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Modelling single nucleotide effects in phosphoglucose isomerase on dispersal in the Glanville fritillary butterfly: coupling of ecological and evolutionary dynamics.

Zheng C, Ovaskainen O, Hanski I - Philos. Trans. R. Soc. Lond., B, Biol. Sci. (2009)

Bottom Line: Based on empirical results for a single nucleotide polymorphism (SNP) in the phosphoglucose isomerase (Pgi) gene, we assume that dispersal rate in the landscape matrix, fecundity and survival are affected by a locus with two alleles, A and C, individuals with the C allele being more mobile.The model was successfully tested with two independent empirical datasets on spatial variation in Pgi allele frequency.Our results indicate that the strength of the coupling of the ecological and evolutionary dynamics depends on the spatial scale and is asymmetric, demographic dynamics having a greater immediate impact on genetic dynamics than vice versa.

View Article: PubMed Central - PubMed

Affiliation: Department of Biological and Environmental Sciences, University of Helsinki, Helsinki, Finland.

ABSTRACT
Dispersal comprises a complex life-history syndrome that influences the demographic dynamics of especially those species that live in fragmented landscapes, the structure of which may in turn be expected to impose selection on dispersal. We have constructed an individual-based evolutionary sexual model of dispersal for species occurring as metapopulations in habitat patch networks. The model assumes correlated random walk dispersal with edge-mediated behaviour (habitat selection) and spatially correlated stochastic local dynamics. The model is parametrized with extensive data for the Glanville fritillary butterfly. Based on empirical results for a single nucleotide polymorphism (SNP) in the phosphoglucose isomerase (Pgi) gene, we assume that dispersal rate in the landscape matrix, fecundity and survival are affected by a locus with two alleles, A and C, individuals with the C allele being more mobile. The model was successfully tested with two independent empirical datasets on spatial variation in Pgi allele frequency. First, at the level of local populations, the frequency of the C allele is the highest in newly established isolated populations and the lowest in old isolated populations. Second, at the level of sub-networks with dissimilar numbers and connectivities of patches, the frequency of C increases with decreasing network size and hence with decreasing average metapopulation size. The frequency of C is the highest in landscapes where local extinction risk is high and where there are abundant opportunities to establish new populations. Our results indicate that the strength of the coupling of the ecological and evolutionary dynamics depends on the spatial scale and is asymmetric, demographic dynamics having a greater immediate impact on genetic dynamics than vice versa.

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Histogram of FST values for all pairs of local populations. (a) Empirical results for 1995 (from Saccheri et al. 2004) and (b) a snapshot from the simulation without Pgi polymorphism are shown. FST was estimated according to Weir & Cockerham (1984).
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fig3: Histogram of FST values for all pairs of local populations. (a) Empirical results for 1995 (from Saccheri et al. 2004) and (b) a snapshot from the simulation without Pgi polymorphism are shown. FST was estimated according to Weir & Cockerham (1984).

Mentions: Assuming the set of genetic markers used in the empirical study by Saccheri et al. (2004) and the parameter values in table 1 and figure 1e,f shows the predicted molecular diversity for one allozyme and one microsatellite marker. Given the mutation rates in table 1, the allozymes have one or two alleles at quasi-equilibrium, while the microsatellites have from approximately five alleles up to the observed number of alleles (table 1; figure 1). The main discrepancy is the much lower molecular diversity in the allozymes than what was observed empirically for some of them, e.g. for pep A with 12 alleles (Saccheri et al. 2004). It is possible that the mutation rate assumed for allozymes was too small. Another possibility is that some allozymes are not neutral and that selection maintains high allelic diversity. This is most likely so for Pgi (§4b; not included as a neutral locus in the simulation), for which there were eight alleles in the dataset analysed by Saccheri et al. (2004). Figure 3 shows that the predicted isolation by distance relationship characterized by the distribution of pairwise FST values among populations matches well with the observed result. This indicates that the assumptions made on the demographic dynamics are consistent with the observed neutral genetic dynamics, and thus the model provides a well-justified baseline for examining non-neutral dynamics.


