The first checklist of alien vascular plants of Kyrgyzstan, with new records and critical evaluation of earlier data. Contribution 1.
Background: National checklists of alien plants and detailed databases of non-native plant occurrences are required to study and control regional and global plant invasions. No country in Central Asia has a national checklist of alien plants. A recent inventory counted 183 alien plant species in Kyrgyzstan, including archaeophytes and neophytes, established and casual. This preliminary checklist, which was developed for the Global Register of Introduced and Invasive Species in 2018, served as a starting point for the present study. New information: A complete inventory of Xanthium in Kyrgyzstan has revealed that three alien species are resident in the country. Their correct nomenclature is X. orientale (syn. X. albinum, X. californicum, X. sibiricum auct.; invasive neophyle of the period of extensive grain import to the USSR after the Second World War), X. spinosum (invasive neophyte of the period of the Second World War, which arrived as a contaminant on the relocated livestock) and X. strumarium (syn. X. chinense, X. sibiricum; archaeophyte of the Neolithic period, introduced with wheat cultivation, which had lost its invasive status and appeared on the verge of extinction when its pool was no longer renewed by contaminated grain). A history of introduction to Central Asia is uncovered for all the species of Xanthium. A further spread is documented for Bunias orientalis, with a new record extending its distribution to the Eastern Tian-Shan; a complex history of its introduction to Europe and Central Asia is inferred from the archaeological data and its recent dispersal, and the pathways of its introduction to Kyrgyzstan are established. Erigeron annuus s.str. is reported as new to Kyrgyzstan and Uzbekistan, and E. lilacinus as new to Kyrgyzstan, Uzbekistan, Kazakhstan, Nepal and Tajikistan (it was previously recorded as E. annuus s.l. from the three latter countries, in which the presence of E. annuus s.str. is not confirmed). These closely related species differ in their pathways of introduction and invasion status: E. annuus s.str. is an invasive established alien which was imported as a contaminant of forage, whereas E. lilacinus is mostly a casual (locally persisting) alien introduced with contaminated seed of ornamental plants or nursery material, and also intentionally introduced and locally established in the Botanical Garden in Bishkek. Bidens tinctoria (syn. Coreopsis tinctoria) is newly recorded as a casual alien from a single locality in Kyrgyzstan; this species name is validly published here in conformity with the phylogeny of Coreopsideae. Point maps of species distributions in Kyrgyzstan are provided on the basis of a complete inventory of the literature data, herbarium specimens and documented observations, and our recent fieldwork. The maps are documented with a dataset of herbarium specimens and observations. Period and pathways of introduction, vectors of dispersal, current and historical invasion status, evidence of impact and distributional trend are established or inferred for each species. Each species is discussed in the context of plant invasions in Central Asia as a whole. These species accounts are part of the national database of alien plants which aims at producing a comprehensive overview and analysis of plant invasions in Kyrgyzstan.