Catalogue of Neophytes in Belgium (1800-2005)

Catalogue of neophytes in Belgium (1800-2005). A catalogue of
Belgian neophytes has been compiled for the first time on the basis of a thorough
and critical revision of the main public and some smaller but nevertheless relevant
Belgian herbaria. All non-native vascular plant species, recorded in Belgium since
1800, are included regardless of degree of naturalization (including occasional
garden escapes and casual aliens as well as invasive taxa). Taxa that were already
naturalized in Belgium in pre-Columbian times, are excluded. The following data
are provided for each taxon: scientific name, synonym, family, mode of introduction
(accidental/deliberate), date of the first collection (except if earlier reliable
records are available), date of the most recent record, native geographic area,
presence or absence in Flanders, Brussels Capital Region and Wallonia (the three
main political units), degree of naturalization and (main) vector(s) of introduction.
1,969 taxa are included. More than 20 % appears to be “new” for the Belgian
flora. On the other hand, at least 30 taxa were erroneously included in the presentday
Flora and need to be omitted in a future edition.
Assessing the exact status of many taxa of the “Belgian” flora proved to be
problematic. On the one hand, the distinction between native and non-native
turned out to be often critical (for instance: interpretation of natural range
extensions). On the other hand, assessing archaeophytic or neophytic status for
(presumed) non-native taxa turned out not to be always obvious. Similarly, the
assessment of the degree of naturalization (measurement of a taxon’s success) was
not always straightforward. In practice, and despite numerous recent international
papers on this subject, the distinction between “naturalized” and “invasive”
regularly proved to be arbitrary.
The Belgian non-native vascular flora is remarkably wealthy and diverse: no
less than 139 families are represented but most families count for only (very) few
taxa. Poaceae and Asteraceae are the largest families and represent more than a
quarter of the total number of alien taxa in Belgium. A huge number of the aliens
were initially introduced deliberately, primarily for horticultural reasons. Among
the naturalized and/or invasive taxa the proportion of deliberate introductions is
even more important (ca. 60 %). Introductions from Europe and temperate Asia
are most common. To a lesser extent, Africa (especially North-Africa) and
America (especially North-America) are also important sources. As expected, the
number of introductions from Australia, tropical Asia and the (sub-) tropics as a
whole is limited. A large majority, at least 75 %, of the introductions remains
strictly casual. At most 20 % is able to become naturalized, locally as well as
widespread. At present, the number of invasive taxa (spreading fast in more or less
natural habitats) and noxious taxa (harmful in terms of biodiversity, public health
or for economic reasons) is limited. Currently, the main vector for plant
introductions appears to be horticulture (garden escapes). Until the 1960’s woolimportation
was chiefly responsible for the occurrence of accidental aliens.
Nowadays, accidental aliens are usually brought in with cereals and grains. The
number of new introductions has much increased in the course of the past decades.
Similarly, the number of newly naturalized taxa has increased.