Effects of watersheds and geographi

Effects of watersheds and geographical distances on
population genetic structure
We first asked whether geographically close sampling sites also
cluster genetically. Because genetic divergence within species is
large (see Results section), methods based on Hardy-Weinberg
equilibrium, e.g. Structure [47], are not appropriate. We therefore
constructed Neighbour Joining population trees using programs
from the PHYLIP package. Note that we use the trees only for
identification of higher-level clusters based on genetic similarities,
and do not make phylogenetic inferences. We used distance
matrices (Cavalli-Sforza chord distances) to create trees separately
for the two species (each analysis including one population of the