Department of Animal Biology and Conservation Science (DABCS)

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    Effects of tea plantations on stream invertebrates in a global biodiversity hotspot in Africa
    (Biotropica, 2009-07) Biervliet, O.V.; Wiśniewski, K.; Daniels, J.; Vonesh, J.R.
    Tropical stream ecosystems in montane forest watersheds are important centers of endemism and diversity and provide essential ecosystem services. These habitats are subject to a variety of stressors, including the conversion of adjacent terrestrial habitats from forest to agriculture, but the impacts of these anthropogenic effects are largely unknown because of the paucity of studies in these systems. In montane habitats in the wet tropics, large-scale cultivation of tea is common and can represent an important source of income at local and national scales. However, little is known about how tea cultivation impacts adjacent stream ecosystems. In this study, we examine stream macroinvertebrate assemblages in a biodiversity hotspot the East Usambara Mountains, Tanzania. Specifically, we compare diversity of macroinvertebrate assemblages found on cobbles in stream riffles in watersheds dominated by forest with those surrounded by tea cultivation. We found that streams surrounded by tea were characterized by significantly lower dissolved oxygen and had lower total estimated species richness and number of families. Furthermore, the richness of invertebrate taxa known to be sensitive to anthropogenic disturbance were substantially reduced in tea streams and general assemblage-level analysis shows significant differences in the composition of macroinvertebrate assemblages between tea and forested streams. Our results suggest that tea cultivation may reduce stream habitat quality and biodiversity in the East Usambaras. Further research is needed to evaluate the effects of tea cultivation on streams over longer times scales and to address methods for minimizing negative effects of agriculture on montane stream communities. Abstracts in Portuguese and French are available at. © 2009 by The Association for Tropical Biology and Conservation.
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    Cross mating studies among five fruit fly parasitoid populations: Potential biological control implications for tephritid pests
    (BioControl, 2008-10) Billah, M.K.; Kimani-Njogu, S.W.; Wharton, R.A.; Overholt, W.A.; Wilson, D.D.; Cobblah, M.A.
    The reproductive compatibility between four different species/populations of the tephritid parasitoid Psyttalia (Walker) species from Kenya and individuals of the morphologically identical Psyttalia concolor (Szépligeti) (Hymenoptera: Braconidae) from a laboratory culture in Italy used in augmentative biological control of olive fly, Bactrocera oleae (Gmelin) (Diptera: Tephritidae) was assessed through cross mating tests using single-pair and group mating methods. Reciprocal crosses among the species resulted in the production of viable offsprings up to the second generation. In spite of the successful production of viable offspring in the laboratory, Psyttalia species are known to have specific host fruit and/or host fly preferences and populations/species may be isolated in one way or the other. However, it is not known whether these populations/species interbreed in the field. We discuss the ability of these parasitoids to interbreed and the potential effects of that on their use as biological control agents, especially in environments where other closely related species are present or in situations where multiple parasitoid introductions are intended. © 2007 International Organization for Biological Control (IOBC).
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    The importance of unmanaged coastal wetlands to waterbirds at coastal Ghana
    (African Journal of Ecology, 2007-04) Gbogbo, F.
    Ghana's 550 km coastline has about 100 wetlands out of which five large ones are managed as Ramsar sites, the rest being unmanaged. Recent pollution and misuse of unmanaged wetlands have necessitated a study into their roles in the support of waterbirds. Waterbird survey on four wetlands between September 2005 and April 2006 revealed that 51 waterbird species make use of the managed compared to 44 in the unmanaged wetlands. Average numbers of waterbirds were higher on the managed wetlands (10,510 ± 4862) than on the unmanaged wetlands (1348 ± 602) (P < 0.05) but mean population density of waterbirds (n/ha) was the same for both the managed (1860 ± 310) and unmanaged (1400 ± 220) (P > 0.05) wetlands. The population densities of waterbirds belonging to guilds 1, 5 and 7 were significantly higher on the managed wetlands (P < 0.05). In contrast, guilds 2 and 4 have significantly higher population densities on the unmanaged wetlands while the population density of guild 3 was the same (P > 0.05). There was an indication that during mid and late periods of the nonbreeding season, the unmanaged wetlands altogether may support a larger number of waterbirds belonging to guilds 2, 3 and 4 than the five managed wetlands. © 2007 The Author.
