Skeletal morphology of the forefoot in shrews (Mammalia: Soricidae) of the genus Cryptotis, as revealed by digital X-rays

Variation in the forefoot skeleton of small-eared shrews (family Soricidae, genus Cryptotis) has been previously documented, but the paucity of available skeletons for most taxa makes assessment of the degrees of intraspecific and interspecific variation difficult. We used a digital X-ray system to extract images of the forefoot skeleton from 101 dried skins of eight taxa (seven species, including two subspecies of one species) of these shrews. Lengths and widths of each of the four bones of digit III were measured directly from the digital images, and we used these data to quantify variation within and among taxa. Analysis of the images and measurements showed that interspecific variation exceeds intraspecific variation. In fact, most taxa could be distinguished in multivariate and some bivariate plots. Our quantitative data helped us define a number of specific forefoot characters that we subsequently used to hypothesize evolutionary relationships among the taxa using the exhaustive search option in PAUP, a computer program for phylogenetic analysis. The resulting trees generally concur with previously published evolutionary hypotheses for small-eared shrews. Cryptotis meridensis, a taxon not previously examined in recent phylogenies, is rooted at the base of the branch leading to the C. mexicana group of species. The position of this species suggests that the mostly South American C. thomasi group shares an early ancestor with the C. mexicana group.     

Biogeographical history of northeastern Asiatic soricine shrews (insectivora, mammalia)

A hypothetical biogeographical history of northeastern Asiatic soricine shrews in the late Quaternary was developed by integrating their present distributions, fossil records, a hypothetical phylogeny, and geological investigations. First, a biological area cladogram of the northeastern Asiatic region was constructed by applying the vicariance hypothesis to the phylogeny of thecaecutiens/shinto group, a monophyletic group proposed by Ohdachi et al. (1997). Comparing the biological area cladogram with a geological hypothesis by Ohshima (1990,1991,1992), we hypothesized a geographical history of northeastern Asia. Species were then located on the dendrogram of the geographical history, referring to the present distributions, fossil records, and phylogeny of shrews. According to our hypothesis, higher species diversity of the northern region of northeastern Asia (Hokkaido, Sakhalin, and Eastern Siberia) was achieved by several series of colonizations and habitat expansion. On the other hand, the shrew communities of the southern region (Honshu, Sado, Shikoku, and Kyushu) were created by extinction and isolation followed by speciation.     

Molecular phylogenetics of soricid shrews (Mammalia) based on mitochondrial cytochrome b gene sequences: with special reference to the Soricinae

Molecular phylogeny of soricid shrews (Soricidae, Eulipotyphla, Mammalia) based on 1140 bp mitochondrial cytochrome b gene (cyt b ) sequences was inferred by the maximum likelihood (ML) method. All 13 genera of extant Soricinae and two genera of Crocidurinae were included in the analyses. Anourosorex was phylogenetically distant from the main groupings within Soricinae and Crocidurinae in the ML tree. Thus, it could not be determined to which subfamily Anourosorex should be assigned: Soricinae, Crocidurinae or a new subfamily. Soricinae (excluding Anourosorex ) should be divided into four tribes: Neomyini, Notiosoricini, Soricini and Blarinini. However, monophyly of Blarinini was not robust in the present data set. Also, branching orders among tribes of Soricinae and those among genera of Neomyini could not be determined because of insufficient phylogenetic information of the cyt b sequences. For water shrews of Neomyini ( Chimarrogale , Nectogale and Neomys ), monophyly of Neomys and the Chimarrogale – Nectogale group could not be verified, which implies the possibility of multiple origins for the semi-aquatic mode of living among taxa within Neomyini. Episoriculus may contain several separate genera. Blarinella was included in Blarinini not Soricini, based on the cyt b sequences, but the confidence level was rather low; hence more phylogenetic information is needed to determine its phylogenetic position. Furthermore, some specific problems of taxonomy of soricid shrews were clarified, for example phylogeny of local populations of Notiosorex crawfordi , Chimarrogale himalayica and Crocidura attenuata .     

