Invasive plant species in Sweden
In Sweden there are an estimated 721 established vascular plants and bryophyte species known to have been introduced since the year 1700. Evaluating these species for their invasive potential is an essential prerequisite for determining where limited resources should be applied to achieve the most value for money. Those species which are regarded as the most invasive and detrimental to native biodiversity and ecosystem services should, where feasible, be managed. The authors of this study assigned an invasion concern value to each of the 721 species. The invasion concern value was calculated by first obtaining individual scores for 6 components: (A) competitive ability in natural vegetation, (B) current population density of the species, (C) dispersal capacity, (D) potential hybridization, (E) time since introduction and (F) distance to native range. Following the scoring of these 6 components the invasion concern value was calculated by:
Invasion concern value (I) = (A + B + C + D) x (E + F) – 4
Thirty of the 721 species obtained an invasive concern value greater than 20 (Table 1) and 150 obtained an index value greater than 15. Of the 30 most problematic species a large number are shrub species (Rubus and Rosa species for example) which can form thick impenetrable stands outcompeting native biodiversity. Only one aquatic species features in the top 30 – Elodea nuttallii – though other invasive alien aquatic species appear in the most problematic 150 species.
Table 1 Thirty established alien plant species from Sweden which obtained an Invasion concern value (I) greater than 20.
|
Species
|
Family
|
Native range
|
I
|
|
Campylopus introflexus
|
Dicranaceae
|
Southern hemisphere
|
28
|
|
Rosa rugosa
|
Rosaceae
|
Asia
|
26.6
|
|
Epilobium adenocaulon
|
Onagraceae
|
Americas/Asia
|
26.6
|
|
Lamiastrum galeobdolon subsp. argentatum
|
Lamiaceae
|
Europe
|
24.9
|
|
Orthodontium lineare
|
Orthodontium
|
Southern hemisphere
|
24
|
|
Rubus armeniacus
|
Rosaceae
|
Americas
|
23.2
|
|
Calystegia sepium subsp. spectabilis
|
Convolvulaceae
|
North & South hemisphere
|
23.2
|
|
Solidago canadensis (EPPO List of Invasive Alien Plants)
|
Asteraceae
|
North America
|
23.2
|
|
Prunus serotina (EPPO List of Invasive Alien Plants)
|
Rosales
|
Americas
|
23
|
|
Epilobium ciliatum
|
Onagraceae
|
Americas
|
23
|
|
Prunus virginiana
|
Rosales
|
North America
|
22.6
|
|
Elodea nuttallii (EPPO List of Invasive Alien Plants)`
|
Hydrocharitaceae
|
North America
|
22.6
|
|
Lamiastrum galeobdolon subsp. montanum
|
Lamiaceae
|
Europe
|
21.6
|
|
Rubus montanus
|
Rosaceae
|
Europe
|
21.6
|
|
Cornus sericea (EPPO List of Invasive Alien Plants)
|
Cornaceae
|
North America
|
21.6
|
|
Amelanchier confusa
|
Rosaceae
|
North America
|
21.5
|
|
Trifolium pratense var. sativum
|
Fabaceae
|
Europe/Asia
|
21.5
|
|
Amelanchier spicata (EPPO List of Invasive Alien Plants)
|
Rosaceae
|
North America
|
21.5
|
|
Impatiens glandulifera (EPPO List of Invasive Alien Plants)
|
Balsaminaceae
|
Asia
|
21.5
|
|
Sorbus graeca
|
Rosaceae
|
Europe
|
21.5
|
|
Spiraea latifolia
|
Rosales
|
North America
|
21.2
|
|
Cotula coronopifolia
|
Asteraceae
|
South Africa
|
21.2
|
|
Solidago gigantea (EPPO List of Invasive Alien Plants)
|
Asteraceae
|
North America
|
21.2
|
|
Prunus pensylvanica
|
Rosales
|
North America
|
20.7
|
|
Rubus spectabilis
|
Rosaceae
|
North America
|
20.7
|
|
Iris versicolor
|
Iridaceae
|
North America
|
20.7
|
|
Glyceria striata
|
Poaceae
|
North America
|
20.7
|
|
Glyceria grandis
|
Poaceae
|
North America
|
20.7
|
|
Senecio inaequidens (EPPO List of Invasive Alien Plants)
|
Asteraceae
|
South Africa
|
20.7
|
|
Lysichiton americanus (EPPO Observation List of Invasive Alien Plants)
|
Araceae
|
North America
|
20.7
|
Sources
Tyler T, Karlsson T, Sahlin U, Sundberg S (2015) Invasive plant species in the Swedish flora: developing criteria and definitions, and assessing the invasiveness of individual taxa. Nordic Journal of Botany 33, 300-317.