Letters and ViewpointsSome Factors Influencing Natural Regeneration of Selected Tree Species in Kakamega Forest, Kenya

Poor regeneration of valuable timber species under closed forest canopy is a major problem affecting regeneration of tree species in Kenyan moist and Afromontane natural forests. This study was conducted in 1998 – 1999 to investigate the influence of shade tolerance, seed sources and insect herbivory on the regeneration of selected heavily exploited timber species (Maesopsis eminii, Zanthoxylum gilletii, Polyscias fulva, and Prunus africana) in Kakamega forest. 58 woody species were recorded in the sample area, most of which occurred at low densities. Twenty species contributed 81.5% of the total stocking. Shade tolerance, seed source, and insect herbivory had influence on the regeneration of the species in varying degrees. Regeneration of Maesopsis eminii and Polyscias fulva appeared to be more influenced by shading (light regime) than insect herbivory. The latter species also seemed to regenerate from seeds stored in soil seed bank. Phytophagous insects seemed to play more significant role in the regeneration of Zanthoxylum gilletii and Prunus africana than that of Maesopsis eminii and Polyscias fulva. As a recommendation, natural forest management should involve creation of “regeneration gaps” to enhance the regeneration of shade intolerant species like Prunus africana and Zanthoxylum gilletii. Sustainable selective logging of valuable timber species is suggested as a way of creating the gaps. Key Words: Natural forest, regeneration, Insect herbivory, Maesopsis eminii, Zanthoxylum gilletii, Polyscias fulva, and Prunus africana Résumé La régénération pauvre des espèces à bois de valeur sous une canopie forestière fermée constitue un problème majeur pour la régénération des espèces d\' arbres dans les forêts humides montagneuses au Kenya. Cette étude, conduite en 1998-1999, a examiné l\'influence de l\'ombrage, de l\'origine des graines et des insectes herbivores sur la régénération des espèces d\'arbres les plus exploitées (Maesopsis eminii, Zanthoxylum giletii, Polyscias fulva et Prunus africana) dans la forêts de Kakamega. Cinquante huit (58) espèces de plantes ligneuses ont été enregistrées, la plupart à faible densité dans les endroits échantillons; 20 espèces constituaient 81.5% du stockage total. Les trois facteurs éxaminés influencent la régénération des espèces étudieés mais á des degrés variés. La régénération de Maesopsis eminii et Polyscias fulva est plus sensible á l\'ombre qu‘à l\'attaque par des insectes. Polyscias fulva se développe aussi à partir des graines enfuies dans le sous sol. Des insectes phytophages influencent plus significativement la régénération de Zanthoxylum giletii et Prunus africana que celle de Maesopsis eminii et Polyscias fulva. Ainsi, l\'aménagement des forêts naturelles doit considérer la création des \"trous de régénération\" pour favoriser des espèces d\'arbres hostiles à l\'ombrage comme Prunus africana et Zanthoxylum giletii. L\'exploitation séléctive soutenue des arbres de valeur est proposée comme moyen de création des ouvertures dans la canopie forestière. Mots clés: Forêt naturelle, régénération, insectes herbivores, Maesopsis eminii, Zanthoxylum giletii, Polyscias fulva, Prunus africanaDiscovery and Innovation Vol 16 (3&4) 2004: 117-12

Repetitive behavior profile and supersensitivity to amphetamine in the C58/J mouse model of autism

Restricted repetitive behaviors are core symptoms of autism spectrum disorders (ASDs). The range of symptoms encompassed by the repetitive behavior domain includes lower-order stereotypy and self-injury, and higher-order indices of circumscribed interests and cognitive rigidity. Heterogeneity in clinical ASD profiles suggests that specific manifestations of repetitive behavior reflect differential neuropathology. The present studies utilized a set of phenotyping tasks to determine a repetitive behavior profile for the C58/J mouse strain, a model of ASD core symptoms. In an observational screen, C58/J demonstrated overt motor stereotypy, but not over-grooming, a commonly-used measure for mouse repetitive behavior. Amphetamine did not exacerbate motor stereotypy, but had enhanced stimulant effects on locomotion and rearing in C58/J, compared to C57BL/6J. Both C58/J and Grin1 knockdown mice, another model of ASD-like behavior, had marked deficits in marble-burying. In a nose poke task for higher-order repetitive behavior, C58/J had reduced holeboard exploration and preference for non-social, versus social, olfactory stimuli, but did not demonstrate cognitive rigidity following familiarization to an appetitive stimulus. Analysis of available high-density genotype data indicated specific regions of divergence between C58/J and two highly-sociable strains with common genetic lineage. Strain genome comparisons identified autism candidate genes, including Cntnap2 and Slc6a4, located within regions divergent in C58/J. However, Grin1, Nlgn1, Sapap3, and Slitrk5, genes linked to repetitive over-grooming, were not in regions of divergence. These studies suggest that specific repetitive phenotypes can be used to distinguish ASD mouse models, with implications for divergent underlying mechanisms for different repetitive behavior profiles