Chemical Communication in the Leaf Mining Moths of the Genus Phyllonorycter
Raimondas Mozūraitis (1,2) Vincas Būda (1) Ilme Liblikas (1,3) Ellen Santangelo (1) Jūratė de Prins (4) Remigijus Noreika (5) Anna-Karin Borg-Karlson (1).
- Department of Chemistry, Royal Institute of Technology, SE-100 44 Stockholm, Sweden
- Laboratory of Chemical and Behavioural Ecology, Institute of Ecology of Vilnius University, Akademijos 2, LT-08412, Vilnius, Lithuania;
- Laboratory of Ecochemistry, Institute of Animal Science, Estonian Agricultural University, EE-51005, Tartu, Estonia;
- Entomology Section, Royal Museum for Central Africa, Leuvensesteenweg 13, B-3080 Tervuren, Belgium;
- Department of Botany, Vilnius Pedagogical University, LT-2034, Vilnius, Lithuania
The research is granted from:
the Fund for Bilateral Co-operation Between Sweden and the Baltic Countries (through Royal Institute of Technology, Stockholm, Sweden); the governmental grants to Chemical Ecology group (Institute of Ecology, Vilnius, Lithuania); the Agricultural and Forest Research Council (Sweden), Carl Trygger Fund (Sweden), and by the Swedish Institute.
Gracillariidae is one of the oldest families within the taxonomic group Ditrysia of Lepidoptera. The family contains about 1400-1600 species altogether, while sex pheromones have been identified for only a few species. Most of the gracillariids are monophagous or oligophagous species mining leaves (Fig. 1) of one or a few host-plant species. It is known that individuals of two to a few species of the family Gracillariidae may co-occur on the same host-plant forming host-plant-leafminer complexes. Competition between species within these complexes is highly probable, which makes the leaf miners of this genus convenient objects for investigation of interspecific interactions, including those effected by allelochemicals in adults. Some species of the genus Phyllonorycter, such as Ph. blancardella, Ph. mespilella, Ph. pyrifoliella, Ph. cerasicoliella, and Ph. populifoliella, are known to be serious pests of orchards and recreation parks, and these species are attracting more and more attention in pest monitoring and control programmes. These facts encouraged us to start detailed investigation of the chemical communication systems of gracillariids.
Our attention in this research area is focused on:
- Interspecific interactions, including those mediated by allelochemicals in adults;
- Identification of semiochemicals for gracillariids of economic importance including Phyllonorycter blancardella (F.), Ph. mespilella (Hbn.), Ph. cerasicolella (H.-S.) and to apply these compounds in integrated pest management programmes;
- Sex pheromone communication in phyllonoryctid species with distorted sex ratio;
- Investigation of Afro-gracillariid fauna using sex attractants.
- Mapping of the chemical structures of sex pheromones with the phylogeny of the genus
Interaction by allelochemicals can occur (i) when the periods of communication activity of the species overlap, (ii) when individuals of one species perceive and react to compounds emitted by organisms of another species, and (iii) when the species are dispersed within distances allowing communication.
Laboratory studies of pheromone release behaviour have revealed that virgin females of all nine species of the genus Phyllonorycter investigated demonstrated the same pheromone release posture (Fig 2). Their calling activity was registered at the beginning of the photophase (Fig 3). This is an unusual time for calling in moths.
The Solid Phase Micro Extraction technique was applied for the first time to collect a sex pheromone from a single calling microlepidopteran female and our data clearly demonstrated the advantages of this method (Borg-Karlson and Mozuraitis, 1996).
Twelve compounds were identified from calling virgin females of seven phyllonoryctid species (Table 1, Fig. 4). All compounds, except E10-12:OAc and Z10-14:OAc, are new in the family Gracillariidae. Moreover, E10-12:OH, 8Z,10E-14:OAc, 8E,10Z-14:OAc, 8E,10E-14:OAc, 8Z,10E-14:OH and 8E,10E-14:OH have not been yet identified from the species of the order Lepidoptera. Thus, our identification extends the number of taxons, in which these compounds are released by calling moth females.
Our field screening tests disclosed new sex attractants for eight phyllonoryctid species (Table2) as well as fourteen sex attraction antagonists for males of seven Phyllonorycter species (Table3). The molecular structures of sex attraction antagonists are usually similar to those of a sex pheromones and sex attractants (Fig. 5). Sex attraction antagonists significantly decrease or completely reduce the attraction of males when applied at amount of 0.1-10% to a sex pheromones or sex attractants. The role of the sex attraction antagonists is to contribute to the specificity of a pheromone signal.
The data we have obtained about chemical communication systems of 3 sympatric phyllonoryctid species clearly demonstrate the role of sex attraction antagonists in achievement of species-specific sex pheromone signal (Fig. 6) (Mozūraitis et all., 2000).
It was found, that the leaf miner moth Ph. emberizaepenella reproduced by parthenogenesis of the thelytoky type (Mozūraitis et all., 2002). Despite a complete lack of males, the females demonstrated a calling posture with a potential sex pheromone release with the typical diurnal rhythm of that behaviour. Both the pattern of behaviour and the chemical characteristics of the potential sex pheromone of Ph. emberizaepenella species were similar to those known for Lepidoptera with the usual amphimictic mode of reproduction. Theoretical speculations that in thelytoky, where there is no need to find a sexual partner, the individuals would obtain certain advantages due to reduction in their sexual behaviour, were, thus, not confirmed for Ph. emberizaepenella.
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13. Mozūraitis R., Liblikas I., Noreika R. Sex pheromone communication of tentiform leaf-miners Phyllonorycter insignitella and Ph. nigrescentella from two related species groups. Chemoecology, 2008, vol. 18, 171-176.