Two Sympatric Spodoptera Species Could Mutually Recognize Sex Pheromone Components for Behavioral Isolation

Abstract

Spodoptera exigua and S. litura are two sympatric species in China and many other countries. Both moths employ a multiple component sex pheromone blend, including a common component Z9,E12-14:OAc, and two specific components Z9-14:OH and Z11-16:OAc for S. exigua, and one specific component Z9,E11-14:OAc for S. litura. For the two species, it has been well documented that males are able to recognize and behaviorally attracted by their species-specific sex pheromone, which functions as a means of reproductive isolation, but whether males could mutually recognize pheromone components of its sympatric species is unknown. In the present study, the electroantennogram (EAG) and field evaluation were conducted to address this topic. The EAG recordings revealed that males of each species could significantly respond to specific components of its sympatric species, although the response values were lower than that to its own major component. In field tests, the specific components Z9-14:OH and Z11-16:OAc of S. exigua strongly inhibited the male catches of S. litura to its conspecific sex pheromone, while specific component Z9,E11-14:OAc of S. litura significantly reduced the male catches of S. exigua to its sex pheromone. Furthermore, the combined lure of the two species completely inhibited male catches of S. litura, and significantly decreased the male catches of S. exigua, compared to the species-specific lure alone. The results demonstrated that males of the two sibling species could perceive the specific components of its counterpart, suggesting that mutual recognition of pheromone components may function to strengthen the behavioral isolation between the two species. Our study has added new knowledge to the reproductive isolation via sex pheromone communication system in sympatric moth species, and provided a base for designing of mating disruption tactics targeting multispecies by using insect sex pheromones.

Functional Characterization of Sex Pheromone Receptors in the Fall Armyworm (Spodoptera frugiperda)

“…In its native range in the Americas, the FAW share a similar geographic distribution with S. exigua [67]; thus, SfruOR13 and SfruOR16 are possibly involved in interspecific recognition between these two Spodoptera species. Very recently, we showed that sympatric S. exigua and S. litura can both perceive specific components, reinforcing behavioral isolation between the two species [68]. To analyze the correlation between PR amino acid sequence identity and the ligand specificity, we summarized the results of previous studies from these four Spodoptera species [18,19,69], and a clear correlation was shown ( Figure 6).…”

Development of a New Sex Attractant via the Peripheral Coding of Pheromones in Mythimna loreyi

“…Interestingly, these components are common pheromones in the genus Spodoptera . For instance, Z 9-14:OH is the minor pheromone component of Spodoptera exigua , and also serves as a behavioral antagonist against Spodoptera litura males , This suggests that one species can recognize the sex pheromone components of other sympatric species, thereby maintaining reproductive isolation.…”

“…For instance, Z 9-14:OH is the minor pheromone component of Spodoptera exigua , and also serves as a behavioral antagonist against Spodoptera litura males , This suggests that one species can recognize the sex pheromone components of other sympatric species, thereby maintaining reproductive isolation. In previous studies, Spodoptera frugiperda , a species from another genus, showed similar pheromone components compared with M. loreyi , which resulted in inaccurate population monitoring of S. frugiperda in different regions. ,− Therefore, this ORN could detect the pheromones of sympatric species, which will be a putative target to screen the repellents of nontarget moths and improve the specificity of sex attractants when used to monitor populations of migratory pests.…”

“…For instance, Z9-14:OH is the minor pheromone component of Spodoptera exigua 50,51 and also serves as a behavioral antagonist against Spodoptera litura males. 52 Z9,E11-14:OAc is the major pheromone component of S. litura and also is an antagonist against S. exigua. 52,53 This suggests that one species can recognize the sex pheromone components of other sympatric species, thereby maintaining reproductive isolation.…”

Pheromone antagonism in Plu tella xylostella (Linnaeus) by sex pheromones of two sympatric noctuid moths

“…6 Females generally produce 'minor' components, which maintain speciesspecificity, and the male antennae express pheromone receptors specifically tuned to each of the pheromone components of the female blend. [7][8][9][10] These components are usually geometric isomers or analogs of the common major pheromone compound, and they share biosynthetic pathways. The species-specific minor components and the overall blend ratio are often detected by heterospecific males and cause these males to cease their pheromone-guided anemotaxis.…”