CHROMOSOMAL VERSUS MITOCHONDRIAL DNA EVOLUTION: TRACKING THE EVOLUTIONARY HISTORY OF THE SOUTHWESTERN EUROPEAN POPULATIONS OF THE SOREX ARANEUS GROUP (MAMMALIA,INSECTIVORA)

The shrews of the Sorex araneus group have undergone a spectacular chromosome evolution. The karyotype of Sorex granarius is generally considered ancestral to those of Sorex coronatus and S. araneus. However, a sequence of 777 base pairs of the cytochrome b gene of the mitochondrial DNA (mtDNA) produces a quite different picture: S. granarius is closely related to the populations of S. araneus from the Pyrenees and from the northwestern Alps, whereas S. coronatus and S. araneus from Italy and the southern Alps represent two well-separated lineages. It is suggested that mtDNA and chromosomal evolution are in this case largely independant processes. Whereas mtDNA haplotypes are closely linked to the geographical history of the populations, chromosomal mutations were probably transmitted from one population to another. Available data suggest that the impressive chromosome polymorphism of this group is quite a recent phenomenon.     

Shrews (Sorex spp.) somatometry and reproduction in Slovakia

The morphometrics and reproduction of shrews (Sorex araneus, S. minutus, S. alpinus) was studied in Slovakia. Significant differences in weight, body length and tail length were recorded in adult and subadult shrews. Adult individuals and males had higher mean somatometric values (apart from tail length of subadults). The hind foot length was the least variable characteristic, which can be considered as the most stable taxonomic somatic characteristic of shrews. Weight and body length varied considerably. Values of somatic characteristics in S. araneus and S. minutus increased with increasing altitude, apart from hind foot length in S. araneus, which decreased with increasing altitude. The values of somatic characteristics declined with increasing continentality, but tail length gradually increased in the direction west — east at the highland level. Sorex minutus was characterized by the greatest reproductive activity (length of reproductive cycle April–October, average number of embryos 6.97). The lowest reproductive activity was observed in S. alpinus (average number of embryos 5.72). The mating season of S. araneus began at the end of March and ended in August with an average number of embryos of 6.12.     

Quantitative estimation of population numbers of shrews (mammalia,insectivora) after wintering

Autumn-winter mortality in shrews (Sorex araneus, S. caecutiens, S. minutus) was estimated on the basis of long-term (12 years) live-trapping on the permanent transect lines in Tver oblast. Relative as well as absolute population numbers were estimated. Lesser shrew (S. minutus) has permanently low population numbers. Fall in this species made 40.1%, and it was scattered through this term. Common shrew (Sorex araneus) lose 89.3% of population and in masked shrew (S. caecutiens) those lost was 73.6%. The most lost was found in autumn and winter fall was as least as 38,2% and 30.4% in the latter two species. The mortality is positively dependent on population density in preceding summer and with severity of winter.     

Aging and cohort dynamics inSorex shrews

In the shrewsSorex araneus Linnaeus, 1758 andS. minutus Linnaeus, 1766 a short period of fast post-natal development in the nest is followed by a longer summer period of developmental stasis and then by autumn regression. The aim of this paper has been to test whether this period of developmental stability also is accompanied by inhibited development of the eye lens — the most continuously growing organ of the mammalian body. If it is not, then can this be used as an age indicator in studies on shrews, and can it serve in distinguishing seasonal cohorts of young born in consecutive summer months? This aspect was examined on material comprising dead shrews collected from live traps and pitfalls set for rodent research in the marshy habitat of a river valley in Bia?owie?a Forest, Poland, in 1997–1999. In fact, the eye lens in shrews was shown to increase in size continuously; therefore it may be used as a reliable age indicator. Body mass of weaned young shrews also continued to increase slowly with age until autumn. On the basis of the distribution of individuals in successive lens-mass classes, three age groups (cohorts) of young could be distinguished each season in theS. araneus population, and two inS. minutus. In the former species, consistent patterns to the relative abundance of the three seasonal cohorts were observed. The consequences of time of birth on individual fitness inSorex shrews are discussed.     

