The mbuna cichlids of Lake Malawi: a model for rapid speciation and adaptive radiation

Mbuna, the dominant fishes on the rocky shores of Lake Malawi, have become a major ‘model system’ for the study of rapid speciation and adaptive radiation. At least 295 putative species are known, of which more than 200 remain undescribed. There is no good evidence for monophyly in the mbuna, rather mitochondrial DNA phylogenies indicate that they are polyphlyetic with respect to benthic feeding cichlids of the genera Aulonocara, Alticorpus and some species of Lethrinops. Male mbuna hold territories for 18 months or more and breed year‐round. All species are maternal mouthbrooders, but females do not guard free‐swimming young. Mbuna are polygamous (both sexes). There is sexual dimorphism in size, colour and fin length, and many species show within‐population colour polymorphism. Mbuna genera are largely differentiated on the basis of head, jaw and tooth morphology, but congeneric species are generally distinguished by male colour. Many morphologically specialized forms have broad diets and often feed on common easily obtainable resources. While it is likely that dietary and habitat niche partitioning contributes to species coexistence, this has never clearly been demonstrated under experimental conditions. Populations on spatially separated habitat patches are often genetically differentiated, probably because most species are specialized for life on rocky shores, and lack a dispersal phase in their life histories. Males seem to disperse more than females, but are able to home several kilometres back to their territories. Some closely related ecologically equivalent allopatric populations are differentiated in male colour. Those tested have been shown to mate at least partially assortatively. Sexual selection acting on male colour seems the most plausible mechanism for initial species divergence. The same colour forms seem to have arisen several times, suggesting frequent parallel evolution. The main conservation threat to mbuna at present seems to be translocation of species within the lake as a result of the aquarium trade. However, deleterious effects on indigenous populations are not documented. In the long run, sedimentation, pollution, introduction of alien species and the development of targeted food fisheries could be more serious threats.     

The Anatomy and Venom-Emitting Mechanism of the Globiferous Pedicellariae of the Urchin Parechinus Angulosus (Leske) With Notes on Their Behaviour

The freshwater snails belonging to the genus Melanoides Olivier, 1804 are widespread across tropical regions of the world and endemic species have evolved in the African Lakes Malawi, Mweru and Tanganyika. The endemic Melanoides species of Lake Malawi have been investigated several times during the last century, due to their large conchological variation, but no unambiguous answer regarding the number of species has been given. The phylogenetic relationship between morphs or genetic clones of Melanoides in Lake Malawi was inferred by phylogenetic analyses of DNA sequence data from the mitochondrial genes 16S and COI. Additional sequences from GenBank were included to investigate the relationship to other morphs from different parts of the world. For the first time, a putative secondary structure was developed for a partial region of 16S in this genus to identify the variability of the secondary structure in stems and loops. The molecular analyses indicated that several genetic clones exist in Lake Malawi and that M. tuberculata is a paraphyletic taxon. It is not clear from the results whether invasions or dispersals account for the complex situation in Lake Malawi. The basal position of M. admirabilis, endemic to Lake Tanganyika, in the inferred phylogeny indicates that Africa might be the origin of the genus. The results further indicate that three major clades of Melanoides, consisting of several genetic clones, are present in Lake Malawi; one clade consisting of invasive M. tuberculata, another of native M. tuberculata and a third consisting of the M. polymorpha- complex. It appears as if the unique development of morphs within the Melanoides genus in Lake Malawi has evolved primarily by divergence of genetic clones instead of species differentiation.     

Perceptions of land‐degradation,forest restoration and fire management: A case study from Malawi

Understanding local perceptions of degradation and attitudes to fire management are critical for gaining support for restoration work and improving livelihoods. Deforestation and annual burning are causing significant land degradation problems in the area around Bandawe, northern Malawi. We mapped evidence of soil erosion and remaining areas of woodland. Gully erosion was common and primarily associated with heavily utilised footpaths. Areas between gullies showed signs of significant soil movement. Remnant patches of native woodland existed but were small, degraded and isolated. We interviewed local households to understand local awareness and impacts of land‐degradation, its perceived cause and preferred methods for restoration. All households were aware of the presence of gullies and reported associated problems of flood damage. Most households believed erosion was a result of deforestation. Burning practices were seen to have exacerbated erosion problems. Changing fire management practice was not seen as realistic as it risked reducing the productivity of grasses and fires were perceived to be too difficult to control. Tree planting was the community's preferred approach to tackling erosion. Their focus was on planting exotic fruit and timber trees around houses and they often requested that such work be done by volunteers. Such attitudes may have been influenced by recent extension work and a desire to secure ownership of utilisable resource. Ecologists in the miombo zone should focus on improving fire management practices and involving communities in creating diverse secondary woodlands that provide a range of goods and services. Copyright © 2010 John Wiley & Sons, Ltd.     

