An investigation of the feeding habits and prey availability in a community of seven species of shrew (Insectivora: Soricidae) inhabiting the taiga of Central Siberia was carried out with the aim of quantifying levels of niche overlap and elucidating modes of ecological separation amongst these coexisting species. All species took a wide range of invertebrate prey, and overlap in the numbers of shared prey taxa was high, but differences in dietary composition of certain taxa reduced overlap between most species. Small species fed almost exclusively on small arthropods, mostly Araneae, Chilopoda and Coleoptera, while medium and large‐sized species took high proportions of oligochaetes. Prey were mostly taken in proportions approximately equal to their availability, although certain prey appeared to be selected. All shrews took prey in a range of sizes, and the high dietary occurrence of small invertebrates reflected their availability and high encounter rate in field samples. Dietary occurrence of small prey was negatively correlated, and large prey positively correlated, with body size of shrew. Smaller shrews were predominantly ground‐surface foragers while larger species were more subterranean, with body size and dietary occurrence of soil prey being positively correlated. Differences in prey size and foraging mode reduced niche overlap between shrew species of widely differing sizes. Each shrew species did not occupy a separate, well‐defined food niche. Instead, the community was sub‐divided into three functional groups: large and small species which tended towards specialization with relatively low levels of overlap, and intermediate, generalist species with higher levels of overlap.

No abstract

With 4 figures in the text)The habitat occurrence and invertebrate prey distribution of nine species of shrew in the midtaiga of central Siberia were investigated. Species richness ranged from 4-9 shrews per habitat. Sorrx araneus and S. cueculiens were numerically dominant in all seven habitats (44 and 36% of the total catch, respectively) while Sorex minutus, S. tundrensis, S. isodon, and S. roboratus each constituted 4-6% and Sores minutissimus, S. dapharnodon, and Neomys,fodiens were rare ( < 1 YO each). There was no overall correlation between abundance of shrews and invertebrate prey, but flood-plain habitats supported the greatest abundance and species richness of shrews, and high density and biomass of prey. Oligochaete-eating shrews were twice as numerous here as in other habitats, coincident with high abundance of oligochaetes. The large, earthwonn-feeding Sorex rohoraru.r occurred only here. The more acid, typical taiga habitats had lower adundance and species richness of shrews. They had the lowest density and biomass of prey, particularly oligochaetes, and far fewer ohgochaete-eating shrews. The relative paucity of shrews in bushmeadow habitats, despite abundant prey, implied that habitat structure influences shrew distribution. Differential numbers of certain species in the presence or absence of larger congeners also suggested that interspecific competitive effects influence habitat selection by shrews. The high species richness of shrews here in the mid-taiga may be accounted for by the heterogeneous nature of the constituent habitats which provide niches for small and large species of shrew with a range of feeding habits.

A range-wide phylogeographic study of the tundra shrew (Sorex tundrensis) was performed using cytochrome b and cytochrome oxidase I (COI) mitochondrial genes. The results based on 121 specimens from 42 localities demonstrate that the tundra shrew is divided into five main mitochondrial DNA phylogenetic lineages with largely parapatric distribution. In addition to a single Nearctic clade (Alaska) four Palearctic clades are identified: Western (Northen Urals, Kazakhstan, South-West Siberia), Eastern (from East Transbaikalia and the Middle Amur to Chukotka), South Central (Central Siberia, the Altai, the Dzhungarian Alatau) and North Central (Northern Siberia, Central Yakutia). Date estimates obtained by use of a molecular clock corrected for potential rate decay suggest Late Pleistocene age for the most recent common ancestor of all contemporary tundra shrew populations. Relatively high genetic divergence between phylogroups (0.95-1.6%) indicates that the observed phylogeographic structure was initiated by historical events that predated the Last Glacial Maximum. We assume that, being more cold-and arid-tolerant, tundra shrew underwent expansion during an early cold phase of the Last Glacial and spread through its recent range earlier than most of other Siberian red-toothed shrews. Comparative phylogeographic analysis of Siberian shrews and rodents suggests that evolutionary histories of species associated with azonal or open habitats show important differences compared to forest species.