From herbarium specimens to contemporary surveys: Tracing the extinction dynamics and performance of endangered plant species in central Germany

Habitat loss and fragmentation, extensive land use, and climate change lead to an unprecedented amount of local extinctions in the Anthropocene. To protect endangered species, population ecological studies are essential to assess the current state of remnant populations. In addition, it is pertinent to investigate changes in the distribution of endangered species over time and space. Given the apparent lack of long-term studies, herbarium records are a valuable source for tracking these changes. In this study, we analyze three endangered plant species (Antennaria dioica, Omphalodes scorpioides, and Viola pumila), with different habitat preferences (dry grassland, riparian forest, and alluvial meadow, respectively) to examine their current status, and performance of the extant populations in central Germany. The analysis of herbarium specimens from the last 200 years indicates a dramatic decline in the occurrence area of all three species. Furthermore, most populations still found in central Germany are very small and strongly fragmented. Our results suggest that of several factors categorized into four groups (population size, climate, soil parameters, and vegetation parameters), the number of individuals or patches, Palmer Drought Severity Index (PDSI), soil depth, and percentage of bare soil exert the most pronounced influence on plant performance of the studied species. However, nature and strength of these correlations vary considerably across species. All this clearly shows an urgent need to prevent species extinction, underlining the imperative importance of species conservation, and the need for initiatives such as conservation breeding and reintroduction or reinforcement, which could lead to success even in small populations.