Ecological correlates of small mammal community structure in the semi-arid Karoo, South Africa

The understanding of the determinants of small mammal community structure in arid and semiarid ecosystems is of importance, both in the light of the role that small mammals play, and the impact of livestock grazing on the flora of these systems. In a study aimed at identifying these determinants, small mammal assemblages and environmental features were quantified at six localities (a gradient of floristic structure, with constant annual rainfall) across the southern Karoo, South Africa. Stepwise variable regression indicated that small mammal diversity was correlated with plant and rock cover, as well as plant cover and horizontal foliage diversity at intermediate heights (40–60 cm). Initially, small mammal diversity increased with increasing plant cover, but decreased at cover levels greater than 30%. This relationship is similar to that found in other desert systems, although the peak in diversity found here is at higher levels of plant cover than found previously. I suggest that this higher peak may be owing to the lack of reliance on granivory by these animals, which are relatively omnivorous. This model may therefore explain the conflicting reports on the impact of livestock grazing on desert small mammals, with small mammal diversity decreasing with grazing below the peak, and increasing with grazing above the peak.     

Low Levels of Genetic Diversity within Populations of Hosta clausa (Liliaceae)

Abstract Genetic diversity of Korean populations in Hosta clausa was investigated using starch gel electrophoresis. Hosta clausa is widespread, grows only along streamsides, and has both sexual and asexual reproduction. Populations of the species are small and isolated. Thirty-two percent of the loci examined were polymorphic, and mean genetic diversity within populations (He_p=0.082) was lower than mean estimates for species with very similar life history characteristics (0.131), particularly for its congener H. yingeri (0.250). The mean number of multilocus genotypes per population was 8.7, and genotypic diversity index (D_G) was 0.84. Significant differences in allele frequencies among populations were found in all seven polymorphic loci (P < 0.001). About one-fifth of the total allozyme variation was among populations (G_ST=0.192). Indirect estimate of the number of migrants per generation (Nm=0.48, calculated from mean G_ST) and nine private alleles found indicate that gene movement among populations was low. The low levels of genetic diversity within populations and the relatively high levels of genetic diversity among populations suggest that strong moist habitat preferences, clonal reproduction, low level of gene flow among populations, genetic drift, and historical events may have played roles in the genetic structuring of the species.     

Small mammal seed consumption in the Karoo,South Africa: further evidence for divergence in desert biotic processes

Summary Annual seed consumption by a small mammal community in the semi-arid Karoo, South Africa, was calculated using population, biomass and dietary estimates and published estimates of field metabolic rate. The community comprised a macroscelid elephant shrew Macroscelides proboscideus, and two rodents Gerbillurus paeba and Desmodillus auricularis. Only G. paeba consumed seed during the study, and then in low amounts (annual mean = 0.4% of diet, insects = 53%, herbage = 47%), with M. proboscideus and D. auriocularis consuming mainly insects (88%) and herbage (90%), respectively. Energy requirements for the G. paeba population averaged 568 kJ ha^–1 day^–1. Total seed consumption was estimated to be 140 g ha^–1, or 155 000 seeds ha^–1 which represents 0.5% of the annual seed production for this site. These levels of granivory by small mammals are significantly lower than those recorded for North American deserts, and raises the question as to why granivory varies between these systems. These findings also refute the hypothesis that as a result of the harshness and similarity of physical conditions in deserts, the properties of desert communities are convergent.     

Selectivity Studies of the Benzene cis -Dihydrodiol Dehydrogenase Enzyme from Pseudomonas putida ML2 with Vicinal Diol Substrates

The enantiopure (1 S, 2 S )- cis -dihydrodiol metabolites 2B - 5B have been obtained in low yield from the corresponding monosubstituted halobenzene substrates 2A - 5A, using a wild-type strain of Pseudomonas putida (ML2) containing benzene dioxygenase (BDO). Benzene cis -dihydrodiol dehydrogenase (BCD) from P. putida ML2 and naphthalene cis -dihydrodiol dehydrogenase (NCD) from P. putida 8859 were purified and used in a comparative study of the stereoselective biotransformation of cis -dihydrodiol enantiomers 2B - 5B. The BCD and NCD enzymes were found to accept cis -dihydrodiol enantiomers of monosubstituted benzene cis -dihydrodiol substrates 2B - 5B of opposite absolute configuration. The acyclic alkene 1,2-diols 10 - 17 were also found to be acceptable substrates for BCD.     

