Residence time determines the distribution of alien plants - Invasive Plants: Ecological and Agricultural Aspects - page 71

Historical invaders: the effect of residence time still detectable
One might expect that in archaeophytes, historical invaders that were arriving
for several millennia since the beginning of Neolithic agriculture until the end
of Medieval, the effect of the time of arrival would be no longer obvious. The
opposite is true: for both data sets providing the information on approximate
dates of the first records ([29, 37]; Tab. 1), the current frequency or range of
archaeophytes in the region increases with MRT, indicating that the earliest new-
comers are more common than those that arrived later (Fig. 3). The rather low
proportion of explained variation (4.1 and 8.3%, Tab. 1) reflects that residence
time is, compared to other factors affecting the present distribution, of lower
importance in archaeophytes than in most data sets covering recent newcomers.
Archaeophytes in the Czech Republic and Great Britain do not differ in the
rate at which their distribution increases with MRT (F = 0.41; df = 1, 232; NS).
This means that in both regions, MRT has the same effect on the invasion by
archaeophytes and neither of the regions appears to have been more suitable
for invasion by this group of species. The reason might be that arable land, a
typical habitat of archaeophytes [33, 37, 55], is to a large extent similar in dif-
ferent regions and so it is the management that affects the occurrence of
archaeophytes [43].
Interestingly, the mean MRT for British archaeophytes is highly signifi-
cantly lower than that of Czech archaeophytes. On average, the invasion of
Figure 3. The relationship between standardized current range (UK) and frequency (Czech Republic)
of archaeophytes and their non-standardized MRT (yrs). Note that for the average standardized range
and frequency (having a zero mean) the MRT is 2,461 years for UK but 3,388 years for the Czech
republic; this difference is statistically significant (F = 23.25; df = 1, 232; P < 0.001). The slopes are
not statistically different (F = 0.42; df = 1, 232; NS); their values for both range (UK) or frequency
(CZ) and MRT standardized are in Table 1.