Article

In this research are analysed the European and Mediterranean floristic representatives established in the most humanized regions of Uruguay as a consequence of the continuous exchange of plant entities occurred since the last five centuries between Europe and South America. As far as Uruguay is concerned, the taxa adventitious and the ones that became spontaneous, have been listed and analyzed according to their occurrence and territorial significance (k). There have been selected the regions from the middle West to South, Centre and East according to the most humanized areas in terms of labored soils and population density. Herbarium samples for all the species found have been collected. In total 174 taxa have been taken into account, 7 of the most represented families includes the 73% of the total species found. According to the chorological scheme, the Mediterranean types and the South European amount 52% of the European contingent surveyed for this work in Uruguay. In relation to the introduction process, the majority of taxa is adventitious (72% naturalized and casuals) in contrast to the ones escaped from cultivation that amount to 28%. The gradient in the species occurrence with the correspondence analysis taxa/sites, shows that there is no defined trend of correlation between territories and colonizing species variability. The gradient on the axis 1 is more related to higher human land use and to the proximity to the more important points connecting with foreign countries. The gradient on the axis 2, instead is likely more related to a specific culture type like rice. Regarding to the species with higher influence (k) in the colonized area, the k value shows that only 5% of the total species number, have value higher than 40. On the other hand, whilst k values lower than 10 represent 54% of the total species number.