Holarctic Marmots as a factor of Biodiversity.
Rumiantsev V.Yu;, Nikol'skii A.A. & Brandler O.V. eds.,
Abstracts, 3d Conference on Marmots (Cheboksary, Russia, 25-30 August 1997),
Moscow ABF 1997, 216p. : 181-182.


MORPHOLOGICAL DIFFERENTIATION OF TWO MARMOT FORMS (MARMOTA BAIBACINA AND M. SIBIRICA) IN SOUTHERN MONGOLIA


E.G. Potapova*, A.Ju. Puzachenko**, D.I. Bibikov*

*Institute of ecology and evolution problems RAS
**Institute of geography RAS, Moscow, Russia


In the framework of the problem of taxonomic differentiation within genus Marmota comparative morphological analysis of forms baibacina and sibirica inhabiting zone of their sympatry and adjacent areas has been conducted. Localities under study are situated on the transect running from the Altai Range through Sailugem Range along Mongolian and Gobi Altai to the Darigang in the Sourth-eastern Mongolia. For the sake of comparison samples of baibacina from Central Tien Shan and of sibirica from Khangai Range, Transbaikalia and Tuva have been studied. Taxonomically, represented Altai marmot belong to two forms - baibacina s. str. and centralis and Mongolian bobak - to sibirica s. str. and caliginosus.

Variability of several dimensional and some qualitative characters outlining main features of skull shape and structure has been studied. Eight measurments that are belived to be, in the first approximation, a quantitative representation of species-specific diagnostic characters were selected. These are as follows: condilobasilar, palatine and nasale bones length, distance between lacrimal foramina, heigh of zigomatic arch and distance between palatine foramen and the palate edge. Among qualitative characters shape of supraorbital process, anterior interorbital width, position of angles on the upper adge of zigomatic arch, shape of maxillary-jugale suture, position of posterior palatine foramina relative to palate suture, etc are examined.

In the course of the study two different approaches were used. According to one of them all marmots were regarded as unified group so that species identity of particular specimens has been ignored. Under second approach baibacina and sibirica have been compared with each other. Different methods of parametric and nonparametric statistics were used.

As a result, under the first approach all unified sample fell into two morphologically distinct groups , one of them being matched, with high significance, with baibacina, and other - with sibirica. Analysis of samples from different localities showed that in most of them both morphotypes are present, although in different proportions. "Pure" sample of baibacina was revealed in the zone of M. b. centralis' terra typica in the Central Tien Shan, and sample of "pure" sibirica - Transbaikalia. In all other localities strict correlations between relative proportions of morphotypes and geographical position of the area were detected. Possible exception could be the Darigang population, where proportion of sibirica morphotype turned out to be less than the expected one. Hypothesis on the existence hybridization between different morphotypes was tested. It was shown that either hybridization was absent or hybrids retained morphotype of one or of another parental form.

So, in the framework of the first approach the hypothesis can be put forward that there are two well differentiated forms of marmot (baibacina and sibirica) that in the extensive overlap zone in Mongolia live in mixed populations.

The second approach (namely, comparison of baibacina and sibirica as that were identified in the field), in spite of considerable morphological variability of animals under studing, has shown that differences between above forms are statistically significant, and discrimination can be done with high probability on base both measurments and structure pattern. Analysis of dimensional characters variability within each form permited to reveal rather obvious geographical component. At the same time, investigation of quantitative characters' diversity appeared to be most informative for the examination of interpopulation interrelations. So, populations of sibirica, in accordance with some features of zygomatic arch and palate, form row from Darigang marmots to Khangai and Tuva ones.
Among baibacina the form centralis is readily distinguished. Significantly, baibacina from the zone of overlap with sibirica is sharply distinct, in respect of palate and zygomatic arch's structure, from other Altai marmots being at the same time similar to sibirica from Khangai and Tuva. From the other hand, sibirica from the same contact zone blend with morphological series of marmots from Mongolian and Gobi Altai.


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