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.