Mount Kasigau, the most northeastern mountain in the Eastern Arc, rises steeply from arid plains to a moist summit at 1641 m. This paper examines the diversity contributions of this afromontane setting by compiling a chorological analysis of tree species richness, measuring ecological differences among forest community types, and interpreting physical-environmental and human-historical factors that influence diversity patterns. Between 2002 and 2006, stem densities and basal areas of woody plants > 10 cm dbh were measured in 55 (0.1 ha) plots placed at different elevations. The study reports 140 species, 46 were measured in only one plot, and affinities for 75 species to the Somalia-Masai (43%), Afromontane (29%), and Zanzibar-Inhambane (Coastal, 28%) floristic regions. Cluster and Indicator Species Analyses identified eight community types. Mount Kasigau uniquely conserves much forest cover and a diversity of woody plant species below evergreen forest at 1000 m. Ordination, using Nonmetric Multidimensional Scaling (NMDS), resulted in a three-dimensional solution that explained 47.9% of the variation among plots. Axis 2 showed the strongest relationship with elevation (R²= 0.523), but lower montane community types also vary by slope form, slope aspect, and past human activities. We show how this biogeographical analysis of diversity patterns at Mount Kasigau can guide local management and support important opportunities for montane forest conservation in East Africa.

Gloriosa minor (Colchicaceae) is a showy dryland wildflower species of northern Kenya. The pollination ecology of G. minor was investigated by direct observation. Gloriosa minor relies on pollinators for fruit-set, but natural fruit set appears to be low. Gloriosa minor was found to have a specialised pollination system, with butterflies (Lepidoptera, Rhopalocera) being the only pollinators/flower visitors observed at South Turkwel, Turkana. Pollinators of Gloriosa minor in northern Kenya were all butterflies from the family Pieridae. Five different species of butterfly were observed visiting the flowers: Belenois aurota, Colotis protomedia, Colotis phisadia, Colotis halimede and Catopsilia florella. Gloriosa minor relies on butterfly pollinators for seed production and hence survival in its arid environment.

The moth Achaea catocaloides Guenee (Lepidoptera: Erebidae, formerly Noctuidae) experiences periodic population irruptions in tropical Africa. Large numbers of adult moths were observed in the Kakamega Forest, Western Kenya in March 2012. Estimated densities of adult moths flying in surveyed forest areas were 6.8 individuals per square metre. Roosting moth density was estimated at 12.7 individuals per 50 cm long branch on two common forest tree species: Croton megalocarpus and Bridelia micrantha. Based on scaled-up data from transect counts we conservatively estimate that this irruption contained 800 million - 1.5 billion moths. The Achaea moths were common throughout the indigenous forest and were being preyed on by birds and monkeys. These population irruptions occur periodically in African forests, but the underlying causes and factors driving them remain undetermined. DNA barcodes of Achaea catocaloides, Achaea catella and Achaea lienardi are provided to facilitate identification of future irruption events.

An investigation to assess the relationship between coarse particulate organic matter (CPOM) and macroinvertebrate communities was undertaken in the Njoro River, Kenya during 2010. Significantly lower macroinvertebrate densities and diversities were observed in study sites with low Coarse Particulate Organic Matter (CPOM) content. The Mugo study site had the highest CPOM content and macroinvertebrate density and diversity. The unidentifiable detritus category (i.e. small CPOM fragments) had the highest influence on macroinvertebrate taxa whereas twigs had the least influence. The benthic samples were dominated by detritivores, but no shredders were recorded. Our results suggest that CPOM is an important determinant of the macroinvertebrate assemblages in streams. Given this, we believe that it is important to conserve tropical stream riparian vegetation due to their important role as a source of CPOM in streams.

From its origins in the South and Central American tropics, Parthenium hysterophorus has invaded locations in Australia, Asia and Africa, often with devastating impacts on health and livelihoods. Following studies on the distribution of parthenium in Ethiopia and southern Africa and subsequent recommendations for regional surveillance, this project investigated the actual extent of invasion by the weed to provide baseline data for its management in Kenya, Tanzania and Uganda. Roadside surveys undertaken on the basis of the CLIMEX simulation recorded parthenium in drainage trenches, dumpsites, abandoned buildings, construction sites, residential areas, rangelands and crop fields, thus emphasising the fact that successive dispersal and establishment of the weed closely follows patterns of disturbance. Results from this survey reiterate the need for immediate control of infestation in critical ecosystems and development of effective policy guidelines and strategies for management of this invasive species.

Characterisation of benthic invertebrate communities, taxonomic abundance and composition provides information that is used during river bioassessment. However, the mesh size of the sieves used during processing of invertebrate samples may affect the estimation of taxonomic abundance and composition. In the current study, the effect of sieve mesh size (>0.5 and <0.5 mm) on the estimation of invertebrate taxonomic abundance and composition was tested in the Honi River (Kenya) in 2011. The abundance of invertebrates retained by the >0.5 mm mesh sieve was significantly (p <0.05) lower than that found in the total sample. At the Honi River midstream site, most invertebrates (85%) belonged to the <0.5 mm fraction and were dominated by chironomids. Hydracarina and ostracods were only found in the <0.5 mm fraction of invertebrates. This study shows that sieve mesh size should be taken into consideration when characterising benthic invertebrates in rivers where invertebrate taxa are unknown and with high abundances of small sized invertebrates.