Parasitoid complexes and patterns of parasitization in the genus Yponomeuta Latreille (Lepidoptera, Yponomeutidae)

Abstract

Sympatric speciation processes initiated by a host plant shift are thought to have occurred within the genus Yponomeuta. To find out whether these shifts may have resulted in an escape from parasitoids, the parasitoid complexes of 7 Yponomeuta‐species have been compared. For that purpose, data from a sampling survey of 10 years in the Netherlands were used. Fluctuations from year to year and/or from one locality to another were excluded by comparing samples of Yponomeuta‐species that were collected at the same place and on the same day. The parasitoid complexes of most of the species studied differ mainly in pattern of parasitisation: the same parasitoid species were reared from each of them, but in significantly different quantities. Only the parasitoid complexes of Y. plumbellus and Y. vigintipunctatus differ in composition from each other and from those of the other species. The results do not give rise to the supposition that shifts to other host plants were attended by an escape from parasitoids restricted to the former host plants. Zusammenfassung Parasitoiden‐Komplexe und Parasitierungsmuster in der Gattung Yponomeuta Latreille (Lepidoptera, Yponomeutidae) Man nimmt an, daß sympatrische Artbildungsprozesse, von Wirtspflanzenwechsel hervorgerufen, innerhalb der Gattung Yponomeuta stattgefunden haben. Um herauszufinden, ob diese Wechsel zu einer Befreiung von den Parasitoiden führten, wurden die Parasitoiden‐Komplexe von 7 Yponomeuta‐Arten verglichen. Hierfür wurden die Daten aus 10 Untersuchungsjahren in den Niederlanden verwendet. Fluktuationen von Jahr zu Jahr und/oder von einer Lokalität zur anderen wurden durch Vergleich von Yponomeuta‐Arten ermittelt, die am selben Ort und am gleichen Tage gesammelt worden waren. Die Parasitoiden‐Komplexe der meisten untersuchten Arten unterschieden sich hauptsächlich im Parasitierungsmuster: die selbe Parasitoiden‐Art kam zwar bei jeder dieser Wirtsarten vor, aber in signifikant unterschiedlicher Quantität. Lediglich die Parasitoiden‐Komplexe von Y. plumbellus und Y. vigintipunctatus unterschieden sich in der Anordnung voneinander und von jenen der anderen Wirtsarten. Die Ergebnisse bestärken die Annahme nicht, daß der Wechsel zu anderen Pflanzen für die Yponomeuta‐Arten von einer Befreiung von Parasitoiden, die an frühere Wirtspflanzen gebunden blieben, begleitet worden wären.

Quantifying the impact of insect predators and parasitoids on populations of the apple ermine moth,Yponomeuta malinellus(Lepidoptera: Yponomeutidae), in Europe

“…The polyembryonic egg-larval endoparasitoid Ageniaspis fuscicollis Dalman (Hymenoptera: Encyrtidae) which attacked host eggs, was detected in all larval instars, and killed the host during the final larval instar. This univoltine species mummifies the final instar larvae and produces 80 parasitoid (Dijkerman et al, 1986). The solitary larval-pupal endoparasitoids E. scutellaris, A. canaliculatum and Herpestomus brunnicornis Gravenhorst (Hymenoptera: Ichneumonidae) and the gregarious larval-pupal endoparasitoid B. evonymellae attacked Y. malinellus larvae from the third or fourth larval instar but only killed their host in the pupal stage.…”

Small Ermine Moths (Yponomeuta): Their Host Relations And Evolution

“…Agria mamillata), Dermaptera, Hemiptera, Coleoptera, and Hymenoptera (ants) have also been observed as predators (32,69,111). Other natural enemies include Nosema and Gregarina species (Protozoa), fungi, and viruses, some of which have been applied to control small ermine moths (96,36).…”

“…A survey of 10 years in western Europe shows that in most species of Yponomeuta the same parasitoid species occur but in different ratios; only Y. plumbellus and Y. vigintipunctatus each harbor a specific set of parasitoid species (29). These include strictly monophagous parasitoids (e.g.…”

“…These include strictly monophagous parasitoids (e.g. Triclistus yponomeutae) as well as species that are either confined to the genus Yponomeuta or have much broader host ranges, in some instances even spanning various insect orders (32). The ability among Yponomeuta species to encapsulate Diadegma armillata eggs, a major mechanism for preventing successful parasitization by this ichneumonid, is positively correlated with percentages of parasitization in natural populations (30,101 Although the impact of parasitoids on Yponomeuta population numbers has been studied little, birds may be the major natural enemies of Yponomeuta (7,69,111).…”

“…Yponomeuta species are attacked by some 20 hymenopterous and dipterous endoparasitoids (29,32,101). A survey of 10 years in western Europe shows that in most species of Yponomeuta the same parasitoid species occur but in different ratios; only Y. plumbellus and Y. vigintipunctatus each harbor a specific set of parasitoid species (29).…”