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1.
Peter  Ward 《Ibis》1971,113(3):275-297
Red-billed Queleas migrate, at the beginning of the wet season, away from their dry-season concentration areas and towards areas where rain started several weeks earlier. Considerable fat deposits are accumulated for this “early-rains migration”. The direction taken by the migrants, the distance they must fly, and the timing of the movement are dependent upon the timing of the rains and the way the rain-front moves. On the return “breeding migration” individuals in breeding condition stop to breed (in large aggregations) wherever they find conditions suitable for the founding of colonies. The location of the colonies can vary greatly from year to year. The migrations performed by several populations, in different parts of Africa, are predicted on the basis of general rainfall patterns, and the predictions tested against the facts available. There is evidence that individual females are able to produce a succession of broods in the same breeding season, at colonies which may be very far apart, and probably with different mates. The adaptive value of this “itinerant breeding” is discussed. Many other bird species, which breed at a particular phase of the wet-season/dry-season cycle, are expected to perform similar “itinerant breeding”.  相似文献   

2.
Summary

The relative abundance of rheophilic macroinvertebrates in the Orange River was assessed before and 15 hrs after two aerial applications of fenthion (QUELETOX® UL) above roosting sites of the red-billed quelea (Quelea quelea). The first treatment had no detectable effect on benthic macroinvertebrate abundance, whereas the second treatment caused mortality among at least 17 taxa (over half the taxa present). The most sensitive species were nymphs of the mayflies Baetis glaucus and Tricorythus discolor, followed by larvae of the midge Rheotanytarsus fuscus. Fenthion had no detrimental effect on the population densities of the mayfly Afroptilum excisum.

The results of this study warn of the dangers of fenthion in water supplies. It is suggested that alternative methods of quelea control along the Orange River should be sought.  相似文献   

3.
《Ostrich》2013,84(3):295-296
The Red-billed Quelea Quelea quelea is a serious pest of agricultural crops throughout most of sub-Saharan Africa. Since the 1980s, it has expanded its range into the Eastern Cape and Western Cape, South Africa, facilitated by changes in agricultural practices. This note documents the first breeding of Red-billed Quelea in the winter rainfall region of South Africa. A colony of 350–600 nests was found, with evidence of recent breeding. Red-billed Quelea numbers were low in this region, but if numbers increase in the future in the Western Cape, winter crops could be under threat.  相似文献   

4.
In Tenkere, Sierra Leone, a community of wild chimpanzees (Pan troglodytes verus) spent long hours eating the fruits and flowers of the Kapok (Ceiba pentandra) tree. The branches of this species are covered in sharp thorns which make movement in their high canopies problematic for the chimpanzees. In an apparent attempt to increase their mobility and to ease the discomfort of lengthy bouts of eating in these trees, some of the Tenkere chimpanzees have been observed using stick tools as foot (“stepping-sticks”) and body (“seat-sticks”) protection against the painful thorns. This form of tool-using is culturally unique to the Tenkere chimpanzees, as at other sites where these apes have been observed eating parts of kapok trees, there are no published records of this tool technology. In three of the stepping-stick tool use incidents, the chimpanzee used the tool(s), held between their greater and lesser toes, in locomotion. This form of tool use is the first recorded case of habitually used tools that can be justifiably categorized as being “worn” by any known wild population of Pan troglodytes. Am J Primatol 41:45–52, 1997. © 1997 Wiley-Liss, Inc.  相似文献   

5.
Summary

The hydrological and habitat value of wetlands is beginning to be recognised in South Africa, but only in parts of Natal Province has an effort been made to map wetlands and to record their status over large areas. While the most accurate method of mapping wetlands is a combination of photogrammetry and field surveys, this is time-consuming and expensive. An alternative “desktop” method was therefore used to draw up a preliminary distribution of wetlands in the south-western Cape Province, and this approach consisted of summarising the information contained on 1:50 000 topographical survey maps. The summary shows that shallow, vegetated wetlands (vleis) occur mainly in the wetter south and south-west of the region, while the non-perennial wetlands (pans) predominate inland, where the land is dryer and flatter. There are many estuarine wetlands along the coast, resulting from the tendency of river mouths to be blocked by sand-bars. Farming requirements and suitable topography account for the many small artificial wetlands (farm dams) in the central southern parts. Farm dams predominate in the region (15067 were counted), followed by pans (1741), riverine wetlands (261), vleis (216) and estuarine wetlands (15).  相似文献   

