Red brome (Bromus rubens subsp. madritensis) in North America: possible modes for early introductions, subsequent spread

Abstract

Although invasions by exotic plants have increased dramatically as human travel and commerce have increased, few have been comprehensively described. Understanding the patterns of invasive species' spread over space and time will help guide management activities and policy. Tracing the earliest appearances of an exotic plant reveals likely sites of introduction, paving the way for genetic studies to quantify founder events and identify potential source populations. Red brome (Bromus madritensis subsp. rubens) is a Mediterranean winter annual grass that has invaded even relatively undisturbed areas of western North America, where it threatens native plant communities. This study used herbarium records and contemporary published accounts to trace the early introductions and subsequent spread of red brome in western North America. The results challenge the most frequently cited sources describing the early history of this grass and suggest three possible modes for early introductions: the California

North American History of Two Invasive Plant Species: Phytogeographic Distribution, Dispersal Vectors, and Multiple Introductions

“…Also, absence of evidence (i.e., no collection in a political unit) does not translate to evidence of absence. Despite these biases, herbarium records have been used to define conservation needs (MacDougall et al 1998), document species changes (Willis and Moat 2003), and recreate species invasions at various spatial scales (Stuckey 1980;Reznicek and Catling 1987;Pysek 1991;Pysek and Prach 1995;Toney et al 1998;Lambrinos 2001;Huebner 2003;Salo 2005). The probability of an individual being collected is dependent on the number of collectors in the field, which is a function of the population density of the area.…”

Restoration handbook for sagebrush steppe ecosystems with emphasis on greater sage-grouse habitat—Part 1. Concepts for understanding and applying restoration

“…At low elevations, non-native annual grasses, such as cheatgrass (downy brome, Bromus tectorum), medusahead, (Taeniatherum caput-medusae), and red brome (Bromus rubens), were introduced into the Intermountain West during the late 1800s and have continued to spread throughout the region (Mack, 1981;Salo, 2005). The combination of land uses degrading native plant diversity and the characteristics that provide a competitive advantage toward these annual grasses have led to their dominance on many of the more arid lands in the region (Harris, 1967;Melgoza and others, 1990;Knapp, 1996).…”

Variation in the establishment of a non-native annual grass influences competitive interactions with Mojave Desert perennials

“…Keywords Creosote bush AE Galleta grass AE Indian ricegrass AE Invasive species AE Plant competition Introduction Non-native annual grasses have threatened arid plant communities in western North America since their introduction and subsequent expansion during the past century (Mack 1981;Billings 1990;Vitousek 1990;D'Antonio and Vitousek 1992;Salo 2005). In the Mojave Desert, abundant shoot production coincides with above-average winter and spring rainfall (Hunter 1991).…”

“…The range and abundance of Bromus madritensis ssp. rubens (red brome) are well documented: this non-native annual grass species is now widespread throughout the Mojave Desert (Beatley 1966;Hunter 1991;Brooks 1999a;DeFalco et al 2001;Salo 2005) and can comprise a large proportion of the total annual plant production (Beatley 1969;Hunter 1991;Brooks 2000;DeFalco et al 2001). Yet, its effect, defined as the percapita or per-biomass influence on native species, is poorly understood.…”