Taxonomic status and origin of the shrews (Soricidae) from the Canary islands inferred from a mtDNA comparison with the European Crocidura species

European island shrews are either relicts of the endemic Pleistocene fauna, e.g.,. Crocidura zimmermanni, or were introduced from continental source populations. In order to clarify the taxonomic status and the origin of the two shrew species from the Canary islands, a 981bp fragment of cytochrome b gene was investigated in all European Crocidura species and compared with the Canary shrew (Crocidura canariensis) and the Osorio shrew (Crocidura osorio). The first shares its karyotype with the Sicilian shrew Crocidura sicula (2N=36), the second with the Greater white-toothed shrew Crocidura russula (2N=42), suggesting possible sister species relationships. Results confirm the monophyly of taxa sharing the same karyotype. Genetic distances between C. sicula and C. canariensis suggest a separation since 5 Myr. The first was probably isolated from the North African ancestor after the Messinian desiccation; the second arrived on the Canary islands by natural jump dispersal. Within the 2N=42 cluster, a first split separated an Eastern line (Tunisia) from a western line (Morocco/Europe) of C. russula. C. osorio clusters together with C. russula from Spain, indicating conspecificy. This suggests a recent introduction from Spain by human.     

Morphometric geographic variation in the Asian lesser white-toothed shrew Crocidura shantungensis (Mammalia,Insectivora) in East Asia

This study investigated geographic variation in the Asian lesser white-toothed shrew, Crocidura shantungensis Miller, 1901, among a number of localities in East Asia, including the Korean Peninsula, Tsushima Island, Cheju Island, and Taiwan, using univariate and multivariate analyses of cranial morphometric characters. Sexual differences were found in Taiwanese shrews, but were not evident in those from Korea or Tsushima. The samples from Taiwan had a larger overall cranial size than those from Korea and Tsushima, and were well separated from the latter two samples in the discriminant analyses. The overall size of the Cheju shrews was also greater, but lay within the variation of those from Taiwan. Crocidura dsinezumi quelpartis Kuroda, 1934, described from Cheju Island, is actually a junior synonym of C. shantungensis, and is not related to C. dsinezumi.     

Lipotyphla limb myology comparison

Fore- and hindlimb muscles were dissected in four species of Lipotyphla: the western European hedgehog Erinaceus europaeus (Erinaceidae, Erinaceinae); the moonrat Echinosorex gymnura (Erinaceidae, Hylomyinae or Galericinae); the tailless tenrec Tenrec ecaudatus (Tenrecidae, Tenrecinae); and the common European white-toothed shrew Crocidura russula (Soricidae, Soricinae). This work completely reviews the limb musculature of these walking mammals. Twelve myological characters were evaluated in order to disclose phylogenetic relationships. The cladogram obtained supported previous ones based on cranial and dental characters. This study shows that myological characters are valuable in phylogenetic analyses.     

Phylogeographical footprints of the Strait of Gibraltar and Quaternary climatic fluctuations in the western Mediterranean: a case study with the greater white-toothed shrew, Crocidura russula (Mammalia: Soricidae)

We used mitochondrial cyt b sequences to investigate the phylogenetic relationships of Crocidura russula (sensu lato) populations across the Strait of Gibraltar, western Europe, Maghreb, and the Mediterranean and Atlantic islands. This revealed very low genetic divergence between European and Moroccan populations. The application of a molecular clock previously calibrated for shrews suggested that the separation of European from Moroccan lineages occurred less than 60 000 bp, which is at least 5 million years (Myr) after the reopening of the Strait of Gibraltar. This means that an overwater dispersal event was responsible for the observed phylogeographical structure. In contrast, genetic analyses revealed that Moroccan populations were highly distinct from Tunisian ones. According to the molecular clock, these populations separated about 2.2 million years ago (Ma), a time marked by sharp alternations of dry and humid climates in the Maghreb. The populations of the Mediterranean islands Ibiza, Pantelleria, and Sardinia were founded from Tunisian populations by overwater dispersal. In conclusion, overwater dispersal across the Strait of Gibraltar, probably assisted by humans, is possible for small terrestrial vertebrates. Moreover, as in Europe, Quaternary climatic fluctuations had a major effect on the phylogeographical structure of the Maghreb biota.     

