Abstract Detail

Hybrids and Hybridization

Wolf, Diana [1], Bowser, Matthew [2], Takebayashi, Naoki [3], Magness, Dawn [2], Morton, John [2].

The role of hybridization in the expansion of Sitka spruce onto Alaska’s Kenai peninsula.

Populations can respond to a changing climate by adapting, migrating, or going extinct. Hybridization may play an important role in these processes.
Lutz spruce (Picea X lutzii Little) is a natural hybrid between continental white spruce (P. glauca (Moench) Voss) and maritime Sitka spruce (P. sitchensis (Bong.) Carr.). The two species hybridize where their habitats contact each other in northern British Columbia, Canada, and on the Kenai Peninsula in southcentral Alaska. Our study investigates hybridization between white and Sitka spruce on the Kenai Peninsula.
We used STRUCTURE analyses of chloroplast and mitochondrial DNA sequence data and (presumably) nuclear microsatellite data to determine the genomic makeup of spruce trees in the western Kenai lowlands. Surprisingly, mitochondrial ancestry was quite different from that of chloroplast and microsatellites. Almost all (99.5%) individuals have mitochondrial genomes that are derived from white spruce, whereas chloroplast and microsatellite data show a mix of white and sitka genomes. Microsatellites indicate that the majority of individuals had predominantly white spruce ancestry (72%), while some had predominantly Sitka spruce ancestry (14%), and some appear to be hybrids (15%; 20-80% white spruce in their genomes). Almost all (98%) of the individuals classified as hybrids or as Sitka spruce using microsatellites have white spruce mitochondria and Sitka spruce chloroplast genotypes. Also, some individuals classified as white spruce using microsatellites have Sitka spruce chloroplast genotypes. Since spruce mitochondria are maternally inherited and chloroplasts are paternally inherited, it appears that white spruce were the ancestral seed parents of nearly all spruce trees in the western Kenai lowlands, while Sitka spruce alleles originate from pollen.
Pollen records show that white spruce colonized the western Kenai Lowland from refugia shortly after the glaciers retreated ~8,500 YBP, whereas Sitka spruce arrived on the eastern Kenai peninsula more recently, ~4,000 YBP after migrating up the Pacific coast. Our data suggest that spread of Sitka spruce into the western Kenai lowlands and/or up the Pacific coast may have occurred not via seed dispersal, but by long distance dispersal of windborne Sitka pollen and hybridization with established white spruce populations. By contrast, Lutz spruce in Southeast Alaska formed when white spruce migrated westward from British Columbia into an established Sitka spruce forest along the coast. Hybridization appears to be an important mechanism allowing Sitka spruce to expand its range in response to climate change.

1 - University Of Alaska Fairbanks, Institute Of Arctic Biology, 2140 Koyukuk Drive, PO Box 757000, Fairbanks, AK, 99775, United States
2 - US Fish and Wildlife Service, Kenai National Wildlife Refuge, P.O. Box 2139, Soldotna, AK, 99669, USA
3 - University Of Alaska Fairbanks, Institute Of Arctic Biology, 2140 Koyukuk Dr., 311 Irving I Bldg, IAB, Fairbanks, AK, 99775, United States

Sitka spruce
Picea sitchensis
White spruce
Picea glauca
Lutz spruce
Picea X lutzii
Kenai Lowlands
climate change
Range expansion
chloroplast capture
mitochondrial capture.

Presentation Type: Oral Paper
Number: HH1004
Abstract ID:947
Candidate for Awards:None

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