Trees bearing novel or exotic gene components are poised to contribute to the bioeconomy for a variety of purposes such as bioenergy production, phytoremediation, and carbon sequestration within the forestry sector, but sustainable release of trees with novel traits in large-scale plantations requires the quantification of risks posed to native tree populations. Over the last century, exotic hybrid poplars produced through artificial crosses were planted throughout eastern Canada as ornamentals or windbreaks and these exotics provide a proxy by which to examine the fitness of exotic poplar traits within the natural environment to assess risk of exotic gene escape, establishment, and spread into native gene pools. We assessed postzygotic fitness traits of native and exotic poplars within a naturally regenerated stand in eastern Canada (Quebec City, QC). Pure natives (P. balsamifera and P. deltoides spp. deltoides), native hybrids (P. deltoides × P. balsamifera), and exotic hybrids (trees bearing Populus nigra and P. maximowiczii genetic components) were screened for reproductive biomass, yield, seed germination, and fungal disease susceptibility. Exotic hybrids expressed fitness traits intermediate to pure species and were not significantly different from native hybrids. They formed fully viable seed and backcrossed predominantly with P. balsamifera. These data show that exotic hybrids were not unfit and were capable of establishing and competing within the native stand. Future research will seek to examine the impact of exotic gene regions on associated biotic communities to fully quantify the risk exotic poplars pose to native poplar forests.
Usage Notes:
R code for fitness trait analyses
This file contains the commented R code for all the fitness trait analyses performed in the manuscript.
All analyses_submit.R
Tree characteristics
This file contains the tree genotype, age, height, and diameter at breast height.
Stand_TreeData.csv
Biomass and yield fitness traits
This file contains the biomass and yield traits measured for trees in this study. The biomass traits are: total catkin biomass, total seed biomass, 100 seed biomass, capsule biomass, stem biomass, and cotton biomass.
Biomass.csv
Germination
This file contains germination fitness data measured for each tree: germination success and number of abnormal germinants.
Disease Susceptibility
This file contains the results from controlled inoculations of three Melampsora species on poplars of known genotypes. Fitness was measured as the number of uredia per square centimeter.
Inoculations.csv
Genotype data
This file contains the genotype data for all trees examined in this study. The data have been formated for input into Structure for admixture analysis.
BPSF_CompletePopRef_Structure.txt