The Bicolored White-Toothed Shrew Crocidura leucodon (HERMANN 1780) Is an Indigenous Host of Mammalian Borna Disease Virus

Borna disease (BD) is a sporadic neurologic disease of horses and sheep caused by mammalian Borna disease virus (BDV). Its unique epidemiological features include: limited occurrence in certain endemic regions of central Europe, yearly varying disease peaks, and a seasonal pattern with higher disease frequencies in spring and a disease nadir in autumn. It is most probably not directly transmitted between horses and sheep. All these features led to the assumption that an indigenous virus reservoir of BDV other than horses and sheep may exist. The search for such a reservoir had been unsuccessful until a few years ago five BDV-infected shrews were found in a BD-endemic area in Switzerland. So far, these data lacked further confirmation. We therefore initiated a study in shrews in endemic areas of Germany. Within five years 107 shrews of five different species were collected. BDV infections were identified in 14 individuals of the species bicolored white-toothed shrew (Crocidura leucodon, HERMANN 1780), all originating from BD-endemic territories. Immunohistological analysis showed widespread distribution of BDV antigen both in the nervous system and in epithelial and mesenchymal tissues without pathological alterations. Large amounts of virus, demonstrated by presence of viral antigen in epithelial cells of the oral cavity and in keratinocytes of the skin, may be a source of infection for natural and spill-over hosts. Genetic analyses reflected a close relationship of the BDV sequences obtained from the shrews with the regional BDV cluster. At one location a high percentage of BDV-positive shrews was identified in four consecutive years, which points towards a self-sustaining infection cycle in bicolored white-toothed shrews. Analyses of behavioral and population features of this shrew species revealed that the bicolored white-toothed shrew may indeed play an important role as an indigenous host of BDV.     

Nonshivering thermogenesis capacity associated to mitochondrial DNA haplotypes and gender in the greater white-toothed shrew, Crocidura russula

A selection gradient was recently suggested as one possible cause for a clinal distribution of mitochondrial DNA (mtDNA) haplotypes along an altitudinal transect in the greater white-toothed shrew, Crocidura russula (Ehinger et al. 2002). One mtDNA haplotype (H1) rare in lowland, became widespread when approaching the altitudinal margin of the distribution. As H1 differs from the main lowland haplotype by several nonsynonymous mutations (including on ATP6), and as mitochondria play a crucial role in metabolism and thermogenesis, distribution patterns might stem from differences in the thermogenic capacity of different mtDNA haplotypes. In order to test this hypothesis, we measured the nonshivering thermogenesis (NST) associated with different mtDNA haplotypes. Sixty-two shrews, half of which had the H1 haplotype, were acclimated in November at semioutdoor conditions and measured for NST throughout winter. Our results showed the crucial role of NST for winter survival in C. russula. The individuals that survived winter displayed a higher significant increase in NST during acclimation, associated with a significant gain in body mass, presumably from brown fat accumulation. The NST capacity (ratio of NST to basal metabolic rate) was exceptionally high for such a small species. NST was significantly affected by a gender x haplotype interaction after winter-acclimation: females bearing the H1 haplotype displayed a better thermogenesis at the onset of the breeding season, while the reverse was true for males. Altogether, our results suggest a sexually antagonistic cyto-nuclear selection on thermogenesis.     

A novel set of microsatellite marker loci linkage-mapped in the house musk shrew, Suncus murinus.

Ten microsatellite DNA loci developed for the white-toothed shrew (Crocidura russula) were tested for PCR amplification and for utility in linkage studies in the house musk shrew, Suncus murinus. Four primer pairs successfully yielded PCR amplicons and showed polymorphism between two mutant strains, BAN-kc,oeb and WZ. Cloning and sequencing of the PCR amplicons of all the four loci confirmed the presence of microsatellite sequences. Alleles segregating in an F2 resource population constructed from the two strains ranged between two and five. Linkage analysis of the four loci together with 18 other polymorphic markers and three mutant loci resulted in five linkage groups containing three newly mapped microsatellite loci. This study reports the first microsatellite markers being registered in this species.     

Morphological variability in Lophyra flexuosa (Fabricius, 1787) (Coleoptera,Cicindelidae) in desert countries is affected by sexual dimorphism and geographic aspect

Lophyra flexuosa, a eurytopic tiger beetle characterized by long phenological activity, wide geographic and altitudinal distribution, and occurring in the highest number of habitats among all Cicindelidae known from North Africa, was chosen to study its geographic variation in morphology and sexual dimorphism. Here, we found significant sexual dimorphism exhibited in larger body size of females and longer mandibles in males, which can be explained by different roles of particular sexes in courtship. Moreover, we recorded significant differences in body sizes between western and eastern Maghreb populations which could suggest genetic isolation between these populations. As the species is related to habitats placed close to the water reservoirs, which in the desert countries are under significant human pressure (including climate change), we expect a reduction of habitat occupied by this taxon. Therefore, the geographic morphological variability that we observe today in the tiger beetle Lophyra flexuosa in the future could lead to speciation.     

