Spatial variation in abundance of the junin virus hosts in endemic and nonendemic Argentine haemorrhagic fever zones

Abstract Argentine haemorrhagic fever (AHF) is caused by Junin (JUN) virus, which is hosted by the drylands vesper mouse (Calomys musculinus). In this work we monitored population abundance of C. musculinus and rodent assemblages for 3 years in and outside the AHF endemic zones (northern Buenos Aires, southern Córdoba and Santa Fe Provinces, Argentina). The study area was divided into endemic and nonendemic zones. In the endemic zone epidemic sites were recognized, characterized by recent emergence and maintenance of AHF cases, and also historical sites, characterized by decreased incidence or disappearance of AHF human cases. In the nonendemic zone AHF has never been recognized. Although differences were statistically significant only during some periods, population abundance of C. musculinus was usually lower in the nonendemic sites. The pattern and magnitude of seasonal fluctuations in C. musculinus populations were also distinct in the nonendemic sites as compared to endemic sites. The relative abundance of C. musculinus in rodent assemblage was lower in nonendemic sites than in the endemic sites. The lower population densities and dampened seasonal dynamics may be at least partly responsible for the absence of AHF cases in the nonendemic zone. It is suggested that the balance between intra and interspecific interactions might be the cause of the pattern of incidence and prevalence of pathogens in the host species.     

Genetic portrait of Lisboa immigrant population from Cabo Verde with mitochondrial DNA analysis

Journal of Genetics -     

Population genomics of wild and laboratory zebrafish (Danio rerio)

Understanding a wider range of genotype–phenotype associations can be achieved through ecological and evolutionary studies of traditional laboratory models. Here, we conducted the first large‐scale geographic analysis of genetic variation within and among wild zebrafish (Danio rerio) populations occurring in Nepal, India, and Bangladesh, and we genetically compared wild populations to several commonly used lab strains. We examined genetic variation at 1832 polymorphic EST‐based single nucleotide polymorphisms (SNPs) and the cytb mitochondrial gene in 13 wild populations and three lab strains. Natural populations were subdivided into three major mitochondrial DNA clades with an average among‐clade sequence divergence of 5.8%. SNPs revealed five major evolutionarily and genetically distinct groups with an overall F_ST of 0.170 (95% CI 0.105–0.254). These genetic groups corresponded to discrete geographic regions and appear to reflect isolation in refugia during past climate cycles. We detected 71 significantly divergent outlier loci (3.4%) and nine loci (0.5%) with significantly low F_ST values. Valleys of reduced heterozygosity, consistent with selective sweeps, surrounded six of the 71 outliers (8.5%). The lab strains formed two additional groups that were genetically distinct from all wild populations. An additional subset of outlier loci was consistent with domestication selection within lab strains. Substantial genetic variation that exists in zebrafish as a whole is missing from lab strains that we analysed. A combination of laboratory and field studies that incorporates genetic variation from divergent wild populations along with the wealth of molecular information available for this model organism provides an opportunity to advance our understanding of genetic influences on phenotypic variation for a vertebrate species.     

Ecological distribution and niche segregation of sibling species: the case of bean beetles, Acanthoscelides obtectus Say and A. obvelatus Bridwell

Abstract.  1. Molecular techniques have greatly added to the number of known sympatric cryptic species in insects. Ecological differences between these newly distinguished species are little explored, but niches often appear to overlap strongly. These cases are good models for exploring new ideas about species coexistence and community structure.
2.  Acanthoscelides obtectus and A. obvelatus are two sister species of bean bruchids, which have been confused until the last decade. One important ecological difference between them has emerged, however: A. obtectus is multivoltine and now distributed worldwide, whereas A. obvelatus is univoltine and restricted to Mesoamerica. Where their ranges overlap, the two species share the same host plants and larvae can sometimes complete development in the same seed.
3. The analysis of 27 622 Mexican individuals of the two species in 2001-2002 and 2002-2003 indicates that their niches overlap, but are differentiated with respect to altitude and the kind of beans (wild vs. domesticated). The principal patterns in their relative abundance in different habitats, and at different seasons, were constant from one year to the next.
4. As sympatry of these species seems to be of recent origin, the observed niche differentiation may not have evolved in response to competition, but could instead be the consequence of physiological differences, evolved independently in each species in allopatry, that pre-adapted them for different altitudes and kinds of resources.
5. The combination of biological and historical factors thus appears to allow these two sibling species to coexist in sympatry, despite their broadly overlapping ecological niches.     

