Morphological Diversity of the Skull and Lower Jaw of Three Shrew Species (Eulipotyphla, Sorex) during Depressions and Abundance Peaks

Environmental conditions can influence the individual development of organisms and their morphological variability at the population level. The dimensions and proportions of the skull and lower jaw of immature shrews (Sorex araneus, S. caecutiens, and S. minutus), which were captured in August in regenerating clearings in the middle taiga of northeastern Europe, depended on the stage of abundance dynamics ("peaks" or "depressions"). For all three species from the same taxocenosis, a statistically significant reduction in the skull and jaw was observed against the background of the high abundance in captures and the multidimensional morphological niches corresponding to different abundance stages were significantly separated. The parameters of morphological diversity (entropy and self-organization index) depended on the amplitude of fluctuations in species occurrence; however, they varied within the limits characteristic of mammals. Along with Dehnel's phenomenon, natural population fluctuations may be one of the main factors determining the pattern of dynamics of the individual development and spatiotemporal variability of the morphological diversity of shrews.