Invasion history of Oenothera congeners in Europe: a comparative study of spreading rates in the last 200 years
The dynamics of spread of some representatives of Oenothera, a genus of New World origin and alien to Europe, was analysed.Location
Distribution data from six European countries., i.e. Austria, Czech Republic, Hungary, Portugal, Serbia and UK were used.Methods
Floristic records covering the last 200 years were collated and the cumulative number of localities was plotted against time. A correction of the number of localities, taking into account the intensity of floristic research in particular countries, was applied based on the total number of available herbarium specimens to make comparisons of the rate of spread in particular countries possible.Results
In total, 35 alien taxa of the genus have been reported from the countries considered, the majority of which has only a limited distribution. So far 1800 records of Oenothera species have been reported from the six countries analysed since 1780, with O. biennis, O. erythrosepala, O. salicifolia, O. stricta, O. cambrica, O. rubricaulis, and O. chicaginensis having more than 50 localities. There is a highly significant negative correlation between the total number of localities in Europe and the year of the first introduction. Marked differences were found in the taxonomical pattern of invasion in particular countries.Main conclusions
Multivariate analyses have shown that in Europe, there are two distinct groups of species of North and South American origin, respectively, whose invasion is determined by climatic conditions, namely temperature and precipitation. The South American group is represented by perennial and annual species preferring oceanic climate (e.g. O. rosea, O. stricta), while the North American group consists of biennial representatives (O. biennis and others) better adapted to inland conditions with lower mean temperature and more balanced monthly precipitations. In addition, there is a transitional group of species, including namely O. erythrosepala and O. fallax, preferring regions with sufficient rainfall and higher temperatures. The relatively hot climate of Balkan Peninsula seems to prevent invasion by Oenothera representatives. Pattern of invasion of particular taxa corresponds well to the climatic conditions in the regions of their natural distribution.