Browsing by Author "Nyeko, P."

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    High resilience of galling insect communities to selective and clear-cut logging in a tropical rainforest
    (BMC Research Notes, 2018) Malinga, G.M.; Valtonen, A.; Nyeko, P.; Roininen, H.
    Increasing anthropogenic disturbance in tropical rainforests is a major challenge to biodiversity conservation. The responses of herbivorous insect communities to habitat changes are not well understood. In this study, we investigated the resilience of galling insect communities associated with Neoboutonia macrocalyx (Euphorbiaceae) trees to logging in Kibale National Park, Uganda. Resilience was measured by comparing the species density, abundance and community structure of gallers in nine differently aged successional forests with those in adjacent primary forests. Insect galls were sampled from the canopy of 10 randomly selected trees in each successional stage, five times in a 10-month period. A total of 7219 individuals representing five galler species were recorded. No significant differences were found in the species density and overall density of gallers between the regenerating and primary forests. The mean tree height was positively correlated with the overall density of gallers. The community structure of gallers differed significantly among the successional stages, but exhibited no clear directional recovery trend. In addition, remarkable seasonal variations were observed in galler communities, with peak abundance being found in the wettest months. The results of the preset study indicate that specialist galling insects whose hosts are pioneer trees can recolonize successional sites rapidly and are resilient to the effects of selective and clear-cut logging in case primary or secondary forests with an established population of Neoboutonia host trees (source populations) are close by. Thus, recovering tropical forests can provide important habitats for galling insect biodiversity, highlighting the need to include them in management and conservation priority plans.
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    Variations In Leptocybe Invasa (Hymenoptera: Eulophidae) Population Intensity And Infestation On Eucalyptus Germplasms In Uganda And Kenya
    (International Journal of Pest Management, 2010) Nyeko, P.; Mutitu, K.E.; Otieno, B.O.; Ngae, G.N.; Day, R.K.
    Leptocybe invasa, an invasive gall-inducing wasp of Australian origin, recently emerged as a serious eucalyptus pest of global importance. We examined the spatial and temporal variations in L. invasa adult populations and evaluated eucalyptus gemplasms for infestations by the wasp in Uganda and Kenya. There were significant differences in L. invasa abundance, gall incidence, severity and damage index between sites. Adults occurred throughout the year, indicating overlapping generations since the adults are known to live <7 d. There was no obvious peak in L. invasa population abundance although a general decline was observed in dry months. Out of 35 eucalyptus germplasms evaluated for L. invasa infestations, only Eucalyptus henryi and the clonal hybrids GC 578 and GC581 were resistant to the pest. Most germplasms were ranked as tolerant or moderately susceptible to wasp attack. Highly susceptible germplasms included Eucalyptus camaldulensis, GC540 and GC784 in Tororo, Uganda, and MAU1, GC14, GC15 and GC10 in Busia, Kenya. Implications of the year-round occurence of L. invasa adult populations and gall infestations, and the potential for host resistance in managing the pest, are discussed.