Data from: Population genetic structure of Picea engelmannii, P. glauca and their previously unrecognized hybrids in the central Rocky Mountains

Areas of geographic overlap between potentially hybridizing species
provide the opportunity to study interspecific gene flow and reproductive
barriers. Here we identified hybrids between Picea engelmannii and P.
glauca by their genetic composition at 17 microsatellite markers, and
determined the broad-scale geographic distribution of hybrids in the
central Rocky Mountains of North America, a geographic region where
hybrids and isolation between species had not previously been studied.
Parameter estimates from admixture models revealed considerable variation
in ancestry within and among collection sites, suggesting that within this
area of geographic overlap, the interaction of the two species varies
extensively. The results document a previously unrecognized patchy
distribution of hybrids between P. engelmannii and P. glauca, including
locations where hybrids were not known or expected to exist. Further, the
ancestry of many hybrids was consistent with multiple generations of
hybridization, with probable directional backcrossing to P. engelmannii,
suggesting a relatively porous species boundary. The identification and
characterization of hybridization between these spruce in this region
raises the question of what factors maintain barriers to gene flow in
these long-lived forest trees. The current research lays the groundwork
for future study of the ecological and evolutionary contexts of their
hybridization, as well as of differential introgression and permeability
of species boundaries.