Non-native Plants
A London Perspective
Mark Spencer Senior Curator, British and Irish Herbarium, Natural History MuseumBSBI vc 21 (Middlesex) Recorder LNHS Vascular Plant Recorder
‘The introduction of alien species is interacting with habitat destruction and degradation, over exploitation of plants and animals in
natural ecosystems, and global climatic change to create an evolutionary revolution’
G.W. Cox (2004) Alien Species and Evolution
May lily - Maianthemum bifolia
London rocket – Sisymbrium irio
Mexican fleabane – Erigeron karvinskianus
Fodder vetch – Vicia villosa Sand lucerne – Medicago sativa ssp. varia
Sycamore – Acer pseudoplatanus
Are all Non-native Species Invasive?
What characterises an invasive species?
“Invasive species are organisms (usually transported by humans) which successfully establish themselves in, and then overcome, otherwise intact, pre-existing native
ecosystems.” http://www.issg.org/
Perception, two non-natives:
Butterfly-bush - Buddleja davidii
A ‘Good’ Plant because:• butterflies like it• and other insects too
Japanese knotweed - Fallopia japonica
A ‘Bad’ Plant because:• it pushes over walls• butterflies don’t like it
Perception, two non-natives:
But should we not consider both ‘bad’?
Buddleia • evidence of benefit to butterflies and other invertebrates is limited • potential evidence of adverse impacts upon pollination biology• adverse impacts on calcareous grassland,cliff and urban and brownfield habitats
Japanese knotweed • most butterflies don’t utilise it (but some flies do)• it too damages built structures• adverse impacts on river margin and woodland habitats
early meadow-grass - Poa infirma
annual meadow-grass - Poa annua
Changes: Native or non-native?
Pre 1969 distribution of early meadow-grass - Poa infirma
© Botanical Society of the British Isles
1970 -1986 distribution of early meadow-grass - Poa infirma
© Botanical Society of the British Isles
1987 -1999 distribution of early meadow-grass - Poa infirma
© Botanical Society of the British Isles
2000 onwards distribution of early meadow-grass - Poa infirma
© Botanical Society of the British Isles
Changes: pseudo-natives’ wayfaring tree - Viburnum lantana
hawthorn – Crataegus x subsphaerica
Changes: Trees & Shrubs
foxglove tree - Paulownia tomentosa
tree-of-heaven – Ailanthus altissima
Tree-of-Heaven – Ailanthus altissima
© Botanical Society of the British Isles
Least duckweed - Lemna minuta Valdivian duckweed - Lemna valdiviana
Changes: Aquatics
Changes: native invaders
False oat-grass – Arrhenatherum elatius Stinging nettle – Urtica dioica
Changes: Bulbous plants Three-cornered leek - Allium triquetrum
Hybrid bluebell - Hyacinthoides x massartiana
Pteris multifida - spider brake
Changes: pteridophytes
Cyrtomium sp. - house holly-fern
Camphylopus introflexus
Changes: bryophytes
Agrocybe rivulosa
Changes: fungi
Austrian chamomile - Anthemis austriaca corncockle - Agrostemma githago
Vectors: Habitat creation and landscaping
Narrow-leaved ragwort - Senecio inaequidans
Vectors: Industry/transport
Vectors: Horticulture
membranous nettle - Urtica membranacea
White ramping-fumitory - Fumaria capreolata
Evolving Ecologies:
Assessing impacts• Population biology
• Inter-specific interaction• Variation in ecological function
• Advent of further non-natives• Demise of natives
False Hampshire-purslane – Ludwigia x kentiana
Creeping Water-primrose – Ludwigia grandiflora
Collaboration: it can be done!
pale galingale - Cyperus eragrostis
Johnson-grass - Sorghum halepense
LISI: ‘Quick wins’
Chalara: how not to do it.