Cactaceae in Europe
The cactus family (Cactaceae) is mainly restricted to the Americas and comprises more than 1800 species. Diversity centres are the Andean region, Central Mexico, and Brazil, where cacti colonise a wide range of dry habitats, although several species occur up to the cool-temperate regions of Patagonia and Alaska.
In Europe, the cacti species which are now found outdoors in the Mediterranean region result from deliberate introductions, but in some cases these introductions have been followed by uncontrolled invasion events. Until the 19th century, the dominant pathway of entry for cacti in Europe was deliberate planting by farmers for economic reasons. For instance, Opontia ficus-indica was widely planted in the Mediterranean region for its edible fruits or for animal forage. In the last decades, deliberate planting in the wild by cacti enthusiasts for ornamental reasons has become the dominant pathway. Once planted, cacti produce seeds that are eaten and dispersed by birds and small mammals, and even by lizards and wild boars. Cacti invasions cause problems for nature conservation, especially when habitats such as rock vegetation, open dry grassland, and Garrigue are invaded. Most climate change scenari for the Mediterranean region predict a considerable reduction in precipitation and an increase of up to 5°C of the average annual temperature by 2100. As cacti are drought resistant and tolerant to high temperatures, it can be expected that climate change will enhance the invasion success of cacti in Europe.
A list of cacti species recorded in Europe has been compiled from different sources (checklists, databases, floras, atlases) for North, West, Central and South Europe. This list contains in total 26 species. All of them are confined to dry, open habitats on acid siliceous bedrocks, and mainly occur in the Mediterranean biogeographic region. By far, the most represented genus is Opuntia with 20 species. The most widespread species is Opuntia humifusa (6 countries), followed by O. ficus-indica and O. maxima (5 countries). Most species are rare and only locally established (28 invasion events) or casual (13 invasion events), whereas 17 invasion events have led to wider invasions. The number of invasion events over a 50-year period increased from three (1801-1851) to nine (1951-2000).
The table below presents the 26 cactus species which have been recorded in Europe with their situation in each country:
|
Species of Cactaceae
|
Casual
|
Locally established
|
Widely established
|
|
Austrocylindropuntia cylindrica
|
|
IT
|
|
|
Cereus peruvianus
|
ES
|
FR
|
|
|
Cereus triangularis
|
|
ES
|
|
|
Cylindropuntia imbricata
|
ES
|
|
|
|
Cylindropuntia spinosior
|
|
ES
|
|
|
Hylocereus undatus
|
|
ES
|
|
|
Opuntia ammophila
|
|
ES
|
|
|
Opuntia bernichiana
|
|
ES
|
|
|
Opuntia caespitosa
|
|
FR
|
|
|
Opuntia crassa
|
FR
|
|
|
|
Opuntia dejecta
|
|
IT
|
|
|
Opuntia dillenii
|
|
IT, PT
|
ES
|
|
Opuntia engelmannii
|
|
ES
|
|
|
Opuntia ficus-indica
|
|
|
ES, FR, HR, IT, PT
|
|
Opuntia huajuapensis
|
ES
|
|
|
|
Opuntia humifusa
|
|
HR, DE, ES
|
CH, FR, IT
|
|
Opuntia imbricata
|
CH, FR
|
ES
|
|
|
Opuntia maxima
|
|
IT
|
ES, FR, HR, PT
|
|
Opuntia microdasys
|
FR, PT
|
ES
|
|
|
Opuntia monacantha
|
CZ, DE, ES
|
|
FR
|
|
Opuntia phaeacantha
|
|
AT, ES
|
IT
|
|
Opuntia robusta
|
|
IT
|
|
|
Opuntia rosea
|
|
ES
|
|
|
Opuntia stricta
|
PT
|
ES, FR, IT
|
|
|
Opuntia subulata
|
PT
|
ES, FR
|
IT
|
|
Opuntia tuna
|
|
FR, IT
|
ES
|
Sources
Essl F, Kobler J (2008) Spiny invaders – Patterns and determinants of cacti invasion in Europe. Flora 204, 485-494.