Invasiveness Ranking System for Non-Native Plants of Alaska

Myriophyllum spicatum L.Ranking SummaryEcoregion known or expected to occur inSouth CoastalInterior BorealArctic AlpineYesYesYesPotential Max. ScoreEcological Impact 40 38Biological Characteristics and Dispersal 22 20Amplitude and Distribution 25 20Feasibility of Control 10 9Relative Maximum 90Climatic ComparisonCollected inAlaska regions?CLIMEXsimilarity?South Coastal No YesInterior Boreal No YesArctic Alpine No YesSpecial Note: This taxonomy and identification of Eurasianwatermilfoil is problematic. It is often synonymized with M.sibiricum Komarov, which is native to Alaska (ITIS Database2004) and the two taxa are known to hybridize (Moody and Les2007). Hultén (1968) and the UAM database treat the nativetaxon in Alaska broadly and as M. spicatum; however, it appearsthat Eurasian watermilfoil in the strict sense is not known fromany locations in Alaska.The very closely related Myriophyllum sibiricum (synonymizedby many authors) has been collected in the south coastal, interiorboreal, and arctic alpine ecoregions in Alaska (Hultén 1968). Thespecies’ range includes the Norland province in Norway, whereit is only occasionally found (Lid and Lid 1994), the climaticsimilarity of this region is similar to the interior boreal and arcticalpine ecoregions of Alaska (CLIMEX 1999). It is known fromsouthwestern Norway which tends to have a strong climaticsimilarity with the Alaskan south coastal ecoregion (Bergen hasa 73% climatic match with Juneau). Last, the closely related M.sibiricum has similar range in Europe and is widespread in Alaska.We suggests that establishment of M. subspicatum in the southcoastal, interior boreal, and arctic alpine ecogeographic regions ispossible.Ecological ImpactScoreImpact on Ecosystem Processes (0–10) 8Dense Eurasian watermilfoil mats alter water quality by raisingpH, decreasing dissolved oxygen under the mats, and increasingtemperature. The dense mats of vegetation can increase thesedimentation rate by trapping sediments (Jacono and Richerson2003, Washington State Department of Ecology 2003).Impact on Natural Community Structure (0–10) 10Eurasian watermilfoil forms dense floating mats of vegetation,preventing light penetration for native aquatic plants (Jacono andRicherson 2003, Remaley 1998, Washington State Department ofEcology 2003).Impact on Natural Community Composition (0–10) 10This aquatic plant is able to displace and reduce natural diversity(Bossard 2004, Jacono and Richerson 2003, Washington StateDepartment of Ecology 2003).common names: Eurasian watermilfoil,myriophylle en epi, spike watermilfoilImpact on Higher Trophic Levels (0–10) 10Monospecific stands of Eurasian watermilfoil provide poorhabitat for waterfowl, fish, and other wildlife (Jacono andRicherson 2003). Loss of nutrient-rich native plants reduces foodsources for waterfowl; it impacts fish spawning; and it disruptspredator-prey relationships by fencing out larger fish. Stagnantwater created by Eurasian watermilfoil mats provides goodbreeding grounds for mosquitoes (Bossard 2004).Total for Ecological Impact 38/40Biological Characteristics and Dispersal ScoreMode of Reproduction (0–3) 3Reproduction is by seeds, rhizomes, fragmentation, and winterbuds. Young populations of Eurasian watermilfoil averaged a seedset of 112 seeds per stalk. Despite the high seed production, it ispropagated predominantly by vegetative fragments (Aiken 1981,Bossard 2004, Remaley 1998, Washington State Department ofEcology 2003).Long-distance dispersal (0–3) 3Fragments can be spread by floating downstream, waterfowl,and other wildlife. Fruits are buoyant for short period and can bedispersed by water (Bossard 2004).Spread by humans (0–3) 3It is spread from lake to lake on boat trailers and fishing gear.A number of populations found in Oklahoma were introducedby earthworm farmers who packed their product in Eurasianwatermilfoil (Jacono and Richerson 2003, Washington StateDepartment of Ecology 2003). It could very likely be moved byfloatplanes and small boats used in Alaska.Allelopathic (0–2) 0No records of allelopathy.Competitive Ability (0–3) 3Eurasian watermilfoil competes aggressively with native aquaticplants (Bossard 2004, Jacono and Richerson 2003). Eurasianwatermilfoil is an extremely adaptable plant, able to tolerate andeven thrive in a variety of environmental conditions. It grows instill to flowing waters, survives under ice, tolerates pH from 5.4to 11, and can grow over a broad temperature range. This plantbegins spring growth earlier than other aquatic plants, quicklygrows to the surface and forming dense canopies (Jacono andRicherson 2003).Thicket-forming/mothering growth form (0–2) 2This aquatic plant forms a large, dense canopy of vegetation(Jacono and Richerson 2003, Remaley 1998).Germination requirements (0–3)N/AGermination of seed is not a significant factor in reproduction.(Remaley 1998, Washington State Department of Ecology 2003).Other invasive species in the genus (0–3) 3Myriophyllum exalbescens Fern. (Royer and Dickinson 1999).M. aquaticum (Vell.) Verdc. (Anderson and Spencer 1999, USDA2002).Aquatic, wetland or riparian species (0–3) 3The typical habitat for Eurasian watermilfoil includes freshto brackish water of fishponds, lakes, slow-moving streams,reservoirs, estuaries, and canals (Bossard 2004, Jacono andRicherson 2003).Total for Biological Characteristics and Dispersal 20/22B-85