6.
What are the ethical dilemmas that conducting anthropological on memory in South Africa poses to the student of violence? In the specific context of “victim support groups” in post-1994 South Africa, one of the most problematic issues relates to the interactions between “trauma experts” and “victims.” In the view of many survivors, the violence of voicelessness, an issue to which there is a particular sensitivity in the country, is re-inscribed in their life through the specific intervention of social scientists. One of the effects of this interventions, which determines the limits and possibilities of any research on memory as it connects to violence, is a widespread reaction against experts, whose work, the production and dissemination of knowledge about trauma on the basis of other people’s experiences, is often perceived by survivors as being part of a broader economy of subtraction where their “voices” have become commodities in a transnational network of prestige.  相似文献   

7.
8.
Whittington-Jones, C.A. 1997. Apparent range expansion of the Redbilled Quelea Quelea quelea in the Eastern Cape Province of South Africa. Ostrich 68 (2–4): 97–103.

Distribution records obtained from the South African Bird Atlas Project (SABAP) and from published literature show that the known distribution of Redbilled Quelea in the Eastern Cape has changed dramatically over the last century. Increased search effort following the initiation of SABAP may explain the range expansion, but changes in agricultural practice have probably been a contributing factor.  相似文献   

9.
The past decade has brought considerable debate on the subject of modern human origins. The nature of the transition from Homo erectus to archaic Homo sapiens to modern H. sapiens has been examined primarily in terms of the relative contribution of archaic populations to later moderns, both within and among geographic regions. The recent African origin model proposes that modern humans appeared first in Africa between 100,000 and 200,000 years ago, and then spread through the rest of the Old World, replacing preexisting populations.1–6 This model has been referred to by a variety of names, including “replacement”, “Garden of Eden”, “Noah's Ark”, and “out of Africa”. The recent African origin model contrasts with the multiregional model, which proposes a species-wide transition to modern humans throughout the Old World during the past million years or more.7–10 Indeed, some proponents of the multiregional model advocate placing Homo erectus and all subsequent species of Homo in the evolutionary species Homo sapiens.11 This contrasts with the view that there were multiple hominid species during the Middle Pleistocene. The debate continues.12,13 Although the multiregional model is often portrayed as proposing a simultaneous transition to anatomically modern humans in different geographic regions, it explicitly allows for varying degrees of continuity across time and space.10 This model, in the broad sense, does not rule out the possibility that modern human morphology appeared first in Africa and then spread through the rest of the Old World through gene flow. However, not all advocates of the multiregional model adhere to this specific subset of the general model.9 Comparison of the African and multiregional models is complicated by considering other, less extreme, hypotheses. Some versions of the recent African origin model imply a speciation event associated with the initial origin of modern humans. Another version, which suggests the possibility of some admixture between “moderns” leaving Africa and preexisting “archaics” elsewhere in the Old World,14,15 is similar to some variants of the multiregional model, which also suggest that modern morphology appeared first in Africa, but involved admixture with other Old World populations.16 The major difference between these views appears to be the extent of admixture, although the exact level is never specified. A further complication is the possibility that multiple dispersals from Africa produced a more complicated pattern of worldwide variation.17  相似文献   

10.
The North Canary Basin (NW Africa) falls within a major eastern boundary upwelling system. This part of the coastal upwelling system is seasonal and is characterised by the development of large filaments migrating seawards. Hence, 16 samples from this location were selected to identify an “upwelling signal” in the composition of the dinoflagellate cyst assemblages.

