Invasiveness Ranking System for Non-Native Plants of Alaska

Linaria vulgaris P. Miller.Ranking SummaryEcoregion known or expected to occur inSouth CoastalInterior BorealArctic AlpineYesYesYesPotential Max. ScoreEcological Impact 40 22Biological Characteristics and Dispersal 25 17Amplitude and Distribution 25 21Feasibility of Control 10 9Relative Maximum 61Climatic ComparisonCollected inAlaska regions?common names: yellow toadflax, butter and eggs,wild snapdragonCLIMEXsimilarity?South Coastal Yes –Interior Boreal Yes –Arctic Alpine No YesLinaria vulgaris has been collected in the south coastal [Seward,Sitka, Juneau, and Skagway (Hultén 1968, UAM 2004)] andinterior boreal [Anchorage, Wasilla, and Fairbanks (AKNHP2003, Hultén 1968, UAM 2004)] ecoregions in Alaska. It hasnot been documented in the arctic alpine ecoregion. Using theCLIMEX matching program, climatic similarity between Nomeand areas where the species is documented is high. The nativerange of the species includes Røros, Norway, Zlatoust, Russia, andStensele, Sweden (Hultén 1968), which has a 76%, 71%, and 70%climatic match with Nome, respectively.Ecological ImpactScoreImpact on Ecosystem Processes (0–10) 5Yellow toadflax likely reduces soil moisture and nutrientavailability and appears to alter soil texture (M.L. Carlson pers.obs.) This rhizomatous plant often grows at very high densities indry and nutrient poor soils in Alaska and very likely it is reducingessential resources for other species. Additionally, a large volumeof below ground biomass is produced in generally organic poorsoils, which also tends to bind the soils.Impact on Natural Community Structure (0–10) 5Yellow toadflax is capable of forming dense colonies throughadventitious buds on creeping rhizomes (Carpenter and Murray1998). Along trails and other disturbed sites in south-centralAlaska it forms a new layer apparently excluding both tallherbaceous and shorter graminoid native species (M.L. Carlsonpers. obs.).Impact on Natural Community Composition (0–10) 7This plant can displace native perennial species (Carpenter andMurray 1998, Whitson et al. 2000).Impact on Higher Trophic Levels (0–10) 5Yellow toadflax produces a poisonous glucoside that is reportedto be unpalatable to moderately poisonous for livestock. Itcan reduce foraging sites (Whitson et al. 2000). Toadflax is analternate host for tobacco mosaic virus (Royer and Dickinson1999). This species is highly attractive to bumblebee (Bombusspp.) and halictid bee (Halictus spp.) pollinators and may alterpollination ecology of sites where it occurs (M.L. Carlson pers.obs.). Flowers are also attacked by number of insect predators(Arnold 1982, M.L. Carlson pers. obs., Goltz 1988)Total for Ecological Impact 22/40Biological Characteristics and Dispersal ScoreMode of Reproduction (0–3) 3Yellow toadflax reproduces by seeds and vegetatively. Seed countper individual is difficult as the definition of individual is uncleardue to its clonal propagation. Darwent et al. (1975) in Albertarecorded up to 824 seeds per stem. Stevens (1932) reported 2,280seeds per plant with nine stems. Nadeau and King (1991) foundseed production of 210,000 seed per m². Common toadflax alsohas the ability to reproduce vegetatively from adventitious budson the roots (Bakshi and Coupland 1960, Nadeau et al. 1991,Nadeau et al. 1992).Long-distance dispersal (0–3) 3Seeds can be carried by the wind (Royer and Dickinson 1999);however, Nadeau and King (1991) report that 80% of seedsfell within 50 cm and a tiny fraction fell more than 1.5 m of theparent plant. This species may also be dispersed by water and ants(Rutledge and McLendon 1996). The seeds are small (1–2 mmlong), flattened with papery wings.Spread by humans (0–3) 3Yellow toadflax is an ornamental plant and has escapedcultivation (Rutledge and McLendon 1996). Toadflax can spreadalong highways (Densmore et al. 2001). It has been found as acontaminant in commercial seed, hay, and ship ballast. It is stillsold by some nurseries (Beck 2001, Zouhar 2001).Allelopathic (0–2) 0NoneCompetitive Ability (0–3) 3This species is a strong competitor for soil moisture withestablished perennials and winter annuals. It is adapted to a widerange of environmental conditions (Carpenter and Murray 1998,Rutledge and McLendon 1996).Thicket-forming/Smothering growth form (0–2) 1Yellow toadflax is capable of forming colonies through buds fromcreeping rhizomes (Carpenter and Murray 1998). However, ingeneral, it is not taller than the surrounding vegetation (M.L.Carlson pers. obs.). In a study of common toadflax in Alberta, adensity of 180 stems per m² was recorded; but, in most areas thisplant occurs at densities of 20 stems per m² or less (Darwent et al.1975).Germination requirements (0–3) 0Yellow toadflax requires open soil for germination (Densmore etal. 2001). Germination success is generally low, especially withcompetition (Rutledge and McLendon 1996, Zouhar 2003).Other invasive species in the genus (0–3) 3Linaria dalmatica (L.) P. Mill. is declared noxious in someAmerican states and Canadian provinces (Invader DatabaseSystem 2003, USDA, NRCS 2002).Aquatic, wetland or riparian species (0–3) 1Yellow toadflax is most commonly found along roadsides, fences,rangelands, croplands, clearcuts, and pastures (Carpenter andMurray 1998). But, it has been reported from cottonwood andspruce dominated riparian habitats in Colorado (Carpenter andMurray 1998, Zouhar 2003); and it is found along the shorelineof Cook Inlet and Turnagain Arm (AKEPIC 2004, M. Shephardpers. comm.).Total for Biological Characteristics and Dispersal 17/25B-67