3. Results
3.1. Global trends in orchid dynamics in Western Europe
Null model 1 yielded the highest SES values of disappearances (SESdisp) in the Northern part of the study area (i.e. Luxembourg and several neighboring administrative units from North Western to North Eastern France and in Belgium, Fig. 1A). The administrative unit ‘Walloon Brabant’ (Belgium) showed significantly more disappearances than in the null model (P < 0.05, Fig. 1A). A significant and positive linear relationship between SESdispand the latitude of administrative units was found (linear model, P < 0.001, R2 = 0.30), but no linear relationship was detected with longitude. Null model 1 further revealed more frequent appearances of orchid species in Central and South Western France (Fig. 1B). The number of appearances was significantly higher than expected in the null model 1 in the French administrative units ‘Ile-de-France’ and ‘Landes’ (P < 0.05, Fig. 1B). Local disparities were observed between administrative units with numerous appearances (e.g. ‘Ile-de-France’) compared to neighboring administrative units with few appearances (Fig. 1B). A significant and negative linear relationship between SESapp and the longitude of administrative units was shown (linear model, P < 0.001, R2 = 0.20), but no linear relationship was detected with latitude.