Data from: Growth gains from selective breeding in a spruce hybrid zone do not compromise local adaptation to climate

Hybrid zones contain extensive standing genetic variation that facilitates
rapid responses to selection. The Picea glauca x P. engelmannii hybrid
zone in western Canada is the focus of tree breeding programs that
annually produce ~90 million reforestation seedlings. Understanding the
direct and indirect effects of selective breeding on adaptive variation is
necessary to implement assisted gene flow polices in Alberta and British
Columbia that match these seedlings with future climates. We decomposed
relationships among hybrid ancestry, adaptive traits and climate to
understand the implications of selective breeding for climate adaptations
and assisted gene flow strategies. The effects of selection on
associations among hybrid index estimated from ~6500 SNPs, adaptive
traits, and provenance climates were assessed for ~2400 common garden
seedlings. Hybrid index differences between natural and selected seedlings
within breeding zones were small in Alberta (average +2%), but larger and
more variable in BC (average -7 %, range -24% to +1%), slightly favoring
P. glauca ancestry. The average height growth gain of selected seedlings
over natural seedlings within breeding zones was 36% (range 12% to 86%).
Clines in growth with temperature-related variables were strong, but
differed little between selected and natural populations. Seedling hybrid
index and growth trait associations with evapotranspiration-related
climate variables were stronger in selected than in natural seedlings,
indicating possible pre-adaptation to drier future climates. Associations
among cold hardiness, hybrid ancestry and cold-related climate variables
dominated signals of local adaptation that were preserved in breeding
populations. Strong hybrid ancestry-phenotype-climate associations suggest
that assisted gene flow will be necessary to match interior spruce
breeding populations with shifting future climates. The absence of
antagonistic selection responses among traits and maintenance of cold
adaptation in selected seedlings suggests breeding populations can be
safely redeployed using assisted gene flow prescriptions similar to those
of natural populations.