Data from: Hybridization has localized effect on genetic variation in closely related pine species

Background: Hybridization is a known phenomenon in nature but its genetic
impact on populations of parental species remains less understood. We
investigated the evolutionary consequences of the interspecific gene flow
in several contact zones of closely related pine species. Using a set of
genetic markers from both nuclear and organellar genomes, we analyzed a
large panel of reference allopatric populations of parental taxa (96
stands, 2601 individuals).   Results: We observed reduced genetic
diversity in maternally transmitted mitochondrial genomes of pure pine
species and hybrids from contact zones compared to reference allopatric
populations. The distribution of mtDNA haplotypes followed geographic
rather than species boundaries. Additionally, no new haplotypes emerged in
the contact zones, instead, these zones contained the most common local
variants. However, species diverged significantly at nuclear genomes, and
populations in contact zones exhibited similar or higher genetic diversity
compared to the reference stands. There were no signs of admixture in any
allopatric population, while clear admixture was evident in the contact
zones, indicating that hybridization has a localized effect on the genetic
variation of the analyzed pine species.  Conclusions: Our results
suggest that hybrid zones act as sinks rather than melting pots of genetic
diversity. Hybridization influences sympatric populations but is confined
to contact zones. The spectrum of parental species ancestry in hybrids
reflects the old evolutionary history of the sympatric populations. These
findings also imply that introgression may play a crucial role in the
adaptation of hybrids to specific environments.