Sarah H. Reichard

Predicting Invasions of Woody Plants Introduced into North America

Plant species continue to be introduced in North America for various purposes. If the trend continues, it is probable that some will escape cultivation and become invasive in native ecosystems. We present a retrospective analysis of several structural, life history, and biogeographical attributes of woody plants introduced in North America to determine which traits characterize species that have and have not invaded. Predictive models derived from discriminant analysis correctly classified 86.2% of the species in cross‐validation, whereas those derived from classification and regression trees classified 76% correctly. From these models we created a hierarchical predictive tree that allows the user to divide species into three categories: admit (low risk of invasiveness), deny admission (high risk of invasiveness), or delay admission for further analyses and/or monitor intensively (risk cannot adequately be assessed based on only the included attributes). We recommend that species that are highly invasive elsewhere not be allowed into the U.S. and that a more conservative introduction policy using a hierarchical predictive method be employed.

Biological invasions: recommendations for U.S. policy and management.

The Ecological Society of America has evaluated current U.S. national policies and practices on biological invasions in light of current scientific knowledge. Invasions by harmful nonnative species are increasing in number and area affected; the damages to ecosystems, economic activity, and human welfare are accumulating. Without improved strategies based on recent scientific advances and increased investments to counter invasions, harm from invasive species is likely to accelerate. Federal leadership, with the cooperation of state and local governments, is required to increase the effectiveness of prevention of invasions, detect and respond quickly to new potentially harmful invasions, control and slow the spread of existing invasions, and provide a national center to ensure that these efforts are coordinated and cost effective. Specifically, the Ecological Society of America recommends that the federal government take the following six actions: (1) Use new information and practices to better manage commercial and other pathways to reduce the transport and release of potentially harmful species; (2) Adopt more quantitative procedures for risk analysis and apply them to every species proposed for importation into the country; (3) Use new cost-effective diagnostic technologies to increase active surveillance and sharing of information about invasive species so that responses to new invasions can be more rapid and effective; (4) Create new legal authority and provide emergency funding to support rapid responses to emerging invasions; (5) Provide funding and incentives for cost-effective programs to slow the spread of existing invasive species in order to protect still uninvaded ecosystems, social and industrial infrastructure, and human welfare; and (6) Establish a National Center for Invasive Species Management (under the existing National Invasive Species Council) to coordinate and lead improvements in federal, state, and international policies on invasive species. Recent scientific and technical advances provide a sound basis for more cost-effective national responses to invasive species. Greater investments in improved technology and management practices would be more than repaid by reduced damages from current and future invasive species. The Ecological Society of America is committed to assist all levels of government and provide scientific advice to improve all aspects of invasive-species management.

Horticulture as a Pathway of Invasive Plant Introductions in the United States

Abstract There must have been plenty of them about, growing up quietly and inoffensively, with nobody taking any particular notice of them…. And so the one in our garden continued its growth peacefully, as did thousands like it in neglected spots all over the world…. It was some little time later that the first one picked up its roots and walked. John Wyndham, The Day of the Triffids

Current practice in the use of subspecies, variety, and forma in the classification of wild plants

Summary Hamilton, C. W. & Reichard, S. H.: Current practice in the use of subspecies, variety, and forma in the classification of wild plants. - Taxon 41: 485-498. 1992. - ISSN 0040-0262. Infraspecific classification of plants continues to be practiced commonly by taxonomists: c. 8 % of species monographed in 26 major journals and series during the period 1987-1990 were subdivided. Of those, c. 42 % were divided into subspecies only, 52 %o into varieties, 3 % into formae, and 3 % into taxa of more than one level. Subspecies and varieties are usually defined as requiring some integrity - geographic, ecologic, and/or phylogenetic beyond the morphological. Despite some attempts to differentiate between subspecies and variety, they are largely equivalent in practice. European taxonomists tend to favor subspecies, whereas their counterparts in the United States usually employ variety. Formae usually are defined as lacking any extramorphological integrity. Given the general inconsistency of practice found, it is imperative that more authors state briefly their philosophy of infraspecific taxonomy so their classifications may be interpreted more clearly. Taxonomists collectively should promote greater standardization of infraspecific classification.

Critical Issues in Invasion Biology for Conservation Science

Modern conservation biology had its origins in the management of game species and later of rare species, focusing attention on understanding the biological origins and causes of population decline, rarity, and endangerment. But while anthropogenic global change has resulted in the decline of some species, others have thrived and proliferated, accompanied by sometimes dramatic impacts on both single populations and whole ecosystems (Office of Technology Assessment 1993). Although some have long recognized invasive, non-native species as a force capable of irreversibly transforming the natural world (Elton 1958; Baker 1965), these scientists were in large part acting in isolation from those doing traditional conservation biology. In fact, even recent books on conservation biology often include only a cursory treatment, if any, of the problem of nonnative species (e.g., Soule 1986; Fiedler and Jain 1992; Given 1994; Jordan 1995).

