Host mating system and the prevalence of disease in a plant population

Abstract

A modified susceptible-infected-recovered (SIR) host-pathogen model is used to determine the influence of plant mating system on the outcome of a host-pathogen interaction. Unlike previous models describing how interactions between mating system and pathogen infection affect individual fitness, this model considers the potential consequences of varying mating systems on the prevalence of resistance alleles and disease within the population. If a single allele for disease resistance is sufficient to confer complete resistance in an individual and if both homozygote and heterozygote resistant individuals have the same mean birth and death rates, then, for any parameter set, the selfing rate does not affect the proportions of resistant, susceptible or infected individuals at equilibrium. If homozygote and heterozygote individual birth rates differ, however, the mating system can make a difference in these proportions. In that case, depending on other parameters, increased selfing can either increase or decrease the rate of infection in the population. Results from this model also predict higher frequencies of resistance alleles in predominantly selfing compared to predominantly outcrossing populations for most model conditions. In populations that have higher selfing rates, the resistance alleles are concentrated in homozygotes, whereas in more outcrossing populations, there are more resistant heterozygotes.

Plant sex and the evolution of plant defenses against herbivores

“…We therefore predict that our results portray a general phenomenon, and we expect that plant mating systems associated with reduced sex will frequently result in the evolution of increased susceptibility to generalist herbivores (but see ref. 20), whereas the effects of plant sex on specialist herbivores will likely be more complex. These macroevolutionary predictions complement microevolutionary studies that show that plants derived from self-fertilized seeds can experience decreased resistance and tolerance to herbivores, presumably because of increased homozygosity of deleterious mutations (47)(48)(49).…”

“…The importance of parasites for the maintenance of sexual reproduction has been well established (16)(17)(18), but the consequences of different plant reproductive systems for the evolution of defense has received little attention (15,19,20). Reproductive mode may be particularly relevant to flowering plants, which exhibit a near continuum in sexual systems, from self-incompatible species with high effective recombination rates to species that produce seeds asexually (21,22).…”

The Role of Natural Enemies in the Expression and Evolution of Mixed Mating in Hermaphroditic Plants and Animals

“…Greater understanding of the genetics underlying the victim–enemy interaction may help to explain the neutral and negative responses; theory finds that when victim–enemy interactions are controlled by interactions between specific resistance and virulence genes (e.g. gene‐for‐gene interactions), inbreeding does not necessarily alter resistance (Koslow and DeAngelis 2006). Although empirical support for selfing increasing victim infection or attack rate are not conclusive, there is evidence in at least some systems that the probability or severity of infection or attack may differ among inbred and outbred individuals or among populations with different levels of inbreeding.…”

Analyses between Reproductive Behavior, Genetic Diversity and Pythium Responsiveness in Zingiber spp. Reveal an Adaptive Significance for Hemiclonality

“…Similarly, little is known about how the population genetic structure of a host species influences disease dynamics in natural conditions, because in evolutionary arms race pathogen competes not with species as a whole, but with populations, which are spatially structured and experience selection mosaics (Forde et al, 2004; Laine, 2006). Also, relatively little is understood about the contributions of different breeding strategy on population fitness, although breeding behavior is indicated to have a role in the emergence and fixation of resistance traits in natural populations (Rice, 2002; Koslow and DeAngelis, 2006; Campbell and Kessler, 2013). Occurrence of clonal lineages that are more adaptive than sexual lineages are reported in certain species (Peck et al, 1998; Johnson et al, 2010) rendering it difficult to explain the survival and the adaptive fitness of genetically narrow asexuals solely on the basis of existing theories of sex.…”