Dept. of Biology, Biotechnical Faculty UL, Večna pot 111, SI-1000 Ljubljana, Slovenia
When comparing the densities of archaeophyte and neophyte species, a clear impression is that the distribution patterns are similar and mostly linked to urbanization. Of course, the floristic data gathered since 18th century are distributed very randomly in time and space, therefore the uneven temporal and spatial floristic coverage of the territory offers a dataset full of gaps. Only for the last four decades, when systematic floristic mapping began taking place, the availability of information has become slightly better. This is also the time period when a number of (not only) invasive neophytes started to increase quickly, and on the other hand, a number of archaeophytic groups such as arable field weeds started decreasing. Archaeophytes and neophytes are plants of foreign origin and in different time periods they entered our flora so we could have expected some comparable patterns of floristic incorporation that would result in comparable distribution patterns.
For the territory of Slovenia, we compared the distribution patterns of archaeophytes and neophytes to other selected geographical patterns that could have been somehow related, for example,the density of Balkan species, endemics, phanerophytes, hydrophytes, high mountain taxa, ratio of widespread species, invasive alien species (IAS), ferns, therophytes, the number of red data list species, protected species, level of floristic uniqueness, average indicator values for temperature, pH and humidity, minimum altitude, maximum altitude and altitudinal span within quadrant and also an average age of floristic data in the quadrant.
Highest positive linear correlation with archaeophyte numbers was (as expected) calculated for neophytes (0,81), therophytes (0,75), total species number (0,71), red data list taxa (0,635), average indicator value for temperature (0,58), number of phanerophytes (0,52) and hydrophytes (0,53), number of widespread species (0,47); highest negative correlation was recognized with altitude span within quadrant (-0,41), number of pteridophytes (-0,41), and the minimal and maximal altitude within a quadrant (both -0,48). Regarding neophyte numbers, the highest positive correlation was with the number of therophytes (0,67), number of IAS (0,54), hydrophytes (0,56), total number of taxa (0,54), average indicator value for temperature (0,45), red data list species (0,49); highest negative correlation for altitude span within quadrant (-0,42), and the minimal and maximal altitude within a quadrant (-0,43 and -0,48, respectively). Evidently, despite the overall similarity in density patterns of archaeophytes and neophytes, there are some slightly different factors connected to their distribution. Not to say that the causal connection is always clear-cut.
The temporal quality of available floristic records do not allow us to unequivocally claim that the number of archaeophytes is declining , but it is very clear that the number of neophytes is increasing and so the ratio of recorded archaeophytes vs. neophytes. In quadrants with predominantly older data (e.g. average data age more than 50 years), the ratio is around 7 and in recently mapped quadrants the ratio is around 5.
For interpretation of such differences we have to bear in mind the differences in processes of selection and introduction of archaeophytes and neophytes. Most important is that archaeophytes originate mostly from Eurasia, a very limited number were introduced intentionally due to their usefulness and others mostly as hitch-hikers (e.g. segetal weeds from Near East). On the other hand, the biggest number of neophytes were brought from other continents or more remote areas of Asia, majority of whichwere brought intentionally for decorative purposes (a motive almost unknown for archaeophytes), so the spectrum of their biological potential is much wider and also the intensity of their introduction (i.e. regarding number of taxa and frequency of introductions). Despite similar density patterns currently, in the future invasive neophytes will achieve bigger secondary ranges.