【作者】 程云霞；

【导师】 罗礼智；

【作者基本信息】 中国农业科学院 ， 农业昆虫与害虫防治， 2012， 博士

【摘要】 草地螟Loxostege sticticalis L.(鳞翅目：螟蛾科)是我国华北、东北和西北地区农牧业生产的重要害虫，解放后已经3次26年暴发成灾，并给我国的农牧业生产造成了巨大的经济损失。迁飞是草地螟在长期的进化过程中形成的一种适应性行为对策，也是其频繁暴发成灾并造成重大产量和经济损失的主要原因。然而，国内外对草地螟迁飞行为发生与调控的基础、以及迁飞在草地螟种群暴发成灾中的作用均知之甚少。为了阐明草地螟的暴发成灾规律，改善和提高预测预报技术水平，本文应用昆虫生态和生理学的原理与方法，研究了未成熟期温度以及成虫期补充营养对草地螟生殖与迁飞行为的调控作用，在此基础上研究明确了生殖对成虫飞行，以及飞行对生殖的影响作用，取得了如下一些原创性结果：明确了草地螟未成熟期（卵至蛹）环境温度是影响成虫迁飞行为的原因之一。为了阐明未成熟期环境因子对草地螟迁飞行为的影响作用，对分别由未成熟期18、22、26和30℃条件发育而来的成虫在22℃条件下的飞行能力、飞行肌干重、生殖特征和卵巢发育等进行了研究。所得的结果表明：虽然由26℃发育而来的成虫飞行肌干重显著大于其他处理的，但不同温度发育而来的成虫飞行能力（飞行距离）无显著差异；由22℃发育而来的成虫卵巢发育速度最慢，产卵前期和历期最长、成虫寿命最长。由18℃发育而来的成虫的各项生殖指标虽然与22℃的均无显著差异，但雌蛾寿命较短；由26℃发育而来的成虫产卵量最大，交配次数最多，产卵孵化率最高；另外，由26℃发育而来的成虫产卵前期显著短于源自18和22℃的，但又显著长于源自30℃条件下的。由30℃发育而来的成虫卵巢发育速度最快、产卵前期及成虫寿命最短。这些结果表明，由18-22℃条件下发育而来的成虫迁飞可能性较大，而由26-30℃条件下发育而来的成虫更适宜留在本地生殖。证实了补充营养对成虫生殖与迁飞的必要性，发现了成虫羽化后48h是成虫“决定”迁飞与否的敏感时期。对是否补充营养、不同时程和阶段无补充营养对成虫生殖与飞行的影响作用进行研究的结果表明：1）与成虫期饲喂10%葡萄糖溶液的成虫相比，饲喂清水的成虫不仅产卵量降低，产卵前期、产卵历期和寿命缩短，而且飞行能力下降、飞行肌发育延缓、甘油三酯含量降低，表明补充营养对草地螟生殖和迁飞都是必要的；2）对1-5天不等时程的持续饥饿对成虫生殖的影响研究表明，1-3天的持续饥饿可使成虫产卵前期缩短，表明这种情况虽然阻碍了迁飞行为的发生却有利于成虫滞留本地生殖，而4-5天持续饥饿则导致成虫产卵前期延长，表明营养缺乏持续3天以上不仅不利于迁飞行为的发生而且延迟了成虫生殖；3）对1-3日龄成虫分别饥饿24h后发现，在其他生殖参数没有变化的情况下，成虫产卵前期经1和2日龄的饥饿后均缩短，而3日龄饥饿则无此效果，表明羽化后48h是成虫“决定”是否迁飞的敏感时期，该时期的饥饿可使成虫由迁飞转向滞留生殖，这种策略调整增加了草地螟对环境变化的适应能力；4）在敏感时期饥饿24h后，成虫飞行能力仅在处理后的第3天显著高于对照的，而成虫飞行肌干重在饥饿后3-4天均显著大于对照的。卵巢发育级别和卵巢管直径在处理后的第1天显著低于对照，第2天已开始大于对照的，而到第4天则显著超过对照的，表明敏感时期饥饿可加速成虫飞行和生殖系统的发育，但对生殖系统发育的促进作用更强，这也是敏感时期饥饿导致成虫由迁飞转向生殖的原因。通过研究生殖对草地螟飞行行为及相关生理特征的影响，明确了生殖后成虫不再迁飞。对产卵或交配后1-5天的雌雄成虫飞行能力、飞行肌干重和甘油三酯含量的研究表明，雌成虫的飞行能力随产卵天数或产卵量的增加而显著下降(y=31.39-0.08x)。另外，与同日龄处女雌成虫相比，产卵雌成虫的飞行能力均显著下降。虽然交配过的雄成虫飞行能力在不同日龄间差异不显著，但与同日龄处女雄成虫相比，多数日龄交配过的雄成虫飞行能力也显著下降；产卵雌成虫的飞行肌干重也随产卵天数或产卵量的增加而显著下降，且与同日龄的处女雌成虫相比，产卵雌成虫飞行肌干重均显著下降。不同日龄的交配雄成虫的飞行肌重量差异不显著，但与同日龄的处女雄成虫相比大多显著下降；产卵雌成虫甘油三酯含量并不随产卵天数或产卵量的增加下降，但与同日龄处女雌成虫相比，甘油三酯含量显著降低约90%。交配过的雄成虫甘油三酯含量的变化趋势与产卵雌成虫的相一致。这些结果表明，开始生殖后的草地螟再次迁飞的可能性很小。这些结果为判别草地螟田间虫源性质提供了进一步的科学依据。明确了草地螟的迁飞不仅无需生殖代价，而且还促进了幼虫种群的大发生。为了阐明迁飞对草地螟生殖的影响及其在大发生种群形成中的作用，分别研究了飞行日龄和飞行测试时程对成虫飞行能力和生殖特征的影响。结果显示，在1日龄，成虫不仅飞行能力弱，而且飞行后成虫产卵前期显著延长；在2-5日龄，成虫飞行能力较强，而且飞行后产卵前期、产卵量、产卵历期、交配率、交配次数、寿命以及卵孵化率均无显著变化；甚至在3日龄飞行测试延长到24h，飞行后成虫的这些生殖参数也无显著变化。又根据文中首次定义的描述成虫产卵同步性的概念PFO（Period of first oviposition），对飞行后成虫的产卵同步性的分析显示，从3日龄开始飞行对成虫的产卵同步性有显著的促进作用，且3日龄不等时程的飞行对成虫的产卵同步性均有显著的促进作用。综合成虫飞行能力和飞行后生殖特征可以判断：1）草地螟成虫开始迁飞的生理时期是3日龄；2）草地螟3日龄后的迁飞不仅对成虫的生殖没有负面影响，而且还促进成虫产卵同步性的显著增加。由于田间成虫产卵同步性的增强将导致卵或幼虫密度的快速升高，从而进一步提升了迁入种群后代的为害程度，因此，草地螟迁飞行为引起的成虫产卵同步性的增加是迁飞行为与种群频繁暴发成灾紧密相连的纽带之一。主要创新点：1.研究阐明了草地螟未成熟期（卵至蛹）温度是影响成虫迁飞行为的环境因子之一：由18-22℃条件下发育而来的成虫迁飞的可能性较大，而在大于26℃条件下发育而来的成虫留在本地生殖的可能性较大。2.研究明确了补充营养对成虫的生殖和迁飞的都是必要的；持续3天之内的饥饿促进成虫生殖提前，而3天以上的饥饿对成虫的生殖和飞行均不利；1-2日龄是成虫由迁飞转向滞留生殖的敏感时期；敏感时期饥饿促进成虫飞行系统和卵巢的发育，但对后者的促进作用更强。3.通过系统研究生殖对成虫飞行能力及相关生理特征的影响，发现成虫飞行能力、甘油三酯含量以及飞行肌干重随产卵量或产卵天数的增加而下降，并且与同日龄雌雄处女成虫相比生殖后成虫的上述相应参数也均下降，阐明了开始生殖后草地螟成虫不再迁飞的原因。4.通过分析飞行能力及飞行后成虫生殖特征的变化规律，明确了3日龄是草地螟成虫开始迁飞的时期；迁飞后成虫不仅不需要付出生殖代价，且结合首次建立的PFO的概念，发现迁飞后成虫产卵同步性的增加是导致草地螟迁入种群发生危害程度加重的主要原因之一。更多还原

