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Palouse Coevolution Discussion Group We meet weekly to discuss papers and current research in coevolution. We are interested in both empirical research and theory work. The group of regular attendees includes faculty, post-docs, and graduate students from Washington State University and the University of Idaho. This is a blog based on the papers and discussions of this group. After each week's reading, I will be putting up a short post describing some of the topics that came up regarding the details of the paper.
Evolutionary change by means of Natural Selection needs a couple of things in order to happen: heritability and variation in fitness. That is, offspring need to resemble their parents at least a little (heritability) and individuals need to differ in their survival and offspring production (fitness). We’ll worry about heritability in another post, but variation is something that seems like it might be hard to maintain. Some forms of Natural Selection will reduce variation as more fit individua........ Read more »
Rouchet R, & Vorburger C. (2012) Strong Specificity in the Interaction between Parasitoids and Symbiont-Protected Hosts. Journal of Evolutionary Biology. DOI: 10.1111/j.1420-9101.2012.02608.x
Conventional wisdom suggests that pathogens and parasites are more rapidly evolving because of various reasons such as short generation time or stronger selection. Yet somehow, they have not completely won the battle against the host. Recently, a theoretical paper on coevolution in Nature caught my eye (Gilman et al., 2012). Here the authors address this paradox: “How do victim species survive and even thrive in the face of a continuous onslaught of more rapidly evolving enemies?”Instead of ........ Read more »
Gilman, R., Nuismer, S., & Jhwueng, D. (2012) Coevolution in multidimensional trait space favours escape from parasites and pathogens. Nature, 483(7389), 328-330. DOI: 10.1038/nature10853
What happens when two parasites infect the same host individual? Is the outcome similar to the Thunderdome: two parasites enter, one parasite leaves? Host-parasite interactions are rarely so simple. While a reductionist approach to understanding the interaction of a parasite or pathogen with its host may decompose the system to a single infection, nature is full of much more complex puzzles. Within the host, the battle itself raging between parasites (within-host competition) may have cascading........ Read more »
BASHEY, F., YOUNG, S., HAWLENA, H., & LIVELY, C. (2012) Spiteful interactions between sympatric natural isolates of Xenorhabdus bovienii benefit kin and reduce virulence. Journal of Evolutionary Biology, 25(3), 431-437. DOI: 10.1111/j.1420-9101.2011.02441.x
What are the evolutionary consequences of parasitesuperinfection (i.e. simultaneous infection by multiple parasites)? Whenparasites are genetically distinct, coexistence within a host generatesconflict because of limited resources. How this conflict is resolved is thesource of evolutionary research on the evolution of parasite life historytraits such as virulence, the negative effects on the host caused by infection,and transmission mode, how parasites infect a new host. The transmission modeof ........ Read more »
BEN-AMI, F., RIGAUD, T., & EBERT, D. (2011) The expression of virulence during double infections by different parasites with conflicting host exploitation and transmission strategies. Journal of Evolutionary Biology, 24(6), 1307-1316. DOI: 10.1111/j.1420-9101.2011.02264.x
Due to a ground swell of interest, we recently read Robert Ricklefs inaugural article (Ricklefs 2010) in to the National Academy of Sciences (of the United States of America) in which he proposes a new mechanistic role for parasites and pathogens to generate diversity within the tree of life. In this paper, Ricklefs (2010) distinguishes between two compartments of the ecological niche of a species: 1) the individual niche space and 2) the population niche space. He contrasts these two concepts o........ Read more »
Ricklefs, R. (2010) Inaugural Article: Evolutionary diversification, coevolution between populations and their antagonists, and the filling of niche space. Proceedings of the National Academy of Sciences, 107(4), 1265-1272. DOI: 10.1073/pnas.0913626107