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    Impact of commercial salt production on wetland quality and waterbirds on coastal lagoons in Ghana
    (Ostrich, 2007-03) Gbogbo, F.
    A comparative study conducted on two saline coastal wetlands that have been developed into saltpans and two others (referred to as 'non-saltpans'), that are also saline but have no saltpans, describes the quality of lagoon water, benthic macroinvertebrates and waterbird communities characterising these wetlands. The wetlands were sampled monthly from September 2005-April 2006. Except for turbidity, which was significantly higher in the non-saltpans, (p < 0.05), all other physico-chemical parameters studied were not significantly different between the two wetland types (p > 0.05). The waterbird communities of the saltpans and non-saltpans, characterised by 48 and 50 species respectively, scored a Sorenson Index value of 0.88, indicating a high similarity. The population density of benthic macroinvertebrates in the saltpans and the non-saltpans was statistically similar (p > 0.05) but the population densities of waterbirds feeding exclusively on benthic macroinvertebrates were significantly higher in the non-saltpans (p < 0.05). Although the shallow ponds created for salt production might be providing more suitable feeding habitats for fish-eating birds, the development of these ponds has also reduced the exploitable area available to the birds feeding exclusively on invertebrates, requiring them to depend largely on the non-saltpans. Birds feeding exclusively on fish had significantly higher population densities in the saltpans (p < 0.05) than in non-saltpans. This was attributed to reduced efficiency of piscivory, due to the high turbidity associated with the non-saltpans. Waterbirds feeding on a wide range of food types showed no significant differences in their population densities (p > 0.05) in the two wetland types. Copyright © NISC Pty Ltd.
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    Field and laboratory studies on water conditions affecting the potency of VectoBac® (Bacillus thuringiensis serotype H-14) against larvae of the blackfly, Simulium damnosum
    (Medical and Veterinary Entomology, 2005-12) Wilson, M.D.; Akpabey, F.J.; Osei-Atweneboana, M.Y.; Boakye, D.A.; Ocran, M.; Kurtak, D.C.; Cheke, R.A.; Mensah, G.E.; Birkhold, D.; Cibulsky, R.
    River water conditions that might influence the efficacy of VectoBac®, a formulation of the microbial insecticide Bacillus thuringiensis H-14 Berliner against Simulium damnosum sensu lato Theobald (Diptera: Simuliidae) larvae were investigated. A standard formulation was assayed 130 times over 15 months using a mini-gutter system at a field station beside the River Pra in Ghana. The lethal concentration (LC) values, river temperature, conductivity, turbidity and pH were analysed using univariate and multivariate statistics to identify which of these parameters influenced its performance. River temperature, conductivity and turbidity (in that order) were identified as having direct effects on the potency of VectoBac®. Water temperature and conductivity were negatively correlated, whereas turbidity and pH were positively correlated with LC values. Analyses of river water samples revealed that despite observed differences in total solids, sodium and potassium cations and chloride concentrations, all the parameters measured did not differ significantly between wet and dry seasons. A simple method for rearing S. damnosum s.l. in the laboratory was then adopted to study the effect of conductivity on potency of VectoBac® under controlled conditions. Increasing the conductivity of the water medium up to 3000 μS enhanced potency by about 42%, whereas increasing that of the insecticide alone raised it by 37%. The results obtained suggest that for effective use of VectoBac® for blackfly control in West Africa, river temperature, conductivity and turbidity should be taken into consideration, perhaps by only selecting rivers with optimal conditions for treatment. The laboratory-based system developed for assaying the product overcomes the vagaries associated with field conditions and also the demand for huge logistic requirements of the mini-gutter system, which has to be sited near rivers. © 2005 The Royal Entomological Society.
