Intraspecific variation in beech scale populations and in susceptibility of their host Fagus sylvatica

Abstract

1. Within a seed orchard in southern England, beech trees (Fagus sylvatica L.) belonging to three clones were artificially infested by introducing beech scale larvae (Cryptococcus fagisuga Lind. Hornoptera: Coccidae) into small cages attached t o the bark.2. Some larvae developed t o fecund adults on trees of two susceptible clones but all failed t o develop on a third, resistant clone.3. Within susceptible clones, survival of larvae on individual trees was positively related t o their degree of natural infestation.4. Larvae deriving from several separate trees differed significantly in their ability to survive when inoculated onto trees of susceptible clones. 5. Five forest trees which acted as both donors of larvae and as hosts for artificial inoculation were each inoculated with larvae from all five trees.6. There was significant variation in survival of inoculated larvae both between the host trees and between sources of larvae on each host. 7. Survival of larvae reinoculated onto their original host was significantly higher than that of larvae originating from other trees.8. Fecundity of adults on the forest trees was positively correlated with the probability of inoculated larvae surviving to the adult stage.

Evaluation of Resistance to the Beech Scale Insect (Cryptococcus fagisuga) and Propagation of American Beech (Fagus grandifolia) by Grafting

“…Only a few studies (MEIER and REUTHER, 1994;WAINHOUSE and HOWELL, 1983) mention grafting of Fagus spp., and there are no published reports on different grafting methods or on the percentage of success for F. grandifolia. DIRR and HEUSER (1987) reported that Fagus spp.…”

“…Hence, the insects were able to establish and develop on the bark of some resistant trees, but they were apparently unable to reproduce. WAINHOUSE and HOWELL (1983) evaluated the adaptation of scale populations to specific hosts in F. sylvatica and found that scales collected from one diseased tree did not establish when inoculated onto another susceptible tree. In the present study, scale eggs used in challenging each graft were mixed from at least three different sources to reduce potential effects of host specificity.…”

“…In the present study, scale eggs used in challenging each graft were mixed from at least three different sources to reduce potential effects of host specificity. The discontinuous pattern of the disease in European forests has been related to the apparent adaptation of the insect to specific hosts only (WAINHOUSE and HOWELL, 1983). In North America, patterns of spread of the disease are continuous and more aggressive (HOUS-TON et al, 1979).…”

Evolution of Specialization and Ecological Character Displacement of Herbivores Along a Gradient of Plant Quality

“…Real foragers need to sample their environment: herbivorous arthropods need time to select their host plant, exhibit stagedependent mobility, and mothers may not always select the best host for their (immobile) offspring (e.g., Wainhouse and Howell 1983;Rauscher 1983;Rauscher and Papaj 1983;Whitham 1983;Robertson 1987;Moran and Whitham 1990;Valladares and Lawton 1991;Underwood 1994). Evidence is accumulating that they can approximate optimal foraging by adaptive learning (Dukas and Bernays 2000;Egas and Sabelis 2001;Egas et al 2003;Nomikou et al 2003).…”

Seed Reproduction Is Associated with a Transient Escape from Parasite Damage in American Beech

“…The hypothesized mechanisms by which seedlings may temporarily escape from parasite attack include the developmental, the ecological, and the genetic: reduced parent-offspring transmission of infections, due to developmental isolation during seed formation (Crocker 1939, Silander 1985, Bierzychudek 1987, Parker 1987; spatial or temporal escape from locally adapted paraAccepted 24 January 1991 0 OIKOS sites (Caten 1974, Edmunds and Alstad 1981, Wainhouse and Howell 1983, Parker 1985, Karban 1989. due to the potentially greater dispersal or longer dormancy of seeds; and increased resistance of novel recombinant progeny, due to time-lagged frequency-dependent selection favouring rare genotypes (Hamilton 1982, Rice 1983, Bell 1985.…”