Providing evidence that supports the role of parasites driving the maintenance of sex (i.e. the Red Queen hypothesis) has been a challenge ever since it was proposed. Both theoreticians and empiricists have tackled this hypothesis with vigor to mixed results. This week we read Lively (2009) which focuses on a singular effect to help build a theoretical argument for the Red Queen, density-dependent virulence. Here virulence is defined as the effect of the parasite on the host population growth........ Read more »
LIVELY, C. (2009) The maintenance of sex: host-parasite coevolution with density-dependent virulence. Journal of Evolutionary Biology, 22(10), 2086-2093. DOI: 10.1111/j.1420-9101.2009.01824.x
Recently Wolinska and Spaak (2009) provide a survey of Daphnia infections by genotype across a number of lakes in Italy and Switzerland. They present their results as empirical evidence of Red Queen dynamics in which coevolution with virulent parasites generates continued evolution. Although Van Valen (1973) originally presented a macroevolutionary argument where by reciprocal selection of hosts and their parasites generates conditions for continuous change, Bell (1982) narrowed the focus as a........ Read more »
Wolinska, J., & Spaak, P. (2009) The cost of being common: evidence from natural Daphnia populations. Evolution, 63(7), 1893-1901. DOI: 10.1111/j.1558-5646.2009.00663.x
In 2004, Otto and Nuismer published a theoretical paper on the evolution of sex where they examined a range of stereotyped models (e.g. gene-for-gene) of species interactions (both antagonistic and beneficial) that are often used by theoreticians. Their results indicated that sex and recombination were generally selected against regardless of the model of interaction given the assumptions of the quasi linkage equilibrium (QLE, in this case, weak selection and strong recombination). In their nu........ Read more »
KOUYOS, R., SALATHE, M., OTTO, S., & BONHOEFFER, S. (2009) The role of epistasis on the evolution of recombination in host–parasite coevolution. Theoretical Population Biology, 75(1), 1-13. DOI: 10.1016/j.tpb.2008.09.007
Hammerschmidt and colleagues (2009) recently published an empirical investigation of optimal host switching. Parasites that must infect multiple hosts to complete their life cycle face a complex set of challenges. One of these is determining the timing of the switch. The authors of this paper look at the trade-off involved in staying in an intermediate host so as to become larger and more fecund in the next host and the increased chance of mortality in the current host. The authors conduct t........ Read more »
Hammerschmidt, K., Koch, K., Milinski, M., Chubb, J., & Parker, G. (2009) Whe to go: Optimzation of host switching in parasites with complex life cycles. Evolution, 63(8), 1976-1986. DOI: 10.1111/j.1558-5646.2009.00687.x
Vale and Little (2009) published recent work on parasite infection variation across a temperature gradient. Specific parasite infections are often the result of genetic interactions of both the host and parasite, sometimes referred to as genotype by genotype interactions (GxG). The authors of this paper used an ideal interaction between Daphnia magna and a bacterial parasite, Pasteuria ramose. The experiment was such that they could test multiple levels on interactions. They isolated multipl........ Read more »
Vale, P., & Little, T. (2009) Measuring parasite fitness under genetic and thermal variation. Heredity. DOI: 10.1038/hdy.2009.54
This past week in Coevolvers, we dropped back into the empirical world and ready a paper from Piculell et al (2008) on evidence of selection mosaics. Selection mosaics describe a case where the fitness function of the interacting players varies across space (Gomulkiewicz et al 2007; Thompson 1999, 2005), sometimes described as GxGxE interactions (G: genetic; E: environment). What does this mean more generally? Simply put, the fitness of a plant may change from one population to the next becau........ Read more »
Piculell, B., Hoeksema, J., & Thompson, J. (2008) Interactions of biotic and abiotic environmental factors on an ectomycorrhizal symbiosis, and the potential for selection mosaics. BMC Biology, 6(1), 23. DOI: 10.1186/1741-7007-6-23
This past week in Coevolvers, we read a brand new paper in Nature from Bastolla et al (2009). The authors create a simple model to understand how network structure can lead to an increase in predicted biodiversity in a community. In this case, the authors were looking at how a network of mutualistic interactions will generally be nested. This network structure can reduce interspecific competition and allow a greater biodiversity. The nestedness of interactions in this kind of community refer........ Read more »
