Chromosomal and molecular characterization of Aethomys kaiseri from Zambia and Aethomys chrysophilus from Tanzania (Rodentia, Muridae)

Experimental treatment-control studies of ecologically based rodent management in Africa: balancing conservation and pest management

Context Rodent pests severely affect crop production, particularly in monocultures where one or two rodent pest species dominate. We predict higher species richness of native small mammal species in more heterogeneous mosaic (crop–fallow–bush) subsistence agro-ecosystems in Africa. Conservation and agro-ecological imperatives require that such diverse natural communities should be maintained and may benefit crop protection through limiting domination of pest species. Ecologically based rodent-management alternatives to rodenticides are urgently required and one such method (community trapping) is herein advocated. Aims To provide baseline information on rodent and shrew communities in agro-ecosystems in three African countries and to demonstrate efficacy of ecologically based rodent management (EBRM) in Africa (e.g. community household trapping). Methods Removal-trapping in a variety of agro-ecological habitats provided accurate small-mammal species lists. Intensive kill-trapping by rural agricultural communities was carried out experimentally where the efforts of communities were scientifically monitored by kill-trapping to measure impact on rodent numbers and the levels of post-harvest damage to stored grains. Key results Our study revealed a high diversity of endemic species in agricultural habitats in Tanzania and Namibia (but not Swaziland) and the existence of undescribed and possibly rare species, some of which may be at risk of extinction from unchecked habitat transformation for agriculture. Treatment-control studies showed that communities in three African countries could effectively reduce pest rodent populations and rodent damage by intensive trapping on a daily basis in and around the community. Conclusions Community trapping reduced pest rodent populations and damage to stored grains. Unlike the use of indiscriminate rodenticide, this practice is expected to have a negligible effect on beneficial non-target rodent and shrew species. Implications Ecologically based rodent management approaches such as community trapping will conserve beneficial non-pest rodent communities and ultimately improve crop protection.

Ecologically based rodent management in Africa: potential and challenges

Rodent management in agriculture remains a major challenge in developing countries where resource-poor farmers are ill equipped to deal with pest species. It is compounded by unpredictable outbreaks, late control actions, lack of/or inadequate expert interventions, expensive rodenticides and other factors. Ecologically based rodent management (EBRM) is recommended as the way forward for rodent management in Africa. EBRM relies on understanding the ecology of pest species and formulating this knowledge into management programs. The present paper evaluates the potential for establishing EBRM in Africa and the challenges that have to be overcome to implement it. The major constraints for establishing EBRM in Africa include the absence of key studies on the taxonomy and ecology of rodents, inadequate research on EBRM, lack of knowledge by farmers on available technologies and agricultural policies that are unfavourable. The development of EBRM and its success in Asia is a strong encouragement to African scientists to develop similar management strategies for the most important pest species such as the multimammate rats, Mastomys natalensis. EBRM initiatives such as the Development of Ecologically Based Rodent Management for the Southern Africa Region (ECORAT) project undertook studies on e.g. rodent ecology, taxonomy, knowledge, attitude and practices and rodent–human interactions in rural agricultural communities. Through this project, EBRM interventions were introduced in Tanzania, Swaziland and Namibia to provide solutions to local rodent-pest problems. Intervention actions including community-based intensive trapping of rodents, habitat manipulation and sanitary measures demonstrated that the impacts of rodents on communities could be drastically reduced. EBRM programs in Africa must address how to change attitudes of target communities, building scientific capacity, implanting rodent-management skills by translating the developed technologies and strategies into simple understandable and easy-to-implement actions and influencing policy makers to accept the concepts and practices to be introduced. Further, we need to demonstrate that EBRM is economically feasible and sustainable and that through community participation, EBRM will become deeply rooted in those communities.

Bioregion heterogeneity correlates with extensive mitochondrial DNA diversity in the Namaqua rock mouse, Micaelamys namaquensis (Rodentia: Muridae) from southern Africa--evidence for a species complex

BACKGROUND

Intraspecific variation within the diverse southern African murine rodents has not been extensively investigated, yet cryptic diversity is evident in several taxa studied to date. The Namaqua rock mouse, Micaelamys namaquensis Smith, 1834 is a widespread endemic murine rodent from the subregion. Currently, a single species with four subspecies is recognised, but in the past up to 16 subspecies were described. Thus, this species is a good candidate for the investigation of patterns and processes of diversification in a diverse but under-studied mammalian subfamily and geographic region. Here, we report genetic differentiation based on mitochondrial DNA (mtDNA) cytochrome b (cyt b) sequences among samples collected over an extensive coverage of the species' range.

RESULTS

Cytochrome b sequences of 360 widely sampled individuals identified 137 unique maternal alleles. Gene tree and phylogeographic analyses of these alleles suggest the presence of at least eight lineages or haplogroups (A-H), with varying degrees of intra-lineage diversity. This differentiation is in contrast with the most recent taxonomic treatment based on cranial morphometrics which only recognised four subspecies. The mtDNA diversity strongly supports earlier views that this taxon may represent a species complex. We further show statistical support for the association of several of these lineages with particular vegetation biomes of southern Africa. The time to the most recent common ancestor (TMRCA) dates to the Pliocene (~5 Mya) whereas coalescent-based divergence time estimates between lineages vary between 813 Kya [0.22-1.36] and 4.06 Mya [1.21-4.47]. The major diversification within lineages occurred during the Pleistocene. The identification of several regions of sympatry of distinct lineages offers future opportunities for the elucidation of the underlying speciation processes in the suggested species complex.

CONCLUSIONS

Similar to other African murine rodents, M. namaquensis radiated during the Pliocene and Pleistocene coinciding with major periods of aridification and the expansion of savanna habitats. The suggested species complex is represented by at least eight lineages of which the majority are confined to only one or a few neighbouring biomes/bioregions. Contrasting intra-lineage phylogeographic patterns suggest differences in adaptation and responses to Plio-Pleistocene climatic and vegetation changes. The role of ecological factors in driving speciation in the group needs further investigation.