Tripartite genetic subdivisions in the ornate shrew (Sorex ornatus)

We examined cytochrome b sequence variation in 251 ornate shrews (Sorex ornatus) from 20 localities distributed throughout their geographical range. Additionally, vagrant (S. vagrans) and montane (S. monticolus) shrews from four localities were used as outgroups. We found 24 haplotypes in ornate shrews from California (USA) and Baja California (Mexico) that differed by 1-31 substitutions in 392 bp of mitochondrial DNA (mtDNA) sequence. In a subset of individuals, we sequenced 699 bp of cytochrome b to better resolve the phylogeographic relationships of populations. The ornate shrew is phylogeographically structured into three haplotype clades representing southern, central and northern localities. Analysis of allozyme variation reveals a similar pattern of variation. Several other small California vertebrates have a similar tripartite pattern of genetic subdivision. We suggest that topographic barriers and expansion and contraction of wetland habitats in the central valley during Pleistocene glacial cycles account for these patterns of genetic variation. Remarkably, the northern ornate shrew clade is phylogenetically clustered with another species of shrew suggesting that it may be a unique lowland form of the vagrant shrew that evolved in parallel to their southern California counterparts.     

Cellular aspects of aging in the pineal gland of the shrew, Crocidura russula

The Greater White-toothed shrew Crocidura russula is short-lived species and the phase of senescence is greatly elongated in captivity. The loss of rhythmicity of biological functions that accompanies its aging is also well documented. C. russula is thus an excellent model to test the effects of aging on biological clocks. Melatonin is a key hormone in the synchronization of behaviors, metabolisms and physiological regulations with environmental factors. In the present work we want to know if the loss of rhythmicity and the reduced melatonin levels registered by the second year of life in this species could be associated to modified ultrastructural features of the pineal parenchyma, site of melatonin synthesis. Transmission electron microscopy (TEM) analysis of young (1-4 months) and old (25-28 months) shrew's pineals show that in older individuals, the parenchyma undergoes alterations affecting mainly nucleus, mitochondria and endoplasmic reticulum cisternae, with increased numbers of dense bodies and the formation of many concretions as well as a depletion of secretory products. These changes suggest a process of slowing pinealocytes metabolism which could explain the gradual reduction of melatonin levels registered during aging in C. russula.     

Cycle length of spermatogenesis in shrews (mammalia: soricidae) with high and low metabolic rates and different mating systems

The aim of the present study was to establish and compare the durations of the seminiferous epithelium cycles of the common shrew Sorex araneus, which is characterized by a high metabolic rate and multiple paternity, and the greater white-toothed shrew Crocidura russula, which is characterized by a low metabolic rate and a monogamous mating system. Twelve S. araneus males and fifteen C. russula males were injected intraperitoneally with 5-bromodeoxyuridine, and the testes were collected. For cycle length determinations, we applied the classical method of estimation and linear regression as a new method. With regard to variance, and even with a relatively small sample size, the new method seems to be more precise. In addition, the regression method allows the inference of information for every animal tested, enabling comparisons of different factors with cycle lengths. Our results show that not only increased testis size leads to increased sperm production, but it also reduces the duration of spermatogenesis. The calculated cycle lengths were 8.35 days for S. araneus and 12.12 days for C. russula. The data obtained in the present study provide the basis for future investigations into the effects of metabolic rate and mating systems on the speed of spermatogenesis.     

北小麝鼩的代谢产热和体温调节特征

为探讨食虫目小型哺乳动物的代谢产热和体温调节特征,本文采用封闭式流体压力呼吸仪测定了北小麝鼩在环境温度5 ～ 30℃下的静止代谢率(RMR),结果显示:在环境温度(Ta)为17 5 ～25℃ 的范围内,北小麝鼩的体温基本维持恒定,平均体温为36.55 ± 0.38℃ ;热中性区(TNZ) 为20 ～ 25℃ ;基础代谢率BMR 为5.46 ±0.23 (mLO₂ /g· h),其中环境温度在25℃ 时静止代谢率最低,为4.84 ± 0.39 (mLO₂ /g· h)。在5 ～ 25℃环境温度范围内,热传导值保持稳定;在此温度范围内,北小麝鼩的热传导率(C) 最低,平均为0.42 ± 0.01mLO₂ / (g·h·℃ )。总之,北小麝鼩的产热和体温调节特征为较高的BMR,中等的热传导率,较低的体温和较宽的热中性区。这些特征可能与该物种体型小、夜行性、主要以无脊椎动物为食等生活习性密切相关。     