Assessment of catch, effort and species changes in the pair-trawl fishery of southern Lake Malawi, Malawi, Africa

Abstract  Catch per unit effort (CPUE) and species composition in the pair-trawl fishery in commercial Area A of southern Lake Malawi were assessed from 1991 to 2001. CPUE declined from 1.7 t day⁻¹ in 1995 to 0.5 t day⁻¹ in 2001 and the fishery is considered depleted. In 2000/2002, catch composition differed significantly from a 1991 survey, and was dominated by haplochromine cichlids (92% by weight). Of 98 haplochromine cichlid taxa identified in the catch, 18 contributed ≥1% by weight. The artisanal fishery targeted similar species of a similar size. It was recommended that: (1) renewed investment and increased effort in the pair-trawl fishery is not advisable; (2) there was a need for effort limitation in Area A and (3) the pair-trawl fishery should not be managed in isolation of the artisanal fishery.     

The factors limiting crop production on the Mubangwe Farm, Malawi

Abstract. Mubangwe Farm, northern Malawi, was brought into cultivation from savanna vegetation with Brachystegia between 1970 and 1983 to produce tobacco, maize and groundnuts. Because of poor yields even with inputs of lime, N, P and K the fields were soon abandoned. The soils were only moderately acidic with little likelihood of Al toxicity. They held only small amounts of exchangeable Ca²⁺ (down to 0.01 cmol_c/kg) particularly at depth. Phosphorus availability was low particularly in the subsoil. A minus-one pot experiment showed that the growth of sorghum in topsoil samples was limited by lack of N, P, S and Ca. The lower availabilities of P and Ca in the subsoil are therefore likely to be major limitations to growth, allowing only limited root penetration. The loamy sand to sandy clay soils generally had small available water capacities (down to 0.07 cm³/cm³) which, with restricted root development, may have lead to drought in dry periods during the growing season. The findings emphasize the need to measure both subsoil and topsoil properties when new areas of land are being developed for crop production.     

The Use of Municipal and Pulp and Paper Sludges to Increase Production in Forestry

Because of their high nutritional content and soil conditioning properties,. municipal and pulp and paper (P&P) sludges-biosolids-can serve as soil amendments for nutritionally deurived or organically soils on forest sites. Studies conducted over the past 20 years at an experimental forest site in Western Washington, USA, have largely confined the potential of biosolids to increase the productivity of many forest lands. These studies clearly demonstrated that application of biosolids at environmentally acceptable rates will result in growth responses for both young seedlings as well as established stands. Municipal biosolids have been applied to a number of different Douglas-fir stands. Young stands applied at 47 Mg ha-1 showed an average of 72%, 14% and 2% height responses for Site Class IV, III and 11, respectively, over a 10 year period. Thinned versus unthinned 55-yeardd Douglas-fir applied with 142 dry Mg ha-l averaged 43% and 48%, respectively, for the 12 year period greater than controls. Average growth responses of 65% and 40% occurred in the 65-year-old stand for the Site Class IV and 11, respectively, from a 47 dry Mg ha1 application. Growth response resulting from application of P&P biosolids to a number of tree species has also been excellent. When properly applied, biosolids can provide an excellent alternaLive to chemical fertilizers as a means of enhancing forest production. Growth response is typically greater and lasts longer when compared to chemical fertilization. Careful consideration has to be made of the site conditions to be certain that environmental risks are minimal and losses through leaching and overland flow will not occur.     