Ten polymorphic microsatellite loci for the endangered Buena Vista Lake shrew (Sorex ornatus relictus)

The ornate shrew (Sorex ornatus) is restricted to the vanishing wetlands of California, USA and Baja California, Mexico. Several subspecies of ornate shrews are considered ‘mammal species of special concern’ in California by the Department of Fish and Game, and one (Sorex ornatus relictus) has recently been listed as endangered. Populations of shrews around Buena Vista Lake have been diminished or extirpated due to habitat deterioration and human development. In order to study the patterns of genetic variation in isolated populations of Buena Vista Lake shrews, we developed 10 polymorphic microsatellite loci. There were 6–27 alleles per locus, and the loci had heterozygosity values that ranged from 20 to 80%. In addition, we screened 20 different populations of S. ornatus, eight species within two subfamilies of shrews (Soricinae and Crocidurinae), as well as in a mole (Talpidae, Neurotrichus gibbsii), to determine if these loci could be informative in other species as well.     

Leaf breakdown in an Atlantic Rain Forest stream

The hypothesis of this study was that colonizers in decaying leaf litter prefer native species (Erythrina verna) to exotic ones (Eucalyptus camaldulensis and Protium heptaphyllum). Therefore, native species are expected to show higher breakdown rates, increased biomass, richness and density of invertebrate species, and increased biomass of decomposer fungi. Breakdown of leaf litter from these three species was assessed in an Atlantic Rain Forest stream. Four samples were collected during a period of 90 days and washed on a sieve to separate the invertebrates. Then, a series of leaf disks were cut to determine ash‐free dry mass and fungal biomass, and the remaining material was oven‐dried to determine the dry weight. Eucalyptus camaldulensis and E. verna showed higher breakdown rates than P. heptaphyllum, due to differences in leaf physical and chemical characteristics. The harder detritus (P. heptaphyllum) broke down more slowly than detritus with high concentrations of labile compounds (E. camaldulensis). The density of the invertebrates associated with detritus increased with time. There were no differences in density, taxonomic richness or biomass of invertebrates among the leaf types, which indicated that the invertebrates did not distinguish between exotic and native detritus. Fungal colonization varied among samples; E. camaldulensis showed the lowest ergosterol concentrations, mainly due to a high concentration of total phenolics. The detritus with the highest hardness value was colonized most slowly by fungi. These results showed that leaf breakdown in Atlantic Rain Forest streams could be affected either by changes in riparian vegetation, or by becoming more savanna‐like process due to climate change.     

Teucrium francoi M. Seq., Capelo, J.C. Costa & R. Jardim, a new species of Teucrium gr. scorodonia (Lamiceae) from Madeira

The species formerly recognized as Teucrium scorodonia in Madeira is here described as new: Teucrium francoi M. Seq., Capelo, J.C. Costa & R. Jardim. Morphologically close to species of Teucrium gr. scorodonia [ T. scorodonia L., T. pseudoscorodonia Desf., T. siculum (Raf.) Guss. and T. kotschyanum Poech], it exhibits, nonetheless, some distinct diagnostic characters. The indumentum density and type of hairs of T. francoi are clearly distinct from those of related species, as are the shape and dimensions of the leaves and bracts, calyx, and corolla, which are all taken as taxonomically significant diagnostic features. A diagnosis and a distribution map are presented for this new species. Morphology, ecology, biogeography, and conservation issues are discussed. Teucrium francoi , which is an endemic from Madeira (Portugal), is to be found mostly in the scope of the association Teucrio francoi–Origanetum virentis J.C. Costa, Capelo, Jardim, Sequeira, Lousã & Rivas-Martínez, but also occurs in somewhat humid habitats, such as open stands of Rosa mandonii Déségl. associated with small streams.  © 2008 The Linnean Society of London, Botanical Journal of the Linnean Society , 2008, 156 , 639–647.     