Additive effects of climate and vegetation structure on the altitudinal distribution of greater white-toothed shrews Crocidura russula in a Mediterranean mountain range

Environmental variation along geographic gradients determines the distribution of animals and plants trough both direct and indirect effects. We analyze the relative contribution of climate and vegetation structure variations along a Mediterranean altitude gradient on the patterns of abundance and occurrence of the greater white-toothed shrew Crocidura russula, a generalist small mammal whose distribution is constrained by cold conditions. Sampling was performed from February 1995 to July 1997 on nine plots covering a wide altitudinal gradient (540–1550 m?a.s.l.). Structural equation models for the direct and indirect effects of climate and vegetation on shrew density and occupancy rates showed a stronger effect of vegetation structure (53 %) than direct climate effects (38 %) on shrew distribution. Shrews were more abundant in the warmer lowland sites, but were able to colonize highland cold areas by selecting habitats with well-developed understory vegetation (low shrubs or bracken). Vegetation effects were additive to climatic restrictions, seemingly providing more favorable microclimatic, and presumably food, conditions under shrub cover. Results indicate that predictions of range changes for shrews under climate change scenarios may underestimate expected range expansions under the current conditions of general land abandonment and shrub encroachment.     

Infraspecific diversity of Cytisus emeriflorus Reichenb. (Leguminosae), an endemic plant with disjunct distribution: Evidence from isozyme data

ABSTRACT

C. emeriflorus is an endemic species occurring in two disjunct areas some 200 km apart: the Pre-Alps of Lombardia and the Pre-Alps of Friuli. Four populations from the western area and five populations from the eastern area were sampled in order to ascertain the amount and the distribution of variation throughout the range of the species. Phenetic measures of isozyme polymorphism were used. Diversity values showed that the species is polymorphic, despite its restricted distribution and the small population size; phenetic distances revealed that partitioning of diversity was largely within rather than among populations. Moreover, little differentiation was found between the two disjunct areas, although the western populations exhibited a slightly higher diversity compared with the eastern ones. The high level of polymorphism and the overall similarity between populations from the two areas may be ascribed to past contacts, and indicate that, despite the present widespread disjunction, the two areas have not evolved independently long enough for divergence to have occurred. There is no evidence that C. emeriflorus is at present genetically depauperated, although its range of distribution must have been much broader in the past; its present reduced distribution area and the small population size may be mainly due to ecological factors.     

Pliocene and Pleistocene diversification and multiple refugia in a Eurasian shrew (Crocidura suaveolens group)

We sequenced 998 base pairs (bp) of mitochondrial DNA cytochrome b and 799 bp of nuclear gene BRCA1 in the Lesser white-toothed shrew (Crocidura suaveolens group) over its geographic range from Portugal to Japan. The aims of the study were to identify the main clades within the group and respective refugia resulting from Pleistocene glaciations. Analyses revealed the Asian lesser white-toothed shrew (C. shantungensis) as the basal clade, followed by a major branch of C. suaveolens, subdivided sensu stricto into six clades, which split-up in the Upper Pliocene and Lower Pleistocene (1.9-0.9 Myr). The largest clade, occurring over a huge range from east Europe to Mongolia, shows evidence of population expansion after a bottleneck. West European clades originated from Iberian and Italo-Balkanic refugia. In the Near East, three clades evolved in an apparent hotspot of refugia (west Turkey, south-west and south-east of the Caucasus). Most clades include specimens of different morphotypes and the validity of many taxa in the C. suaveolens group has to be re-evaluated.     

Evolutionary history of the greater white-toothed shrew (Crocidura russula) inferred from analysis of mtDNA, Y, and X chromosome markers

We investigate the evolutionary history of the greater white-toothed shrew across its distribution in northern Africa and mainland Europe using sex-specific (mtDNA and Y chromosome) and biparental (X chromosome) markers. All three loci confirm a large divergence between eastern (Tunisia and Sardinia) and western (Morocco and mainland Europe) lineages, and application of a molecular clock to mtDNA divergence estimates indicates a more ancient separation (2.25 M yr ago) than described by some previous studies, supporting claims for taxonomic revision. Moroccan ancestry for the mainland European population is inconclusive from phylogenetic trees, but is supported by greater nucleotide diversity and a more ancient population expansion in Morocco than in Europe. Signatures of rapid population expansion in mtDNA, combined with low X and Y chromosome diversity, suggest a single colonization of mainland Europe by a small number of Moroccan shrews >38 K yr ago. This study illustrates that multilocus genetic analyses can facilitate the interpretation of species' evolutionary history but that phylogeographic inference using X and Y chromosomes is restricted by low levels of observed polymorphism.     

