Abstract Detail

Biogeography

Touchette, Lyne [1], Godbout, Julie [2], Lamothe, Manuel [3], Isabel, Nathalie [3], Porth, Ilga [1].

The mystery of North American shrub birches: from researchers to detectives.

Birches (Betula spp.) are an important component of the tundra and forest ecosystems of the northern hemisphere. In North America, more than ten species of this genus have been recorded in temperate and boreal forests and in arctic regions. The genus is also characterized by frequent hybridization and introgression phenomena. Dwarf birch (Betula glandulosa) occupies tundra and boreal territories of North America. The ecosystems in which this shrub grows are already being impacted by climate change (CC), and unlike other species which face range contraction, increases in temperature observed in northern Canada and Alaska are instead contributing to the expansion of dwarf birch. To date, B. glandulosa remains understudied at the genetic level and uncertainties persist regarding its taxonomy and relationship with other birch species. The objective of our project was to use a genomic approach to study the genetic structure and connectivity of B. glandulosa populations within its North American range. Range-wide sampling was carried out by several teams given the vast distribution area of B. glandulosa. Over 500 samples presumed to be B. glandulosa were sampled (leaves; buds) and resequenced for 478 specific genomic regions (yielding > 5,000 SNPs) with a Fluidigm® Access Array System. Since morphological characteristics of dwarf birch are highly similar to those of several other shrub birch species, making it difficult to recognize B. glandulosa in the field, we first aimed at identifying ‘intruders’ in our collection. Further, we used nuclear and chloroplast DNA markers to explore the genetic structure, and also examined the ploidy level of each individual based on the distribution of allelic ratios at heterozygous sites. Overall, five genetic groups were identified through clustering analyses. Furthermore, diploid and polyploid individuals were detected in the sampling. The observed genetic differences (ploidy level, genetic clusters, chlorotypes, etc.) revealed the possible presence of at least three different sampled species with similar morphological traits and interspecific hybrids. Finally, we detected two genetic clusters within the B. glandulosa species in North America: an eastern cluster and a western cluster. These two groups may correspond to two different glacial lineages. Comparison of the nuclear and chloroplast data highlighted a long history of gene exchange between the different taxa and lineages identified. Results of this project should contribute to improve our understanding of the adaptation strategies of dwarf birch in a context of climatic upheaval.

1 - Laval University, Department of Wood and Forest Sciences, 2405 Rue de la Terrasse, Quebec, QC, G1V 0A6, Canada
2 - Ministère des Forêts, de la Faune et des Parcs, Direction de la recherche forestière, 2700 Rue Einstein, Quebec, QC, G1P 3W8, Canada
3 - Natural Resources Canada, Canadian Forest Service, 1055 Rue du Peps, C.P. 10380, succ. Sainte-Foy, Quebec, QC, G1V 4C7, Canada

Keywords:
Betula glandulosa
genomics
biogeography
shrub
North American birches
nuclear DNA
chloroplast DNA
ploidy level.

Presentation Type: Oral Paper
Number: BIOG I008
Abstract ID:97
Candidate for Awards:None