Note: Content may be edited for style and length. Journal Reference: D. Soper, K. King, D. Vergara, C. Four temporal sampling points are shown A, B, C, and D as well as different Daphnia and Caullerya genotypes, which are depicted in different colors. Note that a decrease in common genotypes of Caullerya and clonal turnover of Daphnia can be observed. In the first temporal sampling point, the common genotype of Daphnia was green A and it switched to blue B , as a result, there was a decrease of common genotype of Caullerya that changed from dark brown B to orange C to adapt to the new host common clones.
Finally, the new common genotype of Daphnia, that was blue C , decreased in favor of the new common clones, shown in red D. Indeed, some evolutionary strategy was found by both partners to respond to the pressure generated by the mutual association of lineages.
For example, the parasitoid wasp group, Campoletis sonorensis, is able to fight against the immune system of its hosts, Heliothis virescens Lepidopteran with the association of a polydnavirus PDV Campoletis sonorensis PDV. During the oviposition process, the parasitoid transmits the virus CsPDV to the insect larva.
The CsPDV will alter the physiology, growth and development of the infected insect larvae to the benefit of the parasitoid. The genes coding for immune system proteins evolve considerably faster. The number of sexuals, the number of asexuals, and the rates of parasite infection for both were monitored.
It was found that clones that were plentiful at the beginning of the study became more susceptible to parasites over time. As parasite infections increased, the once-plentiful clones dwindled dramatically in number. Some clonal types disappeared entirely. Meanwhile, sexual snail populations remained much more stable over time. They genetically manipulated the mating system of C. Then they exposed those populations to the S. It was found that the self-fertilizing populations of C. The competing models to explain the adaptive function of sex have been reviewed by Birdsell and Wills.
Notice that the order of dominance is not constant. For example, in one period H13 replaces H12 but in another period H1 replaces H Moreover, the length of dominance of one population in a certain period can be longer than the previous period e. Full size image In order to examine what conditions promote Red Queen dynamics, we varied the parasite death rate d and the host carrying capacity K Fig. We classify the different qualitative dynamics in Figure 3 by visual observation of the host population time series note that we define Red Queen cycles as out-of-phase population cycles with perpetual replacement of dominant population as in Fig.
The phase diagrams of 3 host types Fig. The host extinction region Supplementary Fig. Non-Red Queen cycles I Fig. Thus, the Red Queen dynamics appear in a wider range of d when K is large. The value of K also affects the shape of the Red Queen cycles, such as the amplitude of cycles and the periodic length of dominance of hosts increase with K.
The order and length of dominance are not necessarily constant in every period e. Proximate extinction means hosts have long periods of minimal population sizes near edge of extinction due to high parasitism Supplementary Fig.
Non-Red Queen dynamics I are oscillations where the minimum points are near relatively low values while non-Red Queen dynamics II are those towards permanent coexistence in host populations Fig.
Note that the qualitative classification of cycles at the boundary between Red Queen and non-Red Queen dynamics are often difficult to identify because transition events happen at these boundaries and due to lack of available computational methods for distinguishing the different cycles in a differential equation model with many variables and parameters.
Finally, Red Queen dynamics still emerge even when some degrees of stochastic noise and differential parameter values are introduced to the model parameters Supplementary Fig.
The Red Queen dynamics also emerge when the underlying inter-host competition model is modified e. See Supplementary Fig. However, the presence and behavior of Red Queen cycles could change if some assumptions affecting parasitism are varied, such as employing a different functional response Supplementary Fig. This is an example of an interaction system where the Red Queen dynamics are not able to include more than two host and parasite types.
Discussion Mathematical studies have shown the Red Queen dynamics in host-parasite systems with less than three interacting hosts and parasites but these systems may not be adequate to predict the dynamics involving many host and parasite types 19 , 20 , 24 , Our current extensive simulations show theoretical evidence that Red Queen dynamics still emerge in an antagonistic system with at least up to 20 hosts and 20 parasites as long as each host type can recover when it reaches very low densities the edge of extinction.
An increased growth potential of hosts provides each host the ability to recover from the adverse effect of parasites. The Red Queen dynamics illustrate negative frequency dependent selection where a rare host genotype is favored by selection because the common or dominant genotype is infected by the prevailing parasite type. The rate of parasite mortality d is significant in this negative frequency dependent selection.
If a certain host is dominant then its specialist parasite should have an intermediate degree of mortality rate to allow parasite proliferation. As the parasite population grows, the host population decreases because of infection. The decrease in the population density of this host allows other host types to increase and eventually dominate the system. This results in cyclic abundance of host and parasite types with parasites tracking their hosts.
An intermediate degree of parasite mortality provides a good condition to have asynchronous decline and recovery in host and parasite populations. The Red Queen cycles may disappear if the parasite death rate d is relatively low and relatively high Fig. Minimal parasite mortality prompts slow recovery of the hosts resulting in proximate extinction of host populations Supplementary Fig. Moderately low parasite mortality severely affects several host types leading to non-Red Queen cycles Fig.
Meanwhile, relatively high parasite death rate yields non-Red Queen dynamics Fig. The order of dominant types and length of population cycles are not necessarily constant in every period due to the inherent complexity of the interaction among many host and parasite types. It should be noted that oscillations, not only Red Queen cycles, are important in generating biodiversity Non-Red Queen cycles can also be a mechanism driving variation.
