Competition, Cooperation Among Kin, and Virulence in Multiple Infections

Abstract

3 Both authors contributed equally to this work.

Bacterial cooperation controlled by mobile elements: kin selection versus infectivity

“…We do not deny that altruism among pathogens could evolve by kin selection and there are examples (Koskella et al, 2006;Buckling et al, 2007;Lopez-Villavicencio et al, 2007, 2011. It may well even be that infectivity evolves via kin selection in toxin-producing bacteria, but we contend that the lines of evidence brought in the paper of Rankin et al (2010) and Nogueira et al (2009) are far from sufficient to be conclusive.…”

Influence of Multiple Infection and Relatedness on Virulence: Disease Dynamics in an Experimental Plant Population and Its Castrating Parasite

“…The fungus overwinters in the rosette and strains likely compete to gain access to meristems that will produce flowers in which the fungus sporulates and from which it then disperses [28]. Diseased flowers are sterile, so the main component of virulence for this castrating parasite can readily be estimated as percentage of castrated branches [29]. Other virulence components include mortality and lack of recovery, leading to permanent sterilization.…”

“…Thus we know that multiple infections are common in natural populations, with different, related genotypes occupying different stems but never the same flower [37]. Experimental inoculations can also generate multiple infections [29], [32], [37]–[39]; sequential inoculation experiments reveal selective competitive exclusion: resident strains often exclude a challenging unrelated genotype while multiple infections are facilitated when genotypes are closely related [40].…”

“…Plants were inoculated with different combinations of fungal genotypes differing in their degree of relatedness and additional natural transmission occurred in the garden. We have previously analyzed and published data from the first two years of this experiment, on the establishment of disease and patterns of multiple infections [29]. We reported that 1) strains that coexisted within plants were highly related, indeed far more related than the originally inoculated spore mixtures, and that less related fungal strains were more likely to be lost from multiple infections over the course of the first winter than were more closely related ones, suggesting exclusion of less related strains, 2) fungal strains in multiple infections restricted each others access to territory within the plant, but this restriction was less severe when strains were closely related, implying competitive exclusion that is moderated by high relatedness, and 3) per-flower spore production was greater from plants harboring multiple infections than from those with single infections, implying that multiple infections induced greater conversion of host resources to parasite propagules.…”

“…Here we present data on annual disease dynamics, mortality and recovery from disease over the entire lifespan of the population. Indeed, though mortality was too low to be analyzed in the first two years of the experiment [29], all the plants had died within six years, allowing us to compare annual mortality between infected and healthy plants and those with single or multiple infections.…”