INQUA Project 1606:
Ground squirrels on the march: expansion and speciation in the Quaternary of the Circum-Pontic area and surroundings, 2017
The project is aimed on connections between /among species expansion and speciation events, species expansion and environmental constraints, survival of small isolated populations, survival on the frontiers of the species ranges. Among environmental constraints, we focus on 1) purely geographical (non-climatic) barriers (mountain ridges, great rivers, isthmuses/channels, etc) and 2) interspecific competitive relations.
Why do we expect humble ground squirrels (Spermophilus) to be especially suitable to clarify aforementioned questions on how a species / a population seeks for / loses a place in the severe sun of the Pleistocene?
(1) Range dynamics of Spermophilus species turn out to be indicative of geographical barrier changes. It is a consequence of the main features of ground squirrel ecology and behaviour (burrowing life style, social behaviour, hibernation, high interspecific competition resulting in rather strict allopatry), which limit their ability to overcome the impediments imposed by physical geography. The most obvious thing, the ability to cross water barriers in these animals is especially restricted because they hardly able to swim, meanwhile hybernation impedes crossing rivers over ice. Such events as a change of a river channel, appearance of an isthmus or another, less obvious event, open for the ground squirrel species the way for the expansion.
(2) Thereby, the effects of environmental constraints on species distribution and speciation in Spermophilus is expected to be especially definite and easy to research. Thereby, the expansion events in ground squirrels are the criteria of the changes of geographical barriers.
(3) Surviving of ground squirrel populations in non-optimal environments. It is a rather common situation for a population when its range changes significantly. Fossil ground squirrels provide an important advantage to study the populational consequences of the isolation, bottlenecks phenomenon, hybridisation and so on: their burrow taphocoenoses were accumulated by population processes directly at a settlement place, without any transport, so can be regarded as paleopopulations, and, at the same time, yield abundant material, in contrast to burrow taphocoenoses of non-social burrow mammals.
Last but not least, ‘Ground squirrels on the march’, in addition to their own significance, are an appropriate symbol for any species overcoming environmental constraints. We plan to include into the analysis other species suitable for the reconstruction of changes of geographical barrier during the Pleistocene. These can be some voles, marmot species, fresh-water ichthyofauna. Palaeolithic humans are also a good subject of this inquiry, because of the bulk of data amassed on palaeogeographical changes accompanying events of human expansion.