的排除作用控制指数分别为13.904和12.946.如果没有捕食性天敌的作用,下代种群数量将分别增长到当代的15.1206和74.678倍。病原微生物是影响第4代斜纹夜蛾种群数量的另一重要因子,其排除作用控制指数为2.4726.     

春季香蕉假茎象甲自然种群生命表的研究

通过调查研究,组建了以作用因子为组分的春季香蕉假茎象甲（Odoiporus longicollis Oliver）自然种群生命表,在此基础上运用排除作用控制指数法分析了各种因子对假茎象甲自然种群的作用。结果表明,春季假茎象甲自然种群趋势指数成长蕉株上平均为4．3481,留头蕉茎上平均为3．6628,捕食及其它因子对该虫种群控制最大,排除作用控制指数成长蕉株为1．9256,留头蕉茎上为2．3577;自然死亡作用次之,成长蕉株为1．3607,留头蕉茎上为1．3554;寄生或疾病因子作用最小,成长蕉株为1．1988,留头蕉茎上为1．1668,捕食及其他是该虫种群增长的重要控制因子。     

Parasitoid wasp communities on oil palm plantation: Effects of natural habitat existence are obscured by lepidopteran abundance

The existence of natural habitat around agroecosystem plays a pivotal role in maintaining the presence of natural enemies especially parasitoids. Natural habitat can fail to support biological pest control in agroecosystem due to a particular condition. The objective of this research was to investigate the effect of natural habitat existence on parasitoid wasp communities in oil palm plantation. The ecological research was conducted in the oil palm plantation located in Central Borneo, Indonesia. Twelve plots of oil palm plantations with different habitat characteristics were selected. Insects were sampled using canopy knockdown fogging with a pyrethroid insecticide. In total, 237 species and 2669 individuals of parasitoid wasps belong to 15 families were collected from all research areas. The results showed that species richness and abundance of parasitoid wasps in oil palm plantation was affected by lepidopteran abundance and not by the existence of natural habitat. However, the distance and area of natural habitat influenced the species composition of parasitoid wasps. We concluded that the existence of natural habitat still can maintain the parasitoid wasps in oil palm plantation. Thus, efforts on maintaining parasitoid wasp diversity for management of biological control in oil palm plantation need to pay attention by conserving the natural habitats.     

Importance of semi-natural habitats for the conservation of butterfly communities in landscapes dominated by pine plantations

While the area of plantation forests continues to increase worldwide, their contribution to the conservation of biodiversity is still controversial. There is a particular concern on the central role played by natural habitat remnants embedded within the plantation matrix in conserving species-rich insect communities. We surveyed butterflies in maritime pine plantation landscapes in south-western France in 83 plots belonging to seven habitat types (five successional stages of pine stands, native deciduous woodlands and herbaceous firebreaks). The effect of plot, habitat and landscape attributes on butterfly species richness, community composition and individual species were analysed with a General Linear Model (GLM), partial Canonical Correspondence Analysis (CCA) and the IndVal method. The most important factors determining butterfly diversity and community composition were the presence of semi-natural habitats (deciduous woodlands and firebreaks) at the landscape scale and the composition of understorey vegetation at the plot scale. Pure effects of plot variables explained the largest part of community variation (12.8%), but landscape factors explained an additional, independent part (6.7%). Firebreaks were characterized by a higher species richness and both firebreaks and deciduous woodlands harboured species not or rarely found in pine stands. Despite the forest-dominated landscape, typical forest butterflies were rare and mainly found in the deciduous woodlands. Threatened species, such as Coenonympha oedippus and Euphydryas aurinia, were found in pine stands and in firebreaks, but were more abundant in the latter. In the studied plantation forest, the conservation of butterflies depends mainly on the preservation of semi-natural habitats, an adequate understorey management and the maintenance of soil moisture levels.     

