Distribution and Ecology of Neophyte Lactuca Tatarica Population on the East Baltic Sea Coast in Latvia

There is an increasing need for species occurrence data at a regional level for the global assessment of invasiveness of neophytes. Therefore, the distribution and habitats of Lactuca tatarica (L.) C.A. Mey. in Latvia (Baltic Sea region) was studied. L. tatarica was observed for the first time in Latvia in 1920. During the next 60 years, it was mainly found in synanthropic habitats. Since the 1980s, the species has spread along the Gulf of Riga (the Baltic Sea) coast. In 2019, recent data on the distribution of L. tatarica were obtained in a large-scale habitat mapping project. Lactuca tatarica was observed in 147 polygons (total area of 230 ha) representing nine habitat types of EU importance. The largest proportion of L. tatarica localities was recorded in beach habitats, and the highest abundance and total area in white and grey dunes. Lactuca tatarica was observed in the following associations: Cakiletum maritimae, Honckenyetum peploidis, Elymo-Ammophiletum arenariae, and Festucetum polesicae. In most localities, L. tatarica genets are scattered or in small groups covering small areas. In some coastal sections (southern part of the Gulf), L. tatarica forms dense stands that tend to spread. Lactuca tatarica in Latvia is considered as a neophyte successfully naturalised mainly in coastal dune habitats, and in some locations it corresponds to the criteria of invasive species with a high risk to endanger natural habitats.