花生品种、栽培技术引种马拉维试验初报

为配合福建企业开发马拉维花生产业需要,2013—2014年引种福建省农业科学院作物研究所选育的6个花生品种（系）,结合马拉维4个品种,采用小区随机区组设计和大面积种植,在马拉维共和国进行品种比较和栽培技术示范。结果表明,雨季,7个参试品种品比结果,荚果产量1150.05~2943.75 kg/hm²,其中,‘抗黄1号’产量最高,为2943.75 kg/hm²,cg-7(CK)产量最低,为1150.05 kg/hm²,引种的6个品种比cg-7(CK)增产54.78%~155.98%。籽仁产量654.45~1845.6 kg/hm²,其中,‘抗黄1号’产量最高,为1845.6 kg/hm²,cg-7(CK)最低,为654.45 kg/hm²,引种的6个品种比cg-7(CK)增产55.67%~182.0%。干季,7个参试品种荚果产量2344.5~3559.5 kg/hm²,其中,‘福花0621’产量最高,为3559.5 kg/hm²,cg-7(CK)最低,为2344.5 kg/hm²,引种的6个品种比cg-7(CK)增产7.81%~51.82%,籽仁产量1428.0~2335.05 kg/hm²,其中,‘福花0621’产量最高,为2335.05 kg/hm²,‘福花9号’最低,为1428.0 kg/hm²,除‘福花9号’籽仁比cg-7(CK)减产6.44%外,其他5个品种比cg-7(CK)增产29.85%~52.99%。干季,栽培技术示范结果,马拉维的4个品种荚果产量1900.5~ 3213.0 kg/hm²,其中,BaKa产量最高,为3213.0 kg/hm²,Chalimbana产量最低,为1900.5 kg/hm²,籽仁产量1016.7~2307.0 kg/hm²,其中,BaKa产量最高,为2307.0 kg/hm², Chalimbana产量最低,为1016.7 kg/hm²。试验结果表明,引种的6个花生品种生活习性等方面均适应于马拉维的生态条件和粗放的栽培习惯。福建省农业科学院作物研究所的花生栽培技术也适合马拉维4个花生品种,并取得高产。初步探明,利用马拉维湖等湖岸周遍特殊的生态环境,只要花期空气湿度≥50%,满足花生开花受精的生理需求,采用人工灌溉措施,可以在干季发展花生生产,建议扩大试验,示范后推广。     

Prognosis for long‐term sustainable fisheries in the African Great Lakes

Declines in fish yields and shifts in species composition are serious concerns in the African Great lakes of Tanganyika, Malawi (Nyasa/Niassa) and Victoria. Despite management and regulatory structures, all the lakes remain open‐access fisheries, severely depressing yields, economic returns and threatening biodiversity. While the lakes require an ecosystem‐based approach to management, this has not been realised because of a lack of institutional capacities, insufficient political will or simply being overwhelmed by the scale of the endeavour. Sustainable fisheries management can only be achieved through a refocus towards a stronger socio‐ecological approach and re‐evaluating how to realistically improve fish yield and environmental protection. This requires a combination of the following: (1) acceptance of suboptimal fish yields; (2) community‐enforced regulations that restrict access to fisheries and destruction of inshore habitats; (3) enhanced national and local institutional capacities and collaboration among the riparian states; and (4) major awareness and educational efforts that demonstrate the national and international importance of these lakes for food supply and biodiversity in pursuance of the Sustainable Development Goals. Without such actions, the prognosis for long‐term sustainable fisheries is bleak, and international projects and conferences will merely bear witness to further degradation of resources and the livelihoods they support.     

Effect of intercropping maize and closely spacedLeucaena hedgerows on soil conservation and maize yield on a steep slope at Ntcheu,Malawi

A six-year soil conservation trial was conducted on a steep slope, 44%, with a subhumid climate, based on very closely spaced (90 cm) hedgerows, using three intraspecific hybrids ofLeucaena leucocephala. Soil loss averaged 2.0 t/ha per year on theLeucaena plots compared with an initial 80 t/ha per year on the unprotected control plot, falling to 27 t/ha per year after the top soil had been eroded. After 6 years, micro terraces of 35 cm high and 81 cm wide had developed on the intercropped plots, with substantially improved soil properties. Maize yield (unfertilized) were maintained at 1.5–2.0 t/ha on the protected plots, compared with a progressive fall from 0.8 to 0.5 t/ha on the sole maize control.     

Mapping Land Suitability for Agriculture in Malawi

Population growth, climate sensitivity, and edaphic properties are important factors that influence decision‐making and risk mitigation for agricultural production. Within the agricultural sector in Malawi, continuous cropping without the use of long‐term sustainable strategies and frequent cultivation on marginal lands have resulted in continually declining soil fertility. Improving soil quality of marginal lands using innovative technologies is imperative for increasing agricultural productivity and improving food security. Here, we propose an ensemble approach to map agricultural land suitability and identify the distribution of marginal land in Malawi. Quantitative data available for eight soil and terrain factors were rated individually, and five distinct models were applied to generate a spatial distribution map of land suitability. The results indicate that highly suitable, moderately suitable, marginally suitable, and unsuitable agricultural areas account for 8·2%, 24·1%, 28·0%, and 39·7% of the total land area, respectively. The majority of suitable lands are currently used for agriculture, but more than half (57·4%) of Malawi's total cropland exists on marginally suitable or unsuitable land categories and is likely a candidate for rehabilitation through sustainable agricultural practices. The methods and products herein will be valuable resources for effectively managing and improving Malawi's agricultural lands for increasing food security. Copyright © 2017 John Wiley & Sons, Ltd.