Altitudinal distribution of rodents (Muridae and Gliridae) on Mt Elgon, Uganda

Influence of vegetation structure, seasonality, and soil properties on rodent diversi community assemblages in west Mount Kilimanjaro, Tanzania

Rodent diversity and community assemblages are affected by several biotic and abiotic factors such as vegetation structure and seasonality. Vegetation structure particularly ground cover influences rodent diversity and community assemblages through provision of food resources and protection from predators. Such information is important for understanding species-habitat relationships for management and conservation. This study was conducted to determine the influence of vegetation structure, seasonality, and soil properties on species richness, abundance, community assemblages, and habitat association of rodents in west Mt Kilimanjaro. Rodent trapping was conducted using removal and capture-mark-recapture (CMR) methods with medium-sized Sherman's live traps, snap, and Havarhart traps. Rodents were trapped during wet and dry seasons for three consecutive nights at 4 weeks intervals from April 2020 to March 2021. Environmental variables including vegetation structure, soil physical properties, and disturbance levels were recorded for each habitat type. Fourteen species of rodents were trapped in 25,956 trap nights. Rhabdomys pumilio, Praomys delectorum, and Lophuromys verhageni were the most dominant species across all habitats and seasons. L.verhageni occurred in all habitats while R.pumilio was restricted from occurring in montane forests. Moreover, species richness and abundance were influenced by habitat types, seasonality, soil type, and ground cover. Generally, both species richness and abundance were higher in fallows and montane forests and significantly lower in plantation forest and agricultural fields. In addition, rodent diversity was highest in fallows, followed by montane forests, and lowest in agricultural fields. Furthermore, rodents were associated with habitat types and vegetation structure forming two major community assemblages that significantly differed between habitats. Our study conclude that, community assemblages of rodents on Mt. Kilimanjaro were affected by functional spatial heterogeneity of the habitats occupied. Therefore, use of different habitats by rodents may be indicative of the landscape integrity and ecosystem changes based on species assemblages.

Integrative taxonomy and phylogeography of Colomys and Nilopegamys (Rodentia: Murinae), semi-aquatic mice of Africa, with descriptions of two new species

The semi-aquatic African murine genera Colomys and Nilopegamys are considered monotypic and thought to be closely related to one another. Colomys occurs across forested regions of equatorial Africa, whereas Nilopegamys is known only from the Ethiopian holotype, making it among the rarest mammalian genera in the world – and possibly extinct. Using morphological and genetic data, we reassess the taxonomy of Colomys and Nilopegamys. A multilocus phylogeny with outgroups demonstrates that Nilopegamys is sister to Colomys. In addition, we recognize at least four morphologically diagnosable and genetically distinct species within Colomys: C. eisentrauti (elevated from subspecies and restricted to north-west Cameroon), C. goslingi (with a more restricted range than previously reported) and two new species (one from Liberia and Guinea and one from central and southern Democratic Republic of the Congo and Angola). We also review the status of four other taxa currently recognized within Colomys goslingi (bicolor, denti, goslingi and ruandensis) and demonstrate that these names lack phylogenetic and/or morphological support. Finally, we discuss potential biogeographic barriers that may have played a role in the evolution of Colomys and Nilopegamys, emphasizing the importance of rivers in both facilitating and, possibly, limiting dispersal within these genera.

Bat Species Richness and Community Composition along a Mega-transect in the Okavango River Basin

The Okavango River Basin is a hotspot of bat diversity that requires urgent and adequate protection. To advise future conservation strategies, we investigated the relative importance of a range of potential environmental drivers of bat species richness and functional community composition in the Okavango River Basin. During annual canoe transects along the major rivers, originating in the central Angolan highlands, we recorded more than 25,000 bat echolocation calls from 2015 to 2018. We corrected for possible biases in sampling design and effort. Firstly, we conducted rarefaction analyses of each survey year and sampling appeared to be complete, apart from 2016. Secondly, we used total activity as a measure of sample effort in mixed models of species richness. Species richness was highest in the Angola Miombo Woodlands and at lower elevations, with higher minimum temperatures. In total, we identified 31 individual bat species. We show that even when acoustic surveys are conducted in remote areas and over multiple years, it is possible to correct for biases and obtain representative richness estimates. Changes in habitat heterogeneity will have detrimental effects on the high richness reported here and human land-use change, specifically agriculture, must be mediated in a system such as the Angolan Miombo Woodland.