Samples closest to the most intense upwelling cells are dominated by L. machaerophorum and G. catenatum and Protoperidinium spp. These make up the “upwelling signal” characteristic for the system. Moreover, the “upwelling signal” can be advected offshore, with filaments that may extend as far as 300 km. Finally, the finding of cysts from G. catenatum, a toxic dinoflagellate, raises the need for a better understanding of the relationship between its presence and distribution in the region, and the coastal upwelling system.  相似文献   

11.
Wim C. Mulliè 《Ostrich》2013,84(1-2):15-20
Mullié, W.C. 2000. Traditional capture of Red-billed Quelea Quelea quelea in the Lake Chad Basin and its possible role in reducing damage levels in cereals. Ostrich 71 (1 & 2): 15–20.

Three traditional methods of capturing Red-billed Quelea Quelea quelea practised by different ethnic groups, were studied in the Lake Chad Basin in Chad and Cameroon: capture of birds by triangular hand-held nets by Hadjeraï piégeurs (trappers); with standing fishing nets of the “mist net” type by Gambai; and by cast nets (épervier) by Massa and Mousgoum fishermen.

The Hadjeraï net was found to be both selective for queleas and highly efficient. As many as 1.2 million birds were captured from 13 June to 21 August 1994 around N'Djamena, Chad, alone, until activities ceased due to heavy rains. Birds were trapped in tree roosts during moonless periods of the night. They were plucked and fried the following morning, subsequently dried in the sun, and eventually transported to the market in N'Djamena to be sold. The piégeurs operated in teams of about 6 men and each team could process about 20 000 birds per day. Once this number had been captured, they withdrew from further trapping. The catches were almost entirely composed of queleas, with sometimes a small percentage (<1%) of Golden Sparrow Passer luteus. It was estimated that annually at least 5–10 million queleas were trapped, with a market value of about 19–38 million FCFA (USA37 500–75 000).

The impact of trapping on the population of queleas in the Lake Chad Basin, estimated at about 200 million individuals in 1976/77, was insignificant. Since activities of piégeurs are aimed at maximising revenues, and not at minimising damage levels, there is no causal relationship between crop damage and number of birds trapped. However, compared to crop losses in pearl millet due to quelea damage, revenues from selling quelea are up to 40% of capitalized crop losses due to quelea in the same area.  相似文献   

12.
Members of the family Pteropodidae, also known as Old World fruit bats, are represented in Africa by 14 genera and 44 species. Here, we sequenced 67 complete mitochondrial genomes from African and Asian pteropodids to better understand the evolutionary history of the subfamily Rousettinae, which includes most of the African species. An increased frequency of guanine to adenine transitions is detected in the mtDNA genomes of Macroglossus sobrinus and all species of Casinycteris and Scotonycteris. Our phylogenetic and molecular dating analyses based on 126 taxa and 15,448 characters indicate a low signal for deep relationships within the family, suggesting a rapid diversification during the Late Oligocene period of “warming.” Within the subfamily Rousettinae, most nodes are highly supported by our different analyses (all nucleotide sites, SuperTRI analyses of a sliding window, transversions only, coding genes only, and amino acid sequences). The results indicate the existence of four tribes: Rousettini—distributed from Africa through Mediterranean region and South Asia to South-East Asia; Eonycterini—found in Asia; and Epomophorini and Scotonycterini—restricted to sub-Saharan Africa. Although most interspecies relationships are highly supported, three parts of the Rousettinae mitochondrial tree are still unresolved, suggesting rapid diversification: (a) among the three subtribes Epomophorina (Epomophorus sensu lato, i.e., including Micropteropus, Epomops, Hypsignathus, Nanonycteris), Plerotina (Plerotes), and Myonycterina (Myonycteris, Megaloglossus) in the Late Miocene; (b) among Epomops, Hypsignathus, and other species of Epomophorina at the Pliocene–Pleistocene boundary; and (c) among Myonycteris species in the Early Pleistocene. Within the Epomophorini, Stenonycteris lanosus emerged first, suggesting that lingual echolocation may have appeared in the common ancestor of Epomophorini and Rousettini. Our analyses suggest that multiple events of mtDNA introgression occurred within the Epomophorus species complex during the Pleistocene.  相似文献   