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    The effect of host larvae on three Psyttalia species (Hymenoptera: Braconidae), parasitoids of fruit-infesting flies (Diptera: Tephritidae)
    (International Journal of Tropical Insect Science, 2005-09) Billah, M.K.; Kimani-Njogu, S.; Overholt, W.A.; Wharton, R.A.; Wilson, D.D.; Cobblah, M.A.
    Three species of fruit fly parasitoids, Psyttalia concolor (Szépligeti), Psyttalia cosyrae (Wilkinson) and Psyttalia lounsburyi (Silvestri) (Hymenoptera: Braconidae) were reared on different host larvae to determine the effects of host species, size and colour on parasitoid development. Ovipositor, ovipositor sheath and hind tibia lengths were found to be different for progenies from preferred and non-preferred host larvae. Ratios of ovipositor-tibia and ovipositor sheath-tibia showed no difference when P. concolor was reared on a bigger host (Ceratitis cosyra (Walker) (Diptera: Tephritidae), whereas rearing P. cosyrae on a smaller host (C. capitata (Wiedemann) showed significant differences. Comparison of the linear measurements, ratios and number of flagellomeres of parasitoids reared on preferred hosts, separated the species into their natural groupings. When reared on a different-coloured host, P. lounsburyi lost its dark markings but other characters remained unchanged. Morphometric analysis also indicated differences between parasitoids reared on preferred host larvae and those reared on non-preferred host larvae. Rearing parasitoids on larvae other than their preferred hosts resulted in colour and size changes, and thus, these characters alone were not reliable for the identification of parasitoids. This is especially important in post-release sampling surveys to ascertain establishment of the parasitoids in new environments where they may adapt to new host species. © ICIPE 2005.
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    Ticks associated with wild mammals in Ghana
    (Bulletin of Entomological Research, 2005-07) Ntiamoa-Baidu, Y.; Carr-Saunders, C.; Matthews, B.E.; Preston, P.M.; Walker, A.R.
    The host ranges of a collection of 21 tick species found on wild mammals in the savanna, forests and coastal zone of Ghana suggested that most species were adapted to feeding mainly on host species within a single mammalian order, i.e. on artiodactyls (bovids/suids), carnivores, rodents or pholidotes (pangolins). Only a few species were dispersed evenly across a range of orders. Seven out of ten of the most common ticks on forest mammals were significantly associated with a particular host species or a group of closely related host species, which could be viewed as their major host or hosts, but they were also recorded much less frequently on a wide range of host species. Two other species were confined to their major hosts. Only one species appeared to be widely dispersed on forest mammals and to lack a particular major host. The majority of tick species therefore occurred on hosts with very distinctive biological, behavioural and ecological characteristics. The study provided no evidence to support the view that host specificity is an artefact of sampling. Finding that the tick species on Ghanaian wild mammals occurred on particular hosts, as well as in distinct habitats, indicated that tick-host associations are important for tick survival and confirmed the importance of climate and vegetation in tick distribution. © CAB International, 2005.
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    Host preference and suitability of some selected crops for two biotypes of Bemisia tabaci in Ghana
    (Entomologia Experimentalis et Applicata, 2005-06) Omondi, A.B.; Obeng-Ofori, D.; Kyerematen, R.A.; Danquah, E.Y.
    The economic importance of Bemisia tabaci (Gennadius) (Homoptera: Aleyrodidae) is mainly due to its wide host range, variable kinds of damage, and great intraspecific variation. The delineation of two African biotypes of this pest has been carried by molecular, ecological, and host-affiliation approaches, with largely consistent results. However, an understanding of its intricate host-pest interaction is necessary as a basis of its sustainable integrated control. This study investigated the host preference and suitability of cassava and okra biotypes of B. tabaci, based on multiple-choice landing and oviposition preference assays and stage-specific survival on eight common whitefly hosts. The cassava biotype significantly preferred cassava, Manihot esculenta, for landing and oviposition, but did not oviposit on okra, Abelmoschus esculentus. The okra biotype preferred okra, oviposited on eggplant, Solarium melongena, tomato, Lycopersicon esculentum, garden egg, Solanum integrifolium, and cowpea, Vigna unguiculata, but did not oviposit on cassava. The okra biotype developed on all hosts except cassava, but only survived marginally on cabbage, Brassica oleracea, and pepper, Capsicum annum var. grosum, while the cassava biotype did not develop on okra, cabbage, or pepper. Thus the observed host acceptance of the two biotypes is wider than earlier reported by host transfer experiments and molecular genetic surveys. Mortality was highest in the first instar nymphal stage, during which total mortality occurred on non-hosts. Development time was slightly longer on marginal hosts than on the preferred hosts. Cowpea, garden egg, and tomato are additional common hosts of the two biotypes, whose role as reservoir hosts and biotype interbreeding grounds should be investigated further. © 2005 The Netherlands Entomological Society.