【Abstract】 The beet webworm, Loxostege sticticalis L.(Lepidoptera: Pyralidae) is a very destructive insectpest of crops and fodder plants in the Northern, Northeastern and Northwestern China. It is also along-range migratory pest with larval populations often exploding in regions receiving immigrants.Great yield and economical losses have been caused by the upsurge population of L. sticticalis duringthe26-years since1949. It is known that migration is a major life history strategy evolved fromadaption of the seasonal variations and a major cause for the frequent outbreaks of L. sticticalis.However, the cues that may induce the migratory flight behavior and roles of migration may also playan important role in the formation of outbreak population of L. sticticalis have been less understood inboth home and abroad. In order to demonstrate the environmental cues induced the migratory flightbehavior, and roles of migration played in the formation of outbreak population of L. sticticalis andprovide evidences that may raise the level of forecasting technology. The effect of temperaturesexperienced by the immature stages, and the supplemental nutrition on the migratory and reproductivebehavior, and the interaction between reproduction and migration were investigated by applying theprinciple and methodology of eco-physiology. The major results obtained are summarized as follows.The temperature experienced by the immature stages (from egg to pupae) is an important cueaffecting the migratory behavior of the adult L. sticticalis. The flight capacity, dry weight of flightmuscle, ovarian development and the preoviposition period (POP) of the adults developed from thetemperature of18,22,26and30℃were reared at22℃to determine the impacts of temperatureexperienced by the immature stages on the migratory flight behavior. The results showed that the flightcapacity (distance) of the adults developed from the4temperature conditions were not significantlydifferent during a12-h tethered flight test, even though the adults developed from the temperature of26℃possessed significant greater flight muscle than those derived from other temperatures. Besides, theovarian development or POP, oviposition period, and longevity of the adults developed from thetemperature of22and18℃were significantly slower or longer than that of adults developed from22and18℃. Thirdly, the oviposition period of adults derived from26℃was less than that of adults from22and18℃but was significantly greater than that of adults from30℃. The lifetime fecundity, matingfrequency and egg hatching rate of the adults developed from26℃were the greatest amongst the4treatments. Finally, the POP and longevity of the adults developed from the temperature of30℃aresignificantly shorter than those of the adults from other temperatures. All these results suggest that theadults developed from18and22℃intended to migrate while those developed from26and30℃intended to reproduce in the natal habitat.The roles of supplemental nutrition in the reproduction and migration of L. sticticalis wereconfirmed and the first2days of adult life were the final sensitive period for the adults to determine if they will migrate or not. Results from the present and absent of supplemental nutrition, and starvationdegree and in different stages of the adult life showed that the supplemental nutrition has a significantbut different effect on the migration and reproduction of L. sticticalis.(i) The POP, preovipositionperiod, lifetime fecundity, longevity, flight capacity, weight of flight muscle and content of triglycerideof the adults fed with only water were significantly shorter or less than that of the adults fed with10%glucose solution, indicating that the supplemental nutrition is crucial to both reproduction and migrationof L. sticticalis.