Abstract
The alien crop weed flora of Oranie (Northwest Algeria) presented in this study which is based on fieldwork carried out by the first author up to September 2023, as well as on the literature found to date. The analysis of Oranie's weed flora showed 36 species of alien species which represent 2% of the 1,780 species of the whole spontaneous flora of the Oranian phytogeographic territory and 8% of the local weed flora. Almost 50% of these species were native to the American continent and about 63% came from several tropical regions. The most representative life-history traits of these alien species compared to native ones: were: annual cycle (75% versus 76%), summer germination (78% versus 13%), non-specialized dissemination strategies, but related with anthropic activities (75% versus 46%), self-pollination (73%), and the high proportion of C4 species (36.11% versus 3%). The agricultural biotopes mainly affected are summer-irrigated crops with short rotation and an important nitrogenous fertilizers assignment. There are very few such habitats in Oranie, and few summer annuals in Algeria's flora. The success of alien weeds seems to result from the suitability between environmental conditions of a newly created habitat (summer temperature, humidity, important nitrogen rate, frequent perturbations, short rotations, and ecological niches available) and species characteristics (annual type, summer germination, photosynthetic pathway in C4). Dispersal strategy and fecundation types seemed not to be of much importance in characterizing these alien species.