Inventory of aliens escaping from culture in the National Botanic Garden of Belgium

1. Inventory of aliensescapingfrom culture in the National Botanic Garden of Belgium Anne Ronse

2. A bit of history: the domain in Meise 2 former castle estates: Meise and Bouchout Empress Charlotte of Mexico

3. After 1938: a botanic garden • 92.3 ha • Greenhouses • open air collections • Buildings and roads • Woodlands • Grasslands and lawns • Ponds

4. 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)

5. Some results • About 600 speciesrecorded • 6 categories:

6. Percentage of plant categories in the domain

7. 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

8. (Botanic) garden escapes Botanic gardens have played a significant role in the dissemination of invasive species worldwide (Hulme 2011). Botanic gardens were considered as naturalisationcentres for plants by Devos (1870). An example: Impatiens parviflora

9. Collection escapes in Meise • 180 species recorded • sometimes uncertain origin: escapes or not? Duchesnea indica Cornus sericea

10. Collection escapes in Meise (2) • About 25% are indigenous species (regionally or in Flanders) • Mostly from non-local or foreign origin Oenanthe pimpinelloides

11. 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

12. Collection escapes in Meise (4) • 33% have not been recorded as neophytebefore in Belgium • 85% of them have been recorded as naturalisedoutsidetheirnatural range Nothoscordum gracile

13. Cynanchum louisae

15. 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

16. Ranunculus parviflorus

17. Collection escapes in Meise (6) Among the most persistent and numerousspecies are manywoodyspecieswith fruits that are probablyspread by birds, such as: Diospyros lotus

18. Malus sargentii

19. Cotoneaster moupinense

20. Prunus lusitanica

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

22. rose-ringed parakeets Psittacula krameri Zoochory by birds seems a very efficient spreading method.

23. 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.

24. 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.