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).