Showing papers by "Brad M. Potts published in 2000"

Plant genetics affects arthropod community richness and composition: evidence from a synthetic eucalypt hybrid population.

Abstract: To examine how genetic variation in a plant population affects arthropod community richness and composition, we quantified the arthropod communities on a synthetic population of Eucalyptus amygdalina, E. risdonii, and their F1 and advanced-generation hybrids. Five major patterns emerged. First, the pure species and hybrid populations supported significantly different communities. Second, species richness was significantly greatest on hybrids (F1 > F2 > E. amygdalina > E. risdonii). These results are similar to those from a wild population of the same species and represent the first case in which both synthetic and wild population studies confirm a genetic component to community structure. Hybrids also acted as centers of biodiversity by accumulating both the common and specialist taxa of both parental species (100% in the wild and 80% in the synthetic population). Third, species richness was significantly greater on F1s than the single F2 family, suggesting that the increased insect abundance on hybrids may not be caused by the breakup of coadapted gene complexes. Fourth, specialist arthropod taxa were most likely to show a dominance response to F1 hybrids, whereas generalist taxa exhibited a susceptible response. Fifth, in an analysis of 31 leaf terpenoids that are thought to play a role in plant defense, hybrids were generally intermediate to the parental chemotypes. Within the single F2 family, we found significant associations between the communities of individual trees and five individual oil components, including oil yield, demonstrating that there is a genetic effect on plant defensive chemistry that, in turn, may affect community structure. These studies argue that hybridization has important community-level consequences and that the genetic variation present in hybrid zones can be used to explore the genetic-based mechanisms that structure communities.

Inheritance of Two Chlorophyll Mutants in Eucalyptus globulus

Abstract: Mutations in two independent genes causing chlorophyll deficiency (chl1 and chl2) were identified in two Eucalyptus globulus trees from remnant native forest. In each tree the proportion of albino progeny, following selfing, was found to be consistent with the segregation of a single gene. One of these genes (chl1) was found to be linked to the isozyme locus Gpi-g. The frequencies of the mutants were monitored in open-pollinated seed progeny and, from this, outcrossing rates were calculated. The rate of outcrossing in the chl1 mutant tree was also determined using a multi-locus, maximum likelihood estimation based on three isozyme loci, this agreed closely with the chl1 single locus estimate. This result highlights a role for rare, easily scored, mutants in seed orchards, where they can be utilized to monitor selfing rates.

Genetic variation in susceptibility of Eucalyptus globulus coppice regrowth to shoot-feeding weevils ( Myllorhinus spp.)

Abstract: Genetic variation in damage caused by shootboring weevils Myllorhinus dentiferus (Boheman) (Coleoptera: Curculionidae) and M. bicordata (Boisduval) to juvenile coppice regrowth in a Eucalyptus globulus subsp. globulus base population in north-western Tasmania is reported. The trial contained oneyear-old coppice regrowth from trees grown from 554 open-pollinated seedlots collected from 13 races and 48 localities in the native stands throughout Tasmania and Victoria. Significant variation in susceptibility is reported between races, with the Mount Dromedary race appearing highly susceptible and the King Island race least susceptible to attack. No significant variation in damage was found between localities within races or families within localities.