(ii) POP of the moths starved at the first3days of the adult life was curtailed, incomparison with that of the control. However, POP of the moths was significantly prolonged when theirfood was deprived at the3to4day of the adult life.(iii) It was also showed the POP of the moths wassignificantly decreased when the moth was starved for24h at the1st or2nd day of the adult life while itkept unchanged when the moths were starved for24h at the3rd day of the adult life.(iv) It was showedthat the development of both flight and reproductive system is significantly affected when the mothswere starved for24h at the1st day of the adult life. The flight capacity, flight muscle weight, ovariangrade and basic ovariole width at the1st and2nd day post starvation did not significantly differ fromthat of the control moths at the same age. The flight capacity at day3and flight muscle weight at day3and4of the treated moths was greater than that of the controls, while the basic ovariole width at day4of the treated moths was significantly greater than that of the control moths with same age. The resultsobtained showed that the development of reproductive system is faster than the flight system althoughdevelopment of both reproductive and flight system are enhanced.These results implied that themigratory flight behavior of L. sticticalis could be changed at the first2day of the adult life, whichcould be considered as the sensitive period for the shifting of migrants into residents. That is, the mothswould be shifted from a migrant to resident when they do not have food during the first2days afteremergence.It is generally believed migration in most insects will stop once reproduction begins. However, theunderlying mechanisms have rarely been investigated and understood. In this study, the variations inflight capacity, flight muscle weight, and triglyceride content of adult L. sticticalis at1to5days aftercopulation or oviposition were investigated to understand the impact of reproduction on the flightcapacity. Flight capacity of the oviposited females was decreased as the number of egg lay increased orthe oviposition period extended (y=31.39-0.08x). Furthermore, flight capacity of oviposited femalewas significantly weaker than that of the virgins with same age. Flight capacity of the mated males, ascompared with that of the virgin with same age was also significantly declined although it was notsignificantly different within the observed period. Flight muscle weight in the oviposited females wasobviously declined as the number of eggs they laid or as their oviposition period increased. Besides, itwas significantly lighter in the ovipositing females than in the virgin females with the same age. Thedifference in flight muscle weight between the mated and virgin males was mostly significant althoughit was not significantly different between the days observed. Triglyceride content of the oviposited female was dramatically decreased and was only around10%of that virgin female at any day observedalthough it was not significantly decreased as their oviposition period extended or as the number of eggsthey laid increased. Triglyceride content of the mated males was also significantly less than that of thevirgin male although it was not significantly different between any days within the observed period.These results suggest that the migration will stop once the moths start to reproduce, which can provide areliable basis for judging the sources of adult population in the field.Identifying the