Interactive effects of plant diversity, island size, and population size on the percentage of polymorphic loci.

<p>3a) Interactive effect of plant-species diversity (number of vascular plant species) and island size on the percentage of polymorphic loci (PLP) of <i>Lygaeus equestris</i>. 3b) Interactive effect of island size and population size on PLP of <i>L. equestris</i>.</p

Results of a general linear model on the effects of number of vascular plant species, island size, and population size of <i>Lygaeus equestris</i> on the percentage of polymorphic loci of <i>L. equestris</i>.

<p>The analysis included data from the 10 island populations from the Finnish Archipelago (<a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0094105#pone-0094105-t001" target="_blank">Table 1</a>). The degrees of freedom for all factors are 1 and 3.</p

Characteristics of the 23 study sites.

<p><i>Vincetoxicum hirundinaria</i> is the primary food-plant species of <i>Lygaeus equestris</i>. The number of plant species is the number of all vascular plant species present in the study sites excluding species from family Poaceae and genus <i>Carex</i>.</p

Plant-Species Diversity Correlates with Genetic Variation of an Oligophagous Seed Predator

<div><p>Several characteristics of habitats of herbivores and their food-plant communities, such as plant-species composition and plant quality, influence population genetics of both herbivores and their host plants. We investigated how different ecological and geographic factors affect genetic variation in and differentiation of 23 populations of the oligophagous seed predator <i>Lygaeus equestris</i> (Heteroptera) in southwestern Finland and in eastern Sweden. We tested whether genetic differentiation of the <i>L. equestris</i> populations was related to the similarity of vegetation, and whether there was more within-population genetic variation in habitats with a high number of plant species or in those with a large population of the primary food plant, <i>Vincetoxicum hirundinaria</i>. We also tested whether genetic differentiation of the populations was related to the geographic distance, and whether location of the populations on islands or on mainland, island size, or population size affected within-population genetic variation. Pairwise F_ST ranged from 0 to 0.1 indicating low to moderate genetic differentiation of populations. Differentiation increased with geographic distance between the populations, but was not related to the similarity of vegetation between the habitats. Genetic variation within the <i>L. equestris</i> populations did not increase with the population size of the primary food plant. However, the more diverse the plant community the higher was the level of genetic variation within the <i>L. equestris</i> population. Furthermore, the level of genetic variation did not vary significantly between island and mainland populations. The effect of the population size on within-population genetic variation was related to island size. Usually small populations are susceptible to loss of genetic variation, but small <i>L. equestris</i> populations on large islands seemed to maintain a relatively high level of within-population genetic variation. Our findings suggest that, in addition to geographic and species-specific ecological factors, the plant community affects population genetic structure of oligophagous herbivores.</p></div

Effect of plant-species diversity on expected heterozygosity (H_e) of <i>Lygaeus equestris</i>.

<p>Plant-species diversity was estimated as the number of vascular plant species.</p

Correlation of genetic differentiation and geographic distance among <i>Lygaeus equestris</i> populations.

<p>Genetic differentiation was estimated as pairwise F_ST.</p

Population genetic characteristics of <i>Lygaeus equestris</i>.

<p>PLP is the percentage of polymorphic loci at the 5% level, H_e is expected heterozygosity (Nei's gene diversity) under Hardy-Weinberg genotypic proportions, and S.E. (H_e) is the standard error of expected heterozygosity.</p

Feeding trials of Lygaeus equestris

Data from laboratory experiment. Data file created with Excel 2010

Results of ANOVA testing for adaptation of <i>Lygaeus equestris</i> to a novel host plant in four fitness measures.

<p>Results of ANOVA testing for adaptation of <i>Lygaeus equestris</i> to a novel host plant in four fitness measures.</p

Changes in genetic variation during the selection experiment in <i>Vincetoxicum</i> and <i>Helianthus</i> selection lines.

<p>Panels are a) expected heterozygosity <i>H</i>_e, b) observed heterozygosity <i>H</i>_o and c) allelic richness <i>A</i>_<i>r</i>. Genetic variation was measured with 14 microsatellite markers. Values are least square means (± SE).</p