Environmental factors influencing the distribution of bats (Chiroptera) in South Africa

Environmental factors limiting the distribution of 37 of the 56 bat species in a warm temperate region (South Africa) were determined using GIS software and the Maximum Entropy modelling technique (MaxEnt). Undertaking such a study in a warm temperate region like South Africa is essential as the outcomes of this study could inform our general understanding of distributions of other animals in other parts of the world. Hypotheses related to the ecological niche-based characteristics of species were tested to identify the most important variables influencing the distribution of South African bats and to predict the probability of occurrence for bat species in South Africa. A database that included locality records for bat species from different museums in South Africa was compiled and then combined with the researcher's own data for the Northern Cape Province as there was insufficient knowledge of bat distributions in this province. A total of 23 environmental variables were considered, of which 20 were downloaded from the WorldClim database as potential environmental variables influencing the contemporary distribution of bats in South Africa based on previous studies that use environmental variables from WorldClim to predict the distribution of species. The environmental variables were grouped into broad categories, temperature, precipitation, and biophysical (i.e., vegetation biomes, land use/land cover, geology) variables. As predicted, taxonomic affiliations appear to have no bearing on which factors influenced the geographic distribution of South African bat species. The distributional limits of even closely related species within the same genus appear to be influenced by disparate environmental factors. Geology appeared to be the most important limiting factor for 15 of the 37 species, all of which are known to use roosts associated with geological features (i.e., caves, mines and rock crevices). Land use/land cover influenced the distribution of six bat species most of which are known to use human structures or domesticated crops as roosting sites. Roost availability thus appeared to be an important factor limiting the distribution of bats. The distribution of only one South African bat species, the endemic Rhinolophus capensis, was associated with a biome as being the most important predictor variable. Temperature variables appeared to be the most important factors influencing the distribution of 12 of the 37 species of bats in South Africa. This might be linked directly to the roosting ecology and thermoregulation capability of each species and their need for hibernation and/or torpor. Precipitation parameters were the most influential in the distribution of 9 of the 37 South African bat species whose distribution is centred towards the wet east of the country. This could probably be linked to its effects on the availability of food in the form of fruit or insects. However, the results of this study should be interpreted cautiously. The majority of the environmental variables employed in this study to model the distribution of bats, were correlated to some degree, which could affect the contribution of an individual environmental variable to the performance of a model. Furthermore, certain bat species included in this study have their centres of distribution ranges further north in Africa and have only marginal intrusion into South Africa's political boundary, which means that only a portion of the distribution of these species is modelled; this could yield erroneous results that might not be transferable to other parts of the ranges of these species. Finally, field verification of the occurrence of species in areas where they are predicted to have a high probability of occurrence is crucial in order to verify the reliability of the models

A NEW ENERGY EFFICIENT ADAPTIVE HYBRID ERROR CORRECTION TECHNIQUE FOR UNDERWATER WIRELESS SENSORS NETWORKS

Underwater wireless sensors networks find many applications in today's life. However underwater sensors are still relatively expensive. They suffer from short lifetime which is limited by batteries lifetime as it is difficult to recharge or even replace batteries in harsh aquatic medium. When the battery is depleted the sensor is of no use anymore. So designing energy efficient communication protocols is an important issue for underwater sensors networks. Underwater is characterized by variable channel conditions, whereas underwater sensors are mobile due to water currents leading to variable distances between sensors. This variability in channel conditions and distances between sensors leads to inefficiency in energy consumptions when using fixed type of error correction technique. In this thesis, a mathematical energy efficiency derivations for the two main error correction techniques (Automatic Repeat request (ARQ) and Forward Error Correction (FEC)) in underwater environment has been done. The results from those derivations show that one technique is more energy efficient than the other below specific distance, where as the other is more energy efficient after this distance. This specific distance is found to be unfixed and varies with the variation in channel conditions and packet size. So using fixed error correction technique for specific distance is not accurate. Simulation has been done which validate the mathematical derivations. Based on the above derivation results Adaptive Hybrid Error Correction (AHEC) technique which adaptively changes the error correction technique to the technique that gives the highest energy efficiency for the current channel conditions and distances has been proposed. The technique uses an adaptation algorithm which depends on a pre-calculated packet acceptance rate (PAR) ranges look-up table, current PAR, packet length and current error correction technique used. AHEC viii technique has been found to have better energy saving compared with the techniques that depend on pure ARQ or FEC only. This saving ranges from 10 to 70 % in energy saving in ARQ case , and 7 to 10 % in energy saving in FEC case depending on current channel conditions and distance .It has also been compared with the technique that uses variable power supply in adaptation (Adaptive Variable Power Supply (AVPS)) and it achieves between 20 to 60 % in energy saving depending on current channel conditions and distance. It has also been compared with Adaptive Redundancy Reliable Transport Protocol (ARRTP), and it achieves between 10 to 80 % in energy saving depending on the current channel conditions and distance. The adaptation algorithm which depends on PAR has also been applied in adaptation to the ARRTP which originally depends only on inter-node distance in adaptation. PAR take both of distance and channel conditions into consideration. This technique is called PAR-based ARRTP, and the results shows better adaptation than the basic ARRTP in variable channel conditions cases. AHEC technique has also been applied with the bounded distance routing protocol to minimize the effects of variable channel conditions. Bounded distance routing protocol design depends on choosing specific number of relays between sender and receiver that minimize the total energy consumptions. This specific number of relays varies with the variation in channel conditions. The results show a deviation in number of relays from 6 when fixed error correction technique is used to only 2 when AHEC technique is used with it

