Predator-Prey Dynamics and the Red Queen Hypothesis: Putting Limits on the Evolutionary Arms Race

AbstractThe Red Queen Hypothesis, which suggests that continual evolution can result from solely biotic interactions, has been studied in macroevolutionary and microevolutionary contexts. While microevolutionary studies have described examples in which evolution does not cease, understanding which general conditions lead to continual evolution or to stasis remains a major challenge. In many cases, it is unclear which experimental features or model assumptions are necessary for the observed continual evolution to emerge, and whether the described behavior is robust to variations in the given setup. Here, we aim to find the minimal set of conditions under which continual evolution occurs. To this end, we present a theoretical framework that does not assume any specific functional form and, therefore, can be applied to a wide variety of systems. Our framework is also general enough to cast predictions about both monomorphic and polymorphic populations. We show that the combination of a fast positive and a slow negative feedback causes continual evolution to emerge even from the evolution of one single evolving trait, provided that the ecological timescale is sufficiently separated from the timescales of mutation and the negative feedback. Our approach and results thus contribute to a deeper understanding of the evolutionary dynamics resulting from biotic interactions.

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Parasite Selection and the Fitness of Sexual Reproduction

IU Journal of Undergraduate Research ◽

10.14434/iujur.v1i1.13725 ◽

2015 ◽

Vol 1 (1) ◽

pp. 36

Author(s):

Samantha A. Klosak

Keyword(s):

Sexual Reproduction ◽

Natural Population ◽

Reproductive Mode ◽

Red Queen Hypothesis ◽

Red Queen ◽

Trematode Parasite ◽

Maintenance Of Sex ◽

Fitness Consequence ◽

Offspring Generation ◽

The Red Queen

Sexual reproduction is a very costly process: the growth rate of asexual lineages exceeds that of sexual lineages. Nonetheless, sex is prevalent in nature. The Red Queen Hypothesis argues that, because sex and recombination generate genetically variable offspring that may escape infection by coevolving parasites, parasites select for sex in hosts (Lively & Dybdahl, 2000). Our research directly tests if the Red Queen can explain the maintenance of sex in a natural population. This experiment focuses on a natural population of the snail Potamopyrgus antipodarum, which is native to New Zealand. Individuals of this species are either diploid and sexually reproducing or triploid and asexually reproducing (Lively & Osnas, 2006). This snail is naturally infected by the trematode parasite, Microphallus, which is sterilizing and thus exerts strong selection on its host. The Red Queen Hypothesis predicts that parasites should periodically increase the fitness of sexual relative to asexual individuals. We accordingly established mesocosms containing both sexual and asexual snails from the same natural population. Half of these mesocosms were exposed to parasites and the other half were not. These snails were then allowed to reproduce over the course of a year. We used flow cytometry to determine the frequency of diploids in the parents and the offspring, and thereby the fitness of sexual individuals in the presence and absence of parasites. Interestingly, we find that sexual individuals are currently more susceptible to parasites than are asexual individuals. In tanks in which sexual parents are relatively more infected, the frequency of sexual individuals declined significantly more in the offspring generation, indicating a fitness consequence of parasitism for sexual reproduction. Our findings suggest that parasite selection can indeed operate on reproductive mode. Moreover, our results are consistent with theory (King, Delph, Jokela, & Lively, 2009) and a prior field study in our system indicating that the direction of parasite selection is variable, such that parasites periodically select against sexual reproduction (Vergara, Lively, King, & Jokela, 2013). This current experiment will continue for multiple years in order to track the variation in parasite selection on sex through time.

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Exposure to parasites increases promiscuity in a freshwater snail

Biology Letters ◽

10.1098/rsbl.2013.1091 ◽

2014 ◽

Vol 10 (4) ◽

pp. 20131091 ◽

Cited By ~ 8

Author(s):

D. M. Soper ◽

K. C. King ◽

D. Vergara ◽

C. M. Lively

Keyword(s):

Genetic Variation ◽

Mating Behaviour ◽

Freshwater Snail ◽

Potamopyrgus Antipodarum ◽

Red Queen Hypothesis ◽

Red Queen ◽

Trematode Parasite ◽

Multiple Partners ◽

Males And Females ◽

The Red Queen

Under the Red Queen hypothesis, outcrossing can produce genetically variable progeny, which may be more resistant, on average, to locally adapted parasites. Mating with multiple partners may enhance this resistance by further increasing the genetic variation among offspring. We exposed Potamopyrgus antipodarum to the eggs of a sterilizing, trematode parasite and tested whether this altered mating behaviour. We found that exposure to parasites increased the number of snail mating pairs and the total number of different mating partners for both males and females. Thus, our results suggest that, in host populations under parasite-mediated selection, exposure to infective propagules increases the rate of mating and the number of mates.

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