Elevational filtering reshapes mountain understory communities through diversity decline, functional shifts, and species replacement

Mountain understory communities are shaped by elevation gradients, but the extent to which elevational differences influence community composition, diversity, functional strategies, and species replacement is still unclear. To investigate this, researchers studied 107 herbaceous species across 27 sites ranging from 2,202 to 3,696 meters above sea level in three distinct elevational zones.

The aim was to determine how elevation drives changes in community assembly, hypothesizing that higher elevations lead to distinct community composition, lower diversity, persistence-oriented strategies, and species turnover as the primary drivers of beta-diversity. By examining taxonomic, functional, and beta-diversity patterns across the elevation gradient, the researchers found a consistent pattern: communities become more distinct and less diverse as elevation increases.

Concurrently, functional composition shifts, with an increase in perennial and chamaephytic species and a decrease in annual and therophytic species. The findings indicate that increasing community differentiation is mainly due to species replacement rather than progressive loss of species. Turnover accounts for 97.95% of total Sorensen beta-diversity and increases with elevational separation, while nestedness declines.

The study concludes that elevation reorganizes herbaceous understory communities by simultaneously altering diversity, functional strategies, and species identity, with environmental filtering favoring persistence-oriented strategies and progressively replacing species across elevations. This suggests that taxonomic and functional differentiation within mountain understory community assembly are linked through a common process of species replacement.