reproductive consequences of insect migration is critical to understand itsecological and evolutionary significance. However, many empirical studies are seemingly contradictory,making recognition of unifying themes elusive and controversial. In this study,(i) reproductive costs ofmigratory flight, and (ii) reproductive traits contributing to larval outbreaks of immigrant populationswere examined. It is suggested that the beet webworm does not initiate migratory flight until the3rdnight after emergence. POP, lifetime fecundity, mating capacity, and egg hatch rate for adults thatexperienced prolonged flight after the2nd night did not differ significantly from unflown moths,suggesting these traits are irrelevant to the severity of beet webworm outbreaks after migration.However, the period of first oviposition, a novel parameter measuring synchrony of first egg-laying bycohorts of post-migratory females, for moths flown on days3and5of adulthood was shorter than thatof unflown moths, indicating a tightened time-window for onset of oviposition after migration. Theresulting synchrony of egg-laying will serve to increase egg and subsequent larval densities. A densepopulation offers potential selective advantages to the individual larvae comprising it, whereas the effectfrom the human standpoint is intensification of damage by an outbreak population. The strategy ofsynchronized oviposition may be common in other migratory insect pests, such as locust and armywormspecies, and warrants further study.The major discovery points of this dissertation are summarized as follows:1. It is demonstrated that the temperature experienced at the immature stages is an important cueaffecting the migratory flight behavior in L. sticticalis. The migration propensity is preferred by adultsdeveloped from18-22℃. On the contrast, adults developed from the temperature of>26℃prefer toreproduce in the natal habitat for their shorter POP.2. It is confirmed that supplemental nutrition is critical to the reproduction and migration of L.sticticalis. Both reproductive and migratory flight capacities are significantly decreased when the mothsdo not have food. POP is significantly decreased when the moths are starved at the first2day of adultlife. Neither reproduction nor migration is significantly affected when the moths are starved after twodays of emergence. Development of reproductive and flight system is speeded up when the moths arestarved at day1of adulthood, but the former is favored.3. It is found that the adults of L. sticticalis will not migrate when they are mated or oviposited. This is because the flight capacity, triglyceride content and flight muscle weight in both male andfemale are all remarkably decreased as the number of eggs they laid increased or their ovipositionperiod extended. Besides, any of these3parameters of the reproduced adults is decreased in comparisonwith the virgin male or females at the same age, regardless of the significance.4. It is demonstrated that there is no reproductive cost for the migration of L. sticticalis, andmigration of the moths initiates at the3rd day after emergence based on the evidences from the flightcapacity, and variations in major reproductive parameters in the moths experienced various flight test.Besides, migration can increase the larval population density and thus enhance their damages thoughdecreasing their period of first oviposition.更多还原