Karyological and allozyme survey of the Common shrew, Sorex araneus, from Macedonia

Karyotype and genetic variation of the common shrew (Sorex araneus) from Mt. Pelister in southern Macedonia has been studied. Whereas all autosomes in the chromosomal set (2 n_a, = 28, the only present metacentrics being af, bc, jl, and tu) were of the standard type as well as the sex chromosomes X and Y₂ in males, the Y₁ chromosome was a small metacentric. This chromosomal feature is unique among the common shrew populations studied cytogenetically so far. Three out of 33 loci analysed (Sdh, 6Pgd, Mdh-1) were discriminant between the Mt. Pelister population and Sorex araneus from Slovenia and two loci (Est-3, Ada) were partially discriminant. A relatively high value of Nei's genetic distance (D = 0.137) confirms unique character of the Pelister population.     

Editorial

Interspecific interactions between the shrews Sorex araneus and S. minutus F. J. M. ELLENBROEK Noordbrabants Natuurmuseum, Postbus g24, 5000AX Tilburg, Netherlands Foraging in the European Hedgehog, Erinaceus europaeus ANDREW J. WROOT Department of Zoology, Royal Holloway College (University of London), Egham, Surrey TW20 0EX     

Genetic and morphological variation in a partially isolated population of Caucasian shrew <Emphasis Type="Italic">Sorex satunini</Emphasis> (Mammalia)

Morphological and genetic variation at microsatellite loci of Caucasian shrew Sorex satunini Ogn. is examined and compared with that of the common shrew S. araneus L. Genetic distance at microsatellite loci between the common shrew and Caucasian shrew proved to be threefold higher than between chromosome races of the common shrew. The Caucasian shrew manifested low polymorphism in studies of both microsatellites and morphometric mandibular traits. The heterozygote deficit was also typical. These properties may be a consequence of partial isolation of the population and gene drift.     

Distribution patterns and microhabitat segregation in gastrointestinal helminths of Sorex shrews

We studied the distribution patterns and microhabitat use in gastrointestinal helminths of the shrews Sorex araneus and S. caecutiens in Finland. The distribution of species prevalences was bimodal, and in S. araneus the abundance (mean intensity) was positively associated with commonness (prevalence), as assumed by the core-satellite species hypothesis (Hanski 1982). However, the positive correlation between prevalence and intensity was observed only when the effects of helminth body size and taxonomic group (cestodes vs nematodes) on intensity were controlled for. The nematodes of the genus Longistriata occurred predictably as core species, whereas the identity of the core cestodes was more variable between host species and regions. Helminth body size and taxonomic group were not related to the degree of aggregation in shrew populations, but helminth body size seemed to explain the differences in the distribution patterns of helminths between shrews and voles. The core species did not show more segregation in microhabitat use than randomly selected species. In fact, the two core nematodes showed largely overlapping intestinal distributions. We conclude that linear intestinal space is not a key resource for shrew nematodes, but it may be for shrew cestodes.     

A taxonomical re-evaluation of the Valais chromosome race of the common shrew<Emphasis Type="Italic">Sorex araneus</Emphasis> (Insectivora: Soricidae)

The common shrewSorex araneus Linnaeus, 1758 is subject to intense chromosomal polymorphism. About 65 chromosome races are presently known. One of these chromosome races (the Valais race) is karyologically, morphologically, biochemically, and genetically clearly distinct from all other chromosome races of the species. Recent studies of hybrid zones between the Valais race and other chromosome races in the Swiss and French Alps add further strong evidence for the specific taxonomic status of the Valais race. Chromosomes and diagnostic protein markers reveal sharp frequency clines and strong heterozygote deficits. In one hybrid zone, the maintenance of the strong genetic differentiation of the hybridizing taxa was confirmed by a study with autosomal microsatellites indicating minimal gene flow. A microsatellite marker on the Y-chromosome showed complete absence of male mediated gene flow suggesting hybrid male sterility. To clarify the taxonomic status of this taxon, additional analyses were conducted. A morphometric analysis of the mandible indicated the Valais race is morphologically as distinct from neighbouring chromosome races ofS. araneus as from other relatedSorex species. In a phylogeny based on complete mitochondrial DNA cytochromeb gene sequences, the Valais race clearly appears as the sister taxon to all other races ofS. araneus. Therefore, the chromosome race Valais ofS. araneus herein is elevated to specific status and the nameSorex antinorii Bonaparte, 1840 is applied.     

