Figure 1

Location of the 25 pond clusters (abbreviations) spread over five biogeographic regions in Belgium/Luxembourg: 1) Polders (BKNO, BUIT, BKLE, BDAM, BLAP), 2) Sand region (CKRU, CSTE, CHOU, CBOO, CMEC), 3) Loam region (DHAS, DZOU, DALK, DRIK, DDIE), 4) Chalk region (ESOR, EPES, EBEA, EFOC, EHAI), 5) Gutland (ANOB, ASCH, ABER, ACAP, AUSE).