Evolutionary history of mole rats (genus Nannospalax) inferred from mitochondrial cytochrome b sequence

Mole rats (genus Nannospalax) display prolific chromosomal variation with more than 50 distinct cytotypes. These cytotypes are largely indistinguishable morphologically, are mainly allopatric and their taxonomic ranking is contradictory. We established a cytochrome b phylogeny for 15 cytotypes belonging to all three species recognized on morphological grounds (morphospecies): N. leucodon, N. xanthodon and N. ehrenbergi. Phylogenetic reconstructions yielded two highly divergent groups which are in agreement with the current division into two subgenera (Nannospalax and Mesospalax). The former comprised samples from south‐eastern Turkey, Israel and Egypt (the morphospecies N. ehrenbergi). Basal dichotomy within Mesospalax remained unresolved and the putative sister position of N. leucodon against the two lineages of N. xanthodon was not supported in our analysis. Net divergences between sister cytotypes were low (< 2.0%) and two N. leucodon cytotypes were not even reciprocally monophyletic. Among the three morphospecies, the genetic diversity was lowest in N. leucodon (2.4% ± 0.3%), highest in N. xanthodon (8.8% ± 0.7%) and intermediate in N. ehrenbergi (5.0% ± 0.5%). Our results show that associations between genetic and chromosomal variation are not widespread and common in mole rats, and therefore refute the generalization of a ‘cytotype‐equals‐species’ approach. © 2011 The Linnean Society of London, Biological Journal of the Linnean Society, 2012, 105 , 446–455.     

Evidence of a complex phylogeographic structure in the common dormouse,Muscardinus avellanarius (Rodentia: Gliridae)

This is the first mitochondrial phylogeography of the common dormouse, Muscardinus avellanarius (Linnaeus, 1758), a hibernating rodent strictly protected in Europe (Habitat Directive, annex IV; Bern Convention, annex III). The 84 individuals of M. avellanarius, sampled throughout the distributional range of the species, have been sequenced at the mitochondrial DNA gene (cytochrome b, 704 base pairs). The results revealed two highly divergent lineages, with an ancient separation around 7.7 Mya and a genetic divergence of 7.7%. Lineage 1 occurs in Western Europe (France, Belgium, and Switzerland) and Italy, and lineage 2 occurs in Central–Northern Europe (Poland, Germany, Latvia, and Lithuania), on the Balkan Peninsula, and in Turkey. Furthermore, these two lineages are subdivided into five sublineages genetically isolated with a strong geographical association. Therefore, lineage 1 branches into two further sublineages (Western European and Italian), whereas lineage 2 contained three sublineages (Central–Northern European, Turkish, and Balkan). We observed low genetic diversity within the sublineages, in contrast to the significant level of genetic differentiation between them. The understanding of genetic population structure is essential for identifying units to be conserved. Therefore, these results may have important implications for M. avellanarius conservation. © 2012 The Linnean Society of London, Biological Journal of the Linnean Society, 2012, 105 , 648–664.     

A root is a root is a root? Water uptake rates of Citrus root orders

Knowledge about the physiological function of root orders is scant. In this study, a system to monitor the water flux among root orders was developed using miniaturized chambers. Different root orders of 4‐year‐old Citrus volkameriana trees were analysed with respect to root morphology and water flux. The eight root orders showed a broad overlap in diameter, but differences in tissue densities and specific root area (SRA) were clearly distinguishable. Thirty per cent of the root branch biomass but 50% of the surface area (SA) was possessed by the first root order, while the fifth accounted for 5% of the SA (20% biomass). The root order was identified as a determinant of water flux. First‐order roots showed a significantly higher rate of water uptake than the second and third root orders, whereas the fourth and fifth root orders showed water excess. The water excess suggested the occurrence of hydraulic redistribution (HR) as a result of differences in osmotic potentials. We suggest that plants may utilize hydraulic redistribution to prevent coarse root desiccation and/or to increase nutrient acquisition. Our study showed that the novel ‘miniature depletion chamber’ method enabled direct measurement of water fluxes per root order and can be a major tool for future studies on root order traits.     

Visualization of novel virulence activities of the Xanthomonas type III effectors AvrBs1, AvrBs3 and AvrBs4

Xanthomonas campestris pv. vesicatoria secretes at least 20 effector proteins through the type III secretion system directly into plant cells. In this study, we uncovered virulence activities of the effector proteins AvrBs1, AvrBs3 and AvrBs4 using Agrobacterium‐mediated transient expression of the corresponding genes in Nicotiana benthamiana, followed by microscopic analyses. We showed that, in addition to the nuclear‐localized AvrBs3, the effector AvrBs1, which localizes to the plant cell cytoplasm, also induces a morphological change in mesophyll cells. Comparative analyses revealed that avrBs3‐expressing plant cells contain highly active nuclei. Furthermore, plant cells expressing avrBs3 or avrBs1 show a decrease in the starch content in chloroplasts and an increased number of vesicles, indicating an enlargement of the central vacuole and the cell wall. Both AvrBs1 and AvrBs3 cause an increased ion efflux when expressed in N. benthamiana. By contrast, expression of the avrBs3 homologue avrBs4 leads to large catalase crystals in peroxisomes, suggesting a possible virulence function of AvrBs4 in the suppression of the plant defence responses. Taken together, our data show that microscopic inspection can uncover subtle and novel virulence activities of type III effector proteins.     

