Résumé
Dispersal is important for determining both a species ecological
processes, such as population viability, and its evolutionary processes,
like gene flow and local adaptation. Yet obtaining accurate estimates in
the wild through direct observation can be challenging or even impossible,
particularly over large spatial and temporal scales. Genotyping many
individuals from wild populations can provide detailed inferences about
dispersal. We therefore utilized genomewide marker data to estimate
dispersal in the classic metapopulation of the Glanville fritillary
butterfly (Melitaea cinxia L.), in the Åland Islands in SW Finland. This
is an ideal system to test the effectiveness of this approach due to the
wealth of information already available covering dispersal across small
spatial and temporal scales, but lack of information at larger spatial and
temporal scales. We sampled three larvae per larval family group from
3,732 groups over a six-year period and genotyped for 272 SNPs across the
genome. We used this empirical dataset to reconstruct cases where
full-sibs were detected in different local populations to infer female
effective dispersal distance, i.e. dispersal events directly contributing
to gene flow. On average this was one kilometer, closely matching previous
dispersal estimates made using direct observation. To evaluate our power
to detect full-sib families we performed forward simulations using an
individual-based model constructed and parameterized for the Glanville
fritillary metapopulation. Using these simulations 100% of predicted
full-sibs were correct and over 98% of all true full-sib pairs were
detected. We therefore demonstrate that even in a highly dynamic system
with a relatively small number of markers, we can accurately reconstruct
full-sib families and for the first time make inferences on female
effective dispersal. This highlights the utility of this approach in
systems where it has previously been impossible to obtain accurate
estimates of dispersal over both ecological and evolutionary scales.