Development of polymorphic microsatellite markers in sesame (Sesamum indicum L.)

Fifty microsatellite sequences (SSRs) were isolated from an enriched library of sesame (Sesamum indicum L.) using a modified protocol. After screening, 10 polymorphic microsatellites were used to determine their usefulness in diversity analysis among 16 sesame accessions. The number of alleles ranged from three to six alleles per locus with an average of 4.6 alleles. The fragment size varied from 150 bp to 307 bp. Expected heterozygosites (H_E) and polymorphism information contents (PICs) ranged from 0.437 to 0.858 and 0.34 to 0.80, respectively, which indicates the highly informative nature of the microsatellites reported here. These microsatellite markers will be very useful in diversity analysis among a large germplasm collection of sesame present in our Korean gene bank and also in the establishment of its core collection.     

Scale-dependent foraging costs: habitat use by rock hyraxes (Procavia capensis) determined using giving-up densities

Individuals select for habitats at different scales. Can a species’ response to different spatial and temporal heterogeneities be placed in a common currency? Is it possible to rank the relative importance of different habitat features on the organism's behavior and ecology? Do the effects of different spatial and temporal heterogeneities interact in predictable ways? To address these questions, we quantified hyrax habitat use at a series of rocky outcrops (koppies) and an isolated gorge in Augrabies Falls National Park, South Africa. We measured the hyraxes’ perceptions of feeding opportunities and costs using giving‐up densities (GUDs) within experimental food patches. At very small spatial scales (2–3 m), we tested whether hyraxes have lower GUDs under cover (shrubs or rocks) or 2–3 m away in the open. Hyraxes valued cover highly, consistently showing lower GUDs in cover microhabitats. This preference did not result from differences in energetic costs, as hyraxes did not track sun in winter or shade in summer. At moderate spatial scales (10–80 m), we tested whether hyraxes act as central place foragers with lower GUDs closer to their dens. GUDs increased with increasing distance to dens at four koppies, but not at the gorge. At larger spatial scales, preferences differed between colonies based on differences in habitat structure, with hyraxes on similar structures (koppies) behaving similarly. We evaluated how foraging costs varied with temporal heterogeneity within the day, among days, and among seasons. Hyraxes showed their lowest GUDs in the early mornings and late afternoons. Hyraxes shifted foraging locations among days, which may result from sentinels shifting location on consecutive days and/or hyraxes managing their food. Differences between GUDs during the various sample periods were not seasonally correlated. We conclude that spatial and temporal habitat utilization by hyraxes may be driven more by predation risk rather than other costs.     

Herbivory of clonal populations: cattle browsing affects reproduction and population structure of Yucca elata

The hypothesis that cattle browsing on inflorescences of the soaptree Yucca elata reduces reproductive success was investigated by comparing recruitment and population structure in six populations protected from grazing, six grazed during the flowering season and five grazed outside the flowering season. Cattle consumed 98% of inflorescences, which were found to be highly nutritious. Reduced recruitment in flower-grazed populations could not be attributed to reduced flower survival, as recruitment in non-flower grazed populations was also reduced. Changes in population structure were due to cattle browsing small caudices, including both genets and ramets. An alternate hypothesis of limited germination in soils compacted by cattle was not supported. Cattle browsing of inflorescences reduced reproductive effort, which may be due to the inability of the plants to resorb nutrients after flowering. Browsing also increased branching, probably through lack of apical dominance, whereas physical trampling increased procumbency. Cattle browsing implies a lack of genetic recruitment, possible local extinction of the yucca moth Tegeticula yuccasella, the exclusive pollinator of Y. elata, and local reduction in insect and bird biodiversity.     

