Biomedical subjects

Brad M Potts

Publications and source records attributed to Brad M Potts.

8 recordsLinked to original sources

PubMed2006

A framework for community and ecosystem genetics: from genes to ecosystems.

Can heritable traits in a single species affect an entire ecosystem? Recent studies show that such traits in a common tree have predictable effects on community structure and ecosystem processes. Because these 'community and ecosystem phenotypes' have a genetic basis and are heritable, we can begin to apply the principles of population and quantitative genetics to place the study of complex communities and ecosystems within an evolutionary framework. This framework could allow us to understand, for the first time, the genetic basis of ecosystem processes, and the effect of such phenomena as climate change and introduced transgenic organisms on entire communities.

Animals↗

PubMed2005

Genomic research in Eucalyptus.

Eucalyptus L'Hérit. is a genus comprised of more than 700 species that is of vital importance ecologically to Australia and to the forestry industry world-wide, being grown in plantations for the production of solid wood products as well as pulp for paper. With the sequencing of the genomes of Arabidopsis thaliana and Oryza sativa and the recent completion of the first tree genome sequence, Populus trichocarpa, attention has turned to the current status of genomic research in Eucalyptus. For several eucalypt species, large segregating families have been established, high-resolution genetic maps constructed and large EST databases generated. Collaborative efforts have been initiated for the integration of diverse genomic projects and will provide the framework for future research including exploiting the sequence of the entire eucalypt genome which is currently being sequenced. This review summarises the current position of genomic research in Eucalyptus and discusses the direction of future research.

Agriculture↗

PubMed2005

Inheritance of resistance to mammalian herbivores and of plant defensive chemistry in an Eucalyptus species.

Hybridization in plants provides an opportunity to investigate the patterns of inheritance of hybrid resistance to herbivores, and of the plant mechanisms conferring this resistance such as plant secondary metabolites. We investigated how inter-race differences in resistance of Eucalyptus globulus to a generalist mammalian herbivore, Trichosurus vulpecula, are inherited in their Fl hybrids. We assessed browsing damage of 3-year-old trees in a common environment field trial on four hybrid types of known progeny. The progeny were artificial intra-race crosses and reciprocal inter-race F1 hybrids of two geographically distinct populations (races) of E. globulus north-eastern Tasmania and south-eastern Tasmania. Populations of trees from north-eastern Tasmania are relatively susceptible to browsing by T. vulpecula, while populations from south-eastern Tasmania are more resistant. We assessed the preferences of these trees in a series of paired feeding trials with captive animals to test the field trial results and also investigated the patterns of inheritance of plant secondary metabolites. Our results demonstrated that the phenotypic expression of resistance of the inter-race Fl hybrids supported the additive pattern of inheritance, as these hybrids were intermediate in resistance compared to the pure parental hybrids. The expression of plant secondary metabolites in the Fl hybrids varied among major groups of individual compounds. The most common pattern supported was dominance towards one of the parental types. Together, condensed tannins and essential oils appeared to explain the observed patterns of resistance among the four hybrid types. While both chemical groups were inherited in a dominant manner in the inter-race Fl hybrids, the direction of dominance was opposite. Their combined concentration, however, was inherited in an additive manner, consistent with the phenotypic differences in browsing.

Animals↗

PubMed2005

Inheritance of resistance to mammalian herbivores and of plant defensive chemistry in a Eucalyptus species.

Hybridization in plants provides an opportunity to investigate the patterns of inheritance of hybrid resistance to herbivores, and of the plant mechanisms conferring this resistance such as plant secondary metabolites. We investigated how inter-race differences in resistance of Eucalyptus globulus to a generalist mammalian herbivore, Trichosurus vulpecula, are inherited in their F1 hybrids. We assessed browsing damage of three-year-old trees in a common environment field trial on four hybrid types of known progeny. The progency were artificial intra-race crosses and reciprocal inter-race F1 hybrids of two geographically distinct populations (races) of E. globulus; north-eastern Tasmania and south-eastern Tasmania. Populations of trees from north-eastern Tasmania are relatively susceptible to browsing by T. vulpecula, while populations from south-eastern Tasmania are more resistant. We assessed the preferences of these trees in a series of paired feeding trials with captive animals to test the field trial results and also investigated the patterns of inheritance of plant secondary metabolites. Our results demonstrated that the phenotypic expression of resistance of the inter-race F1 hybrids supported the additive pattern of inheritance, as these hybrids were intermediate in resistance compared to the pure parental hybrids. The expression of plant secondary metabolites in the F1 hybrids varied among groups of individual compounds. The most common pattern supported was dominance towards one of the parental types. Together, condensed tannins and essential oils appeared to explain the observed patterns of resistance among the four hybrid types. While both chemical groups were inherited in a dominant manner in the inter-race F1 hybrids, the direction of dominance was opposite. Their combined concentration, however, was inherited in an additive manner, consistent with the phenotypic differences in browsing.

Animals↗

PubMed2004

Effects of nutrient variability on the genetic-based resistance of Eucalyptus globulus to a mammalian herbivore and on plant defensive chemistry.

