Coleoptera: Cerambycidae) of the Subfamily Lamiinae
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Environmental Entomology, 45(5), 2016, 1271–1275 doi: 10.1093/ee/nvw101 Advance Access Publication Date: 14 August 2016 Chemical Ecology Research Stereochemistry of Fuscumol and Fuscumol Acetate Influences Attraction of Longhorned Beetles (Coleoptera: Cerambycidae) of the Subfamily Lamiinae G. P. Hughes,1 L. R. Meier,2 Y. Zou,3 J. G. Millar,3 L. M. Hanks,2 and M. D. Ginzel1,4 1Department of Entomology, Purdue University, 901 W. State St., West Lafayette, IN 47907 ([email protected]; mginzel@pur due.edu), 2Department of Entomology, University of Illinois at Urbana-Champaign, Urbana, IL 61801 ([email protected]; [email protected]), 3Department of Entomology, University of California, Riverside, Riverside, CA 92521 ([email protected]; [email protected]), and 4Corresponding author, e-mail: [email protected] Downloaded from Received 9 June 2016; Accepted 19 July 2016 Abstract http://ee.oxfordjournals.org/ The chemical structures of aggregation-sex pheromones of longhorned beetles (Coleoptera: Cerambycidae) are often conserved among closely related taxa. In the subfamily Lamiinae, adult males and females of several spe- cies are attracted by racemic blends of (E)-6,10-dimethyl-5,9-undecadien-2-ol (termed fuscumol) and the struc- turally related (E)-6,10-dimethyl-5,9-undecadien-2-yl acetate (fuscumol acetate). Both compounds have a chiral center, so each can exist in two enantiomeric forms. Males of many species of longhorned beetles only produce one stereoisomer of each pheromone component, and attraction may be reduced by the presence of stereoiso- mers that are not produced by a particular species. In a previous publication, analysis of headspace volatiles of adult beetles of the lamiine species Astyleiopus variegatus (Haldeman) revealed that males sex-specifically pro- at ESA Society Member on November 3, 2016 duced (S)-fuscumol and (S)-fuscumol acetate. Here, we describe field trials which tested attraction of this species to single enantiomers of fuscumol and fuscumol acetate, or to blends of enantiomers. We confirmed at- traction of A. variegatus to its species-specific blend, but during the course of the trials, found that several other species also were attracted. These included Aegomorphus modestus (Gyllenhall), attracted to (S)-fuscumol acetate; Astylidius parvus (LeConte), attracted to (R)-fuscumol; Astylopsis macula (Say), attracted to (S)-fuscumol; and Graphisurus fasciatus (DeGeer), attracted to a blend of (R)-fuscumol and (R)-fuscumol acet- ate. These results suggest that chirality may be important in the pheromone chemistry of lamiines, and that spe- cific stereoisomers or mixtures of stereoisomers are likely produced by each species. Key words: Cerambycidae, semiochemical, pheromone, chirality, enantiomer The longhorned beetles (Coleoptera: Cerambycidae) are a large family the genus Monochamus (e.g., Pajares et al. 2010, Teale et al. 2011, of insects that exhibit considerable diversity in their chemical commu- Allison et al. 2012, Fierke et al. 2012). Attraction to monochamol in nication systems (reviewed by Millar and Hanks 2016). Males or fe- other species in the Lamiini (Wickham et al. 2014)providesfurther males of many species produce volatile aggregation-sex pheromones evidence that this compound is a conserved pheromone component (sensu Carde´2014), which serve to bring the sexes together on host within the subfamily. plants (Millar et al. 2009). Among species in the subfamily In contrast, males of the South American lamiine Hedypathes Cerambycinae, males commonly produce volatile pheromones which betulinus (Klug) (tribe Acanthoderini) produce the sesquiterpene are typically 6, 8, or 10 carbons in length with hydroxyl or carbonyl degradation product (E)-6,10-dimethyl-5,9-undecadien-2-one (gera- groups on carbons 2 and 3 (Millar and Hanks 2016). Less is known nylacetone), the corresponding alcohol (fuscumol), and the acetate about the pheromone chemistry of longhorned beetles in the subfam- ester of fuscumol (Fonseca et al. 2010). Blends of these compounds ily Lamiinae, but the evidence to date suggests that pheromone struc- were attractive to beetles in laboratory experiments, although at- tures vary across tribes. For example, males of species in the Lamiini traction in the field has yet to be confirmed. Fuscumol was first iden- and Monochamini produce hydroxyethers and related compounds, tified as the pheromone of the European longhorned beetle including 4-(heptyloxy)butanol and the corresponding aldehyde from Tetropium fuscum (F.), in the small subfamily Spondylidinae (Silk species of Anoplophora (Zhang et al. 2002, Hansen et al. 2015), and et al. 2007, Sweeney et al. 2010). Field screening experiments in 2-(undecyloxy)ethanol (termed monochamol) from many species in North America revealed that several native lamiine species in the VC The Authors 2016. Published by Oxford University Press on behalf of Entomological Society of America. All rights reserved. For Permissions, please email: [email protected] 1271 1272 Environmental Entomology, 2016, Vol. 45, No. 5 tribes Acanthoderini and Acanthocinini were attracted by racemic Table 1. Study sites for field experiments conducted in northwest- fuscumol and fuscumol acetate (Mitchell et al. 2011, Hanks and ern Indiana and east-central Illinois during 2012–2014 Millar 2013), indicating that this motif crosses subfamily State/County Name GPS coordinates Area (ha) boundaries. (long., lat.) Attraction of cerambycids to their aggregation-sex pheromones may be inhibited by compounds produced by related species, includ- IN/Warren Black Rock Barrens 40.358, À87.114 40 a ing stereoisomers of their pheromone components (Millar and Nature Preserve b Hanks 2016). For example, males of the cerambycine Neoclytus IN/Tippecanoe Ross Hills Park 40.404, À87.072 68 IL/Champaign Brownfield Woodsc 40.145, À88.165 26 acuminatus acuminatus (F.) produce a single-component pheromone IL/Vermillion Forest Glen Preserved 40.015, À87.567 3 comprising (2S,3S)-2,3-hexanediol, and attraction of both sexes IL/Champaign Nettie Hart 40.229, À88.358 16 to synthesized pheromone is unaffected by the nonnatural (2R,3R)- Memorial Woodsc enantiomer, but reduced by the (2S,3R)- and/or (2R,3S)- IL/Piatt Robert Allerton Parkc 39.996, À88.651 600 diastereomers (Lacey et al. 2004). Because fuscumol and fuscumol acetate have chiral centers, chirality could play an important role in a NICHES Land Trust (http://nicheslandtrust.org/, accessed 3 August 2016). b imparting species specificity to pheromones of species that utilize Tippecanoe County Parks & Recreation Department (http://www.tippeca these compounds. For example, male H. betulinus produce a blend noe.in.gov/187/, accessed 3 August 2016). c Property of the University of Illinois (http://research.illinois.edu/cna/, of geranylacetone, (R)-fuscumol acetate, and a mixture of (R)- and Downloaded from accessed 3 August 2016). (S)-fuscumol in a ratio of 82% and 18%, respectively (Vidal et al. d Vermilion County Conservation District (http://www.vccd.org/, accessed 2010). However, the activity of nonracemic blends of the enantio- 3 August 2016). mers of the latter two compounds have not been reported. These compounds have an additional stereochemical element in the C5 double bond, but the (Z)-isomer has not yet been identified from Table 2. Treatments for two field experiments which tested attrac- http://ee.oxfordjournals.org/ any longhorned beetle species, to our knowledge. tion of longhorned beetles to individual enantiomers of fuscumol Headspace collections from a male of the North American lam- and fuscumol acetate, or blends of the enantiomers of each iine Astyleiopus variegatus (Haldeman) (Acanthocinini) contained a component blend of (S)-fuscumol and (S)-fuscumol acetate (1:2 ratio; Hughes Treatment et al. 2013). This species already was known to be attracted by a blend of racemic fuscumol þ fuscumol acetate from field experi- Expt. 1 (R)-fuscumol ments (Mitchell et al. 2011). Here, we describe field experiments (R)-fuscumol acetate which tested the attraction of cerambycids to enantiomers of fuscu- (R)-fuscumol þ (R)-fuscumol acetate at ESA Society Member on November 3, 2016 mol and fuscumol acetate in Indiana and Illinois. These experiments (S)-fuscumol confirmed attraction of A. variegatus to its species-specific blend, (S)-fuscumol acetate (S)-fuscumol þ (S)-fuscumol acetate and also assessed attraction of sympatric lamiine species to these Solvent control compounds. Our results provide evidence that the pheromones of at Expt. 2 (R)-fuscumol least some lamiines may be delineated by chirality, and that the chir- (S)-fuscumol ality of fuscumol and fuscumol acetate allows for a variety of dis- (R)-fuscumol acetate tinct blends that could serve as species-specific pheromones among (S)-fuscumol acetate sympatric species. Solvent control Materials and Methods efficiency (Graham et al. 2010, Allison et al. 2016). The supplied Sources of Chemicals trap basins were replaced with 2-liter plastic jars (General Bottle (R)-fuscumol (96.6% enantiomeric excess, ee), (S)-fuscumol (98% Supply Company, Los Angeles, CA) which had their threaded lids ee), (R)-fuscumol acetate (96.6% ee), and (S)-fuscumol acetate modified to accommodate a plastic funnel that received captured (98% ee) were synthesized by enzymatic kinetic resolution of the ra- beetles, allowing for quick removal of the jar when collecting speci- cemic compounds as described in Sweeney et al. (2010) and Hughes mens. Traps were suspended from L-shaped stands constructed