Journal
AMERICAN JOURNAL OF BOTANY
Volume 100, Issue 8, Pages 1651-1662Publisher
WILEY
DOI: 10.3732/ajb.1200654
Keywords
chloroplast; climate; hybrid zone; microsatellites; mitochondria; morphology; Picea; Pinaceae; spruce
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Funding
- Forest Genetics Council of British Columbia
- Natural Sciences and Engineering Research Council of Canada (NSERC)
- NSERC Canada Graduate Scholarship
- University of British Columbia
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Premise of the study: Historic colonization and contemporary evolutionary processes contribute to patterns of genetic variation and differentiation among populations. However, separating the respective influences of these processes remains a challenge, particularly for natural hybrid zones, where standing genetic variation may result from evolutionary processes both preceding and following contact, influencing the evolutionary trajectory of hybrid populations. Where adaptation to novel environments may be facilitated by interspecific hybridization, teasing apart these processes will have practical implications for forest management in changing environments. Methods: We evaluated the neutral genetic architecture of the Picea sitchensis (Sitka spruce) x P. glauca (white spruce) hybrid zone along the Nass and Skeena river valleys in northwestern British Columbia using chloroplast, mitochondrial, and nuclear microsatellite markers, in combination with cone morphological traits. Key results: Sitka spruce mitotype capture, evidenced by this species dominating the maternal lineage, is consistent with earlier colonization of the region by Sitka spruce. This capture differs from the spatial distribution of chloroplast haplotypes, indicating pollen dispersal and its contribution to geographic structure. Genetic ancestry, based on nuclear markers, was strongly influenced by climate and geography. Highly parallel results for replicate transects along environmental gradients provide support for the bounded hybrid superiority model of hybrid zone maintenance. Conclusions: This broad-scale analysis of neutral genetic structure indicates the importance of historic and contemporary gene flow, environmental selection, and their interaction in shaping neutral genetic variation within this hybrid zone, informative to seed transfer development and reforestation for future climates.
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