Ants on a mountain: spatial, environmental and habitat association along an altitudinal transect in a centre of andemism

Date
2012-02-07Author
Munyai, Caswel
Date Created
2011Format Extent
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Show full item recordAbstract
Mountains are biodiversity hotspots and provide
spatially compressed versions of regional and continental
variation. They might be the most cost effective way
to measure the environmental associations of regional
biotic communities and their response to global climate
change. We investigated spatial variation in epigeal ant
diversity along a north–south elevational transect over the
Soutpansberg Mountain in South Africa, to see to what
extent these patterns can be related to spatial (regional) and
environmental (local) variables and how restricted taxa are
to altitudinal zones and vegetation types. A total of 40,294
ants, comprising 78 species were caught. Ant richness
peaked at the lowest elevation of the southern aspect but
had a hump-shaped pattern along the northern slope. Species
richness, abundance and assemblage structure were
associated with temperature and the proportion of bare
ground. Local environment and spatially structured environmental
variables comprised more than two-thirds of the
variation explained in species richness, abundance and
assemblage structure, while space alone (regional processes)
was responsible for\10%. Species on the northern
aspect were more specific to particular vegetation types,
whereas the southern aspect’s species were more generalist.
Lower elevation species’ distributions were more
restricted. The significance of temperature as an explanatory
variable of ant diversity across the mountain could
provide a predictive surrogate for future changes. The effect of CO2-induced bush encroachment on the southern
aspect could have indirect impacts complicating prediction,
but ant species on the northern aspect should move uphill at
a rate proportional to their thermal tolerance and the
regional increases in temperature. Two species are identified
that might be at risk of local extinction.