Byers John A, Fefer Daniela, Levi-Zada Anat
Naturwissenschaften. 2013 Dec;100(12):1115-23. doi: 10.1007/s00114-013-1113-7.
The plant bugs Lygus hesperus, Lygus lineolaris, and Lygus elisus (Hemiptera: Miridae) are major pests of many agricultural crops in North America. Previous studies suggested that females release a sex pheromone attractive to males. Other studies showed that males and females contain microgram amounts of (E)-4-oxo-2-hexenal, hexyl butyrate, and (E)-2-hexenyl butyrate that are emitted as a defense against predators. Using gas chromatography-mass spectrometry, we found that female L. lineolaris and L. elisus have a 4:10 ratio of hexyl butyrate to (E)-2-hexenyl butyrate that is reversed from the 10:1 ratio in female L. hesperus (males of the three species have ~10:1 ratio). These reversed ratios among females of the species suggest a behavioral role. Because both sexes have nearly equal amounts of the major volatiles, females should release more to attract males. This expectation was supported because L. hesperus females released more hexyl butyrate (mean of 86 ng/h) during the night (1800-0700 hours) than did males (<1 ng/h). We used slow-rotating pairs of traps to test the attraction of species to blends of the volatiles with a subtractive method to detect synergism. Each species' major butyrate ester was released at 3 μg/h, the minor butyrate according to its ratio, and (E)-4-oxo-2-hexenal at 2 μg/h. The resulting catches of only Lygus males suggest that (E)-4-oxo-2-hexenal is an essential sex pheromone component for all three species, (E)-2-hexenyl butyrate is essential for L. elisus and L. lineolaris, and hexyl butyrate is essential for L. hesperus. However, all three components are recognized by each species since ratios of the butyrate esters are critical for conspecific attraction and heterospecific avoidance by males and thus play a role in reproductive isolation among the three species. Because L. hesperus males and females are known to emit these major volatiles for repelling ant predators, our study links defensive allomones in Lygus bugs with an additional use as sex pheromones.
牧草盲蝽（Lygus hesperus）、牧草绿盲蝽（Lygus lineolaris）和埃氏盲蝽（Lygus elisus）（半翅目：盲蝽科）是北美洲许多农作物的主要害虫。先前的研究表明，雌虫会释放一种对雄虫有吸引力的性信息素。其他研究表明，雌虫和雄虫体内含有微克量的（E）-4-氧代-2-己烯醛、丁酸己酯和（E）-2-己烯基丁酸酯，这些物质作为抵御捕食者的防御物质释放出来。通过气相色谱-质谱联用仪，我们发现牧草绿盲蝽雌虫和埃氏盲蝽雌虫体内丁酸己酯与（E）-2-己烯基丁酸酯的比例为4:10，与牧草盲蝽雌虫的10:1比例相反（这三个物种的雄虫比例约为10:1）。物种间雌虫的这些相反比例表明其具有行为作用。由于雌雄两性体内主要挥发性物质的含量几乎相等，雌虫应该释放更多来吸引雄虫。这一推测得到了证实，因为牧草盲蝽雌虫在夜间（18:00-07:00）释放的丁酸己酯（平均86纳克/小时）比雄虫（<1纳克/小时）多。我们使用缓慢旋转的诱捕器对来测试这些物种对挥发性物质混合物的吸引力，并采用减法方法来检测协同作用。每种物种的主要丁酸酯以3微克/小时的速度释放，次要丁酸酯按照其比例释放，（E）-4-氧代-2-己烯醛以2微克/小时的速度释放。最终只捕获到了盲蝽属雄虫，这表明（E）-4-氧代-2-己烯醛是这三个物种必不可少的性信息素成分，（E）-2-己烯基丁酸酯对埃氏盲蝽和牧草绿盲蝽必不可少，丁酸己酯对牧草盲蝽必不可少。然而，所有三个成分都能被每个物种识别，因为丁酸酯的比例对于雄虫的同种吸引和异种回避至关重要，因此在这三个物种的生殖隔离中发挥作用。由于已知牧草盲蝽的雌雄虫都会释放这些主要挥发性物质来驱赶蚂蚁捕食者，我们的研究将盲蝽属昆虫的防御异源信息素与作为性信息素的额外用途联系了起来。