Cases of coat colour anomalies in the common shrew, Sorex araneus L

Coat colour anomalies in the common shrew, Sorex araneus L., in the geographical range of this species, including Poland, are extremely rare. This study describes atypically coloured common shrews. Light colouration of the coat is a result of lack ofpigment in the entire hair or hair fragments. It appears that atypically coloured shrews occur more often in isolated populations whose gene transfer with neighboring populations is limited.     

Habitat use and potential interactions between the house mouse and lesser white-toothed shrew on an island undergoing habitat restoration

To forecast the potential impact of plant community and dry-stone wall restoration on an insular population of the lesser white-toothed shrewCrocidura suaveolens Pallas, 1811, shrew and house mouseMus musculus Linnaeus, 1758 abundances were assessed in 3 anthropogenic habitats on Béniguet Island, Brittany, France, by a standardised annual trapping system checked yearly for 9 years and in 6 “natural” habitats by trap-lines. The standardised trapping system showed that abundances of both species fluctuated synchronously for nine years, suggesting that interactions between the species had little impact if any on abundances. Mice were trapped in all habitats, but shrews only in “stone” habitats except for rare occurrences in one damp depression. Ruderal habitat was rarely used by either species. Data suggest that on Béniguet Island: (1)M. musculus is associated with anthropogenic habitats but is not as strictly tied to them as at nearby continental sites; (2)C. suaveolens is synanthropic, as has been reported in continental northern France; (3) shingle beaches and seashore food resources are particularly important forC. suaveolens; (4) the relationship betweenC. suaveolens andM. musculus could not be determined by the experiments and, if it exists at all, appears to be more competitive than predatory. Grassland restoration is unlikely to affect shrew populations. Dry-stone wall restoration may temporarily affect shrews but should ultimately benefit them.     

Origin and evolution of homologous repeated sequences in the mitochondrial DNA control region of shrews

The complete mitochondrial DNA (mtDNA) control region was amplified and directly sequenced in two species of shrew, Crocidura russula and Sorex araneus (Insectivora, Mammalia). The general organization is similar to that found in other mammals: a central conserved region surrounded by two more variable domains. However, we have found in shrews the simultaneous presence of arrays of tandem repeats in potential locations where repeats tend to occur separately in other mammalian species. These locations correspond to regions which are associated with a possible interruption of the replication processes, either at the end of the three-stranded D-loop structure or toward the end of the heavy-strand replication. In the left domain the repeated sequences (R1 repeats) are 78 bp long, whereas in the right domain the repeats are 12 bp long in C. russula and 14 bp long in S. araneus (R2 repeats). Variation in the copy number of these repeated sequences results in mtDNA control region length differences. Southern blot analysis indicates that level of heteroplasmy (more than one mtDNA form within an individual) differs between species. A comparative study of the R2 repeats in 12 additional species representing three shrew subfamilies provides useful indications for the understanding of the origin and the evolution of these homologous tandemly repeated sequences. An asymmetry in the distribution of variants within the arrays, as well as the constant occurrence of shorter repeated sequences flanking only one side of the R2 arrays, could be related to asymmetry in the replication of each strand of the mtDNA molecule. The pattern of sequence and length variation within and between species, together with the capability of the arrays to form stable secondary structures, suggests that the dominant mechanism involved in the evolution of these arrays in unidirectional replication slippage.      

Does bite force provide a competitive advantage in shrews? The case of the greater white‐toothed shrew

Competition for resources has long been considered a major driver of evolution by natural selection. Thus, the ability to gain access to resources not available to other individuals and species should be under strong selection. In the present study, we focus on the potential role of biting in a shrew (Crocidura russula) because this trait may confer two advantages: (1) a broadening of the dietary niche and (2) the provision of direct superiority in interspecific interactions. The model chosen is the greater white‐toothed shrew, which is considered as invasive in northern Europe and which is also known to displace native species of shrew in this area. Moreover, its distribution appears to constrain the distributional ranges of other species of shrew in the Maghreb. We use geometric morphometrics and a simple biomechanical model to describe shape variation and to evaluate the mechanical potential of the mandible of ten species of white‐toothed shrews, with a special emphasis on C. russula and Crocidura suaveolens. We find that C. russula possesses an intermediate mechanical potential linked with an intermediate level of shape variability. Our results suggest that the higher mechanical potential may explain the observed pattern of colonization of the Atlantic islands by C. russula at the expense of C. suaveolens. Finally, our results also suggest that the ability to bite hard may be under strong selection in shrews. © 2015 The Linnean Society of London, Biological Journal of the Linnean Society, 2015, 114 , 795–807.