Geographic Variation in Sexual Attraction of Spodoptera frugiperda Corn- and Rice-Strain Males to Pheromone Lures

Abstract

The corn- and rice-strains of Spodoptera frugiperda exhibit several genetic and behavioral differences and appear to be undergoing ecological speciation in sympatry. Previous studies reported conflicting results when investigating male attraction to pheromone lures in different regions, but this could have been due to inter-strain and/or geographic differences. Therefore, we investigated whether corn- and rice-strain males differed in their response to different synthetic pheromone blends in different regions in North America, the Caribbean and South America. All trapped males were strain-typed by two strain-specific mitochondrial DNA markers. In the first experiment, we found a nearly similar response of corn- and rice-strain males to two different 4-component blends, resembling the corn- and rice-strain female blend we previously described from females in Florida. This response showed some geographic variation in fields in Canada, North Carolina, Florida, Puerto Rico, and South America (Peru, Argentina). In dose-response experiments with the critical secondary sex pheromone component (Z)-7-dodecenyl acetate (Z7-12:OAc), we found some strain-specific differences in male attraction. While the response to Z7-12:OAc varied geographically in the corn-strain, rice-strain males showed almost no variation. We also found that the minor compound (Z)-11-hexadecenyl acetate (Z11-16:OAc) did not increase attraction of both strains in Florida and of corn-strain males in Peru. In a fourth experiment, where we added the stereo-isomer of the critical sex pheromone component, (E)-7-dodecenyl acetate, to the major pheromone component (Z)-9-tetradecenyl acetate (Z9-14:OAc), we found that this compound was attractive to males in North Carolina, but not to males in Peru. Overall, our results suggest that both strains show rather geographic than strain-specific differences in their response to pheromone lures, and that regional sexual communication differences might cause geographic differentiation between populations.

Female sex pheromone of a nettle caterpillar, Monema flavescens, in China

“…Wind tunnel and field tests demonstrated that Z7,9‐10:OH markedly increased the number of attracted M. flavescens males in the Chinese population, when the compound was added to the sex pheromone mixtures. Isomers of a pheromone component are usually critical for attracting males, as shown for the two pheromone strains of Ostrinia nubilalis (Hübner) (Lassance, ; Unbehend et al., ). If we added Z9,11‐12:OH to the pheromone blend, it resulted in a marked synergistic effect in the wind tunnel and field tests.…”

A key compound: (Z)-9-tetradecen-1-ol as sex pheromone active component of Hypsipyla robusta (Lepidoptera: Pyralidae)

“…This indicated that the sex pheromone components of China populations of H. robusta were different from other regions. However, the phenomenon of (Qingyuan, Guangdong, China, 2014) insect sex pheromone variation is universal, such as Hemileuca electra (McElfresh and Millar 1999), Hyphantria cunea (Su et al 2008), genus Adoxophyes (Yang et al 2009), Cydia strobilella (Wang et al 2010), Spodoptera frugiperda (Unbehend et al 2014).…”

Pheromone races of Cydia splendana (Lepidoptera, Tortricidae) overlap in host plant association and geographic distribution

“…Pheromone races in moths are sometimes associated with different host plants, for example in the European corn borer Ostrinia nubilalis (Leppik and Frerot, 2012;Unbehend et al, 2014). In comparison, pheromone races in C. splendana demonstrate that separate pheromone communication channels alone can account for premating isolation, despite overlapping host use and geographical distribution.…”

“…However, the EZ/EEpheromone blend of C. splendana from Swedish oak forests did not attract males in chestnut plantations in France. Host races of several moths, including European corn borer, fall armyworm and larch budmoth are known to use different pheromone blends (Guerin et al, 1984;Leppik and Frerot, 2012;Unbehend et al, 2014). This led us to reinvestigate the sex pheromone of C. splendana from chestnut, showing that C. splendana uses two different pheromone blends that probably contribute to reproductive isolation.…”