Naturalized alien flora of the Indian states: biogeographic patterns, taxonomic structure and drivers of species richness

Abstract

Despite an existing India-wide inventory of alien plant species, an inventory documenting the occurrence of naturalized alien plant species in each of the Indian states (including union territories) was not available yet. We compiled from the literature a list of naturalized alien vascular plant species with data on their occurrence in 33 Indian states, and related the richness of naturalized species per state to climate, socioeconomic parameters and human influence. In total, we report 471 naturalized species in India, which represents 2.6% of the total flora of this country, and for 449 of them we provide the distribution in the states. The highest and lowest numbers of naturalized species are reported from Tamil Nadu (332) and the island Lakshadweep (17), respectively. The families richest in naturalized species are Compositae (75), Leguminosae (60) and Poaceae (36). The highest numbers of naturalized aliens occurs in states located at lower latitudes in the tropics, and in more northernly located states that even in the dry period still have relatively high amounts of precipitation. Naturalized species richness of a state is furthermore positively related to socioeconomic factors represented by the percentage of the population living in urban areas, and human population density. The state-wise inventory of naturalized alien species improves our knowledge on threats associated with plant invasions in India, and can be used to provide arguments for promoting programs on conservation of native biodiversity in the country as well as in particular states.