Genetic data analysis == Genalex6.2 [34] was used to calculate observed heterozygosity, expected heterozygosity, fixation index, quantity of alleles, the Shannon index ELN484228 of allelic diversity and pairwiseF-statistics between populations. strongly reducing genetic variation and increasing genetic differentiation in small populations. To our surprise, differentiation between the growing populations was smaller when they coevolved with parasites, suggesting parallel managing selection. Hence, our results experimentally vindicate Haldane’s unique hypothesis 60 years after its conception. Keywords:hostparasite coevolution, genetic variation, Reddish Queen hypothesis, natural selection == 1. Intro == The persistence of high genetic ELN484228 variability in natural populations is a classical evolutionary puzzle because the majority of evolutionary forces, such as drift [1,2] and directional selection [35], reduce genetic variability. Haldane [6] suggested that selection by pathogens might be important in maintaining genetic variance in populations. Theoretical support for this hypothesis comes from models of antagonistic hostparasite coevolution, where a sponsor population is kept inside a genotypically varied state through the effects of time-lagged negative-frequency-dependent selection [7,8]. If this happens in spatially separated populations, variations in local selection patterns can potentially lead to quick sponsor human population divergence, while keeping allelic diversity on a metapopulation level [911]. With this soul, Haldane also suggested that parasites facilitate the speciation of their hosts [6]. Whereas theory is definitely well developed, direct experimental evidence for the hypothesis that antagonistic coevolution can preserve genotypic diversity in populations is definitely virtually absent [10]. On the other hand, there is ample evidence for the importance of genetic variation in the defence against parasites [1219]. For example, it has been shown the rate of recurrence of sexuals correlates positively with illness prevalence [20], that social insect colonies with a low genetic diversity showed a higher infection intensity than colonies with a high diversity [21] and that infectedDaphniapopulations show a higher clonal diversity than non-parasitized populations [22]. Furthermore, sponsor resistance is generally based on a few loci [23], but there is also good evidence for any complex genetic architecture of resistance, with strong effects of epistasis between loci, primarily those on different chromosomes [24,25]. Hence, it is expected that the effects of parasite-mediated selection on sponsor genetics may work on genome-wide diversity and are not restricted to confined parts of the genome [23,2628]. To experimentally test Haldane’s hypothesis that selection by parasites maintains genotypic diversity in host populations, we set up a coevolution experiment using the Reddish Flour Beetle (Tribolium castaneum) and its natural specific microsporidian parasiteNosema whitei[29,30]. To assess whether selection by coevolving parasites might override the effects of genetic drift, we included populace size as an additional factor, and we statement the results after 12 discrete generations of coevolution. We have previously shown that under these conditions, both host and parasite populations coevolve with one another [31]. Here, we specifically asked: (i) is usually genetic diversity of host populations higher when coevolving with parasites than under control conditions? (ii) How strong is this effect relative to genetic drift? (iii) Does selection by parasites lead to divergent evolution as expected from your postulate of local adaptation [11,32]? That is, do coevolving populations diverge more from each other than control populations? == 2. Material and methods == == (a). Experimental evolution regime == To increase genetic variability, we first crossed different pairs of stock lines that have been kept under standard conditions for Rabbit Polyclonal to OR4L1 over 50 generations [24,31]. Populace crosses were carried out as explained in [31] and the resulting fully hybrid F1adults ELN484228 were pooled as the starting breeder population of the line. A total of eight such populations were used to form eight experimental lines [31]. Each experimental collection was subsequently divided into two lines of small populace size (n= 50) and two lines of large populace size (n= 500). One of these two lines for each populace size was assigned to the coevolution treatment and subjected to selection by coevolvingN. whitei. The remaining lines (for both small and large populace size) were assigned to the respective control treatment, i.e. were kept on standard medium free of parasites. Thus, the total of eight lines two populace sizes two treatments = 32 populations represented eight different genetic backgrounds,.