Species composition and community structure of small pest rodents (Muridae) in cultivated and fallow fields in maize-growing areas in Mayuge district, Eastern Uganda

Pest rodents remain key biotic constraints to cereal crops production in the East African region where they occur, especially in seasons of outbreaks. Despite that, Uganda has scant information on rodents as crop pests to guide effective management strategies.A capture-mark-recapture (CMR) technique was employed to study the ecology of small rodents, specifically to establish the species composition and community structure in a maize-based agro ecosystem. Trapping of small rodents was conducted in permanent fallow land and cultivated fields, with each category replicated twice making four study grids. At each field, a 60 × 60 m grid was measured and marked with permanent trapping points spaced at 10 × 10 m, making a total of 49 trapping points/grids. Trapping was conducted monthly at 4-week interval for three consecutive days for two and half years using Sherman live traps.Eleven identified small rodent species and one insectivorous small mammal were recorded with Mastomys natalensis being the most dominant species (over 60.7%). Other species were Mus triton (16.1%), Aethomys hendei (6.7%), Lemniscomys zebra (5.2%), Lophuromys sikapusi (4.8%), Arvicanthis niloticus (0.9%), Gerbilliscus kempi (0.1%), Graphiurus murinus (0.1%), Steatomys parvus (0.1%), Dasymys incomtus (0.1%), and Grammomys dolichurus (0.1%). Spatially, species richness differed significantly (p = 0.0001) between the studied field habitats with significantly higher richness in fallow land compared with cultivated fields.Temporally, total species richness and abundance showed a significant interaction effect over the months, years, and fields of trapping with significantly (p = 0.001) higher abundances during months of wet seasons and in the first and third year of trapping. In terms of community structure, higher species diversity associated more with fallow field habitats but also with certain rare species found only in cultivated fields.Synthesis and applications. Based on these findings, management strategies can be designed to target the key pest species and the most vulnerable habitats thus reducing the impact they can inflict on field crops.

Afromontane small mammals do not follow the hump-shaped rule: altitudinal variation in the Soutpansberg Mountains, South Africa

Altitudinal transects of biodiversity are important to understanding macro-ecological patterns. Hump-shaped altitudinal profiles in species richness are a common pattern in terrestrial small-mammal communities studied previously mostly in New World mountain ranges. Based on capture–mark–recapture live-trapping conducted over four seasons (four nights per session) along an altitudinal transect from 1000 to 1747 m asl on the southern slopes of the Soutpansberg Mountains of northern South Africa, we recorded 12 species of small mammal, including nine rodents, two shrews and one elephant shrew (sengi). Three species of rodent and the sengi dominated the communities whilst six species were recorded with three or fewer captures. Although we found no effect of season, we found a significant linear increase in terrestrial small-mammal richness (but not Simpson's diversity, D) with altitude in the Soutpansberg Mountains located just north of the Tropic of Capricorn in South Africa. This trend could best be explained by an increase in the proportion of rocky cover and a change in vegetation from savanna to grassland. Peak densities of three common rodent species and one common insectivore varied from 10 ha−1 (Elephantulus myurus) to 54 ha−1 (Micaelamys namaquensis) and density showed no significant variation with season. However, density either declined (Aethomys ineptus) or increased (Rhabdomys dilectus and Elephantulus myurus) significantly with altitude; this variation was best explained by the proportion of rocky cover. Seasonal variation had a significant effect on body mass of two rodent species. A review of small-mammal studies from major mountain ranges in Africa and Madagascar found that the hump-shaped pattern is not common. Declines in richness with increasing altitude as well as cases of no significant altitudinal change were the most common patterns noted. Tropical African mountains (including the Soutpansberg with 27 species) have far higher small-mammal diversity than temperate African mountains.

Skull size and shape of Dasymys (Rodentia, Muridae) from sub-Saharan Africa

Three morphological datasets (traditional measurements, dorsal and ventral skull shape coordinates) were used to examine craniometric variation in the water rat