农林复合系统中灌木篱墙对异色瓢虫种群分布的影响

以北京大兴农区农林复合系统为对象,围绕灌木篱墙(沙棘绿篱和杨树萌条带)上和麦田中的主要捕食性天敌——异色瓢虫对栖息地的选择趋向及灌木篱墙对异色瓢虫种群分布的影响进行了研究。结果表明:(1)小麦生长前期(返青期至抽穗期或扬花期)灌木篱墙上异色瓢虫种群密度是麦田的3.25—9.57倍,是异色瓢虫由越冬地向麦田过渡前的主要栖息地,是农林复合系统中异色瓢虫种群建立的"种库";(2)异色瓢虫对栖息生境有较强的选择性,明显趋向于蚜虫密集分布的生境,小麦生长前期趋向于灌木篱墙,小麦生后期(扬花期或灌浆期至完熟期)趋向于麦田,整个小麦生长期内异色瓢虫种群在不同生境斑块间存在明显的移动现象;(3)麦收后,邻近麦田的杨树萌条带上异色瓢虫种群密度相比于完熟期增加了42%,为异色瓢虫提供了重要的庇护场所。     

Non-crop habitats concurrently drive crop colonization by the millet head miner and regulation by natural enemies

Non-crop habitats, depending on their composition, can enhance the abundance and diversity of natural enemies of crop pests, but also at the same time provide resources to pests, thereby reducing the effect on pest incidence and resulting yield losses. The objective of the present study was to test (1) the effect of semi-natural habitats in the landscape on crop colonization by pests and natural regulation, and (2) the relationship between natural regulation and pest incidence. The pearl millet head miner (MHM) was selected as a case study because it is a key pest of millet cultivated in traditional pesticide-free tree-crop agroforestry systems in which its control mostly relies on the action of natural enemies.A set of 24 millet fields were selected in a 20×20 km area in Senegal, from the analysis of high-resolution satellite images (Pléiades), and hypotheses on the relative abundance of semi-natural habitats (here trees and rangelands) in the agricultural landscape. Millet fields were monitored for pest infestation of panicles and pest natural regulation. We used partial least squares structural equation modelling (PLS-PM) to evaluate the relationships between the abundance and diversity of semi-natural habitats at the landscape scale, crop colonization, natural pest regulation, and pest incidence.Panicle colonization by the MHM was generally high (14–92%) and increased with the abundance of trees and to a lesser extent with the rangeland area at a 1000 m-radius around millet fields. However, regulation provided by natural enemies was amplified by the abundance of trees at a local scale (250 m-radius around millet fields). This was particularly true at early crop colonization of the MHM with parasitism and direct predation on eggs and young larvae. This multi-scale effect of semi-natural habitats on crop colonization and natural regulation could explain why no clear relationship between crop colonization and pest incidence, nor natural regulation and pest incidence, was observed. Future studies on the identification of complex species-specific interactions between trees and natural enemies should provide a better understanding of the ecological processes underlying the performance of natural regulation of MHM populations.     

Spatial differences in breeding success in the pied avocet Recurvirostra avosetta: effects of habitat on hatching success and chick survival

I studied the breeding biology of pied avocets Recurvirostra avosetta in natural habitats (alkaline lakes), and in semi-natural sites (dry fishpond, reconstructed wetlands) in Hungary to relate habitat selection patterns to spatial and temporal variation in breeding success. Colonies were initiated earlier in semi-natural sites than in natural habitats, and earlier on islands than on the mainland. Hatching success was higher on islands than on the mainland, in semi-natural sites than in natural habitats, in colonies of at least 15 pairs than in smaller colonies, and for nests initiated earlier than later within a colony. Fledging success was higher in the wet years (1999–2000) than in the dry year (1998), decreased strongly by season in both habitats and increased with average daily temperature in the first week post-hatch in 1999–2000. Most pairs hatching young in semi-natural sites attempted to lead their chicks to feeding areas in natural habitats, whereas no such movement occurred in the opposite direction. Chick mortality due to predation was high during brood movements and only 23% of the pairs moving their young produced fledglings, compared to 43% for pairs remaining in semi-natural sites and 68% for pairs hatching and rearing young in natural habitats (total n=192 broods). These results suggest that semi-natural sites were more suitable for nesting, whereas natural habitats were more suitable for chick-rearing. The opposing trends in habitat-related breeding success between nesting and chick-rearing suggest sub-optimal habitat selection by Pied Avocets due to an incorrect assessment of the potential for successful reproduction of semi-natural sites, which may thus function as ecological traps.     