Plant resistance to herbivores can be influenced not only by the independent effects of plant genotype and environmental variation, but by interactions between the two. The main aim of this study was to assess the effects of environmental variability (nutrient treatment) on the known genetic-based expression of resistance and defensive chemistry of Eucalyptus globulus to browsing by the generalist mammalian herbivore Trichosurus vulpecula. In a captive feeding trial, we measured intake of seedlings from one relatively resistant (Blue Gum Hill) and one relatively susceptible (St Helens) population of E. globulus grown under two nutrient treatments (no fertiliser, plus fertiliser). There was a significant genotypexfertiliser interaction effect on intake of E. globulus foliage by T. vulpecula, and the predicted genetic-based resistance of the two populations was expressed only for the non-fertilised treatment. Expression of resistance largely reflected the combined and inverse effects of nitrogen and condensed tannin concentrations. The expression of plant secondary metabolite concentration differed between compounds, but in all cases the effects of plant genotype and fertiliser treatment were independent. The formylated phloroglucinol compounds differed significantly between genotypes but not between fertiliser treatments. In contrast, the effect of plant genotype on the expression of condensed tannins was weak but they were significantly reduced by fertiliser. Essential oils were influenced by both plant genotype and fertiliser treatment and were significantly higher in the fertilised seedlings than in the non-fertilised seedlings. This study highlights interactive effects of plant genotype and environment in influencing the phenotypic expression of resistance in a eucalypt species to a mammalian browser. It also demonstrates that this interactive effect is the net result of independent effects of genotype and environment on plant chemistry and finally, that different groups of compounds within a plant can respond very differently to variation in environmental conditions.

Adaptation, Physiological↗

PubMed2004

Glacial refugia and reticulate evolution: the case of the Tasmanian eucalypts.

Tasmania is a natural laboratory for investigating the evolutionary processes of the Quaternary. It is a large island lying 40-44 degrees S, which was repeatedly glaciated and linked to southeastern continental Australia during the Quaternary. Climate change promoted both the isolation of species in glacial refugia, and an exchange between Tasmanian and mainland floras. Eucalyptus is a complex and diverse genus, which has increased in abundance in Australia over the past 100 kyr, probably in response to higher fire frequency. Morphological evidence suggests that gene flow may have occurred between many eucalypt species after changes in their distribution during the Quaternary. This paper summarizes recent genetic evidence for migration and introgressive hybridization in Tasmanian Eucalyptus. Maternally inherited chloroplast DNA reveals a long-term persistence of eucalypts in southeastern Tasmanian refugia, coupled with introgressive hybridization involving many species. Detailed analysis of the widespread species Eucalyptus globulus suggests that migration from mainland Australia was followed by introgression involving a rare Tasmanian endemic. The data support the hypothesis that changes in distribution of interfertile species during the Quaternary have promoted reticulate evolution in Eucalyptus.

Climate↗

PubMed2004

The rare silver gum, Eucalyptus cordata, is leaving its trace in the organellar gene pool of Eucalyptus globulus.

The process of genetic assimilation of rare species by hybridizing congeners has been documented in a number of plant genera. This raises the possibility that some of the genetic diversity found in phylogeographical studies of widespread species has been acquired through hybridization with species that are now rare or extinct. In this fine-scale phylogeographical analysis, we show that a rare eucalypt species is leaving its trace in the chloroplast genome of a more abundant congener. The heart-leafed silver gum, Eucalyptus cordata, is a rare endemic of south-eastern Tasmania. Its populations are scattered amidst populations of more abundant related species, including the Tasmanian blue gum, Eucalyptus globulus. Using 339 samples from across the full range of both species, we compared chloroplast (cp) DNA haplotype phylogeography in E. globulus and E. cordata. The genealogy and distribution of chloroplast haplotypes suggest that E. globulus has acquired cpDNA from E. cordata in at least four different mixed populations. Shared haplotypes are highest in E. globulus sampled within 2 km of known E. cordata populations and drop to zero at a distance of 25 km from the nearest known E. cordata population. Localized haplotype sharing occurs in the absence of obvious hybrid zones or locally shared nuclear ribosomal DNA sequences. Given that the future loss of E. cordata from some mixed populations is likely, these findings indicate that phylogeographical analyses of organellar DNA should consider the possibility of introgression, even from species that have been eliminated from the sites of interest.

Base Sequence↗

PubMed2003

Additive and non-additive genetic parameters from clonally replicated and seedling progenies of Eucalyptus globulus.

The first estimates of the importance of epistatic effects within Eucalyptus globulus were obtained from analysis of clonally replicated full-sib progeny tests grown in Portugal. Parents comprised diverse selections from the Portuguese landrace. Variance components were estimated for 4-year-old diameter growth and pilodyn penetration, an indirect measure of wood density, both key traits in the pulpwood breeding objective. The experimental components of variance were used to estimate heritabilities and proportions of the phenotypic variance due to dominance and epistasis. The additive variance was the only significant genetic component affecting either diameter or pilodyn. Estimates of the additive, dominance and epistatic effects accounted for 8-10%, 0-4% and 0.4% of the phenotypic variance in diameter, and for 11-17%, 0% and 5% of the phenotypic variance in pilodyn, respectively. A comparison of residual coefficients of variation within seedling and cloned progenies indicated that C effects within clones were not a serious source of random variability. Despite the test sites encompassing a diverse range of locations, no important genotype by environment interaction was detected. The results suggested that an improvement strategy combining both recurrent selection for additive genetic merit and clonal testing may be adequate for optimizing genetic gains from this genetic base.

Analysis of Variance↗