title: Rival male chemical cues evoke changes in male pre- and post-copulatory investment in a flour beetle.
abstract: Males can gather information on the risk and intensity of sperm competition from their social environment. Recent studies have implicated chemosensory cues, for instance cuticular hydrocarbons (CHCs) in insects, as a key source of this information. Here, using the broad-horned flour beetle (Gnatocerus cornutus), we investigated the importance of contact-derived rival male CHCs in informing male perception of sperm competition risk and intensity. We experimentally perfumed virgin females with male CHCs via direct intersexual contact and measured male pre- and post-copulatory investment in response to this manipulation. Using chemical analysis, we verified that this treatment engendered changes to perfumed female CHC profiles, but did not make perfumed females "smell" mated. Despite this, males responded to these chemical changes. Males increased courtship effort under low levels of perceived competition (from 1-3 rivals), but significantly decreased courtship effort as perceived competition rose (from 3-5 rivals). Furthermore, our measurement of ejaculate investment showed that males allocated significantly more sperm to perfumed females than to control females. Together, these results suggest that changes in female chemical profile elicited by contact with rival males do not provide males with information on female mating status, but rather inform males of the presence of rivals within the population and thus provide a means for males to indirectly assess the risk of sperm competition.
authors.affiliation: Centre for Ecology and Conservation, College of Life & Environmental Sciences, University of Exeter, Penryn Campus , Cornwall TR10 9EZ , UK .
authors.forename: Sarah M
authors.initials: SM
authors.lastname: Lane
authors.affiliation: Centre for Ecology and Conservation, College of Life & Environmental Sciences, University of Exeter, Penryn Campus , Cornwall TR10 9EZ , UK , ; Liverpool School of Tropical Medicine, Vector Control Department , Pembroke Place, Liverpool L3 5QA , UK .
authors.forename: Joanna H
authors.initials: JH
authors.lastname: Solino
authors.affiliation: Centre for Ecology and Conservation, College of Life & Environmental Sciences, University of Exeter, Penryn Campus , Cornwall TR10 9EZ , UK , ; Hawkesbury Institute for the Environment, University of Western Sydney, Hawkesbury Campus , Penrith, New South Wales 2751 , Australia , and.
authors.forename: Christopher
authors.initials: C
authors.lastname: Mitchell
authors.affiliation: Centre for Ecology and Conservation, College of Life & Environmental Sciences, University of Exeter, Penryn Campus , Cornwall TR10 9EZ , UK .
authors.forename: Jonathan D
authors.initials: JD
authors.lastname: Blount
authors.affiliation: Laboratory of Evolutionary Ecology, Graduate School of Environmental Science, Okayama University , Tsushima-naka 1-1-1, Okayama , Japan.
authors.forename: Kensuke
authors.initials: K
authors.lastname: Okada
authors.affiliation: Centre for Ecology and Conservation, College of Life & Environmental Sciences, University of Exeter, Penryn Campus , Cornwall TR10 9EZ , UK .
authors.forename: John
authors.initials: J
authors.lastname: Hunt
authors.affiliation: Centre for Ecology and Conservation, College of Life & Environmental Sciences, University of Exeter, Penryn Campus , Cornwall TR10 9EZ , UK .
authors.forename: Clarissa M
authors.initials: CM
authors.lastname: House
keywords: Gnatocerus cornutus; chemical cues; cuticular hydrocarbons; ejaculate expenditure; sperm competition risk.