Bastolla, U., Fortuna, M., Pascual-García, A., Ferrera, A., Luque, B., & Bascompte, J. (2009) The architecture of mutualistic networks minimizes competition and increases biodiversity. Nature, 458(7241), 1018-1020. DOI: 10.1038/nature07950
We recently read a theory paper by Gandon and Day (2009). In this paper they describe a valuable method for dissecting how interactions between a host and parasite alter mean fitness. Their method uses an understanding built from Fisher's fundamental theorem. They partition changes in mean fitness based on three different factors: natural selection, environmental change, and mutation. We know that the rate of adaptation is going to result from the amount of genetic variance in the focal organism........ Read more »
Gandon, S., & Day, T. (2009) EVOLUTIONARY EPIDEMIOLOGY AND THE DYNAMICS OF ADAPTATION. Evolution, 63(4), 826-838. DOI: 10.1111/j.1558-5646.2009.00609.x
This week we continued along our current path of pathogen models and looked at a recent paper (Sorrell et al 2009) investigating covert infections, a common and unexplained phenomenon of some pathogens exhibiting long periods of infection where they are silent (or covert in the language of the paper). During this silent/covert stage, the infections are mostly avirulent and non-infectious. These authors extend a previous SI type model that incorporated a covert state (Boots et al 2003) to underst........ Read more »
Sorrell, I., White, A., Pedersen, A., Hails, R., & Boots, M. (2009) The evolution of covert, silent infection as a parasite strategy. Proceedings of the Royal Society B: Biological Sciences. DOI: 10.1098/rspb.2008.1915
This week the Coevolvers read a brand new paper by King et al (2009). The authors present a pathogen model that incorporates within host dynamics of pathogen growth as well as multiple forms of transmission among hosts which depend on pathogen load. The authors do motivate the study by telling us about two human disease pathogens, Bordetella pertussis and Bordetella parapertussis (which can cause whooping cough), but model is not meant to be a predictive model of future outbreaks. The main messa........ Read more »
King, A., Shrestha, S., Harvill, E., & Bjørnstad, O. (2009) Evolution of Acute Infections and the Invasion‐Persistence Trade‐Off. The American Naturalist, 173(4), 446-455. DOI: 10.1086/597217
In their recent paper, Morgan et al (2009) look at the role of an antagonistic interaction in promoting coexistence among different hosts. Using a bacteria and phage system (bacterium: Pseudomonas fluorescens and bacteriophage: SBW25Φ2), they determined that in the presence of a coevolving phage, a slower growing, but phage resistant host would persist with a susceptible faster growing host. Without the phage, the better competitor became fixed in experimental lines. This paper did not explicit........ Read more »
MORGAN, A., CRAIG MACLEAN, R., & BUCKLING, A. (2009) Effects of antagonistic coevolution on parasite-mediated host coexistence. Journal of Evolutionary Biology, 22(2), 287-292. DOI: 10.1111/j.1420-9101.2008.01642.x
This week's paper (Bordes et al 2009) looked for forces that influence the parasite diversity or parasite species richness (PSR) among mammals. While it may seem almost impossible to think that there might be a single factor, there have been many different proposed influences (e.g. body size, geographic range, population density). The host home range, "area used in daily and seasonal movements" (Bordes et al 2009), could be related to the parasite diversity in two distinct ways. T........ Read more »
In their recent paper, Vigneux et al (2008) address a classic idea in the evolution of virulence. When multiple genotypes of a parasite infect a single host, competition can influence the overall virulence. The paper is examines the interaction of relatedness and virulence. One viewpoint is that with a low level of relatedness, virulence should increase as competition among genotypes overexploits the host. Another hypothesis that the authors test is that different genotypes may engage in a "........ Read more »
VIGNEUX, F., BASHEY, F., SICARD, M., & LIVELY, C. (2008) Low migration decreases interference competition among parasites and increases virulence. Journal of Evolutionary Biology, 21(5), 1245-1251. DOI: 10.1111/j.1420-9101.2008.01576.x
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