Alien flora of Iran: species status, introduction dynamics, habitats and pathways

This first inventory of casual, naturalized, and invasive alien plants in Iran provides a knowledge base for managing the threats associated with plant invasions in this country. Based on a wide range of data sources, including published work, reports, online databases, botanical records, and field observations, we identified 311 alien vascular plants, of which 131 are classified as casual, 167 naturalized, and 13 invasive. Therophytes are most represented among naturalized plants (50.9%), while phanerophytes (49.6%) are most represented among casuals. Poaceae, Fabaceae and Asteraceae are the families with the highest richness of alien species (35, 28, and 24, respectively). The largest fractions of naturalized taxa originated from South America and Central America (22.2% and 20.4% of all naturalized aliens, respectively). Horticulture and agriculture are the main pathways of new introductions of alien plants to Iran; this is reflected in naturalized species playing a major role in the weed flora of Iran, with about a half of them growing in agricultural habitats. Naturalized plants are also common in ruderal habitats, while casual plants commonly occur not only in these two types of human-disturbed habitats but also in open forest. We suggest that exploring the effect of bioclimatic conditions along with human population density in this large and diverse country could provide further information about alien species invasions; for that, future research should focus on mapping alien species spatial distribution in Iran and continue monitoring new arrivals in order to develop robust quarantine system at the national level.