INQUA Project 1606: Ground squirrels on the march: expansion and speciation in the Quaternary of the Circum-Pontic area and surroundings
Lilia Popova (Taras Shevchenko National University of Kyiv, Ukraine). Email
Lutz Christian Maul (Senckenberg Research Institute, Research Station of Quaternary Palaeontology, Weimar, Germany). Email
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?
- 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.
- 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.
- 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.
- testing the hypothesis of an ‘opportunistic mode’ in ground squirrel evolution (‘opportunistic mode’ in analogy to ‘opportunistic species’ in ecology). In the case of the Pleistocene evolution of ground squirrels, ‘opportunistic’ implies the absence of well-defined chronoclinal shifts, i.e., on the ground squirrel phylogenetic tree short-living ‘sprouts’ expected to be dominate in number. It seems to be the most safe mode of evolution (safe for the longevity of the high taxon, not for the short-living species-sprouts, of course). Short-living sprouts ‘move off’ from the core adaptation either in a proper sense, geographically, or ecologically, or both. Although species-sprouts take chances, it does not matter until the steam persists: they can be easily replaced by new ones. As species-sprouts have to fill peripheral niches time after time (after extinctions), and the steam has to stay multipotent to meet its role, all the system goes round in the circles. So, it is at the same time similar and dissimilar to the hominins around MPT and, more important, may turned out to be a way to regulate (to brake) tempo of evolution.
- ‘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.
Our activities of this year are as follows:
Field training: Pyvykha mountain
The venue for this event is a special nature reserve the Pyvykha mountain, near Gradizhsk town, Poltava region, Ukraine; the coordinator is Dr. V. V. Ogar (Taras Shevchenko National University of Kyiv, Institute of Geology); the meeting is planned for the first half of June, duration is a week; contacts: Email
The Pyvykha is the continuation south of the belt of glaciodislocated rocks along the Dnieper. The geological section of the mountain is knotty enough (the very thing is needed for young scientists). The scope of discussed issues is expected to be broad: from the source of the moraine material to (even!) underwater archaeology; and, the most important for our project, the species expansion. This geologically unusual area may conceal evidences on so called the open-gate event for the Middle-Pleistocene fauna.
The backwoods: at the periphery of the adaptive zone
A working meeting coordinated by Dr. A. Nadachowski , Institute of Systematics and Evolution of Animals, Krakow, Poland; the last week of August -beginning of September 2017.
This will be a preamble to the main event of the year, the workshop in Chernivtsi. Generally speaking, the Pleistocene range expansions repeatedly dislocated ground squirrels species in rather unexpected places, like Britain or Netherlands. However, the extinct Early Pleistocene ground squirrel Spermophilus polonicus looks the most peculiar and provides a useful possibility to clarify what it is, as a matter of fact, to be the ground squirrel.
International field workshop: Populations in the non-optimal environment
Coordinated by Dr. B. Ridush, Yuriy Fedkovych Chernivtsi National University, 20-23d of September 2017, Chernivtsi region, Ukraine
The populations withstanding unfavourable conditions will be one of the focus there. Any data on populations being (were being) in a short step from extinction or populations after the natural introduction, as well as related phenomena (small population isolates and populations in fragmented landscapes, hybridisation of all kinds, competitive exclusion, changes in the population niche, terminal phases of human cultures, cultural interactions etc) will be welcomed, as well as any information on state of palaeogeographical barriers through the Quaternary of Circum-Pontic-Sea area.