Muscle capillary supply in hind limb and diaphragm of the common shrew (Sorex araneus)

Shrew species of the subfamily Soricinae have unusually high metabolic rates when compared to Crocidurinae shrews and other similar-sized mammals. The aim of this study was to clarify whether the high basal metabolic rate of Soricinae shrews is reflected in a high capillary density in their muscles. To this end, the capillary supply of four limb muscles and diaphragm of the common shrew (Sorex araneus) was quantified from cross-sectioned muscles. The capillary densities of the limb muscles were 2575 ± 329, 3111 ± 299, 2812 ± 197 and 2752 ± 173 capillaries mm⁻² fibre area in gastrocnemius lateralis, g. medialis, plantaris and soleus, respectively. Capillary density of the shrew diaphragm (6691 ± 1057) was double that of the limb muscles. This value is among the highest ever measured in mammals. In general, the capillary supply in the hind limb of the common shrew is about 3–4 times higher than commonly found in the leg muscles of the laboratory rat or other bigger mammals, but similar to those in Crocidurinae shrews and some small rodents. Thus the high resting metabolism of the common shrew is not associated with an extraordinarily high capillary density. The apparent disparity between basal metabolic rate and muscle capillary supply in S. araneus is probably due to the small aerobic scope of shrews in the subfamily Soricinae. Accepted: 22 January 1998     

Phylogenetic relationships of caucasian shrew Sorex satunini Ogn. (Mammalia) in the superspecies Sorex araneus inferred from the data of karyological analysis and the mtDNA cyt b gene sequencing

Using the data of karyological analysis, the phylogenetic relationships of Caucasian shrew Sorex satunini and the cryptic species of superspecies Sorex araneus were examined. In the population of Sorex satunini from the plain of North Ciscaucasia two deeply radiated cytochrome b genes (A and B) were identified. Genetic distance between haplotype A and B groups constituted 0.0675 ± 0.008, which is higher than any distance in superspecies S. araneus. Possible introgression of type B haplotypes from the populations of the evolutionary lineage S. subaraneus-S. araneus in Pleistocene and the time of the appearance of the chromosomal polymorphism of S. araneus is discussed. Our results show that the use of only one mitochondrial marker can lead to false conclusions on taxonomic diversity.     

Analysis of biodiversity parameters of shrew communities of the Altai Mountains

The communities of insectivorous mammals of the Altai Mountains, each consisting of 4–9 species, are quite similar in species composition and principles of organization. The forest belt of mountains is dominated by the common shrew (Sorex araneus), with the Laxmann’s (Sorex caecutiens), lesser (Sorex minutus), and tundra (Sorex tundrensis) (rarely even-toothed (Sorex isodon)) shrews being codominants. With altitude, the dominants change and some species disappear but no significant changes in the dominance structure of the community occur. Positive correlations between abundance rates recorded in different years and on different plots indicate the stability of communities under study. Analysis of informational indices of diversity reveals four basic possible conditions of communities: a) relatively safe, b) slightly disturbed, c) disturbed, and d) high-altitude slightly evened.     

