Repeated unidirectional introgression towardsPopulus balsamiferain contact zones of exotic and native poplars

Abstract

Repeated unidirectional introgression towards Populus balsamifera in contact zones of exotic and native poplarsThompson, S.L.; Lamothe, M.; Meirmans, P.G.; Périnet, P.; Isabel, N. General rightsIt is not permitted to download or to forward/distribute the text or part of it without the consent of the author(s) and/or copyright holder(s), other than for strictly personal, individual use, unless the work is under an open content license (like Creative Commons). Disclaimer/Complaints regulationsIf you believe that digital publication of certain material infringes any of your rights or (privacy) interests, please let the Library know, stating your reasons. In case of a legitimate complaint, the Library will make the material inaccessible and/or remove it from the website. Please Ask the Library: http://uba.uva.nl/en/contact, or a letter to: Library of the University of Amsterdam, Secretariat, Singel 425, 1012 WP Amsterdam, The Netherlands. You will be contacted as soon as possible. AbstractAs the evolutionary significance of hybridization is largely dictated by its extent beyond the first generation, we broadly surveyed patterns of introgression across a sympatric zone of two native poplars (Populus balsamifera, Populus deltoides) in Quebec, Canada within which European exotic Populus nigra and its hybrids have been extensively planted since the 1800s. Single nucleotide polymorphisms (SNPs) that appeared fixed within each species were characterized by DNA-sequencing pools of pure individuals. Thirty-five of these diagnostic SNPs were employed in a high-throughput assay that genotyped 635 trees of different age classes, sampled from 15 sites with various degrees of anthropogenic disturbance. The degree of admixture within sampled trees was then assessed through Bayesian clustering of genotypes. Hybrids were present in seven of the populations, with 2.4% of all sampled trees showing spontaneous admixture. Sites with hybrids were significantly more disturbed than pure stands, while hybrids comprised both immature juveniles and trees of reproductive age. All three possible F1s were detected. Advanced-generation hybrids were consistently biased towards P. balsamifera regardless of whether hybridization had occurred with P. deltoides or P. nigra. Gene exchange between P. deltoides and P. nigra was not detected beyond the F1 generation; however, detection of a trihybrid demonstrates that even this apparent reproductive isolation does not necessarily result in an evolutionary dead end. Collectively, results demonstrate the natural fertility of hybrid poplars and suggest that introduced genes could potentially affect the genetic integrity of native trees, similar to that arising from introgression between natives.

Human-induced hybridization among congeneric endemic plants on Tenerife, Canary Islands

“…Although STRUCTURE is best known for its ability to discern the number of population clusters (but see Kalinowski 2011), it can also be used as a powerful tool to detect admixture when the number of species is known in advance (Vaha and Primmer 2006;Thompson et al 2010), as is the case here. Since three species have been described we started by running the analysis with K = 3 using the AFLP data of the uniform populations only to see if the morphologically defined species were also genetically separated.…”

“…These populations contained not only putative F1 individuals that showed approximately 50 % admixture between two species, but also backcrossed individuals and even some individuals that showed admixture between all three parental species. Such complex patterns of hybridization are usually interpreted as evidence that hybridization has been going on for several generations (Lepais et al 2009;Thompson et al 2010).…”

Next-generation hybridization and introgression

“…This has been used for a range of genetic studies (for example, Tian et al, 2011). An alternative for SNP typing is the Sequenom MassARRAY platform (Hamburg, Germany), which uses single termination mix multiplexed PCR and identifies different SNPs based on their different masses (applied by Thompson et al, 2009). For phylogenetic analyses, 9000 informative SNPs were used to produce a well-supported phylogeny for the bacterial genus Brucella, with markers designed from whole genomes, with rigorous qualitycontrol checks to ensure orthology (Foster et al, 2009).…”

“…Large-scale SNP typing is already used for evolutionary model systems, such as Populus, where 35 diagnostic SNPs have been assayed for 635 individuals (Thompson et al, 2009); however, NGS will aid marker design and application for systems with no current genomic resources. Focused studies of hybrid swarms should be expanded to include samples from across a species ranges, in order to accurately assess the degree of admixture and introgression.…”

Genetic control of flowering in spotted gum, Corymbia citriodora subsp. variegata and C. maculata

“…Thompson et al 2010;Millar et al 2012), and in some groups including eucalypts and pines, this is largely attributed to weak intrinsic reproductive barriers (e.g. Ledig 1998;Potts et al 2003).…”