Juvenile development of Douglas-fir, red alder and snowbrush associations in Western Oregon

The juvenile development of Douglas-fir, red alder and snowbrush associations was investigated in western Oregon. The relationship between Douglas-fir and red alder was studied and compared in the Coast, Willamette Valley and Cascade regions. Snowbrush- Douglas-fir stands were sampled in the western Cascades. Alder- Douglas-fir relationships were studied on clearcuts supporting at the same time mixtures of alder and Douglas-fir and open-grown Douglas-fir. Sites where snowbrush and Douglas-fir grew together were selected on the same basis. Total heights of alder and Douglas-fir were expressed as cumulative one-year growth measurements. Canopy height of snowbrush was measured at various ages to determine growth rate. Information pertaining to moisture, vegetation, slope, aspect, elevation and stand structure was recorded at each sample plot. The data were analyzed with the aid of a multiple regression program. Height and (height)² were treated as independent variables, and annual height increment as the dependent variable. Results indicate that early establishment of Douglas-fir is expected to aid its dominance-takeover and allow it to evade suppression by red alder. Douglas-fir trees growing on wet sites need to be established earlier than those on drier habitats for the same degree of suppression evasion. The rapid juvenile growth rate of red alder is a major threat for the successful establishment of Douglas-fir. Height growth curves of the two species intersected at an earlier age on non-wet as compared to wet sites. The two trees grow in direct competition up to about age 40 years on wet habitats, with alder able to suppress Douglas-fir during this period. Douglas-fir has virtually no chance áf survival when it is established concurrently with red alder or after its appearance. Snowbrush retards the growth of Douglas-fir trees during their first ten years of development. Trees that are delayed more than five years in establishment suffer a loss of more than 50% in total height as a result of the suppressive effect of the shrub. It is expected that the trees will compensate for some of this loss, but their growth may never equal that of comparable open-grown Douglas-fir developing under similar conditions

Genetic variation and population structure of Sudanese populations as indicated by 15 Identifiler sequence-tagged repeat (STR) loci

<p>Abstract</p> <p>Background</p> <p>There is substantial ethnic, cultural and linguistic diversity among the people living in east Africa, Sudan and the Nile Valley. The region around the Nile Valley has a long history of succession of different groups, coupled with demographic and migration events, potentially leading to genetic structure among humans in the region.</p> <p>Result</p> <p>We report the genotypes of the 15 Identifiler microsatellite markers for 498 individuals from 18 Sudanese populations representing different ethnic and linguistic groups. The combined power of exclusion (PE) was 0.9999981, and the combined match probability was 1 in 7.4 × 10¹⁷. The genotype data from the Sudanese populations was combined with previously published genotype data from Egypt, Somalia and the Karamoja population from Uganda. The Somali population was found to be genetically distinct from the other northeast African populations. Individuals from northern Sudan clustered together with those from Egypt, and individuals from southern Sudan clustered with those from the Karamoja population. The similarity of the Nubian and Egyptian populations suggest that migration, potentially bidirectional, occurred along the Nile river Valley, which is consistent with the historical evidence for long-term interactions between Egypt and Nubia.</p> <p>Conclusion</p> <p>We show that despite the levels of population structure in Sudan, standard forensic summary statistics are robust tools for personal identification and parentage analysis in Sudan. Although some patterns of population structure can be revealed with 15 microsatellites, a much larger set of genetic markers is needed to detect fine-scale population structure in east Africa and the Nile Valley.</p