Distribution of cryptic shrew species of the genus Sorex (Mammalia) on the plain between the Don and Kuban rivers as inferred by molecular markers

Microsatellite and mtDNA markers have been used to identify two pairs of cryptic species Sorex araneus L. (Sorex satunini Ogn.) and Sorex minutus L. (S. volnuchini Ogn.). The new data were obtained on the distribution of these species on the plain between the Don and Kuban rivers. The shrew S. volnuchini and Caucasian mole are distributed on the plain areas up to the Eya River. The endemic species of the Caucasus, the shrews S. satunini and S. volnuchini, are widely distributed across the valleys alongside small streams on the steppe plain. Both species are most abundant on thick grasslands, bushy scrub, and deciduous woodlands. They don??t show any clear differences in habitat preferences.     

Behavioural mechanisms of conflict avoidance among shrews

Stable co-existence of similar species should be facilitated by mechanisms impairing, besides exploitative, interference competition. We investigated avoidance of intra- and interspecific conflicts in a four-species community of shrews [Sorex minutus Linnaeus, 1766,S. araneus Linnaeus, 1758,Neomys anomalus Cabrera, 1907, andN. fodiens (Pennant, 1771)], using the method of dyadic encounters in a neutral arena. We tested whether the use of passive (habituation, reduction of mobility, increase of inter-individual distance, and stillness) and active (‘to-and-fro’ and ‘keeping distance’ behaviours) forms of conflict avoidance depends on species, size or domination rank. The duration of conflicts was positively correlated with mobility and negatively with inter-individual distance, whereas it was unrelated to time of stillness and the active forms. The repertoire of conflict avoidance mechanisms was not species-specific and the display of these mechanisms depended rather on the size and domination rank of animals participating in a given interaction. In contrast to rodents, shrews did not avoid conflicts by the most passive forms: freeze and stillness reactions. All other forms were used with a higher or lower efficiency by all species. However, consistent with our predictions, large shrews (asN. fodiens) used mainly the passive mechanisms of conflicts avoidance (‘wait-and-see’ strategy), whereas small shrews (asS. minutus) invest proportionally more time in active forms (‘escape’ strategy).     

Habitat occurrence and prey distribution of a multi-species community of shrews in the Siberian taiga

The habitat occurrence and invertebrate prey distribution of nine species of shrew in the mid-taiga of central Siberia were investigated. Species richness ranged from 4–9 shrews per habitat. Sorex araneus and S. caecutiens 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 Sorex minutissimus, S. daphaenodon , and Neomys fodiens were rare (< 1% 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, earthworm-feeding Sorex roboratus 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 oligochaete-eating shrews. The relative paucity of shrews in bush-meadow 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.     

Contribution of genetic distances studies to the taxonomy ofAteles,particularlyAteles paniscus paniscus andAteles paniscus chamek

We studied 20 electrophoretic loci in two populations ofAteles (Ateles paniscus paniscus andAteles paniscus chamek). We observed intrapopulational variation at the following loci: esterase D, glyoxalase 1, adenosine deaminase (A. p. chamek) and carbonic anhydrase 2 (A. p. paniscus). The two populations share the most frequent alleles at 17 loci, but we noted great differences in glyoxalase 1, adenosine deaminase and phosphoglucomutase 1.A. p. paniscus is monomorphic for theGLO1 ^*1 allele, which has a frequency of 6% inA. p.chamek. They did not share alleles in relation to the ADA and PGM1 loci. We found a CA2 allele, named hereCA2 ^*1, which has not been described previously in other neotropical primates (Sampaio et al., 1991a), inA. p. paniscus. The present results suggest that the geographical isolation represented by the Rio Amazonas has lasted long enough to support this level of divergence. These observations taken together with chromosomal findings, led us to endorse the proposal of two distinct species:Ateles paniscus andAteles chamek.     

Fiber capillarization relative to mitochondrial volume in diaphragm of shrew.

