Post-glacial biogeography of trembling aspen inferred from habitat models and genetic variance in quantitative traits

Chen Ding,Stefan G Schreiber,Andreas Hamann,David R Roberts,Jean S Brouard

doi:10.1038/s41598-017-04871-7

Chen Ding, Stefan G Schreiber + Show 3 more

Open Access

PDF Available

https://doi.org/10.1038/s41598-017-04871-7

Copy DOI

Export

Save

Cite

Journal: Scientific Reports	Publication Date: Jul 5, 2017
Citations: 15	License type: open-access

Affiliation: University of Alberta

Abstract
Highlights/Summary
Full-Text PDF
Similar Papers

Abstract

Listen

Using species distribution models and information on genetic structure and within-population variance observed in a series of common garden trials, we reconstructed a historical biogeography of trembling aspen in North America. We used an ensemble classifier modelling approach (RandomForest) to reconstruct palaeoclimatic habitat for the periods 21,000, 14,000, 11,000 and 6,000 years before present. Genetic structure and diversity in quantitative traits was evaluated in common garden trials with 43 aspen collections ranging from Minnesota to northern British Columbia. Our main goals were to examine potential recolonisation routes for aspen from southwestern, eastern and Beringian glacial refugia. We further examined if any refugium had stable habitat conditions where aspen clones may have survived multiple glaciations. Our palaeoclimatic habitat reconstructions indicate that aspen may have recolonised boreal Canada and Alaska from refugia in the eastern United States, with separate southwestern refugia for the Rocky Mountain regions. This is further supported by a southeast to northwest gradient of decreasing genetic variance in quantitative traits, a likely result of repeated founder effects. Stable habitat where aspen clones may have survived multiple glaciations was predicted in Mexico and the eastern United States, but not in the west where some of the largest aspen clones have been documented.

Highlights

Trembling aspen (Populus tremuloides Michx.) is the most frequent and genetically diverse forest tree in North America, occupying many ecological site types from Mexico to Alaska in the west, and across Canada and the United States to the Atlantic ocean in the east[1,2,3]
Because aspen clones may have persisted for thousands of years, any adaptational lag relative to current environments may provide additional clues as to what climate conditions they have experienced in the past and what migration direction would be consistent with the observed lag
The modelled Alaska refugium was very small with a low-probability of presence, the possibility of aspen recolonisation from the north should not be excluded based on habitat reconstructions alone

Summary

Introduction

Trembling aspen (Populus tremuloides Michx.) is the most frequent and genetically diverse forest tree in North America, occupying many ecological site types from Mexico to Alaska in the west, and across Canada and the United States to the Atlantic ocean in the east[1,2,3]. In the eastern United States, the average clone size has been estimated to be approximately 0.04 ha, with exceptional individuals reaching 14 ha[4, 9, 10]. In a recent range-wide study of genetic structure and diversity based on microsatellite markers, Callahan, et al.[20] identified a pronounced geographic differentiation into a genetically more diverse northern cluster (Alaska, Canada, northeastern US) and a slightly less diverse southwestern cluster (western US and Mexico) while showing no evidence of higher genetic diversity in Alberta. Due to different rates and mechanisms of mutations in isozyme versus microsatellite marker systems the outlined results may not be contradictory[14, 23]

Methods

Results

Conclusion