Fig 1.
Locations of sampling with indication of ploidy level.
A solid line indicates the southern limit of the area of A. millefolium. Within this area, dotted lines delimit the areas where the species is absent. The two points in South Iberia represent the most probable localities where the species currently grows (see “Plant material” for details). Base map from Natural Earth (http://www.naturalearthdata.com/).
Table 1.
Populations of Achillea millefolium investigated in the present study.
K: chromosome count; S: stomatal size. Altitudes are expressed in meters above sea level.
Fig 2.
Selected metaphases of the four ploidy levels.
A) Diploid plate with 2n = 18 (pop. Gi1); B) Hexaploid plate with 2n = 54 (pop. Sa2); C) Octoploid plate with 2n = 72 (pop. Cs1); D) Tetraploid plate with 2n = 36 (pop. Pa1). Scale bar = 10 μm
Table 2.
Main parameters of genetic diversity for the 26 populations surveyed and the four ploidy levels of Spanish A. millefolium.
N, number of individuals; k, total number of alleles; Na, mean number of alleles; Ne, number of effective alleles; PA, number of private alleles; uh, unbiased diversity. For abbreviations of populations, see Table 1.
Table 3.
Nei’s unbiased genetic distance (D) is shown below diagonal and values for population genetic differentiation (ΦPT) are shown above diagonal. For abbreviations of populations, see Table 1. *P<0.05.
Table 4.
Nei’s unbiased genetic distance (D) is shown below diagonal and values for genetic differentiation (ΦPT) are shown above diagonal. *P<0.05.
Fig 3.
a) Ln P(D), mean (±standard deviation) of log-likelihood values for each value of K = 1–15 (10 independent runs per K).
b) Mean absolute difference of the second order rate of change with respect to K (ΔK, following [44]). Most supported K value: K = 3.
Fig 4.
Percentage assignment of each individual (represented by vertical bars) to each of the three genetic clusters (represented by different colours) inferred by the program Structure [43].
See Table 1 for population codes.
Fig 5.
Screening for the most likely number of groups (K) with non-hierarchical K-means clustering [45], performed with 100000 independent runs for each value of K.
The runs maximising ΔK values were initially considered as optimal (K = 7 and K = 12), and because K = 12 added little gain to ΔK, we kept K = 7 as the optimal final value.
Fig 6.
Percentage of individuals that belong to each of the seven genetic clusters (represented by different colours) inferred by the nonhierarchical K-means clustering analysis [46].
Each vertical column corresponds to a population. See Table 1 for population codes.
Fig 7.
Principal component analysis performed from pairwise Nei’s genetic distances between populations.
Orange asterisk: 2x; blue star: 4x; pink diamond: 6x; green dot: 8x. See Table 1 for population codes.
Fig 8.
Mantel test correlating geographic distance and genetic distance.
Results of the IBD test searching for a correlation between geographic distance and genetic distance.