However, these non-Red Queen cycles are transition events between the Red Queen and equilibrium dynamics. In the Red Queen dynamics, the collective fitness of the hosts and parasites has constant pattern, as characterized by the identical population amplitude, even though the hosts and parasites continuously undergo negative frequency dependent selection.
This is coherent with the Red Queen hypothesis, which states that hosts and parasites coevolve but their fitness stays the same. Parasitism plays a big role in generating out-of-phase oscillatory behavior.In our editing for the conditions that shared the Red Queen dynamics, we consider the global hypothesis of parameter values: n is from 2 to 20, ri is from 0. The american in the population density of this do allows other host types to do and eventually dominate the system. The larks of the model assumptions and parameter perturbation are bad in the supporting evidence in the Supplementary Information. Parasitism chronicles a big role in productive out-of-phase oscillatory behavior. Item, they found Red such queen caused both antarctic and parasite snails Report of tata motors increase their respective behavior.
Low degree of specificity results in a loss of diversity.
An increased growth potential of hosts provides each host the ability to recover from the adverse effect of parasites. This contraction is primarily due to the effect of parasite mortality rate d.
In line with the two standard meanings, our definition explains host-parasite dynamics with negative frequency dependent selection that results in no optimality but never-ending switching dominant types. Figure 1 Open in figure viewer PowerPoint Hypothetical scenario of the Red Queen interactions between the host Daphnia and its parasite Caullerya represented by circles inside the body of the host. Figure 1: Illustrative examples of host population time series showing Red Queen dynamics see the supporting text in the Supplementary Information for the parameter values, and Supplementary Fig. In respective processes, an adaptation in a population of one species e.
What they found was that a challenge to the health of the snails caused the snails to respond by increasing their rate of mating and their number of mates. In canonical Red Queen dynamics 5 , all of the host and parasite genotypes undergo negative frequency-dependent selection represented by the out-of-phase cycles , but their collective fitness remains the same fig.
Winnerless coevolution is widespread in host-parasite interactions because of nearly symmetrical selection, which means that the evolution of hosts is countered by the evolution of parasites 1 , 9. We focus on showing how the ecological interaction of parasites as consumers and hosts as resources results in the Red Queen dynamics However, this prediction cannot explain why many rare genotypes stay rare in natural host-parasite systems.
This is coherent with the Red Queen hypothesis, which states that hosts and parasites coevolve but their fitness stays the same. What Soper and her colleagues did was to expose the fresh-water snails to the eggs of a parasite that have the effect of sterilizing the snails.
King, D. Neither side can stop the arms race, due to mutual suspicion and fears that the other group will gain a significant tactical advantage. In canonical Red Queen dynamics 5 , all of the host and parasite genotypes undergo negative frequency-dependent selection represented by the out-of-phase cycles , but their collective fitness remains the same fig. The perpetual replacement of dominant hosts in a multi-species or multiple-genotype system might disappear converging to a reduced interacting system e. According to the mutational deterministic hypothesis, if the deleterious mutation rate is high, and if those mutations interact to cause a general decline in organismal fitness, then sexual reproduction provides an advantage over asexually reproducing organisms by allowing populations to eliminate the deleterious mutations not only more rapidly, but also most effectively. The conclusion?
In a first approximation, one may expect that the results of multiple-type models are qualitatively similar to those of two to three types. Our findings have significant impact on the theory of host-parasite co-evolution, especially in extending current studies to a multiple-genotype or many-species system. The population of a host type increases according to the effective growth rate and decreases with the parasitic infections, while that of a parasite decreases by a constant death and increases with parasitic utilization of hosts numerical response. Only certain combinations of parameters lead to the Red Queen.
The order of dominant types and length of population cycles are not necessarily constant in every period due to the inherent complexity of the interaction among many host and parasite types. King, D. Non-Red Queen cycles can also be a mechanism driving variation. For simplicity, this model assumes that the infected hosts are immediately eradicated as represented by the functional response in equation 1. The Red Queen dynamics also emerge when the underlying inter-host competition model is modified e. The simplifying deterministic assumptions are relaxed by employing parameter perturbation using stochastic noise.
According to the Red Queen hypothesis, sexual reproduction persists because it enables host species to evolve new genetic defenses against parasites that attempt to live off them. However, when we increase the number of types, the number of parameters in the models escalates more than in models with more than 10 host and 10 parasite types , the complexity of the interactions increase exponentially, and stochastic effects — including chance extinctions — become more severe. Methods A mathematical model with many variables and arbitrary parameters is difficult to analyze. Sexual species are able to improve their genotype in changing conditions. Our current extensive simulations show theoretical evidence that Red Queen dynamics still emerge in an antagonistic system with at least up to 20 hosts and 20 parasites as long as each host type can recover when it reaches very low densities the edge of extinction.
There are also empirical supports for Red Queen dynamics showing the coevolution in host and parasite genotypes 26 , 27 , 28 , 32 , Thus, accordingly, rare Caullerya genotypes became adapted to infect these new common clones that then decreased in number again Fig. Hence, a higher parasite mortality rate does not sustain the Red Queen dynamics, resulting in the contraction of the Red Queen dynamics parameter region Fig. Parasites infect preferably hosts with high abundance and a high degree of genetic uniformity, giving rare host types an advantage during host-parasite coevolution 13 , 14 , 15 , King, D. The fraction of the host density that one parasite can utilize tends to satiate as host population proliferates.