3.2 Genetic diversity within populations and metapopulations
Levels of genetic diversity within populations varied among areas but were lower in the two metapopulations located in areas above the tree-line (Skåarnja 1 and 2) as compared to those in areas below the tree-line (Table S4, Figure 5, Figure S3-S7). In the above tree-line systems, heterozygosities (expected as well as observed) were always below 20 percent, while the corresponding estimates for below tree-line areas were at or above 20 percent (Table S4). The same trend was observed in the allelic diversity measures (A R,N A, and P L) where lower estimates were observed in the above tree-line systems. This difference was significant for all measures at both points in time, except for allelic richness, differing only in present samples (p-values varying between <0.001 and 0.012; Table S4).
We observe temporal fluctuations in levels of diversity within populations (clusters) and metapopulations but with no general, overall trend of increase or decrease over time for any of the five diversity measures among the 29 populations that occur at both points in time (all p>0.05; Sign test; Figure 5, Figures S3-S5; Table S5). Most striking is the pronounced decrease of genetic diversity in three out of six populations in the above tree-line metapopulations Skåarnja 1 and 2 (Figure 5, 7; Figure S3-S5; Table S5). The opposite trend is observed in e.g. metapopulation Hotagen 4 where genetic diversity is increasing in all subpopulations and significantly so in three out of seven (Figure 5, 7).