Taxonomic self-descriptiveness of some craniological features by the example of bobak group marmots (Marmota, Rodentia). Sistematitcheskaia ??informativnost’?? nekotorykh kraniologitcheskikh oriznakov na primere sourkov grouppy ??bobak?? (Marmota, Rodentia).

Résumé

The geographical variations of color and dimension of body are traditionally used in taxonomy of palaearctic marmots to distinguish between sub-species, while a complex of habituaI (qualitative features of color, dimensions and proportions of body) and craniological (mainly constitution features) signs are applied to distinguish between species. Some researchers also take into account the differences of baculum structure (Galkina, 1962; Kapitonov, 1966; Chervyakova, 1966). All these signs can be divided into three groups: color, metric (dimensions and proportions) and qualitative (discrete). When studying morphological differentiation of ??bobac?? species group we used all of the listed sign groups. Their significance for sub-species taxonomy of marmots was considered by the example of grey marmot Marmota baibacina Kastschenko, 1899. In this message we are dealing only with some craniological indexes, both metrical and qualitative. We comparatively analyzed the following samples: 1 - M. baibacina (the Salair mountain-ridge - n=50; South-Eastern Altai - n=270; South-Western Altai -n=50; Kalbinsk Altai - n=50); 2 - M. bobak Muller, 1776 (Northern Kazakhstan - n=48); M. sibirica Radde, 1862 (South Tuva and Transbaikalia - n=48). The representatives of M. kastschenkoi (Salair mountain-ridge) were considered in the sample of M. baibacina as sub-species M. b. kastschenkoi. The analysis was made based on 31 craniometrical and several qualitative indexes. All digital information was processed by the method of discriminant analysis and the method of principle components by means of STATISTICA 6.0 software. Mean differences reliability was evaluated by t -criterion. This analysis involved only mature animals. As a result we came to a conclusion that discrete (first of all) and metric (in the second place) features of the skull shall be used to distinguish between species. The first group includes the structure and form of postorbital outgrowth, the form of lachrymal bone, peculiarities of the lower P4 structure. The second group includes condilo-basal length of skull, interorbital and postorbital width, dimensions of auditory tympanum, alveolar length of upperteeth. These signs are less variable and more important in terms of differences between the samples of species rank by t-criterion. The whole specter of craniometrical indexes is suitable for distinguishing between sub-species. But it should be noticed that an external group needs to be included in the analysis.