The vascular flora of Pécs and its immediate vicinity (South Hungary) I.: species richness and the distribution of native and alien plants.

Urbanization is one of the major causes of species loss and the homogenization of the world's flora. Our coarse-scale floristic mapping project of the largest south Transdanubian city, Pécs, is the first grid-based urban study in Hungary that reveals the current pattern of the vascular flora. Beyond the general description of the project, the species richness, the number of native, archaeophyte, neophyte and legally protected taxa are presented in the scale of the grid units (2.2 km) and according to the residential area of the city. Relationships between the number and proportion of natives, archaeophytes, neophytes, protected species versus the proportion of built-up areas, forest coverage and elevation are estimated by linear regression models. Among the 1458 spontaneous or subspontaneous vascular plant species of the study area 131 are legally protected. The average number of species per grid unit is 338. Regression models show that the number of aliens decreases with forest coverage and increases with the rate of built-up areas, while number of natives shows opposite trends as a function of the same variables. These opposite trends lead to the conclusion that in the case of the vascular flora of Pécs the "poor get richer" theory is supported. Among the most frequent species hemicryptophytes, widespread, native and zoochorous plants are dominant. The most widespread four invasive taxa are native to North America.