The objective was to examine fiber capillarization in relation to fiber mitochondrial volume in the highly aerobic diaphragm of the shrew, the smallest mammal. The diaphragms of four common shrews [Sorex araneus; body mass, 8.2 +/- 1.3 (SE) g] and four lesser shrews (Sorex minutus, 2.6 +/- 0.1 g) were perfusion fixed in situ, processed for electron microscopy, and analyzed by morphometry. Capillary length per fiber volume was extremely high, at values of 8,008 +/- 1,054 and 12,332 +/- 625 mm(-2) in S. araneus and S. minutus, respectively (P = 0.012), with no difference in capillary geometry between the two species. Fiber mitochondrial volume density was 28.5 +/- 2.3% (S. araneus) and 36.5 +/- 1.4% (S. minutus; P = 0.025), yielding capillary length per milliliter mitochondria values (S. araneus, 27.8 +/- 1.5 km; S. minutus, 33.9 +/- 2.2 km; P = 0.06) as high as in the flight muscle of the hummingbird and small bats. The size of the capillary-fiber interface (i.e., capillary surface per fiber surface ratio) per fiber mitochondrial volume in shrew diaphragm was also as high as in bird and bat flight muscles, and it was about two times greater than in rat hindlimb muscle. Thus, whereas fiber capillary and mitochondrial volume densities decreased with increased body mass in S. araneus compared with S. minutus Soricinae shrews, fiber capillarization per milliliter mitochondria in both species was much higher than previously reported for shrew diaphragm, and it matched that of the intensely aerobic flight muscles of birds and mammals.     

A new perspective on the evolutionary history of western European Sorex araneus group revealed by paternal and maternal molecular markers

The species of the common shrew (Sorex araneus) group are morphologically very similar, but have undergone a spectacular chromosomal evolution. We investigate here the evolutionary history of the Sorex araneus group distributed in western Europe. In particular, we clarify the position of a difficult species, S. granarius, using sex-specific (mtDNA and Y-chromosome) markers. The karyotype of S. granarius is generally considered similar to the common ancestor of the restricted group considered here. The mtDNA data (1.4 kb) confirms the close relationship between S. granarius and S. araneus sensu stricto (hereafter S. araneus s.s.), but the Y-chromosome (3.4 kb) produces a quite different picture: S. granarius is closely related to another species, S. coronatus. Comparison of mtDNA and Y-chromosome phylogenies suggests that the genetic and chromosomal evolution in this group are disconnected processes. The evolutionary history of the south-western European populations of the S. araneus group can only be understood considering secondary contacts between taxa after their divergence, implying genetic exchanges by means of hybridization and/or introgression.     

Invalidation of Stobnica chromosome race of the common shrewSorex araneus

In Central Poland, two similar chromosome races of the common shrewSorex araneus Linnaeus, 1758 were earlier described: Drnholec race (arm combinationsgm, hi, ko, nr) and Stobnica race (gm, hi, ko, np). Great similarity in size and G-banding patterns between thenr andnp metacentrics leave open to doubt the actual existence of both races in Poland. The present study, which is based on good quality karyotypes of common shrews from 18 sites, showed the presence of thenr arm combination. There is therefore strong evidence that thenp arm combination was wrongly described and thus the Stobnica race should not be considered valid.     

Synchrony between small mammal population dynamics in marshes and adjacent grassland in a landscape of the Jura plateau, France: a ten year investigation

Small mammal populations were studied during a 10 year multi-annual fluctuation of vole populations in marshes and adjacent grassland of the basin in the Jura mountains, France. Nine species were monitored:Microtus agrestis, Clethrionomys glareolus, Apodemus flavicollis, Sorex araneus Icoronatus, Neomys fodiens, Crocidura leucodon, Mustela nivalis in marshes andArvicola terrestris andMicrotus arvalis in grassland, using live-trapping and index methods during July from 1993 to 2002. Populations of A.terrestris, M. arvalis, M. agrestis, S. araneus I coronatus andM. nivalis exhibited a relatively strong inter-specific temporal synchrony in their multi-annual fluctuations.C. glareolus population fluctuations were not synchronous to theArvicola I Microtus I Sorex group, and were closer to those ofApodemus flavicollis, Neomys andCrocidura. Those results are discussed in the light of earlier studies carried out in the same region and in northern ecosystems.