Abstract :
Altitudinal gradients provide excellent opportunities to study relationships between species
distribution and climatic variables. We studied the species composition of 39 samples of moss-inhabiting
diatoms, collected at 50 m intervals from 100–650 m above sea level. The samples contained a total of 130
diatom species, of which 51 occurred in 10 or more samples. Altitude appeared to be the most important
variable explaining variation in species composition. Of the 51 common species, 33 showed a significant
relationship with altitude. Although the majority of the latter declined with increasing altitude, for nine
species the probability of occurrence first increased with increasing elevation, but decreased again at higher
altitudes, and four species increased systematically with elevation. As a result, expected species richness per
sample decreased from an estimated 43 at 100 m to 25 species per sample at 650 m. Diatom distribution
patterns proved to be suitable predictors of the altitudinal position of sample sites. Cross-validation yielded
a strong relationship between predicted and observed altitudes