European cave shrimp species (Decapoda: Caridea: Atyidae), redefined after a phylogenetic study; redefinition of some taxa,a new genus and four new Troglocaris species

Endemic atyids of southern Europe have been ascribed to Dugastella, and to subterranean Typhlatya and Troglocaris: Dugastella is epigean, and Typhlatya and Troglocaris are subterranean. An extensive collection from all centres of distribution in southern Europe (excepting the Caucasus) was morphologically examined. A taxonomic redefinition of the group, at different levels, is based on recently published and newly generated molecular phylogeny, whereas newly established taxa have also been morphologically defined. The accordance between the phylogenetic tree and the geographical distributions suggested that a re‐evaluation of some traditionally used morphological characters should generate the most parsimonious solution: this enabled a novel taxonomic division. Gallocaris gen. nov. is erected for the French Troglocaris inermis Fage, 1937, which is more closely related to the epigean Dugastella valentina (Ferrer Galdiano, 1924) than to its supposed congeners. Both western Mediterranean Typhlatya species are closely related to their Caribbean congeners. All other European cave shrimps constitute a monophylum, Troglocaris, which is divisible into subgenera (already with available names): the holo‐Dinaric Troglocaris (Troglocaris) Dormitzer, 1853, south‐eastern mero‐Dinaric Troglocaris (Troglocaridella) Babi?, 1922, and Troglocaris (Spelaeocaris) Matja?i?, 1956, and the Caucasian Troglocaris (Xiphocaridinella) Sadovsky, 1930. Four new species are described: Troglocaris (Troglocaris) bosnica sp. nov. , Troglocaris (Spelaeocaris) prasence sp. nov. , Troglocaris (Spelaeocaris) kapelana sp. nov. , and Troglocaris (Spelaeocaris) neglecta sp. nov. The distribution of all established species is shown, and the value of the morphological characters is discussed. © 2009 The Linnean Society of London, Zoological Journal of the Linnean Society, 2009, 155 , 786–818.     

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.     

Functional Electron Microscopy in Studies of Plant response and adaptation to Anaerobic Stress

This article reviews the contribution made by functional electronmicroscopy towards identifying and understanding the reactionsof plant roots and shoots to anaerobic stress. Topics examinedinclude: (1) unexpected hypersensitivity, rather than hyper-resistance,to anoxia of root tips of flooding-tolerant plants; (2) protective,rather than damaging, effects of a stimulated energy metabolism(glycolysis and fermentation) under anaerobic conditions; (3)the concept of two main strategies of plant adaptation to anaerobicenvironments, namely avoidance of anaerobiosis on the wholeplant level, termed ‘apparent’ tolerance, and metabolicadaptation at the cellular and molecular levels, termed ‘true’tolerance; (4) the importance of protein synthesis during hypoxiaand anoxia for enhanced energy production and metabolic adaptation;(5) a general adaptive syndrome in plants to stress at the ultrastructurallevel and a possible molecular mechanism for its realizationunder anoxia; (6) the physiological role of anaerobically synthesizedlipids and nitrate as alternative electron acceptors in an oxygen-freemedium; and (7) the selection of cell lines derived from calluscultures that possess enhanced tolerance to anoxia and can regeneratewhole plants with improved tolerance of soil waterlogging.     

Rarity and decline in palaeoendemic Martino's vole Dinaromys bogdanovi

• 1 Martino's vole Dinaromys bogdanovi is the only living member of the Tertiary genus Dinaromys, and probably also the only surviving member of the Pliomys lineage. The range of the genus Dinaromys has historically been small and its rate of evolution has been low.
• 2 Martino's vole shows all three attributes of rarity in accordance with Rabinowitz's ‘seven forms of rarity’ model: (i) its range is estimated at 43 545 km² but the area of occupancy is <5200 km²; (ii) its habitat requirements are narrow and the species is strictly tied to exposed, karstified bedrock; and (iii) current populations are invariably small and frequently isolated.
• 3 The Pleistocene range of Martino's vole exceeded the recent one, at least in the north‐western part of the Balkans, and its shrinkage continued into the Holocene.
• 4 Martino's vole may be in competition with the European snow vole Chionomys nivalis, which has a very similar morphology and presumably identical habitat requirements, but is shifted towards an r‐selected life‐history strategy. Long‐term sympatry of these voles has probably resulted in competitive exclusion of the relatively K‐selected Martino's vole by the relatively r‐selected European snow vole.
• 5 Martino's vole consists of two deeply divergent (about one million years ago) phylogeographical lineages, which may represent distinct cryptic species. Rarity is particularly pronounced in the north‐western lineage to the west of the Neretva River, where rocky habitats are largely occupied by the European snow vole.
• 6 In the IUCN Red List of Threatened Animals, Martino's vole is classified as ‘near threatened’. However, the north‐western lineage, which is phylogeographically most divergent and has the greatest genetic diversity, is classed as a ‘vulnerable’ evolutionary significant unit on the basis of its small area of occupancy (<2000 km²). Long‐term population monitoring is an essential step in evaluating the conservation needs of Martino's vole.