Cassava leaf harvesting as vegetables; a cause of vulnerability of cassava plant to cassava mosaic disease and eventual yield reduction: Ernte von cassavablättern als gemüse; eine ursache für die anfälligkeit der cassavapflanze für die cassava-mosaikkrankheit und für spätere ertragseinbußen

The consequence of harvesting young leaves of cassava as vegetable on the vulnerability of the crop to cassava mosaic disease (CMD) and on storage root yield was investigated using 30 cassava genotypes planted in IITA fields located in the humid forest (Port Harcourt?:?Onne), forest-savannah transition (Ibadan), southern guinea savannah (Mokwa) and northern guinea savannah (Zaria) agroecologies in Nigeria. Tender apical leaves and shoots of the cassava genotypes were removed from forty plants per cassava genotype with the same number of plants considered as control. Whitefly infestation, disease incidence (DI) and symptom severity (ISS) of the disease were assessed at monthly interval for six months and also at the ninth month after planting (MAP). Yield reduction due to this treatment was calculated as percentage harvest index (HI). Whitefly population fluctuated throughout the period of observation at all locations with higher population obtained generally for treated plants compared to control plants. Sprouting leaves of some treated genotypes were observed with severe mosaic symptoms, while corresponding control showed no mosaic symptoms. Contrarily, no remarkable difference was observed in Zaria between the mean ISS of treated and control cassava genotypes. There was a highly significant difference (P?<?0.01) in DI and ISS among cassava genotypes across all locations. Also, there was a highly significant interaction (P?<?0.01) in symptom severity between location (loc) and genotype, genotype and treatment (trt), loc and trt. Interaction between loc, genotypes and trt with regard to DI was highly significant at 2, 3 and 4 MAP, while with ISS, the interaction was highly significant all through the counting period. There was a positive relationship between DI and ISS on plants of genotypes 96/1039 and ISU. The percentage HI (27.4) of treated plants of genotype 95/0166 in Ibadan was remarkably lower than the value obtained for corresponding control (41.9) plants. Also, sharp distinction in% HI of treated (39.5) and control (43.8) ISU was observed in Onne with their respective ISS values as 3.7 and 3.2. Therefore, harvesting tender apical leaves and shoots of cassava as vegetables should be discouraged as it increases the severity of CMD infection in the regenerating shoots of cassava with attendant storage root yield reduction.     

Standardising Home Range Studies for Improved Management of the Critically Endangered Black Rhinoceros

Comparisons of recent estimations of home range sizes for the critically endangered black rhinoceros in Hluhluwe-iMfolozi Park (HiP), South Africa, with historical estimates led reports of a substantial (54%) increase, attributed to over-stocking and habitat deterioration that has far-reaching implications for rhino conservation. Other reports, however, suggest the increase is more likely an artefact caused by applying various home range estimators to non-standardised datasets. We collected 1939 locations of 25 black rhino over six years (2004–2009) to estimate annual home ranges and evaluate the hypothesis that they have increased in size. A minimum of 30 and 25 locations were required for accurate 95% MCP estimation of home range of adult rhinos, during the dry and wet seasons respectively. Forty and 55 locations were required for adult female and male annual MCP home ranges, respectively, and 30 locations were necessary for estimating 90% bivariate kernel home ranges accurately. Average annual 95% bivariate kernel home ranges were 20.4 ± 1.2 km², 53 ±1.9% larger than 95% MCP ranges (9.8 km² ± 0.9). When home range techniques used during the late-1960s in HiP were applied to our dataset, estimates were similar, indicating that ranges have not changed substantially in 50 years. Inaccurate, non-standardised, home range estimates and their comparison have the potential to mislead black rhino population management. We recommend that more care be taken to collect adequate numbers of rhino locations within standardized time periods (i.e., season or year) and that the comparison of home ranges estimated using dissimilar procedures be avoided. Home range studies of black rhino have been data deficient and procedurally inconsistent. Standardisation of methods is required.     