13.
Respiratory Activity in Stem, Branches and Leaves of Evergreen Trees in Tropical Rain Forest and of Deciduous Trees in Temperate Climate.— Reduced to the same temperature, the respiratory activity of different parts of tropical rain forest trees and of corresponding parts of temperate deciduous trees is approximately the same. In particular, the leaf-blades of Danish deciduous trees and of tropical rain forest trees from the lowland of Côte d'Ivoire (57° north. lat.) have nearly the same respiratory activity at 20°C: the blades of the extreme shade leaves about 0.1 mg CO2, those of the extreme sun leaves about 0.8 mg CO2 per 50 cm2 (one side only) per hour at 20°C. This is in accordance with the fact that the blades of shade leaves, respectively Sim leaves, of the tropical rain forest trees are built in the same way as the blades of deciduous trees in our temperate climate. The respiratory activity shows that they have the same “concentration” of living cells, the same “concentration” of active plasma. The respiratory activity of trunk and branches depends mainly on three factors: diameter of the stem-section or branch-section, nutritional condition, and temperature. The respiratory activity of trunk and branches of hardwoods in temperate climate is also dependent on the season. The estimations on stems and branches from the temperature trees were made In July–August. There was in most cases a remarkable agreement in respiratory activity between temperate and tropical hardwoods: Branches with a diameter of about 0.5–2 cm have a respiration of about 70–100 mg CO2 per kg fresh weight per hour at 20°C. Trunk sections with a diameter over 20 cm have a respiratory activity of about 3–5 mg CO2, per kg fresh weight per hour at 20°C. In the older parts of a stem most of the cells are dead. The agreement in respiratory activity probably means that the “concentration” of living cells in the older parts of the stem of tropical and temperate hardwoods is the same.  相似文献   

14.

The study of African cinema is often assumed to be the study of black film. This paper examines this notion with respect to definitions of Africa, questions of identity, and different historical discourses of resistance. Western psychocentric approaches to film criticism are criticized. The issue of authorship is revisited with the question: Can a white director make a film reflecting the “black” experience? This question is explored with reference to debates about Spike Lee's Malcolm X and South African director Oliver Schmitz's Mapantsula. In the process, J examine how meanings are articulated and rearticulated in specific contexts by both those who define them and audiences which interpret them. The articulations of “race wars” in the USA and South Africa respectively are discussed, as is the relationship between race and class in the anti‐apartheid struggle. The disarticulation of Black Consciousness in South Africa from its popularizer, Steve Biko, by film activists in the Mass Democratic Movement during the 1980s, provides a background for the emergence of “non‐racial” cinema. Reception is suggested as a more subtle means of film categorisation. Mapantsula, for example, though made by a mainly white crew, is understood by black audiences to be a film accurately reflecting the experience of the black oppressed in South Africa. Though reception is a dynamic response, shifting and responding to historical trajectories and new discourses, with interpretations fragmenting between different classes and class fractions at different times, such a strategy for area and cultural classification of films avoids the pitfalls of categories based on ideology, myth, race and language.  相似文献   

15.
Thespesia consists of 16 species of trees and shrubs from Southeast Asia–Oceania, Africa and America, the most well known being T. populnea, a small tree of tropical coastal areas around the world. Phylogenetic relationships in the genus and among its allies in tribe Gossypieae were inferred using three plastid and two nuclear regions to ascertain its generic delimitation and explore its biogeographical history. Maximum‐likelihood and Bayesian analyses confirmed that Thespesia is not monophyletic and, based on these results, Azanza is reinstated to accommodate the two species previously placed in Thespesia section Lampas. Dating analyses and ancestral range estimation indicated that Thespesia s.s. most likely originated in Southeast Asia–Oceania c. 30 Mya, but extant species did not begin to differentiate until the late Miocene. Two dispersal events, one into Africa c. 11 Mya and another into America (Antilles) c. 9 Mya, gave rise to the African and the Greater Antillean endemics, respectively. The two most widespread hydrochorous species, T. populnea and T. populneoides, originated in Southeast Asia–Oceania from where they spread to other parts of the world. Our analysis also indicated a much earlier origin than previously reported for the eumalvoid clade and its tribes Gossypieae, Malveae and Hibisceae suggesting that vicariance might have had an important role early in the history of these groups.  相似文献   

