Don C. Ohadike: The Man, his Intellectual Legacy and African Historiography

It is difficult to completely understand the life history of an intellectual excluding an understanding of his family upbringing and formative years. Family upbringing and childhood environment, often the less known part of a life history, play crucial roles in shaping the ideas and values individuals espouse in their adult life. Notwithstanding, this paper is not concerned with Don C. Ohadike’s childhood. It rather focuses on the professional career of our able historian – that is the part of his life as revealed by his most outstanding published writings. Ohadike’s published works contain a wellspring of idioms that tell much about his values, quality of mind, and his mission as an African historian. Ohadike was a humanist, an African patriot, and a nationalist crusader. His entire philosophy centered on safeguarding his African identity in an emergent world of cultural imperialism. The funds for this research were provided by a NEH-funded fellowship at the Schomburg Center, New York in the Spring of 2007. I owe a lot of gratitude to Professor John McLeod and Dean Blaine Hudson for granting me the extra incentives to pursue my research in New York. While all errors and misinterpretations are mine, I wish to thank the editors and anonymous reviewers for Journal of Dialectical Anthropology for their perspective comments and suggestions on earlier drafts of this paper.     

The trophic impact of small mammals in successional grasslands

The habitat use and diets of small mammals inhabiting grassland plots of different successional ages were investigated by live-trapping and faecal analysis over a period of 16 months. The contribution of the major plant life forms and the structural profile of the vegetation of each plot and the availability of insect prey were assessed. The dominant species of small mammal found on each plot were Sorex araneus, S. minutus, Apodemus sylvaticus and Microtus agrestis . Small mammals were most commonly found in the late and mid-successional stages, reflecting the habitat structure and food availability. A wide range of insects and other invertebrates were eaten by all four species and insects formed 50–62% of the animal prey taken. The incidence of certain prey in the diets differed between plots. The daily consumption rate of invertebrates by shrews and mice was estimated at some 6800 prey per ha. The greatest predatory impact came from shews but A. sylvaticus showed increased consumption of invertebrates in spring. The combined predatory impact of the grassland small mammal community on insect populations alone was estimated to average 0.01% per day and is predicted to be greatest in the mid-successional stages.     

Evidence for African origins of founders of the asiatic lion species survival plan

The Asiatic lion (Panthera leo persica) exists in the wild as a single relict population of approximately 250 individuals in the protected Gir Forest Sanctuary in western India. In 1981, a species survival plan (SSP) for the Asiatic lion was established by the American Association of Zoological Parks and Aquariums to manage the 200 + descendants of Asiatic lions in captivity in western zoological facilities. This captive population was derived from seven founders. In order to compare the genetic structure of the Gir Forest population with that of the captive SSP population, a genetic survey of 46 electrophoretic allozyme systems resolved from extracts of lion blood was undertaken by using 29 SSP Asiatic lions and 28 wild-caught or captive-bred lions maintained at the Sakkarbaug Zoo in India but originally derived from the Gir Forest. The Gir lion population was found to be genetically monomorphic at each of 46 allozyme loci. This was in contrast to several African lion (Panthera leo leo) populations, which show moderate levels of allozyme variation at the same loci. The SSP lion population was polymorphic at three allozyme loci (IDHI, TF, and PTI) for alleles that were previously found only in African lion populations. Pedigree analysis of the genetic transmission of these three biochemical loci demonstrated that two of the five primary founder animals of the SSP Asiatic lion population (a breeding pair originally imported from the Trivandrum Zoo in southern India) were descendants of the African subspecies. Three other founder animals were pure Asian. A retrospective SSP pedigree analysis of two morphologic characters (prominent abdominal fold and pairing of infraorbital foramen) that are partially diagnostic for persica vs leo was consistent with this conclusion as well. The implications for the management of small captive populations of threatened species and of the Asiatic lion SSP population are discussed.     

云南建水早第三纪哺乳类的发现

本文记述了在云南省建水县岔科地区发现的哺乳动物化石。根据豫鼠(Yuomys),定地层时代为晚始新世。这套地层暂称岔科组,以示滇南地区第一个含早第三纪哺乳动物的地点和层位。     

Ribosomal DNA non-transcribed spacer polymorphism in subterranean mole rats: genetic differentiation,environmental correlates and phylogenetic relationships

Summary An analysis is presented of genetic differentiation in the non-transcribed spacers of ribosomal DNA (NTS rDNA). Diversity, environmental correlates and the phylogenetic relationships are examined within and between species of the actively speciating subterranean mole rat, superspeciesSpalax ehrenbergi (2n=52, 54, 58, 60) in Israel. This analysis is based on a previous study of the geographic distribution of restriction fragment length polymorphisms of NTS rDNA. Here we present results indicating that NTS rDNA diversity exists mostly (66%) within populations, while 20% is between populations within species, and 14% between species. Multivariate discriminant analysis succeeded in separating 10 of the 13 populations (77%) into their correct chromosomal species, on the basis of the combination of three NTS rDNA repetypes. The phylogenetic relationships suggest that the complex involves two pairs of closely related species (2n=52–54 and 2n=58–60). NTS rDNA diversity, as well as the decrease southward in frequency of repetype C, are correlated with climatic factors of humidity and temperature. These data are discussed in terms of the evolutionary forces of migration and selection which may cause NTS rDNA differentiation. Climatic selection appears to be the major differentiating factor of NTS rDNA.     

