title: The extent of hybridization and its impact on the genetic diversity and population structure of an invasive tree, Ulmus pumila (Ulmaceae).
abstract: Ulmus pumila is considered an invasive tree in 41 of the United States. In this study, we examined the extent of hybridization in naturalized populations of U. pumila, its impact on genetic diversity and genetic structure and its potential role in explaining the invasion process of U. pumila. Genetic analyses indicated widespread hybridization with native Ulmus rubra in naturalized U. pumila populations. Hybridization increased the genetic diversity of U. pumila populations and affected their genetic structure. The level of genetic diversity in 'mature' accessions, many of which may represent original plantings throughout the USA, was high and similar to the diversity of East Asian accessions. Hybridization with the native red elm may play an important role in the success of Siberian elm as an invader in temperate regions of the USA.
authors.affiliation: Department of Forest and Wildlife Ecology, University of Wisconsin Madison, WI, USA.
authors.forename: Juan E
authors.initials: JE
authors.lastname: Zalapa
authors.affiliation: USDA, Agricultural Research Service, Vegetable Crops Research Unit, Department of Entomology, University of Wisconsin Madison, WI, USA.
authors.forename: Johanne
authors.initials: J
authors.lastname: Brunet
authors.affiliation: Department of Forest and Wildlife Ecology, University of Wisconsin Madison, WI, USA.
authors.forename: Raymond P
authors.initials: RP
authors.lastname: Guries
keywords: Siberian elm; Ulmus pumila; Ulmus rubra; genetic diversity; hybridization; invasive species