The Epidemiology and Evolution of Symbionts with Mixed-Mode Transmission

  title={The Epidemiology and Evolution of Symbionts with Mixed-Mode Transmission},
  author={Dieter Ebert},
  journal={Annual Review of Ecology, Evolution, and Systematics},
  • D. Ebert
  • Published 25 November 2013
  • Biology
  • Annual Review of Ecology, Evolution, and Systematics
Vertical and horizontal transmission are terms that describe the transfer of symbionts from parents to offspring and among unrelated hosts, respectively. Many symbionts, including parasites, pathogens, mutualists, and microbiota, use a combination of both strategies, known as mixed-mode transmission (MMT). Here I review what is known about the evolution, ecology, and epidemiology of symbionts with MMT and compare MMT with our expectations for single-mode strategies. Symbionts with MMT are… 

Tables from this paper

Transmission mode is associated with environment type and taxa across bacteria-eukaryote symbioses
Estimated rates for each symbiotic transmission mode were calculated, revealing bias for horizontal transmission in the ocean and vertical transmission on land and barriers exist that reduce the rate of these events.
Mode and Fidelity of Bacterial Symbiont Transmission and Its Impact on Symbiont Genome Evolution
This work supports the existence of mixed transmission modes in symbiotic associations and indicates they have distinct consequences for symbiont evolution.
Hitchhiking of host biology by beneficial symbionts enhances transmission
The mechanistic basis for the recruitment of the beneficial bacterium, Aeromonas veronii by the leech, Hirudo verbana is determined, and it is demonstrated that host mucosal secretions complement imperfect symbiont vertical transmission.
Transmission mode is associated with environment type and taxa across bacteria-eukaryote symbioses: a systematic review and meta-analysis
  • S. Russell
  • Environmental Science
    FEMS microbiology letters
  • 2019
Data from the literature on bacteria-multicellular eukaryote associations for which transmission mode data was available was compiled, suggesting that many vertically transmitted bacteria are capable of mixed mode transmission and barriers exist that reduce the rate of horizontal transmission events.
Factors Affecting Transmission Mode Evolution in Symbioses
Three aspects of transmission evolution are investigated, including how symbionts that are transmitted from parent to offspring and between unrelated individuals are predicted to evolve to benefit their hosts and intermediate virulence that maximizes their ability to infect new hosts.
The evolution of transmission mode
Research on the evolutionary mechanisms leading to different transmission modes, including changes in transmission associated with host shifts and with evolution of the unusually complex life cycles of many parasites, is reviewed.
Molecular causes of an evolutionary shift along the parasitism–mutualism continuum in a bacterial symbiont
It is shown that a dramatic shift in the frequency of genetic variants, coupled with major changes in gene expression, allow the symbiont to alter its position in the parasitism–mutualism continuum depending on the mode of between-host transmission.
Interplay between Endophyte Prevalence, Effects and Transmission: Insights from a Natural Grass Population
A demographic population modeling approach was used to identify the mechanisms operating in a natural stand of an intermediate population of the native grass Festuca eskia, and showed that a positive benefit of the endophyte and vertical transmission rates of about 0.6 could lead to the coexistence of symbiotic and non-symbiotic F. esKia plants.
Evolution of transmission mode in conditional mutualisms with spatial variation in symbiont quality
This work modeled transmission evolution in symbionts, which evolved high horizontal and vertical transmission, indicating a possible host-symbiont conflict over transmission mode and suggests an eco-evolutionary feedback where the component of host fitness that a conditionally mutualistic symbiont influences affects its distribution in the population.
The role of hyperparasitism in microbial pathogen ecology and evolution
It is argued that the diversity and dynamics of micro-hyperparasites are an important component of natural host–pathogen systems and will shed light on many aspects of microbial ecology and disease biology, including resistance–virulence evolution, apparent competition, epidemiology and ecosystem stability.


Symbiont survival and host-symbiont disequilibria under differential vertical transmission.
Analytical and numerical investigation of the effects of host genetic heterogeneity in the rate of vertical transmission of a symbiont shows that simple evolutionary forces can create substantial nonrandom associations between two species.
Diversification of Transmission Modes and the Evolution of Mutualism
This article investigates how symbionts’ transmission mode and virulence should evolve, depending on the relationship between these two traits, and shows that the force that stabilizes mutualism in such situations is the competition for transmission between symbiont.
Transmission Modes and Evolution of the Parasitism‐Mutualism Continuum a
  • P. Ewald
  • Biology
    Annals of the New York Academy of Sciences
  • 1987
This framework drawing attention to the need for detailed reviews of relationships between transmission modes and the nature of symbiotic interactions, and experimental manipulations of transmission, and the hypothesized severity of vector-borne and waterborne transmission.
A Gene’s‐Eye View of Symbiont Transmission
It is shown that SGEs are in fact consistent with the transmission mode hypothesis if one measures transmission from the perspective of host genes instead of host organisms, and gene‐centered perspective is presented, applicable to symbioses at all levels of selection.
The evolution of uniparental transmission of fungal symbionts in fungus-growing termites (Macrotermitinae)
In Microtermes bellicosus and Macrotermitinae horizontal transmission is the ancestral state with two independent origins to uniparental, vertical transmission, whereas in fungus-growing ants where unip Children'siosis is the rule, despite this fundamental difference both groups evolved a similar symbiosis that is probably the key for their ecological success.
A shift to parasitism in the jellyfish symbiont Symbiodinium microadriaticum
  • Joel L. Sachs, T. Wilcox
  • Biology, Environmental Science
    Proceedings of the Royal Society B: Biological Sciences
  • 2005
The dynamic nature of this symbiosis is demonstrated and the potential ease with which beneficial symbionts can evolve into parasites is illustrated, as a trade-off was detected between harm caused to hosts and symbiont fitness.
Ectoparasite virulence is linked to mode of transmission
  • D. Clayton, D. Tompkins
  • Biology
    Proceedings of the Royal Society of London. Series B: Biological Sciences
  • 1994
Compared the virulence of lice and mites infesting a single group of captive rock doves, results support the hypothesis that ectoparasite virulence is linked to the mode of transmission.
The tradeoff hypothesis, which predicts that the density of uninfected hosts in the environment should determine the optimum balance between modes of parasite transmission, and evolutionary predictions using conjugative plasmids and the bacteria that they infect are tested.
Virulence and transmission modes of two microsporidia in Daphnia magna
It is shown that horizontal and vertical transmission contribute additively to a parasite's ability to invade and persist and only very low transmission probabilities per host-to-host contact are necessary for the persistence of parasites occurring in large populations such as those commonly found for Daphnia.