Invasiveness Ranking System for Non-Native Plants of Alaska

Allelopathic (0–2)UThere is no data concerning allelopathy. The small volume ofliterature on this species suggests that it has not been tested.Competitive Ability (0–3) 1Wall lettuce almost always occurs as a component of sparsevegetation and is rarely found in closed swards. It may competewith co-occurring species in closed woodland vegetation (Clabbyand Osborn 1999).Thicket-forming/Smothering growth form (0–2) 0Wall lettuce does not form thickets or patches. It usually occursin small groups or as scattered individuals (Clabby and Osborne1999).Germination requirements (0–3) 2Wall lettuce germinates mainly on barren or sparsely vegetatedsites (Clabby and Osborn 1999).Other invasive species in the genus (0–3) 0The genus Mycelis is monotypic (USDA 2002).Aquatic, wetland or riparian species (0–3) 0Wall lettuce is a species of moist to mesic forests in the lowlandand montane zones. It is commonly found in open woods, woodmargins, and woodland clearings, but also occurs in scrub and onwalls and rock outcrops (Clabby and Osborne 1999, Cronquist1955, Douglas et al. 1998, Gubanov et al. 1995).Total for Biological Characteristics and Dispersal 11/23Ecological Amplitude and Distribution ScoreHighly domesticated or a weed of agriculture (0–4) 0The species is not known as an agricultural weed.Known level of impact in natural areas (0–6) 1Though wall lettuce occurs mainly on disturbed sites (Clabby andOsborn 1999), it has been observed to invade forest communitiesin Oregon (M.L. Carlson pers. obs.). Wall lettuce has been foundalong old logging roads in southeast Alaska (AKEPIC 2004).Role of anthropogenic and natural disturbance in0establishment (0–5)Wall lettuce habitats are often associated with natural oranthropogenic disturbances such as storms, fires, and clearcuts(Clabby and Osborne 1999).Current global distribution (0–5) 5Wall lettuce is native to most of temperate continental Europe.Its distribution extends eastward to Turkey and the CaucasusMountains and north in Norway at 68.5°N. Wall lettuce alsooccurs in North Africa, North America, and New Zealand(Clabby and Osborn 1999).Extent of the species U.S. range and/or occurrence of2formal state or provincial listing (0–5)Wall lettuce has been found in Maine, Massachusetts, Michigan,Minnesota, New Hampshire, New York, Oregon, Vermont, andWashington (USDA 2002). Mycelis muralis is exotic to NorthAmerica but is not listed as noxious (Invaders Database System2003, USDA 2002).Total for Ecological Amplitude and Distribution 8/25Feasibility of ControlScoreSeed banks (0–3) 2In laboratory experiments, dry seeds stored in a refrigeratorremained viable for at least 3 years. Seeds stored at roomtemperature lost viability after 2 years (Clabby and Osborne1999). In Kellman’s (1974) study the number of viable seedsdeclined during the 3 years of monitoring, suggesting a shortperiod of seed viability.Vegetative regeneration (0–3) 0Wall lettuce does not regenerate vegetatively (Clabby and Osborn1999).Level of effort required (0–4) 2Control options have not been investigated. Kellman (1974)suggested that wall lettuce will not persist on sites withestablished perennials.Total for Feasibility of Control 4/10Total score for 4 sections 30/98§B-84