Local and landscape environmental heterogeneity drive ant community
structure in temperate semi-natural upland grasslands
Abstract
Environmental heterogeneity is an important driver of ecological
communities. Here, we assessed the effects of local and landscape
spatial environmental heterogeneity on ant community structure in
temperate semi-natural upland grasslands of Central Germany. We surveyed
33 grassland sites representing a gradient in elevation and landscape
composition. Local environmental heterogeneity was measured in terms of
variability of temperature and moisture within and between grasslands
sites. Grassland management type (pasture vs. meadows) was additionally
included as a local environmental heterogeneity measure. The complexity
of habitat types in the surroundings of grassland sites were used as a
measure of landscape environmental heterogeneity. As descriptors of ant
community structure, we considered species composition, community
evenness, and functional response traits. We found that extensively
grazed pastures and within-site heterogeneity in soil moisture at local
scale, and a high diversity of land cover types at the landscape scale
affected ant species composition by promoting nest densities. Ant
community evenness was high in wetter grasslands with low within-site
variability in soil moisture and surrounded by a less diverse landscape.
Fourth-corner models revealed that ant community structure response to
environmental heterogeneity was mediated mainly by worker size, colony
size, and life history traits related with colony reproduction and
foundation. We discuss how within-site local variability in soil
moisture and low intensity grazing promote ant species densities, and
highlight the role of habitat temperature and humidity affecting on
community evenness. We hypothesize that a higher diversity of land cover
types in a forest-dominated landscape buffers less favorable
environmental conditions for ant species establishment and dispersal
between grasslands. We conclude that spatial environmental heterogeneity
at local and landscape scale plays an important role as deterministic
force in filtering ant species and, along with neutral processes (e.g.
stochastic colonization), in shaping ant community structure in
temperate semi-natural upland grasslands.