University of Venda
School of Maths & Natural Sciences
As part of a three-year study to develop ecologically-based rodent management (EBRM) in southern Africa, a capture-mark-recapture study was carried out in Tanzania, Namibia and Swaziland to establish the demographic patterns and... more
As part of a three-year study to develop ecologically-based rodent management (EBRM) in southern Africa, a capture-mark-recapture study was carried out in Tanzania, Namibia and Swaziland to establish the demographic patterns and population dynamics of rodents. Two study grids were established in each country. In Tanzania, ten species of rodents and one shrew (Crocidura sp.) were identified in the study area. The rodent species consisted of Mastomys natalensis, Aethomys chrysophilus, Arvicanthis neumanni, Gerbilliscus vicina, Acomys spinosissimus, Lemniscomys griselda, Lemniscomys zebra, Rattus rattus, Graphiurus sp. and Mus minutoides. Mastomys natalensis was dominant and contributed more than 70% of the captures. In Namibia, five species were captured, namely Mastomys natalensis, Gerbilliscus leucogaster, Saccostomus campestris, Mus minutoides and Steatomys pratensis. Mastomys natalensis contributed about 50% of the captures. In Swaziland, only M. natalensis was captured in the study grids. There was a clear pattern in the population dynamics, with breeding confined to the wet seasons in the three countries. Mastomys natalensis was the dominant pest species, for which EBRM should focus on. The highest population density of M. natalensis occurred during and after the rains, which coincided with the most susceptible phenological stage of crops. The breeding seasonality and density fluctuations observed in the three countries conform with observations made elsewhere in Africa, which support the hypothesis that rainfall events promote primary productivity on which murid rodents depend. Development of EBRM in these countries will be determined by the local conditions and how they influence the demographic processes of the rodent populations. EBRM should make use of the available ecological knowledge of the local rodent pest species and the focus should be on (ecological) management practices applicable at the community level including community based intensive trapping, field hygiene, removing cover and sources of food for rodents.
- by Rhodes Makundi and +3
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- Zoology
Bats are important indicator species which can help in identifying areas where conservation efforts should be concentrated and whether these areas are affected by ongoing climate change. To elucidate factors limiting and influencing the... more
Bats are important indicator species which can help in identifying areas where conservation efforts should be concentrated and whether these areas are affected by ongoing climate change. To elucidate factors limiting and influencing the elevational distribution of bats in a recognised biodiversity hotpot, the Soutpansberg mountain range (in Vhembe Biosphere Reserve) of northern South Africa, we collected data in and around the Luvhondo Private Nature Reserve, by catching and acoustically monitoring bats over an altitudinal gradient from 900 to 1,748 m. A total of 18 different species could be recorded. Two species, namely Pipistrellus hesperidus and Chaerephon cf. ansorgei appeared to be present and dominant at all altitudes. Activity, species richness and diversity significantly decreased with increasing altitude, whereas community composition was not related to altitude and no endemics to either low or high altitude were detected. It is likely that the change of species richness and diversity over altitude is caused by other factors correlated with altitude such as vegetation type, area size, energy availability and climatic differences. Our research demonstrated that lower altitudes are richer and more diverse in bat species and since no highland endemics have been discovered, conservation efforts in the area, regarding bats, should not ignore these lower altitudes which are most susceptible to human impacts leading to habitat degradation due to over-grazing, bush encroachment, cultivation and denudation of large trees for firewood collection.
- by Peter J Taylor
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Much attention has been paid to the effects of climate change on species' range reductions and extinctions. There is however surprisingly little information on how climate change driven threat may impact the tree of life and result in... more
Much attention has been paid to the effects of climate change on species' range reductions and extinctions. There is however surprisingly little information on how climate change driven threat may impact the tree of life and result in loss of phylogenetic diversity (PD). Some plant families and mammalian orders reveal nonrandom extinction patterns, but many other plant families do not. Do these discrepancies reflect different speciation histories and does climate induced extinction result in the same discrepancies among different groups? Answers to these questions require representative taxon sampling. Here, we combine phylogenetic analyses, species distribution modeling, and climate change projections on two of the largest plant families in the Cape Floristic Region (Proteaceae and Restionaceae), as well as the second most diverse mammalian order in Southern Africa (Chiroptera), and an herbivorous insect genus (Platypleura) in the family Cicadidae to answer this question. We model current and future species distributions to assess species threat levels over the next 70 years, and then compare projected with random PD survival. Results for these animal and plant clades reveal congruence. PD losses are not significantly higher under predicted extinction than under random extinction simulations. So far the evidence suggests that focusing resources on climate threatened species alone may not result in disproportionate benefits for the preservation of evolutionary history.