Feedlot performance of Sudanese desert lambs fed with mash or pelleted diet of varying energy levels

AbstractThis experiment was conducted using 18 Sudan desert ram lambs (22±5.7kg) to examine the effects of feeding with diets of different energy levels and physical forms on feedlot performance. These lambs were randomly divided into three feed groups of six animals each in a completely randomized design (CRD). Following an acclimatization period of three weeks, three experimental diets were offered, each for one group. High Energy Pellets (HEP) and High Energy Mash (HEM) diets (10.50MJME/kg DM) of a pelleted and mash form, respectively and Low Energy Diets (LEP) was a pelleted and low energy diet (8.5MJME/kg DM).The experiment continued for all diets to an average 40kg live weight lamb. Results revealed lower Dry Matter Intake (DMI) (P>0.001), improved Feed Conversion Ratio (FCR) (P<0.01) and higher Average daily gain (ADG) (P<0.01) for the high energy groups compared to the low energy diet group. No significant (P>0.05) differences were observed due to pelleting between the two higher energy groups. No significant (P>0.05) differences were observed among treatment groups in the Metabolizable Energy (ME) required to put a unit of body weight gain

The impact of three stocking intensities and four grazing treatments on the carbohydrate reserves of perennial ryegrass (Lolium perenne L.)

A study was conducted during 1974 and 1975 to evaluate the impact of stocking intensity and season of grazing upon carbohydrate concentration, biomass of storage organs, and total carbohydrate per plant in the roots and crowns of perennial ryegrass (Lolium perenne L.) in improved rangelands in Western Oregon. The stocking intensities were 7.4 ewes per hectare (moderate), 9.9 ewes per hectare (heavy), and 12.4 ewes per hectare (overstocking). The grazing treatments were Complete Protection, Fall Protection, Fall Grazing, and Yearlong Grazing. Another study was established during the same period to relate the seasonal carbohydrate reserve cycle and plant growth to phenological stages of development. The influence of stocking intensity on carbohydrate concentration was significant for both roots and crowns. Effects of season of grazing on the concentration in these plant parts were also significant. Ryegrass plants under the moderate stocking intensity had a significantly higher concentration of total available carbohydrate (TAC) than those under each of the other two higher stocking rates. Fall grazing resulted in higher total available carbohydrate concentration than the other seasonal grazing treatments. Stocking intensity impact was significant on the crown biomass, but not on root biomass. Plants under moderate stocking intensity had significantly greater biomass than those under heavy and overstocking rates. Season of grazing as well as interaction among year and season of grazing had a significant effect on both crown and root biomass. Stocking intensity had a significant effect on total carbohydrate per plant. The TAC per perennial ryegrass plant was higher in moderately stocked pastures than in pastures with heavy or overstocking rates. A significant effect was shown for the season of grazing treatments on root TAC per plant, but not for the crowns. Perennial ryegrass displayed clearly defined seasonal trends in TAC concentration during the period of data collection. The crowns maintained greater TAC levels than the roots at all phenological stages. The carbohydrate reserve curve for different phases of development displayed the expected spring and winter depletion of reserves for meeting growth initiation and further development. It had its greatest slope during these phenological stages, concurrent with sharp reserve depletion. Fall regrowth did not result in a sharp decline in reserve level as did spring and winter growth. The management implications were discussed. Ryegrass showed a high tolerance to season of grazing. Grazing during the early phase of spring is recommended to be at moderate intensity, since the combination of high grazing pressure and early defoliation is detrimental to the carbohydrate reserves. Winter grazing at overstocking rates may be potentially harmful to perennial ryegrass. Moderate to heavy stocking intensities are recommended, if yearlong grazing is considered. Grazing at overstocking rates is possible through a program that considers deferment during one or two seasons of grazing

