Oviposition strategies employed by the western spruce budworm: tests of predictions from the phylogenetic constraints hypothesis

Abstract

1 Predictions from the Phylogenetic Constraints Hypothesis were tested for the first time in an eruptive forest Lepidopteran species, the western spruce budworm. 2 In previous work, we established that western spruce budworm females exhibit oviposition preferences with regard to tree age, tree vigour and host species. However, there was no evidence to support a link between oviposition preference and larval performance, which supports the Phylogenetic Constraints Hypothesis. 3 Our preference data led us to test whether female budworms use oviposition strategies to select the sites where they lay their egg masses. Our experiments were designed to make direct comparisons between latent and eruptive insect herbivores with respect to two oviposition behaviours: egg retention and avoidance of conspecifics. This type of research has not previously been conducted on any eruptive forest Lepidopteran. 4 Female budworms retained eggs instead of laying them on less preferred hosts in two of three experiments, but the percentage of eggs they retained was significantly less compared to latent insect herbivores. 5 In addition, female budworms actively avoided oviposition in areas with the highest density of conspecific egg masses, but they laid egg masses in all the other locations provided. This contrasts with the pattern seen in latent insect herbivores, which consistently avoid laying their eggs near any sites already used by conspecifics. 6 Our research indicates that there are extreme differences between latent and eruptive insect herbivores with respect to egg retention and avoidance of conspecifics, thus supporting the Phylogenetic Constraints Hypothesis.

Croissance des branches et des tiges d'épinette noire :

“…Outre ce phénomène, Leyva et al (2000) ont montré que la tordeuse occidentale de l'épinette {Choristoneura occidentalis) (Freeman) avait une préférence pour les pousses plus longues lors de la ponte. Les TBE vont par ailleurs éviter de pondre non seulement sur des branches déjà défoliées, mais aussi à proximité d'oeufs pondus par leurs semblables (Leyva et al, 2003). Par conséquent, ce lépidoptère pondrait ses oeufs au niveau des étages un peu plus supérieurs n'ayant pas été encore perturbés.…”

Feeding and Oviposition Behavior Do Not Explain Douglas-fir Resistance to Defoliation by the Western Spruce Budworm (Lepidoptera: Tortricidae): Fig. 1.

“…The female pupae came from the same laboratory colony and were comparable in size (unpublished data), making it reasonable to assume that they also had about the same number of oocyctes when they emerged as moths and thus would be likely to lay similar numbers of egg masses. The number of egg masses is a reasonable index of the number of eggs laid (Leyva et al 2003), indicating that females who lay more egg masses retain fewer eggs. Needles bearing egg masses were also measured to evaluate potential differences in the lengths of the resistant and susceptible Douglas-Þr needles selected for oviposition.…”

“…In similar no-choice experiments, Levya et al (2003) reported that budworm moths retained a higher percentage of eggs when they had branches from only one host (Douglas-Þr, white Þr, Engelmann spruce) or nonhost (limber pine [Pinus flexilis James]) to oviposit on, compared with when they had branches from all four tree species for oviposition substrate. Leyva et al (2003) concluded that budworm moths were induced to lay more of their eggs when they had a variety of host species available for oviposition. Host plant cues are obviously important factors inßuencing budworm oviposition behavior.…”

“…The ability of both C. occidentalis and C. fumiferana (Clemens) to feed and oviposit selectively has been demonstrated in numerous studies (Guertin and Albert 1992;Langevin 1994, 1995;Dodds et al 1996;Leyva et al 2000Leyva et al , 2003. However, previous experiments used artiÞcial diets and substrates to measure budworm responses.…”

Oviposition of the Fir Sawyer Beetle (Monochamus urussovi Fisch.) on the Tree Stem: Analysis Using Models of Random Point Fields

“…(Исаев и др., 1988;Janz, 2002;Leyva et al, 2003;Holland et al, 2004;Horn, Holland, 2010;Castillo et al, 2013).…”