Landscape-scale forest cover increases the abundance of Drosophila suzukii and parasitoid wasps

Agricultural landscapes rich in natural and semi-natural habitats promote biodiversity and important ecosystem services for crops such as pest control. However, semi-natural habitats may fail to deliver these services if agricultural pests are disconnected from the available pool of natural enemies, as may be the case with invasive species. This study aimed to provide insights into the relationship between landscape complexity and the abundance of the recently established invasive pest species Drosophila suzukii and a group of natural enemies (parasitoid wasps), which contain species that parasitize D. suzukii in native and invaded ecosystems. The importance of landscape complexity was examined at two spatial scales. At the field scale, the response to introduction of wildflower strips was analysed, while the relationship with forest cover was assessed at the landscape scale. Half of the surveys were done next to blueberry crops (Vaccinium corymbosum), the other half was done in landscapes without fruit crops to examine effects of D. suzukii host presence. As expected, the number of observed parasitoid wasps increased with amount of forest surrounding the blueberry fields, but the number of D. suzukii individuals likewise increased with forest cover. Establishment of wildflower strips did not significantly affect the abundance of D. suzukii or parasitoid wasps and insect phenology was similar in landscapes with and without blueberry crops. This suggests that D. suzukii is enhanced by landscape complexity and is largely unlinked from the species group that, in its native range, hosts key natural enemies. Although management practices that rely on enhancing natural enemies through habitat manipulations can contribute to the long-term stability of agroecosystems and to control agricultural pests, other control measures may still be necessary in the short term to counteract the benefits obtained by D. suzukii from natural habitats.     

温度对新菠萝灰粉蚧生长发育和繁殖的影响

新菠萝灰粉蚧是近年在我国新发现的一种重要外来入侵害虫,温度是决定新菠萝灰粉蚧能否建立稳定种群的最基本因素.本研究以南瓜作为寄主,探索恒温条件对新菠萝灰粉蚧生长发育和繁殖的影响.在17、20、23、26、29和32 ℃,光周期14L∶10D,相对湿度(75±5)%的实验室条件下,测定了新菠萝灰粉蚧各虫态的发育历期、发育速率、存活率和繁殖力,组建了新菠萝灰粉蚧的实验种群生命表.结果表明: 在20～29 ℃,各虫态的发育历期均随温度的升高而缩短,在20 ℃下雌、雄若虫期的发育历期最长,分别为46.95和50.26 d;29 ℃时雌虫若虫期的发育历期最短,为20.28 d;而雄虫若虫期在32 ℃时最短,为20.70 d.各虫态的温度与发育速率的关系均符合二次回归关系.此外,温度显著影响新菠萝灰粉蚧的存活率,在29 ℃时雌、雄若虫期的存活率均最高,分别为70.3%和69.3%;雌虫世代的发育起点温度为13.80 ℃,有效积温为491.50日·度;雄虫世代的发育起点温度为11.61 ℃,有效积温为388.85日·度.新菠萝灰粉蚧的产卵前期和成虫寿命随着温度的升高而缩短;成虫产卵量在29 ℃时最高,达每雌442.2粒;最小为20 ℃,仅为每雌111.8粒;29和20 ℃下种群趋势指数分别为168.2和19.1,且在17和32 ℃时,新菠萝灰粉蚧1龄若虫和3龄若虫均表现为生长停滞.说明温度过高或过低均不利于其生长发育.温度对新菠萝灰粉蚧的生长发育、存活、繁殖及种群增长有显著的影响,23～29 ℃是最适宜新菠萝灰粉蚧生长发育和繁殖的温度范围.     