- by Peter J Taylor
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Abstract: In order to gain insight into the pattern of bat species composition over altitude and the environmental variables driving the observed pattern, we compared data from moist southern and drier northern aspects of the Soutpansberg... more
Abstract: In order to gain insight into the pattern of bat species composition over altitude and the environmental variables driving the observed pattern, we compared data from moist southern and drier northern aspects of the Soutpansberg range in northern South Africa. Acoustical monitoring and additional capturing of bats was used for analysis of species distribution patterns and comparisons of community composition. Bat activity generally followed a linear decline with increasing altitude, possibly related to reproductive females preferring lower altitudes. Species richness followed a hump-shaped distribution on the northern aspect and across the transect, whereas a pattern of a linear decline was observed on the southern aspect. Our study strongly supports a previously published climate model for insectivorous bats which assumes that water availability linked with temperature determines the shape of altitudinal distribution in bat species.
- by Peter J Taylor
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Non-geographic morphometric variation, particularly at the level of sexual dimorphism and ontogenetic (age-related) variation, has been documented in rodents, and useful for establishing whether to analyse sexes separately or together,... more
Non-geographic morphometric variation, particularly at the level of sexual dimorphism and ontogenetic (age-related) variation, has been documented in rodents, and useful for establishing whether to analyse sexes separately or together, and for selecting adult specimens for subsequent data recording and analysis. However, such studies have largely been based on traditional morphometric analyses of linear measurements that mainly focus on overall size, rather than shape-related morphometric variation. Unit-free, landmark/outline-based geometric morphometric analyses are considered to offer a more appropriate tool for assessing shape-related morphometric variation. In this study, we used geometric cranial morphometric analysis to assess the nature and extent of sexual dimorphism and age variation within the Tete veld rat, Aethomys ineptus (Thomas and Wroughton, 1908) from southern Africa and the African Nile rat, Arvicanthis niloticus (Desmarest, 1822) from Sudan. The results obtained were in turn compared with previously published results based on independent geometric and traditional cranial morphometric data from the same sampled populations examined in the present study. While our geometric morphometric results detected statistically significant sexual dimorphism in cranial shape within Ar. niloticus only, previously published results based on traditional morphometric data failed to detect significant sexual dimorphism within this species. However, similar to previously published traditional morphometric data, our geometric morphometric results detected statistically significant age-related variation in cranial shape and size within both Ae. ineptus and Ar. niloticus, with individuals of age classes 5 and 6 being considered to represent adult specimens. Our results highlight the importance of carefully evaluating both size-and shape-related non-geographic morphometric variation prior to the analysis of geographic ARTICLE IN PRESS (E.H. Abdel-Rahman). variation and the delineation of species. Erroneous conclusions of non-geographic variation may have implications in the interpretation of geographic and evolutionary processes that may be responsible for morphological differences at both the inter-and intra-specific levels.
- by Peter J Taylor
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(2015). Afromontane small mammals do not follow the hump-shaped rule: altitudinal variation in
- by Peter J Taylor
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Recent studies have documented the economically significant impact of bats as predators of agricultural pest insects. We used Next Generation Sequencing (NGS) of the cytochrome oxidase I gene to elucidate the diet of six species of bats... more
Recent studies have documented the economically significant impact of bats as predators of agricultural pest insects. We used Next Generation Sequencing (NGS) of the cytochrome oxidase I gene to elucidate the diet of six species of bats based on faecal pellets collected from individuals and roosts in macadamia orchards at Levubu, Limpopo Province, South Africa. For five of these species, we compared the molecular data with published results from microscopic analysis of faecal pellets, culled parts and stomach contents. We provide the first description of the molecular diet of the large African molossid bat, Mops midas. Expectations from skull morphology and a single limited study of stomach contents were that this species should be a beetle-specialist. However, NGS revealed that the diet of M. midas contained a much higher prevalence and diversity of lepidopteran (81 taxa from 17 families) compared to coleopteran (two taxa) prey. While this result is predicted by the allotonic frequency hypothesis for a bat species with low echolocation frequency, it could also be explained by unequal PCR amplification, a constraint of amplicon sequencing. Apart from the above-mentioned species where our sample was probably unbiased (24 pellets from multiple roosts and occasions), sample sizes of the other five species were very low and therefore potentially biased (1–6 pellets). Nevertheless, these samples revealed for each bat species surprisingly many prey taxa spanning several insect orders, indicating that individual bats were capable of consuming a wide diversity of prey during one or two nights of foraging. Contrary to expectations, bats of all foraging groups (clutter, clutter-edge and open-air) fed opportunistically on mostly-flightless cockroaches (Order Blattodea). About one third of all faecal pellets tested from five species of bats of all foraging groups contained DNA from the significant macadamia pest species, Nezara viridula (Order Heteroptera), indicating the value of intact bat communities in the biological control of pest stink bugs in macadamia orchards. Contrary to the general expectations of the allotonic frequency hypothesis, all six bat species studied fed predominantly on tympanate versus non-tympanate species of moths (57–75% of lepidopteran prey taxa), even those 'non-allotonic' bat species having intermediate echolocation peak frequencies that encompass the frequency sensitivity of hearing (tympanate) moths.
- by Peter J Taylor and +3
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- Bats (Mammalogy)