Interactions among non-native plants and birds

Humans have introduced many non-native plants into urbanizing landscapes. In numerous cases, the dispersal and establishment of non-native plants are facilitated by birds. We have reviewed documented relationships between birds and non-native plants with specific attention to the urbanizing environment. Birds consume fruits and disperse seeds of non-native plants. They may also increase seed production or plant/seed survival by pollinating non-native plant species or consuming insect predators, respectively. Some avian frugivores facilitate the spread of, and benefit from, non-native plant species. In contrast, some avian nectarivores and insectivores have evolved mutualisms with specific plants and have been negatively influenced by the spread of competing, non-native plants. We enumerate the characteristics of successful, avian-dispersed fruit displays, and then highlight conditions in the urbanizing landscape that influence avian community structure and the spread of non-native plants. Finally, we discuss how these characteristics should influence management decisions and future research directions.

Invasive Species Defined in a Policy Context: Recommendations from the Federal Invasive Species Advisory Committee

Summary Invasive species are those that are not native to theecosystem under consideration and that cause or are likelyto cause economic or environmental harm or harm tohuman, animal, or plant health. Plant and animal speciesunder domestication or cultivation and under humancontrol are not invasive species. Furthermore for policypurposes, to be considered invasive, the negative impactscaused by a non-native species will be deemed to outweighthe beneficial effects it provides. Finally, a non-nativespecies might be considered invasive in one region but notin another. Whether or not a species is considered aninvasive species depends largely on human values. Byattempting to manage invasive species, we are affirming oureconomic and environmental values. Those non-nativespecies judged to cause overall economic or environmentalharm or harm to human health may be consideredinvasive, even if they yield some beneficial effects. Societystruggles to determine the appropriate course of action in Beck et al.: Invasive Species Definition N

Prevalence of Different Horticultural Taxa of Ivy (Hederaspp., Araliaceae) in Invading Populations

Abstract‘English’ ivy (Hedera spp.) is a complex of invasive plant pests that are separated into several distinct taxa. To better understand the invasion by ivy of Pacific Northwest native forests, we investigated the taxonomic identity of 58 selected invasive populations in the Pacific Northwest. Random amplified polymorphic DNA (RAPD) markers revealed that 83% of the 119 samples from invading populations were derived form H. hibernica (Kirchner) Bean, which has been frequently sold as English ivy, although this apparently is an incorrect common name. It is used widely in urban landscapes in the Northwest. The remaining 20 samples were either H.helix ‘California,’ ‘Pittsburgh,’ ‘Star,’ other cultivars not investigated in the study or possible hybrids.

Invasive competitor and native seed predators contribute to rarity of the narrow endemic Astragalus sinuatus Piper.

The conservation of rare plant species hinges on our ability to identify the underlying mechanisms that limit rare plant populations. Theory on rarity suggests that both predispersal seed predation and competition can be important mechanisms influencing abundance and/or distribution of rare plant populations. Yet few studies have tested these interactions, and those that have evaluated each mechanism independently. Astragalus sinuatus Piper (Whiteds milkvetch) is a narrow endemic plant species restricted to eight populations within a 10-km2 area in eastern Washington. We used experimental and observational methods to test the effects of native insect predispersal seed predators and an invasive grass (Bromus tectorum L. [cheatgrass]) on seed set and population density of A. sinuatus. We quantified per capita seed production and pod predation rates across four sites and among four years. Seed predation rates were high across four sites (66-82%) and all years (65-82%). Experimental reduction of predispersal seed predators significantly increased per capita seed set of A. sinuatus (164-345%) at two experimental sites. Concurrently, two seed addition experiments demonstrated the effect of seed loss and presence of B. tectorum on seedling recruitment and establishment of A. sinuatus over four growing seasons. In the first seed addition experiment, we found no difference in recruitment and establishment between low (40) and high (120) seed addition levels. In the second addition experiment (one level of addition; 40 seeds), we found that recruitment and survivorship increased 200% in plots where B. tectorum was removed compared to plots where B. tectorum was present. Thus, seed addition had no impact in the presence of B. tectorum; conversely, in the absence of B. tectorum, seed addition was highly effective at increasing population numbers. Results suggest that, in areas where B. tectorum is present, recruitment is site limited, and it is seed limited when B. tectorum is absent. We recommend that managers reduce B. tectorum in an effort to increase population growth of A. sinuatus; in areas where B. tectorum is absent, short-term reduction of insect predators should be considered as a strategy to increase population growth of this rare species.

Invasion biology: An emerging field of study

Biological invasions are increasingly recognized as a key problem for the conservation of biological diversity. However, the scientific recognition that some species, when introduced outside their native range, cause a decline in indigenous species, goes back to at least the writings of Charles Darwin. In the 1950s another British biologist, Charles Elton, wrote the first book attempting to describe the biology of invasive organisms. It was not until the 1980s, however, that the field of invasion biology as a discipline began to emerge. This emergence has resulted from two forces: the development of the scientific basis for invasion biology based on a substantial and accumulating literature, and the urgency of the invasive species issue because increased world trade and travel are increasing the frequency of invasions.