绿盲蝽及其天敌在不同生态条件下的发生动态研究

2005年～2007年,在山东省德州市农科院良种场棉田内系统研究了不同生境对抗虫棉绿盲蝽及其天敌发生动态的影响。试验设5个试验10种处理：即远离果园棉、紧靠果园棉,亩株数3600株均行、亩株数3000株并大小行种植棉,合理化控棉、不化控棉,纯作棉田和插种葵花棉田,双基因抗虫棉和单基因抗虫棉。在棉花的整个生育期系统调查不同生境棉田主要害虫及其天敌的种群数量。结果表明,不同生境抗虫棉田内绿盲蝽天敌的种类基本相同,主要为龟纹瓢虫、七星瓢虫、中华草蛉、大草蛉、华姬蝽、小花蝽、T-纹豹蛛、三突花蛛、草间小黑蛛等。不同生境抗虫棉田内绿盲蝽及其天敌种群数量差异明显。远离果园棉、低密度亩株数3000株并大小行种植棉、合理化控棉能减轻绿盲蝽的发生,但不利于绿盲蝽天敌的发生;种植双基因抗虫棉能减轻绿盲蝽的发生且对绿盲蝽天敌影响不大;插种葵花的棉田即能增加绿盲蝽天敌的数量,又能减轻绿盲蝽的发生。研究还表明绿盲蝽及其天敌在远离果园棉、紧靠果园棉下发生趋势基本一致,仅是发生量存在明显差异,远离果园棉田的绿盲蝽及其天敌百株发生量显著低于紧靠果园棉田（P〈0.05）;合理化控棉田、亩株数3000株大小行棉田内的绿盲蝽及其天敌发生数量显著低于不化控棉田、亩株数3600株均行棉田内的发生数量（P〈0.05）;双基因抗虫棉田内的绿盲蝽百株发生量显著低于单基因抗虫棉田发生数量（P〈0.05）;插种葵花棉田内的绿盲蝽百株发生量极显著低于纯作棉田（P〈0.01）、插种葵花棉田内的绿盲蝽天敌百株发生量显著高于纯作棉田（P〈0.05）,葵花对绿盲蝽及其天敌的诱集效果非常显著,在转基因棉田插种葵花是保益灭害控制绿盲蝽的有效方法之一。     

Diversity and specificity of host‐natural enemy interactions in an urban‐rural interface

1. Urbanisation and agricultural intensification cause the replacement of natural ecosystems but might also create novel habitats in urban and rural ecosystems promoting some insect communities by providing food and nesting resources. 2. This study investigated how host–natural enemy communities change in urban and rural landscapes and their transitional zone, the urban–rural interface, by using trap nests for cavity‐nesting Hymenoptera in gardens and rapeseed fields that were either isolated or paired in the urban–rural interface. 3. Host dynamics were important for natural enemy occurrence, species richness and parasitism rates, and landscape effects were evident for natural enemy variables except for the richness of bee natural enemies. The number of parasitised brood cells was at its highest in the urban–rural interface, but the highest parasitism rates of bees were observed in isolated gardens. Parasitism rates of bees were negatively affected by host abundance, while parasitism rates of wasps were positively affected. 4. Higher specialisation and lower connectivity of host–natural enemy interactions were found in paired habitats than in isolated habitats. This indicates that paired habitats comprise more specific natural enemies and vulnerable interactions, while isolated habitats comprise more generalist natural enemies, and thus interactions appear more stable. 5. These results confirm that host dynamics play an essential role in the abundance and richness of natural enemies and drive parasitism. However, high habitat heterogeneity found in the urban–rural interface can also have an effect on host–natural enemy communities. This highlights that the provisioning of resources in the urban–rural interface can benefit insect communities in these areas.