Non-native Plants A London Perspective Mark Spencer Senior Curator, British and Irish Herbarium, Natural History Museum BSBI vc 21 (Middlesex) Recorder LNHS Vascular Plant Recorder

over exploitation of plants and animals in ‘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

Are all Non-native Species Invasive? Fodder vetch – Vicia villosa Sand lucerne – Medicago sativa ssp. varia Mexican fleabane – Erigeron karvinskianus Sycamore – Acer pseudoplatanus

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

Changes: Native or non-native? early meadow-grass - Poa infirma annual meadow-grass - Poa annua

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

foxglove tree - Paulownia tomentosa Changes: Trees & Shrubs foxglove tree - Paulownia tomentosa

tree-of-heaven – Ailanthus altissima

Tree-of-Heaven – Ailanthus altissima © Botanical Society of the British Isles

Changes: Aquatics Valdivian duckweed - Lemna valdiviana Least duckweed - Lemna minuta Valdivian duckweed - Lemna valdiviana

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

Changes: pteridophytes Cyrtomium sp. - house holly-fern Pteris multifida - spider brake

Changes: bryophytes Camphylopus introflexus

Changes: fungi Agrocybe rivulosa

Vectors: Habitat creation and landscaping Austrian chamomile - Anthemis austriaca corncockle - Agrostemma githago Vectors: Habitat creation and landscaping

Narrow-leaved ragwort - Senecio inaequidans Vectors: Industry/transport Narrow-leaved ragwort - Senecio inaequidans

Vectors: Horticulture White ramping-fumitory - Fumaria capreolata membranous nettle - Urtica membranacea

Evolving Ecologies: Assessing impacts Population biology Inter-specific interaction Variation in ecological function Advent of further non-natives Demise of natives

Collaboration: it can be done! Creeping Water-primrose – Ludwigia grandiflora False Hampshire-purslane – Ludwigia x kentiana

LISI: ‘Quick wins’ pale galingale - Cyperus eragrostis Johnson-grass - Sorghum halepense

Chalara: how not to do it.