Male pheromone composition depends on larval but not adult diet in Heliconius melpomene

1. Condition-dependent traits can act as honest signals of mate quality, with fitter individuals able to display preferred phenotypes. Nutrition is known to be an important determinant of individual condition, with diet known to affect many secondary sexual traits. 2. In Heliconius butterflies, male chemical signalling plays an important role in female mate choice. Potential male sex pheromone components have been previously identified, but it is unclear what information they convey to the female. 3. Here, we test the effect of diet on androconial and genital compound production in male Heliconius melpomene rosina. To manipulate larval diet, we rear larvae on three different Passiflora host plants: P. menispermifolia, the preferred host plant, P. vitifolia, and P. platyloba. To manipulate adult diet, we rear adult butterflies with and without access to pollen, a key component of their diet. 4. We find no evidence that adult pollen consumption affects compound production in the first ten days after eclosion. We also find strong overlap in the chemical profiles of individuals reared on different larval host plants. The most abundant compounds produced by the butterflies do not differ between host plant groups. However, some compounds found in small amounts differ both qualitatively and quantitatively. We predict some of these compounds to be of plant origin and the others synthesized by the butterfly. Further electrophysiological and behavioural experiments will be needed to determine the biological significance of these differences.KD was supported by a Natural Research Council Doctoral Training Partnership and a Smithsonian Tropical Research Institute Short Term Fellowship. KJRPB and CDJ were supported by a European Research Council grant number 339873 SpeciationGenetics. WOM was supported by the Smithsonian Tropical Research Institute and NSF grant DEB 1257689. SS thanks the Deutsche Forschungsgemeinschaft (DFG) for support through grant Schu984/12-1

Floral odors and the interaction between pollinating Ceratopogonid midges and Cacao

Most plant species depend upon insect pollination services, including many cash and subsistence crops. Plants compete to attract those insects using visual cues and floral odor which pollinators associate with a reward. The cacao tree, Theobroma cacao, has a highly specialized floral morphology permitting pollination primarily by Ceratopogonid midges. However, these insects do not depend upon cacao flowers for their life cycle, and can use other sugar sources. To understand how floral cues mediate pollination in cacao we developed a method for rearing Ceratopogonidae through several complete lifecycles to provide material for bioassays. We carried out collection and analysis of cacao floral volatiles, and identified a bouquet made up exclusively of saturated and unsaturated, straight-chain hydrocarbons, which is unusual among floral odors. The most abundant components were tridecane, pentadecane, (Z)-7-pentadecene and (Z)-8-heptadecene with a heptadecadiene and heptadecatriene as minor components. We presented adult midges, Forcipomyia sp. (subgen. Forcipomyia), Culicoides paraensis and Dasyhelea borgmeieri, with natural and synthetic cacao flower odors in choice assays. Midges showed weak attraction to the complete natural floral odor in the assay, with no significant evidence of interspecific differences. This suggests that cacao floral volatiles play a role in pollinator behavior. Midges were not attracted to a synthetic blend of the above four major components of cacao flower odor, indicating that a more complete blend is required for attraction. Our findings indicate that cacao pollination is likely facilitated by the volatile blend released by flowers, and that the system involves a generalized odor response common to different species of Ceratopogonidae

Plant volatile compounds in growth

Plants synthesise volatile organic compounds (VOCs) in various tissues against stresses regarding herbivores, plant viruses, pathogens, temperature, humidity, light ozone, food usability, etc., and for physiologic processes such as plant development, seed formation and germination, pollination and fruit ripening. These compounds are synthesised in all parts of plants, especially flowers, fruits, roots, xylems and cells, and just as they may be effective in the tissues they are produced, they may be transferred to other parts of the plants and show their effect there. Plants communicate with living things around them by emitting numerous different volatile compounds. They develop morphological and physiological defence mechanisms by repulsing or attracting their enemies with these compounds. Plants store these compounds produced for defence and release them in the form of volatile gases when needed. Plant volatile compounds include isoprene, terpene, fatty acid derivatives, alcohols, esters, volatile oils, plant development regulators (abscisic acid, auxin, cytokinin, etc.), phenolic compounds and secondary metabolites. © Springer Nature Singapore Pte Ltd. 2017. All rights reserved

Multimodal cues provide redundant information for bumblebees when the stimulus is visually salient, but facilitate red target detection in a naturalistic background

Our understanding of how floral visitors integrate visual and olfactory cues when seeking food, and how background complexity affects flower detection is limited. Here, we aimed to understand the use of visual and olfactory information for bumblebees (Bombus terrestris terrestris L.) when seeking flowers in a visually complex background. To explore this issue, we first evaluated the effect of flower colour (red and blue), size (8, 16 and 32 mm), scent (presence or absence) and the amount of training on the foraging strategy of bumblebees (accuracy, search time and flight behaviour), considering the visual complexity of our background, to later explore whether experienced bumblebees, previously trained in the presence of scent, can recall and make use of odour information when foraging in the presence of novel visual stimuli carrying a familiar scent. Of all the variables analysed, flower colour had the strongest effect on the foraging strategy. Bumblebees searching for blue flowers were more accurate, flew faster, followed more direct paths between flowers and needed less time to find them, than bumblebees searching for red flowers. In turn, training and the presence of odour helped bees to find inconspicuous (red) flowers. When bees foraged on red flowers, search time increased with flower size; but search time was independent of flower size when bees foraged on blue flowers. Previous experience with floral scent enhances the capacity of detection of a novel colour carrying a familiar scent, probably by elemental association influencing attentionPeer reviewe