Résumé
Genetic datasets can be used to date evolutionary events, even on recent
time scales if sufficient data are available. We used statistics
calculated from multilocus microsatellite datasets to estimate population
ages in data generated through coalescent simulations and in samples from
populations of known age in a metapopulation of Daphnia magna in Finland.
Our simulation results show that age estimates improve with additional
loci and define a time frame over which these statistics are most useful.
On the most recent time scales, assumptions regarding the model of
mutation (infinite sites vs. stepwise mutation) have little influence on
estimated ages. In older populations, size homoplasy among microsatellite
alleles results in a downwards bias for estimates based on the infinite
sites model. In the Finnish D. magna metapopulation, our genetically
derived estimated ages were biased upwards. Potential sources of this bias
include: the underlying model of mutation, gene flow, founder size, and
the possibility of persistent source populations in the system. Our
simulated data show that genetic age estimation is possible, even for very
young populations, but our empirical data highlight the importance of
factors such as migration and founding size when these statistics are
applied in natural populations.