Spatial patterns of vascular plant species richness in Poland: relations among species group richness and hot spot locations

Knowledge of spatial patterns of species richness (SR) is highly relevant for theoretical research in ecology and the development of conservation plans. In Poland, despite a long tradition of botanical surveys, vascular plant SR has not been mapped, nor have the correlations in richness among different plant species groups been explored. Here we used a recently published data set to examine spatial patterns and relationships among the joined SR of vascular plant species, including native species, archeophytes, neophytes, and species with high conservation value (i.e., red list species). The basic spatial unit employed was a 10 x 10 km grid from the Atlas of Distribution of Vascular Plants in Poland (ATPOL). We found that the richness patterns of native species, archeophytes, neophytes, and red-list species were positively correlated. The main patterns of SR and the percentage of particular groups in the joined SR were based on three components: (1) gradient of overall SR, (2) invasion level, and (3) peculiarity of flora in some regions resulting from the high number and proportion of rare species that often have high conservation value. In general, northeastern Poland was species-poor, while the Carpathian Mountain range, the uplands in southern Poland, and some parts of Wisa River valley had the highest SR concentrations. The location of SR hotspots usually did not overlap with the existing system of national parks. The correlations among native SR, high conservation value species, and neophyte SR suggest that biological invasions are among the most important threats to vascular plant diversity in Poland. Finally, we demonstrated that the presented maps, despite likely biases in SR assessments, seem to reflect general ecological gradients influencing vascular plant distribution in Poland.