The alien flora of Greece: taxonomy, life traits and habitat preferences

The aim of the paper is the state-of-the-art assessment of the alien flora of Greece and its traits. The dataset consists of a total of 343 alien taxa, including 49 archaeophytes. The taxonomy, life traits and habitat of the 294 neophytes are analysed vs their naturalisation status. Out of the 122 (41%) naturalised neophytes, 50 are identified as exhibiting invasive behaviour. Poaceae, Asteraceae, Amaranthaceae, Solanaceae, Fabaceae, and Polygonaceae are the plant families richest in alien taxa. The majority of them are of American origin, followed by those of Asiatic and Mediterranean origin. The neophytes are predominantly herbs, most of them annuals. Yet, the perennial life cycle is equally frequent with the annual one and the proportion of phanerophytes in the alien flora is increased compared to the one of the native flora. Regarding flowering traits, most of the aliens have a long flowering period (over 1 month) and flower in late spring, summer and autumn, when few of the native plants are in bloom. Vertebrate zoochory and anemochory are the two dispersal modes mostly utilised by the alien plants (43 and 28%, respectively), while more than one dispersal mechanisms are functional for 56% of them. Artificial habitats have the highest frequencies of alien plants. The natural habitats with the highest numbers of aliens are the coastal ones and inland surface waters. Opuntia ficus-barbarica, Ailanthus altissima, Oxalis pes-caprae, Erigeron bonariensis, Amaranthus albus and Symphyotrichum squamatum are typical cases of plants characterised as invasive, having established in almost all the habitat groups identified. The diversity of the ecological characteristics of the plants suggests a potential of impacts that needs to be further assessed.