title: Fitness dynamics within a poplar hybrid zone: II. Impact of exotic sex on native poplars in an urban jungle.
abstract: 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.
authors: Natural Resources Canada, Canadian Forest Service Québec, Québec, Canada ; Natural Resources Canada, Canadian Forest Service Sault Ste. Marie, Ontario, Canada.
authors: Amanda D
authors: AD
authors: Roe
authors: Natural Resources Canada, Canadian Forest Service Sault Ste. Marie, Ontario, Canada.
authors: Chris Jk
authors: CJ
authors: MacQuarrie
authors: Natural Resources Canada, Canadian Forest Service Québec, Québec, Canada.
authors: Marie-Claude
authors: MC
authors: Gros-Louis
authors: Natural Resources Canada, Canadian Forest Service Fredericton, New-Brunswick, Canada.
authors: J Dale
authors: JD
authors: Simpson
authors: Natural Resources Canada, Canadian Forest Service Sault Ste. Marie, Ontario, Canada.
authors: Josyanne
authors: J
authors: Lamarche
authors: Natural Resources Canada, Canadian Forest Service Fredericton, New-Brunswick, Canada.
authors: Tannis
authors: T
authors: Beardmore
authors: Natural Resources Canada, Canadian Forest Service Québec, Québec, Canada ; Umeå University, Department of Ecology and Environmental Science, Umeå Plant Science Centre Umeå, Sweden.
authors: Stacey L
authors: SL
authors: Thompson
authors: Natural Resources Canada, Canadian Forest Service Québec, Québec, Canada.
authors: Philippe
authors: P
authors: Tanguay
authors: Natural Resources Canada, Canadian Forest Service Québec, Québec, Canada.
authors: Nathalie
authors: N
authors: Isabel
keywords: Anthropogenic disturbance; Populus; SNP genotyping; disease susceptibility; hybridization; postzygotic fitness; urban–forest interface