Inventory of aliens escaping from culture

in the National Botanic Garden of Belgium

Anne Ronse

A bit of history: the domain in Meise

2 former castle estates: Meise and Bouchout

Empress Charlotte of Mexico

After 1938: a botanic garden

92.3 ha

•Greenhouses•open air collections•Buildings and roads•Woodlands•Grasslands and lawns•Ponds

Inventory of the flora of the domain

• From 2002 to 2011 • Wild and naturalized vascular

plants• Detailed results: per sector• Results in Scripta Botanica Belgica

n° 47 (2011)

Some results

• About 600 species recorded• 6 categories:

Category Name

Indigenous species

Local origin

escaped from

collections

Deliberate introduction

1 ‘Truly’ indigenous species

+ + - -

2 External neophytes - - - -

3 Garden escapes +/- +/- + -

4 ‘Stinsen’ plants - - - +

5 Wood lawn neophytes(Grassameneinkömmlinge)

- - - -

6 Indigenous introductions

+ +/- - +

Percentage of plant categories in the domain

Garden escapes: an important source of invasive exotic plants

• Australia: 66% of all plant species that have become naturalised are garden escapes (Groves et al. 2005) (increasing)

• The worlds 100 worst invasive organisms (Lowe et al. 2000): 56% of the plants are garden escapes

(Botanic) garden escapesBotanic gardens have played a significant role in the dissemination of invasive species worldwide (Hulme 2011).Botanic gardens were considered as naturalisation centres for plants by Devos (1870).

An example: Impatiens parviflora

Collection escapes in Meise• 180 species recorded• sometimes uncertain origin: escapes or not?

Duchesnea indica Cornus sericea

Collection escapes in Meise (2)• About 25% are indigenous species (regionally

or in Flanders)• Mostly from non-local or foreign origin

Oenanthe pimpinelloides

Collection escapes in Meise (3)

• 9 species from the list of invasive species in Belgium (Branquart et al. 2011)

• Watch list: Ambrosia artemisiifolia, Lysichiton americanus, Quercus rubra, Rhus typhina

• Black list: Ailanthus altissima, Cornus sericea, Crassula helmsii, Heracleum mantegazzianum, Mahonia aquifolium

Collection escapes in Meise (4)• 33% have not been recorded as neophyte before in Belgium• 85% of them have been recorded as naturalised outside

their natural range

Nothoscordum gracile

Cynanchum louisae

Collection escapes in Meise (5)• The numbers of plants for each escaped species varies between 1

to more than 100• The distance from the collections varies from 3m to 1000m

(maximal distance within domain)• The survival time for each escape is different, and is largely

dependent on the management• Means of dispersion: anemochory, zoochory, …

risk assessment for invasive species

Ranunculus parviflorus

Among the most persistent and numerous species are many woody species with fruits that are probably spread by birds, such as:

Diospyros lotus

Collection escapes in Meise (6)

Malus sargentii

Cotoneaster moupinense

Prunus lusitanica

Why woody plants? Woodland sectors are the less disturbed areas in the domain, as they are not weeded or mown.

Zoochory by birds seems a very efficient spreading method.

rose-ringed parakeetsPsittacula krameri

Collection escapes in Meise (6)

Have some species escaped from the Domain into the surroundings?

Yes, mainly woody species, such as Prunus lusitanica and Malus sargentii.

Some conclusions•Nearly one third of the spontaneously occurring species in the domain are escapes from the collections • Some species manage to escape outside the domain as well, especially woody species with fruits eaten by birds •the monitoring of the escapes at regular time intervals is advisable.