Expression of the HNK-1/NC-1 epitope in early vertebrate neurogenesis

Summary A family of glycoconjugates has recently been shown to share a common carbohydrate epitope recognized by the mouse monoclonal antibody HNK-1. The specificity of HNK-1 was found to be similar to that of another monoclonal antibody, NC-1. These two IgM monoclonal antibodies were raised after immunization of mice with a human T-cell line and avian neural crest-derived ganglia, respectively. The antigens recognized by these antibodies include the myelin-associated glycoprotein, MAG, a glycolipid of defined structure, and a set of molecules involved in cell adhesion. The timing and pattern of appearance of these antigens are distinct. Moreover, the epitope may be absent on an antigen at a given stage or in a given tissue. Therefore, although the molecules able to carry the NC-1/ HNK-1 epitope are numerous and expressed in various tissues, the use of the monoclonal antibodies on tissue sections has proven adequate for following the migration of avian neural crest cells, the major cell lineage recognized by NC-1 and HNK-1 during early embryogenesis. Analogies in several other species have been found on the basis of HNK-1 reactivity. In this study we show that NC-1 and HNK-1 can be used successfully to label migrating neural crest cells in dog, pig and human. On the other hand, the NC-l/HNK-1 epitope was not present on migrating crest cells in amphibians or mice and was found only transiently on the neural crest of rats.     

Adaptive variation of pelage color within and between species of the subterranean mole rat (Spalax ehrenbergi) in Israel

Summary Color notations of dorsal pelage were analyzed in 451 adult subterranean mole rats, comprising 19 populations and 4 chromosomal species (2n=52, 54, 58 and 60) of the Spalax ehrenbergi superspecies in Israel. In addition, the color notations of soil samples from the collection sites were measured. In an attempt to evaluate the degree of correlation between pelage color of mole rats and the local soil color, each color was compared both macro- and microgeographically. The macrogeographic comparisons were among populations of the 4 chromosomal species, and the microgeographic comparisons were among pairs of geographically neighboring subpopulations which occur under similar climatic conditions but differ in soil type and color. The results indicate that 1. no differences in pelage color notation exist between the sexes; 2. pelage of mole rats is generally characterized by an over-all grayish color, but its shades vary regionally and locally in accordance with varying soil color; 3. a positive correlation was found between pelage and local soil colors in the macrogeographic analysis and this correlation was verified in a microgeographic comparison; 4. specimens from populations of the northern chromosomal species (2n=52, 54) mainly inhabit terra rossa and basalt soils, respectively, with reddish brown tones, and they tend to have a more reddish shade, whereas animals from the central species (2n=58), which inhabits mainly dark soils including alluvial clays, terra rossa and brown rendzina and the souther species 2n=60, which occurs mainly in light soil types such as pale rendzina, sandy loams and loess, tend to have a more yellowish shade. The general appearance of specimens from 2n=58 was dark gray while that of 2n=60 specimens was light gray; 5. mole rats living in xeric environments (particularly 2n=60, but also 2n=54) are lighter than those which live in mesic environments (2n=52, 58). The results support the conclusion that pelage color of strictly subterranean mole rats is subject to selection pressures of overground predation of disharmonious types with their background soil color. The possibility that the pelage color variation and patterns also contributes to better thermoregulation while mole rats are above ground is discussed.     

Scales and costs of habitat selection in heterogeneous landscapes

Summary Two scales of habitat selection are likely to influence patterns of animal density in heterogeneous landscapes. At one scale, habitat selection is determined by the differential use of foraging locations within a home range. At a larger scale, habitat selection is determined by dispersal and the ability to relocate the home range. The limits of both scales must be known for accurate assessments of habitat selection and its role in effecting spatial patterns in abundance. Isodars, which specify the relationships between population density in two habitats such that the expected reproductive success of an individual is the same in both, allow us to distinguish the two scales of habitat selection because each scale has different costs. In a two-habitat environment, the cost of rejecting one of the habitats within a home range can be expressed as a devaluation of the other, because, for example, fine-grained foragers must travel through both. At the dispersal scale, the cost of accepting a new home range in a different habitat has the opposite effect of inflating the value of the original habitat to compensate for lost evolutionary potential associated with relocating the home range. These costs produce isodars at the foraging scale with a lower intercept and slope than those at the dispersal scale.Empirical data on deer mice occupying prairie and badland habitats in southern Alberta confirm the ability of isodar analysis to differentiate between foraging and dispersal scales. The data suggest a foraging range of approximately 60 m, and an effective dispersal distance near 140 m. The relatively short dispersal distance implies that recent theories may have over-emphasized the role of habitat selection on local population dynamics. But the exchange of individuals between habitats sharing irregular borders may be substantial. Dispersal distance may thus give a false impression of the inability of habitat selection to help regulate population density.     

