Composition and pattern of alien species in the Egyptian flora

• Based on literature and herbarium records, the Egyptian flora comprised 136 alien species: 49 causals, 81 naturalized and 6 invasive.
• Invasions by old world species were more severe than those from the Americas.
• Date of introduction covers a period of 250–300 years (1750 till now).
• Time lags between introduction and spread of the invasive species ranged between 15 and 181 years.
• Characterization of the alien plant species can help in evaluating their impact upon biodiversity.

The present study aims to determine the alien and invasive species in the Egyptian flora, their origin and lags between the time of the first record and that of rapid growth. A list of alien species was prepared from literature, field trips and herbaria. The national distribution was gathered from the literature, while the global distribution was assessed according to the system of Good who divided the globe into six kingdoms, three subkingdoms and thirty nine floristic regions. The year of the first record was detected by searching in the references, and sometimes by checking herbarium sheets deposited in national herbaria. The final list included 136 species classified into three categories: 49 casuals, 81 naturalized and 6 invasive species. Most of these species occur in the Nile region (108 species = 79%) mainly due to the increasing human activities. Four natural and eight anthropogenic habitats were supporting the distribution of these species. Many of these species belong to the Boreal and Palaeotropical Kingdoms. Forty nine species matched with each of the periods of 1850–1900 and 1950–2000. Time lags of the invasive species ranged between 15 (Azolla filiculoides) and 181 years (Dalbergia sissoo). The dynamic patterns of alien species over a long period (≥ 500 years) as well as the role of hybridization in their spreading will be assessed in a future study.