16.
Phylogeny of birch mice is estimated using sequences of ten nuclear genes and one mitochondrial gene. Based on the results of tree reconstructions and molecular dating, five major lineages are recognized: “tianschanica,” “concolor,” “caudata,” “betulina,” and “caucasica.” It is established that the three latter lineages constitute a clade and that the long‐tailed birch mouse Sicista caudata is the sister group of the “caucasica” lineage. The “tianschanica” lineage is placed as the sister branch to all other species, however, with insufficient support. The cytochrome b tree is generally concordant with the nuclear topology. The molecular clock results suggest that the radiation among the main lineages occurred in the Late Miocene–Early Pliocene (6.0–4.7 Mya). The correspondence between molecular dating and the fossil record is discussed. Based on nuclear data, a high level of divergence between cryptic species in the “tianschanica” lineage is confirmed. Mitochondrial and nuclear data suggest the existence of a potential cryptic species within Sicista strandi.  相似文献   

17.
Summary

The impacts of larvicides used in the control of blackflies (Diptera: Simuliidae) on macroinvertebrates in the stones-in-current biotope were assessed during 8 field trials in the middle Orange River, South Africa. Two Bacillus thuringiensis var. israelensis (B.t.i.) products (VectobacR 12AS and TeknarR HP-D) and the organophosphate temephos (AbateR 200EC) were applied at recommended and high dosages to simulate “operational” and “worst-possible” scenario's respectively. Mortality was evaluated either by direct counting of invertebrates on stones before and after application, or by ranking invertebrates on a 4-point relative abundance scale before and after application. In addition, the re-appearance of benthic invertebrate population densities after temephos application was examined.

At the recommended dosage (1.2 ppm/10 min), B.t.i. significantly reduced blackfly larval numbers (P<0.001) and those of the chironomid Rheotanytarsus fuscus Freeman (P<0.05). At high dosage (20 ppm/10 min), numbers of the filter-feeding mayfly Tricorythus discolor (Burmeister) (P<0.01) and the chironomid Cardiocladius sp. (P<0.05) were also significantly reduced. No Simulium predators were directly affected by B.t.i., but there were indications of food shortage amongst Hydropsychidae and Hirudinea.

Temephos caused significant reductions in the relative abundance of 5 taxa at 0.05 ppm, 3 to 6 taxa at 0.1 ppm, and 9 taxa at 1.0 ppm (P<0.05). “Non-target” organisms which were most affected included the chironomid R. fuscus, the mayflies Baetis glaucus Agnew and Choroterpes elegans Barnard, and the caddisflies Cheumatopsyche thomasseti Ulmer and Amphipsyche scottae Kimmins. The mayfly T. discolor was tolerant of temephos, even at high dosage (1.0 ppm/10 min). In winter, most taxa re-appeared within 19 days, and population densities were back to pre-treatment levels within 35 days.