Trophic status of small mammals in the semi-arid Karoo, South Africa

The feeding habits of a community of small mammals from the semi-arid Karoo, South Africa were analysed by microscopic examination of the stomach contents of animals caught during a 13-month snap-trapping study. The community comprised eight rodent species ( Gerbillurus paeba, Mus minutoides, Rhabdomys pumilio, Otomys unisulcatus, Saccostomus campestris, Desmodillus auricularis, Malacothrix typica, Mastomys natalensis ) and a single macroscelid elephant shrew ( Macroscelides proboscideus. ) The rodents were all predominantly herbivorous, while the elephant shrew ate mainly insects. No granivores or omnivores were represented in this community. The results presented here (including the first analysis of the diet of M. typica ) indicate a greater emphasis on herbivory than previously described for these species. Limited dietary overlap was recorded between these species, although some instances of potential dietary competition that deserve further study were identified. The paucity of granivorous small mammals in the semi-arid Karoo contrasts the patterns of trophic specialization for North American and Israeli semi-arid communities, but is similar to that of South American, Australian and other southern African semi-arid communities.     

In vitro inhibition of mouse dental development by tetracycline

Embryonic molars and incisors were dissected from mandibles of 15-day post-fertilization C57BL/10 mouse embryos and were cultured in vitro for six days on agar-solidified Eagle's basal medium. Experimental explants were cultured on medium which was the same as the control except that 50, 75 or 100 microgram/ml tetracycline was added. Treated explants of both incisors and molars were suppressed in development and reduced in size. Enamel organs and dental papillae of all tooth germs subjected to higher tetracycline concentrations were abnormal in structure and differentiation of ameloblasts and odontoblasts was inhibited. Explants treated with higher dosage levels of the drug were more severely affected than those exposed to lower concentrations. Recovery from the suppression induced by tetracycline was observed in explants transferred to control medium for four days of growth following treatment. Differentiated ameloblasts and odontoblasts observed in the recovering tooth germs indicated that the inhibition in development was temporary. The results of this study showed that tetracycline can alter dental development in vitro prior to mineralization. The observed inhibition may be related to a disruption of collagen biosynthesis which is thought to play a role in the controlling epithelial-mesenchymal interaction involved in tooth germ morphogenesis.     

Accessibility maps as a tool to predict sampling bias in historical biodiversity occurrence records

Historical biodiversity occurrence records are often discarded in spatial modeling analyses because of a lack of a method to quantify their sampling bias. Here we propose a new approach for predicting sampling bias in historical written records of occurrence, using a South African example as proof of concept. We modelled and mapped accessibility of the study area as the mean of proximity to freshwater and European settlements. We tested the model's ability to predict the location of historical biodiversity records from a dataset of 2612 large mammal occurrence records collected from historical written sources in South Africa in the period 1497–1920. We investigated temporal, spatial and environmental biases in these historical records and examined if the model prediction and occurrence dataset share similar environmental bias. We find a good agreement between the accessibility map and the distribution of sampling effort in the early historical period in South Africa. Environmental biases in the empirical data are identified, showing a preference for lower maximum temperature of the warmest month, higher mean monthly precipitation, higher net primary productivity and less arid biomes than expected by a uniform use of the study area. We find that the model prediction shares similar environmental bias as the empirical data. Accessibility maps, built with very simple statistical rules and in the absence of empirical data, can thus predict the spatial and environmental biases observed in historical biodiversity occurrence records. We recommend that this approach be used as a tool to estimate sampling bias in small datasets of occurrence and to improve the use of these data in spatial analyses in ecological and conservation studies.     

Short‐term foraging responses of a generalist predator to management‐driven resource pulses

Generalist predators characteristically switch prey in response to resource pulses. Ungulate population reinforcement through translocation provides stressed and vulnerable prey, and apex predator reintroduction provides carrion, both resources that can be exploited by generalist predators. We investigated the dietary response of black‐backed jackal to two management interventions in the Karoo National Park, South Africa, namely the reinforcement of the springbok population, and then the reintroduction of lions. By analysing jackal diets from scats collected before and after each management intervention, we show that the relative per cent occurrence and biomass consumed of springbok increased in the diet following the population reinforcement of springbok. In contrast, large ungulates were more prevalent in the diet following apex predator reintroduction. These results suggest that jackals took advantage of a potentially vulnerable abundant springbok population following their population reinforcement, and then switched to foraging on carrion provided by reintroduced lions. These results provide insights into the dietary response of a generalist mesopredator to management interventions. A key lesson from the study is that the diet of generalist predators is context‐dependent and should be interpreted in that light.     