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    The relative susceptibilities of juvenile and adult Bulinus globosus and Bulinus truncatus to the molluscicidal activities in the fruit of Ghanaian Blighia sapida, Blighia unijugata and Balanites aegyptiaca
    (Annals of Tropical Medicine and Parasitology, 2005-04) Anto, F.; Aryeetey, M.E.; Anyorigiya, T.; Asoala, V.; Kpikpi, J.
    The relative susceptibilities of juvenile (2- to 3-week-old) and adult (5- to 7-week-old) Bulinus globosus and Bu. truncatus to the molluscicidal activities of aqueous preparations of the powdered, dried fruits of Blighia sapida, Bl. unijugata and Balanites aegyptiaca were investigated under laboratory conditions. For the extract prepared from the freeze-dried, semi-ripe fruits of Bl. sapida, the concentrations killing 95% of the snails after an exposure for 24 h (LC95) were, respectively, 232.7 and 161.2 ppm for the juveniles and adults of Bu. globosus and 187.6 and 140.2 ppm for the juveniles and adults of Bu. truncatus. The corresponding values for Bl. unijugata were 136.9 and 98.7 ppm for Bu. globosus and 132.2 and 98.5 ppm for Bu. truncatus, respectively. Extracts of the freeze-dried, ripe fruit of Bu. aegyptiaca were much more active, however, giving LC95 of just 16.9 and 19.7 ppm for the juveniles and adults of Bu. globosus, and 14.2 and 12.0 ppm for the juveniles and adults of Bu. truncatus, respectively. In general, similar results were obtained when the fruit were oven-dried rather than freeze-dried but the potency of Balanites extracts produced from oven-dried fruit was relatively low. That the juvenile snails appeared less susceptible than the adults to the molluscicidal activity in each Blighia extract is interesting. This observation may have implications for snail control, in terms of the optimal frequency, timing and concentration of molluscicides applied in a particular habitat. © 2005 The Liverpool School of Tropical Medicine.
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    Sea-level rise and coastal biodiversity in West Africa: A case study from Ghana
    (Climate Change and Africa, 2005-01) Armah, A.K.; Wiafe, G.; Kpelle, D.G.
    Available evidence points to an eventual rise of sea level for coastal areas as a result of global warming. Sea-level rise would introduce or aggravate existing threats to the continued survival of the biodiversity of low-lying coastal areas. In Ghana and the coastal states of West Africa, vulnerable habitats include the strand zone, lagoons, wetlands, and intertidal sandy and rocky areas. Physical and biological parameters of several of these habitats would change substantially as a result of submersion and increased salinity regimes. This would adversely affect, for example, the habitats of water birds, nesting beaches of sea turtles, and the brackish-water dependent fauna and flora of the estuaries and lagoons. Species extirpation leading to local loss of genetic diversity is envisaged to affect fauna like ghost crabs (Ocypoda spp.) and the fiddler crab (Uca tangeri). Plants in this category include five species of true mangroves (Rhizophora racemosa, R. harrisonii, R. mangle, Avicennia germinans and Laguncularia racemosa) and their associates (Conocarpus erectus, Acrostichum aureum and the uncommon creeper, Phylloxerus vermicularis). Strategies that would mitigate or protect biodiversity of the coastal zone from the anticipated effects of rising sea level are advanced. The potential role of coastal infrastructures in biodiversity conservation is addressed. © Cambridge University Press 2005.