At the foot of the shrew: manus morphology distinguishes closely‐related Cryptotis goodwini and Cryptotis griseoventris (Mammalia: Soricidae) in Central America

Small‐eared shrews (Mammalia, Soricidae) of the New World genus Cryptotis are distributed from eastern North America to the northern Andes of South America. One well‐defined clade in this genus is the Central American Cryptotis mexicana group, whose members are set off from other species in the genus by their variably broader fore feet and more elongate and broadened fore claws. Two species in the C. mexicana group, Cryptotis goodwini Jackson and Cryptotis griseoventris Jackson, inhabit highlands in Guatemala and southern Mexico and are presumed to be sister species whose primary distinguishing feature is the larger body size of C. goodwini. To better characterize these species and confirm the identification of recently‐collected specimens, we obtained digital X‐ray images of the manus from large series of dried skins of both species. Measurements of the metacarpals and phalanges successfully separated most specimens of C. goodwini and C. griseoventris. These measurements also show that the fore feet of C. griseoventris from Chiapas, Mexico, are morphologically distinct from those of members of the species inhabiting Guatemala. Univariate, bivariate, and multivariate analyses indicate that fore foot characters are more conservative within species of the C. mexicana group than are cranio‐mandibular characters. Patterns of evolution of fore foot characters that superficially appear to be linear gradations are actually more complex, illustrating individual evolutionary trajectories. No claim to original US government works. Journal compilation © 2010 The Linnean Society of London, Biological Journal of the Linnean Society, 2010, 99 , 118–134.     

中国鼩鼱亚科的系统分类和分布的评论(英文)

中国动物区系中的鼩(鼠青)类,或称赤齿鼩类,包括31个种;除此之外,东北省份还可能存在另外2个种。生物地理类群包括:1)东北寒温带针叶林(泰加)-Neomys fodiens,Sorex caecutiens,S.daphaenodon,S.gracillimus,S.isodon,S.mirabilis,S.roboratus,S.tundrensis以及S.unguiculatus;2)在山区针叶林中具有孤立居群的东北寒温带针叶林-Sorex minutissimus;3)中国喜马拉雅地区-Chimarrogale himalayica,Nectogale elegans,Sorex bedfordiae,s.thibetanus,Soriculus caudatus,S.leucops,S.macrurus,及S.nigrescens;4)中国特有种,或接近于特有种-Anourosorex squamipes,Blarinella quadraticauda,Chimarrogale styani,So-rex asper,S.cansulus,S.cylindricauda,S.excelsus,S.sinalis,Soriculus fumidus,S.hypsibius,S.lamula,S.parca,S.salenskii,及S.smithii。Sorex minutus的生物地理位置(仅见于天山)目前尚不清楚。     

Patterns of morphological variation amongst semifossorial shrews in the highlands of Guatemala,with the description of a new species (Mammalia,Soricomorpha, Soricidae)

Members of the Cryptotis goldmani group of small‐eared shrews (Mammalia, Soricomorpha, Soricidae) represent a clade within the genus that is characterized by modifications of the forelimb that include broadened forefeet, elongated and broadened foreclaws, and massive humeri with enlarged processes. These modifications are consistent with greater adaptation to their semifossorial habits than other members of the genus. The species in this group occur discontinuously in temperate highlands from southern Tamaulipas, Mexico, to Honduras. In Guatemala, there are three species: the relatively widespread Cryptotis goodwini and two species (Cryptotis lacertosus, Cryptotis mam) endemic to highland forests in the Sierra de los Cuchumatanes of western Guatemala. Ongoing studies focusing on the relationships of variation in cranial and postcranial skeletal morphology have revealed a fourth species from remnant cloud forest in the Sierra de Yalijux, central Guatemala. In this paper, I describe this new species and characterize its morphology relative to other species in the C. goldmani group and to other species of Cryptotis in Guatemala. In addition, I summarize available details of its habitat and ecology. © 2011 The Linnean Society of London, Zoological Journal of the Linnean Society, 2011, 163 , 1267–1288.     

Holarctic phylogeography of the tundra shrew (Sorex tundrensis) based on mitochondrial genes

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. © 2010 The Linnean Society of London, Biological Journal of the Linnean Society, 2010, 101 , 721–746.