Species richness of Orthoptera declines with elevation while elevational
range of individual species peaks at mid elevation.
Abstract
Species richness has been shown to decrease, and elevational range
increase (the Rapoport effect), with elevation as a consequence of
biotic and abiotic factors, but patterns are inconsistent across
taxonomic groups. Despite being an important indicator taxon and
component of local communities, Orthoptera distributions at higher
elevations in Europe remain unclear. We investigated the relationship of
Orthoptera species richness and elevational range with elevation by
conducting field studies at 28 sites across three study areas in the
Pyrenees mountains, Europe. We found that species richness declined with
elevation. Study area and the site-specific factors of sampling effort,
topography (slope) and vegetation structure (density and cover) were
also important predictors of species richness. We did not observe a
Rapoport effect, with elevational range peaking at mid-elevation
instead. Smaller elevational ranges found at high elevations may be due
to a combination of sampling over a restricted elevational range and the
presence of specialist high-elevation species. We also explored the
composition of Orthoptera assemblages using multivariate methods,
finding no clear effect of elevation, slope or vegetation structure on
these communities, although study area somewhat influenced assemblages.
To our knowledge, this is the first study of the Rapoport effect along
an elevational gradient using insects as a study system in Europe. We
argue that our findings are useful for understanding species
distributions with elevation at the interface between local and regional
scales. Clarifying the biotic and abiotic predictors of species
distribution is important for informing conservation efforts and
predicting consequences of climate change.