Local extinctions of the wetland specialist Swertia perennis L. (Gentianaceae) in Switzerland: a revisitation study based on herbarium records

We studied population extinction of the locally abundant fen plant Swertia perennis in Switzerland and used up to 127-year old herbarium records to relocate 63 sites that had once hosted this species. We recorded current site characteristics and related them to the absence or abundance of populations. Fifty-four sites (86%) were still traditionally used (extensively mown or grazed). Fifteen populations (24%) had gone extinct. Extinction was more likely at lower altitude, in the peripheral distribution range of S. perennis (58% peripheral, 9% central populations extinct), on the smallest fens (75% extinct on fens <400 m) and on fens with intensified land use. However, even on traditionally managed wetlands 18.5% of the populations had gone extinct. Moreover, 40% of all remaining populations were smaller than 250 flowering plants. We conclude that both intensified agricultural practice and habitat fragmentation contributed to local extinction of S. perennis. Small populations, especially, may not be able to persist in the long term. # 2001 Elsevier Science Ltd. All rights reserved.