Refugial ecosystems in central Asia as indicators of biodiversity change during the Pleistocene–Holocene transition
2017
Site-scale species richness (alpha diversity) patterns are well
described for many present-day ecosystems, but they are
difficult to reconstruct from the fossil record. Very little is
thus known about these patterns in Pleistocene full-glacial
landscapes and their changes following Holocene climatic
amelioration. However, present-day central Asian ecosystems
with climatic features and biota similar to those of the
full-glacial periods may serve as proxies of alpha diversity
variation through both space and time during these periods. We
measured alpha diversity of vascular plants, bryophytes,
macrolichens and land snails, as well as environmental
variables, in 100-m(2) plots located in forests and open
habitats in the Russian Altai Mountains and their northern
foothills. This region contains adjacent areas that possess
climatic and biotic features similar to mid-latitude Europe for
both the Last Glacial Maximum and contemporaneous Holocene
ecosystems. We related alpha diversity to environmental
variables using generalized linear models and mapped it from
the best-fit models. Climate was identified as the strongest
predictor of alpha diversity across all taxa, with temperature
being positively correlated to number of species of vascular
plants and land snails and negatively correlated to that of
bryophytes and macrolichens. Factors important for only some
taxa included precipitation, soil pH, percentage cover of tree
layer and proportion of grassland areas in the landscape around
plots. These results, combined with the high degree of
similarity between the current Altai biota and dry-cold
Pleistocene ecosystems of Europe and northern Asia, suggest
that vascular plant and land snail alpha diversity was low
during cold phases of the Pleistocene with a general increase
following the Holocene climatic amelioration. The opposite
trend probably existed for terricolous bryophytes and
macrolichens.
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