Experiments with trap crops against African bollowrm, Heliothis armigera, in Ethiopia

In a 1 ha haricot bean (HB) (Phaseolus vulgaris L.) field strip-cropped with 2 rows of maize (MZ) (Zea mays L.) on either side and then at 25 m intervals, the number of African bollworm (ABW) (Heliothis armigera (Hubner) (Lepidoptera: Noctuidae)) eggs + larvae on MZ was higher than that on HB by a factor of nearly 18. In a replicated experiment where five trap crops were compared with HB, as a check, all of them contained significantly greater numbers of ABW eggs + larvae than the check. Among the crops tested, lupin (LP) (Lupinus termis Forsk.) and pigeon pea (Cajanus cajan (L.) Millsp.) followed by hyacinth bean (Dolichos lalab L.) contained the highest ABW egg + larval population while sunflower (Helianthus annuus L.) contained the lowest; MZ was intermediate. On the other hand, HB plots bordered with MZ suffered significantly lower percent pod damage by ABW than did the check. Although grain yield differences among treatments were not significant, MZ-bordered plots gave nearly 22% higher yield than the check during the heavy ABW infestation in 1982. These differences were less obvious during the 1983 season because of low ABW infestation. In hot pepper (Capsicum spp.) strip-cropped with lupin, egg + larval counts on the latter were greater by a factor of nearly four in 1981 and 18 in 1982. It is concluded that trap-cropping has a great potential in the integrated management of ABW.

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Résumé En 1981, dans un champ de haricot (Phaseolus vulgaris), des cultures pièges de maïs (Zea mays) ont été semées en rangs doubles tous les 25 m et de chaque côté du champ, soit un total de 5 rangs doubles. Le nombre d'H. armigera (oeufs + chenilles) a été près de 18 fois plus élevé sur maïs que sur haricot.En 1982 et 1983, l'attractivité de 5 cultures pièges: Dolichos lablab, Lupinus termis, Z. mays, Cajanus cajan et Helianthus annuus, a été comparée à celle du haricot. Toutes ces plantes portaient un nombre d'oeufs et de chenilles supérieur au témoin (P. vulgaris). L'ordre décroissant des contaminations était: L. termis, C. cajan, D. lablab, Z. mays et H. annuus. Les rangs de P. vulgaris bordés par des rangs de Z. mays étaient moins contaminés que les témoins. Bien que les différences de rendements en graines suivant les expériences n'aient pas été significatives, les parcelles bordées de maïs ont fourni une récolte supérieure de 22%, pendant l'année 1982, où la contamination par H. armigera a été forte. En 1983, où l'infestation a été faible, les différences étaient moins claires.En 1981 et 1982, 5 rangs de L. tremis à 25 m d'intervalle ont été utilisés comme pièges pour protéger le piment fort (Capsicum spp.). Les décomptes d'oeufs et de chenilles ont été respectivement près de 4 et 18 fois plus élevés.La conclusion est que les cultures pièges ont un grand avenir dans la lutte intégrée contre H. armigera.

     

The seasonality of phytoplankton in African lakes

Although some study of the subject began in 1899, wide-ranging information from African water-bodies has only become available since 1950. Important developments included the establishment of long-term centres of research, the adoption of improved methods for quantitative algal sampling, the more intensive study of environmental conditions, the beginnings of experimental testing, and the improvement of taxonomic knowledge.At higher latitudes (> 20 °) examples of pronounced algal seasonality are long-established; they are accompanied and influenced by marked changes in radiant energy income and so water temperature, and often by effects of seasonal water input. Illustrations are given from lakes in Morocco and South Africa.More generally in Africa, including the tropical belt, annual patterns of phytoplankton seasonality are usually either dominated by hydrological features (water input-output) or by hydrographic ones (water-column structure and circulation). Examples of both types are discussed, together with instances (e.g. L. Volta) of combined hydrological and hydrographic regulation. In both the seasonal abundance of diatoms is often distinct and complementary to that of blue-green algae, with differing relationships to vertical mixing and water retention.Horizontal variability in the seasonal cycle is especially pronounced in the larger or morphometrically subdivided lakes. Some inshore-offshore differentiation is also known to affect phytoplankton quantity (e.g. L. George) and species composition (e.g. L. Victoria). Longitudinal differentiation is common in elongate basins especially when with a massive or seasonal inflow at one end (e.g. L. Turkana, L. Nubia, L. Volta); occasional terminal upwelling can also be influential (e.g. southern L. Tanganyika). Such examples grade into the longitudinally differentiated seasonality of flowing river-reservoir systems, as studied on the Blue and White Niles.The annual amplitude of population density, expressed in orders of magnitude (=log₁₀ units), is one measure of seasonal variability. It can exceed 3 orders both in systems subject to hydrological wash-out (e.g. Nile reservoirs) and in the more variable species components of lakes of long retention (e.g. L. Victoria). Low amplitudes can be characteristic of some components (e.g. green algae in L. Victoria) or of total algal biomass (e.g. L. George, L. Sibaya).Seasonal changes may be subordinated to inter-annual ones, especially in shallow and hydrologically unstable lakes (e.g. L. Nakuru).