Demography of American chestnut populations: effects of a pathogen and a hyperparasite

Abstract

Summary1 Matrix models were used to evaluate the effect of chestnut blight infection on transition probabilities and population growth rates for American chestnuts. Diseasefree, epidemic and recovering (i.e. pathogen infected with a double-stranded (ds) RNA hypovirus) populations were compared. 2 Population growth rates ( λ ) did not differ significantly over time or with disease status. However, predicted stable stage distributions differed between population types, with disease-free and recovering populations more similar to each other than either was to epidemic populations. 3 Survival had the highest proportional contribution to population growth rates as revealed by elasticity analyses. However, reductions in stasis of the largest trees contributed most to reductions in population growth rate when comparing diseased with disease-free populations using LTRE. 4 The presence of hypovirus reduces pathogen virulence, allowing individual American chestnut trees to increase in size. Where dsRNA has spread, chestnut populations in Michigan have attained population dynamics similar to those found in disease-free populations. 5 Matrix models and life table response experiments can be used to detect important pathogen-mediated changes in the dynamics of host populations.

Consequences of Shifts in Abundance and Distribution of American Chestnut for Restoration of a Foundation Forest Tree

“…We observed 84% of the population in the seedling size classes for contemporary C. dentata populations. This proportion is larger than the 73% of the population reported in the seedling class for mature stands of American chestnut in Michigan [19]. Indeed, our number is much closer to the 81% reported by Davleos and Jarosz [19] for populations in Michigan that were experiencing an epidemic of blight.…”

“…This proportion is larger than the 73% of the population reported in the seedling class for mature stands of American chestnut in Michigan [19]. Indeed, our number is much closer to the 81% reported by Davleos and Jarosz [19] for populations in Michigan that were experiencing an epidemic of blight. This comparison indicates that C. dentata is still experiencing the blight epidemic throughout its range and that the proportion of trees in the seedling size class is likely much higher than in historical populations.…”

“…Many of the populations we document to the west of the original range, particularly those in Wisconsin and Michigan, are known translocations [23,24]. These populations were often initially started through plantings that spread through natural reproduction, though some populations in Michigan may also have been initiated without human assistance [19].…”

An evolutionary ecology perspective to address forest pathology challenges of today and tomorrow

“…The best studied examples of hyperparasites of fungi are hypovirulent viruses, which decrease the virulence of their fungal hosts [e.g., Cryphonectria Hypovirus1 (CHV1) infecting the chestnut blight fungus and Dutch elm fungi O. ulmi and O. novo-ulmi]. Their role in the regulation of diseases has been established (Davelos and Jarosz 2004;Springer et al 2013;Swinton and Gilligan 1999). Insights gained in CHV1 ecology (phenotypic and genetic diversity, transmission and evolution), which is used for biocontrol in chestnut orchards (Grente 1981) could help to improve biocontrol strategies.…”

THE SIZE OF Araucaria angustifolia (Bertol.) Kuntze ENTERING INTO REPRODUCTIVE STAGES AS A BASIS FOR SEED MANAGEMENT PROJECTS

“…Furthermore, this information could contribute to conservation studies, for example, by projecting population growth using matrices. For example, the work of Davelos and Jarosz (2004), who created transition matrices using just height and d.b.h. size classes.…”