Comparison of acid and alkaline soil and liquid culture growth systems for studies of shoot and root characteristics of white lupin (Lupinus albus L.) genotypes

Four quantitative trait loci (QTLs) for P uptake were previously identified in a rice population that had been developed from a cross between the indica landrace Kasalath (high P uptake) with the japonica cultivar Nipponbare (low P uptake). For further studies, near isogenic lines (NILs) were developed for a major QTL linked to marker C443 on chromosome 12 and for a minor QTL linked to C498 on chromosome 6. On a highly P-deficient upland soil (aerobic conditions), NIL-C443 had three to four times the P uptake of Nipponbare, whereas the advantage of NIL-C498 was in the range of 60–90%. The superiority of NILs over Nipponbare vanished when grown in the same soil under anaerobic paddy conditions. All genotypes had high P uptake when P was supplied at a rate of 60 kg P ha^–1, regardless of soil conditions. These results confirmed the presence of both QTLs and furthermore implied that QTLs affected absorption mechanisms that specifically increased P uptake in a P deficient upland soil.Additional experiments were conducted to investigate if the effect of QTLs is linked to an increase in root growth or due to more efficient P uptake per unit root size (higher root efficiency). Root size did not differ significantly between genotypes in the plus-P treatment. P deficiency, however, reduced the root surface area of Nipponbare by more than 80% whereas NIL-C443 maintained almost half of its non-stress root surface area. The low root growth of Nipponbare observed under P deficiency was probably the result of insufficient P uptake to sustain plant growth, including root growth. Genotypic differences in the ability to maintain root growth, therefore are likely caused by some mechanism that increases the efficiency of roots to access P forms not readily available. This however, only had an effect in aerobic soil. Potential mechanisms leading to higher P uptake of NILs are discussed.     

Opportunistic feeding by lions: non-preferred prey comprise an important part of lion diets in a habitat where preferred prey are abundant

Optimal foraging theory predicts less diverse predator diets with a greater availability of preferred prey. This narrow diet niche should then be dominated by preferred prey, with implications for predator–prey dynamics and prey population ecology. We investigated lion (Panthera leo) diets in Hluhluwe–iMfolozi Park (HiP), South Africa, to assess whether lions in a site with a high density of preferred prey (prey species weighing 92–632 kg as estimated from a published meta-analysis) have a narrow diet, consisting primarily of preferred prey. HiP is a useful study site to investigate this prediction because it is a productive landscape (with a high density of prey) where lion-preferred prey constitutes up to 33% of the prey available to lions. Furthermore, to investigate whether lions in HiP exhibit sex-specific diets as documented in other southern African populations, we estimated male and female lion diets separately. We were specifically interested in testing whether traditional approaches of estimating lion diets at the population level mask sex-specific predation patterns, with possible implications for management of lions in small to medium-sized fenced reserves. Lions in HiP preferred larger prey species (63–684 kg) and had diets with a larger proportion of preferred prey than reported in an African-wide meta-analysis. However, despite the high density of preferred prey species, 36% of lion diets still consisted of typically non-preferred species such as nyala (Tragelaphus angasii). This finding suggests that lions in HiP maintain a degree of opportunism even when preferred prey are abundant. Therefore, abundant, non-preferred prey are likely to be an important resource for lion populations. Sex-specific differences in lion diets were evident in HiP, suggesting that estimation of lion resource use and carrying capacity should consider opportunistic hunting and sex-specific differences in lion diets.