Mediation of a Plant-Spider Association by Specific Volatile Compounds

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Mediation of a Plant-Spider Association by Specific Volatile Compounds Ximena J. Nelson & Andrew J. Pratt & Xavier Cheseto & Baldwyn Torto & Robert R. Jackson

Received: 18 February 2012 / Revised: 27 June 2012 / Accepted: 27 July 2012 # Springer Science+Business Media, LLC 2012

Abstract Evarcha culicivora, an East African jumping spider (Salticidae), is the only spider for which there is evidence of innate olfactory affinity for particular plant species. Evarcha culicivora also actively chooses as preferred prey the females of Anopheles mosquitoes, and both sexes of Anopheles are known to visit plants for nectar meals. Here, we identified compounds present in the headspace of one of these species in Kenya, Lantana camara, and then used 11 of these compounds in olfactometer experiments. Our findings show that three terpenes [(E)-β-caryophyllene, αhumulene and 1,8 cineole] can be discriminated by, and are salient to, E. culicivora. The spiders experienced no prior training with plants or the compounds we used. This is the first experimental demonstration of specific phytochemicals being innately attractive to a spider, a group normally characterized as predators. Keywords Plant-arthropod interactions . Evarcha culicivora . Lantana camara . Salticidae . Sensory ecology . Plant volatiles X. J. Nelson (*) : R. R. Jackson School of Biological Sciences, University of Canterbury, Private Bag 4800, Christchurch, New Zealand e-mail: [email protected] A. J. Pratt Department of Chemistry, University of Canterbury, Private Bag 4800, Christchurch, New Zealand X. Cheseto : B. Torto International Centre of Insect Physiology and Ecology, P.O. Box 30772-00100, Nairobi, Kenya R. R. Jackson International Centre of Insect Physiology and Ecology, Thomas Odhiambo Campus, P.0. Box 30, Mbita Point, Kenya

Introduction Many nectar feeding and herbivorous insects associate with particular plant species, and several are known to rely on specific blends of plant-derived volatile compounds for identifying the particular plant species exploited as feeding or oviposition sites (Pichersky and Gershenzon, 2002; Bruce et al., 2005; Waser and Ollerton, 2006; Kessler and Morrell, 2010). That spiders (Araneae) sometimes associate with particular types of plants (e.g., bromeliads: Romero and Vasconcellos-Neto, 2005) might be surprising, as spiders typically are characterized as being predators that feed primarily on insects and other arthropods (Foelix, 2011). Yet numerous examples are now known of spiders also feeding on nectar (Jackson et al., 2001; Taylor and Pfannenstiel, 2008; Meehan et al., 2009), and associating with plants can also reward spiders with opportunities to feed on the insects that visit the plants (Ruhren and Handel, 1999; Whitney, 2004). Chemoreception is known to have considerable importance for spiders in the context of intraspecific and predator-prey interactions (Pollard et al., 1987; Gaskett, 2007; Nelson and Jackson, 2011). It is customary to distinguish between olfaction and contact chemoreception (Foelix, 1985