The development of potential screens based on shoot calcium and iron concentrations for the evaluation of tolerance in Egyptian genotypes of white lupin (Lupinus albus L.) to limed soils

European cultivars of white lupin (Lupinus albus L.) grow poorly in limed or calcareous soils. However, Egyptian genotypes are grown successfully in highly calcareous soil and show no stress symptoms. To examine their physiological responses to alkaline soil and develop potential screens for tolerance, three experiments were conducted in limed and non-limed (neutral pH) soil. Measurements included net CO2 uptake, and the partitioning of Fe2+ and Fe3+ and soluble and insoluble Ca in stem and leaf tissue. Intolerant plants showed clear symptoms of stress, whereas stress in the Egyptian genotypes and in L pilosus Murr. (a tolerant species) was less marked. Only the intolerant plants became chlorotic and this contributed to their reduced net CO2 uptake in the limed soil. In contrast, Egyptian genotypes and L pilosus showed no change in net CO2 uptake between the soils. The partitioning of Ca and Fe either resulted from the stress responses, or was itself a stress response. L pilosus and some Egyptian genotypes differed in soluble Ca concentrations compared with the intolerant cultivars, although no significant difference was apparent in the Ca partitioning of the Egyptian genotype Giza 1. In a limed soil, Giza 1 maintained its stem Fe3+ concentration at a level comparable with that of plants grown in non-limed soil, whereas stem [Fe3+] of an intolerant genotype increased. Gizal increased the percentage of plant Fe that was Fe2+ in its leaf tissue under these conditions; that of the intolerant genotype was reduced. The potential tolerance of the Egyptian genotypes through these mechanisms and the possibility of nutritional-based screens are discussed.     

Bleomycin, unlike other male-mouse mutagens, is most effective in spermatogonia, inducing primarily deletions

Dominant-lethal tests [P.D. Sudman, J.C. Rutledge, J.B. Bishop, W.M. Generoso, Bleomycin: female-specific dominant lethal effects in mice, Mutat. Res. 296 (1992) 205-217] had suggested that Bleomycin sulfate (Blenoxane), BLM, might be a female-specific mutagen. While confirming that BLM is indeed a powerful inducer of dominant-lethal mutations in females that fails to induce such mutations in postspermatogonial stages of males, we have shown in a specific-locus test that BLM is, in fact, mutagenic in males. This mutagenicity, however, is restricted to spermatogonia (stem-cell and differentiating stages), for which the specific-locus mutation rate differed significantly (P<0.008) from the historical control rate. In treated groups, dominant mutations, also, originated only in spermatogonia. With regard to mutation frequencies, this germ-cell-stage pattern is different from that for radiation and for any other chemical studied to date, except ethylnitrosourea (ENU). However, the nature of the spermatogonial specific-locus mutations differentiates BLM from ENU as well, because BLM induced primarily (or, perhaps, exclusively) multilocus deletions. Heretofore, no chemical that induced specific-locus mutations in spermatogonia did not also induce specific-locus as well as dominant-lethal mutations in postspermatogonial stages, making the dominant lethal test, up till now, predictive of male mutagenicity in general. The BLM results now demonstrate that there are chemicals that can induce specific-locus mutations in spermatogonia without testing positive in postspermatogonial stages. Thus, BLM, while not female-specific, is unique, (a) in its germ-cell-stage specificity in males, and (b) in inducing a type of mutation (deletions) that is atypical for the responding germ-cell stages (spermatogonia).