Chemical communication in leaf mining moths of the genus phyllonorycter

Abstract

Laboratory studies of pheromone release behaviour haverevealed that virgin females of all of the nine species of thegenus Phyllonorycter investigated demonstrated the samepheromone release posture. Their calling activity wasregistered at the beginning of the photophase. This is anunusual time for calling in moths. Our hypothesis is, that thisuncommon timing of the pheromone communication may have beencaused by the sensitivity of the males to sex attractionantagonists, released into the environment by females of otherspecies at other times of the day. The diurnal calling behaviour of virgin Ph. junoniellafemales was more pronounced under a cyclic thermal regime(close to the natural conditions) than under constanttemperature. We assume, that the occurrence of an extra peak inthe pheromone release behaviour as well as the extension of thecalling period to cover the larger part of the light period maybe adaptive for Ph. junoniella with a sex ratio stronglyshifted towards females (8:1 females to males), as it may leadto an increased proportion of males mated. It was found, that the leaf miner moth Ph. emberizaepenellareproduced by parthenogenesis of the thelytoky type. Despite acomplete lack of males, the females demonstrated a callingposture with a sex pheromone release with the typical diurnalrhythm of that behaviour. Theoretical speculations that in thelytoky, where there is no need to attract a sexual partner, thefemales benefit by reducing their sexual behaviour, was notconfirmed for Ph. emberizaepenella. Ten compounds used in the sex communication of fivephyllonoryctid species were identified from calling virginfemales: Z10-, Z8- and E10-14:OAc for Ph. acerifoliella;E10-12:OAc, 12:OAc and E10-12:OH for Ph. blancardella;E8,E10-14:OAc and E8,E10-14:OH for Ph. emberizaepenella;Z8-14:OAc, 14:OAc and Z8-14:OH for Ph.heegerella; as well asZ10-14:OAc for Ph. ulmifoliella. The Solid Phase MicroExtraction technique was applied for the first time to collecta sex pheromone from a single calling microlepidopteran femaleand our data clearly demonstrated the advantages of thismethod. Our field screening tests in Lithuania disclosed new sexattractants for five phyllonoryctid species: E10-12:OH for Ph.sorbi; E10-12:OAc for Ph. cydoniella and Ph.oxyacanthae;Z10-12:OAc for Ph. junoniella; as well as Z10-14:OAc in a 1:10mixture with E9-14:OAc for Ph. acerifoliella. The lattermixture was also found to be a potential sex attractant for Ph.coryli and Ph. heegerella. In addition, field trapping experiments revealed fourteensex attraction antagonists for males of seven Phyllonorycterspecies: E10-12:OH for Ph. acerifoliella and Ph.cydoniella;E10-12:OAc and Z10-14:OAc for Ph. heegerella; Z10-, E10-12:OHand E10-14:OH for Ph. mespilella; Z10-12:OH for Ph.oxyacanthae; Z7-, Z9- and Z10-12:OAc for Ph. sorbi; as well asZ8-, Z9-, E9-, E10- and E11-14:OAc for Ph.ulmifoliella. Schemes of probable interactions by means of allelochemicalsacting between Ph.blancardella and 7 other moth species, Ph.ulmifoliella and 414,Ph. sorbi and 243, Ph.mespilella and 11as well as Ph. acerifoliella and 7 other moth species arepresented. Basing both on our own results and on data published byothers, we conclude that the pheromones used by gracillariidshave appeared at a period lasting between the formation oflower and of higher Heteroneura. Key words: Phyllonorycter, Gracillariidae, Lepidoptera, sexpheromone, sex attractant, sex attraction antagonist, callingbehaviour, calling posture, olfactometer, sex ratio,parthenogenesis, evolution, ecology, Solid Phase MicroExtraction.NR 2014080