It is concluded that good reduction of blackfly populations may be obtained with minimal direct impact on the “non-target” fauna, provided recommended dosages of temephos are not exceeded. Overdosing with temephos may result in high mortality of “non-target” organisms, including blackfly predators, and should be avoided.  相似文献   

18.
Most data on species associations and vector potential of mosquitoes in relation to arboviral infections in South Africa date back from the 1940s to late 1990s. Contextual information crucial for disease risk management and control, such as the sampling effort, diversity, abundance, and distribution of mosquitoes in large parts of South Africa still remains limited. Adult mosquitoes were collected routinely from two horse farms in Gauteng Province; two wildlife reserves in Limpopo Province, at Orpen Gate in Kruger National Park (KNP) and Mnisi Area in Mpumalanga Province between 2014–2017, using carbon dioxide‐baited light and tent traps. Mosquito diversity and richness are greater in untransformed natural and mixed rural settings. In untransformed wilderness areas, the most dominant species were Culex poicilipes, Anopheles coustani, and Aedes mcintoshi, while in mixed rural settings such as the Mnisi area, the two most abundant species were Cx. poicilipes and Mansonia uniformis. However, in peri‐urban areas, Cx. theileri, Cx. univittatus, and Cx. pipiens sensu lato were the most dominant. Aedes aegypti, Ae. mcintoshi, Ae. metallicus, Ae. vittatus, Cx. pipiens s.l., Cx. theileri, and Cx. univittatus had the widest geographical distribution in northern South Africa. Also collected were Anopheles arabiensis and An. vaneedeni, both known malaria vectors in South Africa. Arbovirus surveillance and vector control programs should be augmented in mixed rural and peri‐urban areas where the risk for mosquito‐borne disease transmission to humans and domestic stock is greater.  相似文献   

19.
Freshwater crayfish invasions have been studied around the world, but less so in Africa, a continent devoid of native freshwater crayfish. The present study reviews historical and current information on alien freshwater crayfish species introduced into South Africa and aims to indicate which areas are at risk from invasion. As is the case elsewhere, South Africans have shown a keen interest in both farming and keeping freshwater crayfish as pets, which has resulted in Cherax cainii, Cherax destructor, Cherax quadricarinatus and Procambarus clarkii being introduced to the country. There is evidence of successful establishment in the wild for C. quadricarinatus and P. clarkii in different parts of the country. Species distribution models suggest that the eastern part of the country and parts of the Eastern and Western Cape are at higher risk of invasion. At present, illegal translocations represent the most likely pathway of crayfish spread in South Africa. A continued risk of invasion by freshwater crayfish species in South Africa is highlighted, which reinforces the need for more research, as well as for strong mitigation measures, such as stronger policing of existing regulations, management or eradication where feasible and public education.  相似文献   

20.
The genus Glauconycteris Dobson, 1875 currently contains 12 species of butterfly bats, all endemic to sub‐Saharan Africa. Most species are rarely recorded, with half of the species known from less than six geographic localities. The taxonomic status of several species remains problematic. Here, we studied the systematics of butterfly bats using both morphological and molecular approaches. We examined 45 adult specimens for external anatomy and skull morphology, and investigated the phylogeny of Glauconycteris using DNA sequences from three mitochondrial genes and 116 individuals, which in addition to outgroup taxa, included nine of the twelve butterfly bat species currently recognized. Four additional nuclear genes were sequenced on a reduced sample of 69 individuals, covering the outgroup and Glauconycteris species. Our molecular results show that the genus Glauconycteris is monophyletic, and that it is the sister‐group of the Asian genus Hesperoptenus. Molecular dating estimates based on either Cytb or RAG2 data sets suggest that the ancestor of Glauconycteris migrated into Africa from Asia during the Tortonian age of the Late Miocene (11.6–7.2 Mya), while the basal diversification of the crown group occurred in Africa at around 6 ± 2 Mya. The species G. superba is found to be the sister‐group of G. variegata, questioning its placement in the recently described genus Niumbaha. The small species living in tropical rainforests constitute a robust clade, which contains three divergent lineages: (i) the “poensis” group, which is composed of G. poensis, G. alboguttata, G. argentata, and G. egeria; (ii) the “beatrix” group, which contains G. beatrix and G. curryae; and (iii) the “humeralis” group, which includes G. humeralis and a new species described herein. In the “poensis” group, G. egeria is found to be monophyletic in the nuclear tree, but polyphyletic in the mitochondrial tree. The reasons for this mito‐nuclear discordance are discussed.  相似文献   

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