Ecotone delimitation: Epigean–hypogean transition in cave ecosystems

Abstract The ecotone zone between epigean and hypogean environments has been delimited for two limestone caves using a new method proposed herein. The richness and the diversity of the ecotone, epigean and hypogean environments and their similarities have also been determined. The ecotones were delimited using a similarity matrix between the inner and outer sectors of each cave. The ecotone of Dona Rita's cave was estimated to be 12 m long and the ecotone of Retiro's cave 16 m. The richness (S) of arthropods in Dona Rita's cave was higher in the ecotone (S = 131), intermediate in the epigean environment (S = 75) and lower in the hypogean system (S = 45). The invertebrate diversity (H′) was lower in the hypogean environment (H′ = 2.89) and not statistically different between the epigean environment and the ecotone (H′ = 3.56 and H′ = 3.76, respectively). The richness in Retiro's cave was higher in the ecotone (S = 86), intermediate in the epigean environment (S = 39) and lower in the hypogean system (S = 12). The invertebrate diversity was lower in the hypogean environment (H′ = 0.48), intermediate in the ecotone (H′ = 3.02) and higher in the epigean region (H′ = 3.29). Species migration patterns, differential environmental barriers and determination of accidental versus trogloxenes/troglophylous species are topics that are primarily approached by establishing ecotone zones in caves. The aim of the present paper is to establish the delimitation of theses zones.     

Transfer of nitrogen from a tropical legume tree to an associated fodder grass via root exudation and common mycelial networks

Symbiotic dinitrogen fixation by legume trees represents a substantial N input in agroforestry systems, which may benefit the associated crops. Applying ¹⁵N labelling, we studied N transfer via common mycelial networks (CMN) and root exudation from the legume tree Gliricidia sepium to the associated fodder grass Dichantium aristatum . The plants were grown in greenhouse in shared pots in full interaction (treatment FI) or with their root systems separated with a fine mesh that allowed N transfer via CMN only (treatment MY). Tree root exudation was measured separately with hydroponics. Nitrogen transfer estimates were based on the isotopic signature of N ( δ ¹⁵N) transferred from the donor. We obtained a range for estimates by calculating transfer with δ ¹⁵N of tree roots and exudates. Nitrogen transfer was 3.7–14.0 and 0.7–2.5% of grass total N in treatments FI and MY, respectively. Root δ ¹⁵N gave the lower and exudate δ ¹⁵N the higher estimates. Transfer in FI probably occurred mainly via root exudation. Transfer in MY correlated negatively with grass root N concentration, implying that it was driven by source-sink relationships between the plants. The range of transfer estimates, depending on source δ ¹⁵N applied, indicates the need of understanding the transfer mechanisms as a basis for reliable estimates.     

Thermal tolerance and recovery behaviour of Thorectes lusitanicus (Coleoptera,Geotrupidae)

1. Population differences in physiological responses are examined in Thorectes lusitanicus, an endemic Iberian dung beetle species, by submitting individuals of different populations to the same experimental and acclimation conditions. 2. An infrared thermography protocol was used, consisting of three assays: start of activity, cold response, and heat response. Individuals of 12 populations were studied and the comparative explanatory capacities of several environmental factors in relation to the observed inter‐population differences were examined. 3. The heating rate from chill coma to the beginning of activity was the variable with the highest discrimination power among the studied populations, accounting for 94% of the observed variance. Regarding the heat response, only six of the 16 thermal variables reached significance (inter‐population differences accounted for 52–74% in these six thermal parameters). 4. From the three considered environmental factors (Mediterranean climate, land cover, and trophic characteristics) only land cover characteristics remain statistically significant, affecting the cold response of individuals. 5. Thorectes lusitanicus is a species characterised by a high diversity of thermotolerance and recovery traits across populations with a low degree of association with broad environmental factors. Finally, it is suggested that the apterous character of this species could be a determinant factor explaining the high diversity of ecophysiological traits related to thermal stress tolerance and the recovery time.