Modelling single nucleotide effects in phosphoglucose isomerase on dispersal in the Glanville fritillary butterfly: coupling of ecological and evolutionary dynamics.

Zheng C, Ovaskainen O, Hanski I - Philos. Trans. R. Soc. Lond., B, Biol. Sci. (2009)

Histogram of FST values for all pairs of local populations. (a) Empirical results for 1995 (from Saccheri et al. 2004) and (b) a snapshot from the simulation without Pgi polymorphism are shown. FST was estimated according to Weir & Cockerham (1984).
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC2690501&req=5

fig3: Histogram of FST values for all pairs of local populations. (a) Empirical results for 1995 (from Saccheri et al. 2004) and (b) a snapshot from the simulation without Pgi polymorphism are shown. FST was estimated according to Weir & Cockerham (1984).
Mentions: Assuming the set of genetic markers used in the empirical study by Saccheri et al. (2004) and the parameter values in table 1 and figure 1e,f shows the predicted molecular diversity for one allozyme and one microsatellite marker. Given the mutation rates in table 1, the allozymes have one or two alleles at quasi-equilibrium, while the microsatellites have from approximately five alleles up to the observed number of alleles (table 1; figure 1). The main discrepancy is the much lower molecular diversity in the allozymes than what was observed empirically for some of them, e.g. for pep A with 12 alleles (Saccheri et al. 2004). It is possible that the mutation rate assumed for allozymes was too small. Another possibility is that some allozymes are not neutral and that selection maintains high allelic diversity. This is most likely so for Pgi (§4b; not included as a neutral locus in the simulation), for which there were eight alleles in the dataset analysed by Saccheri et al. (2004). Figure 3 shows that the predicted isolation by distance relationship characterized by the distribution of pairwise FST values among populations matches well with the observed result. This indicates that the assumptions made on the demographic dynamics are consistent with the observed neutral genetic dynamics, and thus the model provides a well-justified baseline for examining non-neutral dynamics.

Bottom Line: Based on empirical results for a single nucleotide polymorphism (SNP) in the phosphoglucose isomerase (Pgi) gene, we assume that dispersal rate in the landscape matrix, fecundity and survival are affected by a locus with two alleles, A and C, individuals with the C allele being more mobile.The model was successfully tested with two independent empirical datasets on spatial variation in Pgi allele frequency.Our results indicate that the strength of the coupling of the ecological and evolutionary dynamics depends on the spatial scale and is asymmetric, demographic dynamics having a greater immediate impact on genetic dynamics than vice versa.

View Article: PubMed Central - PubMed

Affiliation: Department of Biological and Environmental Sciences, University of Helsinki, Helsinki, Finland.

ABSTRACT
Dispersal comprises a complex life-history syndrome that influences the demographic dynamics of especially those species that live in fragmented landscapes, the structure of which may in turn be expected to impose selection on dispersal. We have constructed an individual-based evolutionary sexual model of dispersal for species occurring as metapopulations in habitat patch networks. The model assumes correlated random walk dispersal with edge-mediated behaviour (habitat selection) and spatially correlated stochastic local dynamics. The model is parametrized with extensive data for the Glanville fritillary butterfly. Based on empirical results for a single nucleotide polymorphism (SNP) in the phosphoglucose isomerase (Pgi) gene, we assume that dispersal rate in the landscape matrix, fecundity and survival are affected by a locus with two alleles, A and C, individuals with the C allele being more mobile. The model was successfully tested with two independent empirical datasets on spatial variation in Pgi allele frequency. First, at the level of local populations, the frequency of the C allele is the highest in newly established isolated populations and the lowest in old isolated populations. Second, at the level of sub-networks with dissimilar numbers and connectivities of patches, the frequency of C increases with decreasing network size and hence with decreasing average metapopulation size. The frequency of C is the highest in landscapes where local extinction risk is high and where there are abundant opportunities to establish new populations. Our results indicate that the strength of the coupling of the ecological and evolutionary dynamics depends on the spatial scale and is asymmetric, demographic dynamics having a greater immediate impact on genetic dynamics than vice versa.

Show MeSH