Tolerance of Roselle (Hibiscus Sabdariffa L.) Genotypes to Drought Stress at Vegetative Stage

Background: Hibiscus sabdariffa L. is an important medicinal and fiber plant in Sudan. Among other stresses, drought extremely limits the growth, quality and net yield of the crop. The drought effects the crop plants by imposing certain morphological, physiological and biochemical changes at different periods of growth.Methods: Current study was carried out in greenhouse settings at Center of Excellence in Molecular Biology (CEMB) to investigate the effects of drought stress. Five (5) different genotypes of Hibiscus Sabdariffa L., namely Baladimostadir (H1), Um shiak (H2), Abu shankal (H3), Rahad mix (H4) and Abu Najma (H5) were studied. Thirty (30) days old Roselle seedlings were drought stressed for 10 days and its implications on plant growth, gas exchange, water relation, chlorophyll content and proline accumulation were estimated. Substantial genotypic differences in their adaptive response to drought were observed.Results: Drought stress significantly affected the plant height; lowered the relative gas exchange efficiency and altered the physiological and biochemical responses.  In comparison with others, H2 and H4 genotypes tolerated the osmotic stress well with lower osmotic potential and higher osmotic adjustment, better water content, higher stomatal conductance, photosynthetic efficiency and chlorophyll content. Accumulation of osmoprotectant and gas exchange indicators clearly distinguished the responses of different genotypes towards water stress.Conclusion: Our results can be used for evaluation, screening, and manipulations of Hibiscus Sabdariffa L. genotypes for improvement of drought tolerance through conventional breeding or drought responsive gene isolation

Automated daily human activity recognition for video surveillance using neural network

Surveillance video systems are gaining increasing attention in the field of computer vision due to its demands of users for the seek of security. It is promising to observe the human movement and predict such kind of sense of movements. The need arises to develop a surveillance system that capable to overcome the shortcoming of depending on the human resource to stay monitoring, observing the normal and suspect event all the time without any absent mind and to facilitate the control of huge surveillance system network. In this paper, an intelligent human activity system recognition is developed. Series of digital image processing techniques were used in each stage of the proposed system, such as background subtraction, binarization, and morphological operation. A robust neural network was built based on the human activities features database, which was extracted from the frame sequences. Multi-layer feed forward perceptron network used to classify the activities model in the dataset. The classification results show a high performance in all of the stages of training, testing and validation. Finally, these results lead to achieving a promising performance in the activity recognition rate

Phenotypic convergence in genetically distinct lineages of a Rhinolophus species complex (Mammalia, Chiroptera)

Phenotypes of distantly related species may converge through adaptation to similar habitats and/or because they share biological constraints that limit the phenotypic variants produced. A common theme in bats is the sympatric occurrence of cryptic species that are convergent in morphology but divergent in echolocation frequency, suggesting that echolocation may facilitate niche partitioning, reducing competition. If so, allopatric populations freed from competition, could converge in both morphology and echolocation provided they occupy similar niches or share biological constraints. We investigated the evolutionary history of a widely distributed African horseshoe bat, Rhinolophus darlingi , in the context of phenotypic convergence. We used phylogenetic inference to identify and date lineage divergence together with phenotypic comparisons and ecological niche modelling to identify morphological and geographical correlates of those lineages. Our results indicate that R. darlingi is paraphyletic, the eastern and western parts of its distribution forming two distinct non-sister lineages that diverged ~9.7 Mya. We retain R. darlingi for the eastern lineage and argue that the western lineage, currently the sub-species R . d. damarensis , should be elevated to full species status. R. damarensis comprises two lineages that diverged ~5 Mya. Our findings concur with patterns of divergence of other co-distributed taxa which are associated with increased regional aridification between 7-5 Mya suggesting possible vicariant evolution. The morphology and echolocation calls of R. darlingi and R. damarensis are convergent despite occupying different biomes. This suggests that adaptation to similar habitats is not responsible for the convergence. Furthermore, R. darlingi forms part of a clade comprising species that are bigger and echolocate at lower frequencies than R. darlingi , suggesting that biological constraints are unlikely to have influenced the convergence. Instead, the striking similarity in morphology and sensory biology are probably the result of neutral evolutionary processes, resulting in the independent evolution of similar phenotypes