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Tamiru A.,International Center for Insect Physiology and Ecology | Getu E.,Addis Ababa Institute of Technology | Jembere B.,Addis Ababa Institute of Technology | Bruce T.,Rothamsted Center for Sustainable Pest and Disease Management
Bulletin of Entomological Research | Year: 2012

The spotted stemborer, Chilo partellus (Swinhoe) (Lepidoptera: Crambidae), is one of the most important insect pests attacking maize and sorghum in Ethiopia. Recent studies have indicated that the pest is spreading to new locations where it was not reported before. In the current study, laboratory investigations were carried out to determine the combined effect of different levels of relative humidity and temperature regimes on the development and fecundity of C. partellus, as these physical factors are known to play an important role in the life cycle of insects and adaptability to local climate. Developmental time, longevity, potential fecundity and realized fecundity of C. partellus were measured under controlled conditions. Three temperature regimes (22°C, 26°C and 30°C) and three relative humidity levels (40%, 60% and 80%) were tested. It was found that temperature, relative humidity (RH) and their interaction significantly affected the developmental time, adult longevity, potential fecundity and realized fecundity of the pest. Developmental time was inversely related to temperature. Mean duration of C. partellus life cycle was 70.2 days at 22°C and 80% RH, whereas it took only 26.5 days to complete its life cycle at 30°C and 40% RH. Male and female longevity were similar in most cases. The adult life span ranged between 6.9-11.1 days at 22°C and 3.1-7.2 days at 30°C for different levels of relative humidity. The most suitable conditions for C. partellus development and fecundity were 26-30°C temperatures regimes and 60-80% RH levels. © Copyright Cambridge University Press 2011.

Fand B.B.,Indian Council of Agricultural Research | Tonnang H.E.Z.,International Center for Insect Physiology and Ecology | Kumar M.,Indian Council of Agricultural Research | Kamble A.L.,Indian Council of Agricultural Research | Bal S.K.,Indian Council of Agricultural Research
Crop Protection | Year: 2014

The temperature-dependent population growth potential of Phenacoccus solenopsis Tinsley, a highly polyphagous and invasive mealybug species, was studied on sprouted potatoes under laboratory conditions at six constant temperatures (15-40°C). Several non-linear equations were fitted to the obtained data to model temperature-dependent population growth and species life history. The established equations for each life age/stage of the species were compiled to obtain an overall temperature-dependent phenology model. The life table parameters of P.solenopsis were estimated using stochastic simulation centred on a rate summation and cohort up-dating approach. The theoretical lower development threshold temperatures estimated using linear regressions applied to mean development rates were 11.2, 8.9, 9.8 and 12.7°C, and the thermal constants for development were 93.7, 129.8, 97.1 and 100.0 degree days (DD) for nymph 1, nymph 2, nymph 3 and male pupa stages, respectively. The developed phenology model predicted temperatures between 25 and 35°C as the favourable range for P.solenopsis development, survival and reproduction. P.solenopsis population attained a maximum net reproductive rate (107-108 females/female/generation) and total fecundity (216.6-226.5 individuals/female/generation) at temperatures between 25 and 30°C. Mean length of generations decreased from 75.6 days at 15°C to 21 days at 40°C. The maximum finite rate of increase (1.12-1.16 females/female/day) and shortest doubling time (4.3-6.1 days) were also observed at temperatures between 25 and 35°C. The simulation of phenology model at fluctuating temperatures indicated that P.solenopsis populations might potentially increase with a finite rate of 1.06 females/female/day with an average generation time of 58.7 days and a doubling time of 12.1 days. The obtained life table parameters were reasonably similar when compared with literature data. The present model can be simulated spatially for estimating the pest risk and undertaking agro-ecoregion specific pest management strategies. © 2013 Elsevier Ltd.

Fischer A.,International Center for Insect Physiology and Ecology | Fischer A.,Kenya International Livestock Research Institute | Shapiro B.,Pennsylvania State University | Muriuki C.,Kenya International Livestock Research Institute | And 6 more authors.
PLoS ONE | Year: 2012

The 'Mycoplasma mycoides cluster' comprises the ruminant pathogens Mycoplasma mycoides subsp. mycoides the causative agent of contagious bovine pleuropneumonia (CBPP), Mycoplasma capricolum subsp. capripneumoniae the agent of contagious caprine pleuropneumonia (CCPP), Mycoplasma capricolum subsp. capricolum, Mycoplasma leachii and Mycoplasma mycoides subsp. capri. CBPP and CCPP are major livestock diseases and impact the agricultural sector especially in developing countries through reduced food-supply and international trade restrictions. In addition, these diseases are a threat to disease-free countries. We used a multilocus sequence typing (MLST) approach to gain insights into the demographic history of and phylogenetic relationships among the members of the 'M. mycoides cluster'. We collected partial sequences from seven housekeeping genes representing a total of 3,816 base pairs from 118 strains within this cluster, and five strains isolated from wild Caprinae. Strikingly, the origin of the 'M. mycoides cluster' dates to about 10,000 years ago, suggesting that the establishment and spread of the cluster coincided with livestock domestication. In addition, we show that hybridization and recombination may be important factors in the evolutionary history of the cluster. © 2012 Fischer et al.

Smith D.A.S.,Eton College | Gordon I.J.,International Center for Insect Physiology and Ecology | Allen J.A.,University of Southampton
Ecological Entomology | Year: 2010

1. The aim of this paper is to investigate mechanisms of reinforcement between two semi-isolated semispecies of the African savannah butterfly Danaus chrysippus. The biogeography of colour genes suggests that four semispecies evolved in once isolated refugia. They expanded their ranges in response to Holocene climatic changes to form a hybrid zone in central-east Africa. 2. Danaus chrysippus is a superspecies within which cycles of alternating cladogenesis and reticulation among semispecies have probably operated over some 4 Myr. Semispecies are inter-fertile but show Haldane rule effects in crosses; gene flow is massive but subject to isolation by distance. 3. One semispecies shows linkage disequilibrium, vis- à-vis others, for haplotype, karyotype (W-linkage of colour genes which function as reproductive isolating barriers) and all-female broods caused by a male-killer endosymbiont. Introgression of colour genes between D. c. dorippus and D. c. chrysippus is constrained by sex linkage and male killing. 4. Reinforcement in hybrid zones comprises allochronic migration, assortative mating, (assumed) sex chromosome incompatibility and sex-ratio distortion. Gene introgression from D. c. dorippus to other semispecies is maintained by a high frequency of backcrossing between hybrid males and females of the latter. © 2010 The Royal Entomological Society.

Metcalfe K.,University of Exeter | Metcalfe K.,University of Kent | Ffrench-Constant R.,University of Exeter | Gordon I.,International Center for Insect Physiology and Ecology
ORYX | Year: 2010

Sacred sites, particularly in forests, often form unofficial protected areas because their biodiversity is preserved and protected by the local people looking after the sites. Here, we survey the biodiversity of the Three Sisters Cave complex, a sacred site or kaya in a fragment of East African coastal forest in south-east Kenya. We show that, despite the tiny size of this non-gazetted forest reserve, it contains many of the threatened species of both flora (121 species) and fauna (46 species) representative of Kenya's coastal forest. Following the overexploitation and widespread destruction of coastal rainforests in Kenya, such sacred sites represent key biodiversity hotspots as well as forest islands in the now largely deforested coastal plain. Other non-gazetted forest sacred sites may represent undocumented sources of biodiversity that may contribute towards conservation of this threatened coastal habitat. © 2009 Fauna & Flora International.

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