Browsing by Author "Mwabvu, Tarombera."
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Item Assemblages of surface-active arthropods in pristine and disturbed savannah.(2022) Mavasa, Risuna Wain.; Tsvuura, Zivanai.; Yekwayo, Inam.; Mwabvu, Tarombera.Savannahs are structurally complex ecosystems rich in biodiversity, and the conversion of savannahs into human-modified landscapes poses a significant risk to organisms with limited dispersal abilities. Surface-active arthropods have limited dispersal abilities and are sensitive to changes in their environment; as a result, they are restricted to specific habitats with the resources that they need. Surface-active arthropods are essential in ecosystem processes, such as playing a direct or indirect role in water infiltration into the soil and its storage, decomposition of plant and animal matter, nutrient cycling, humification and biological pest control. Many landscapes of natural vegetation in South Africa have been transformed into croplands, residential and commercial areas. In Mpumalanga province, croplands (including fruit plantations) dominate the landscape where savannah vegetation occurred previously. This study investigated the influences of disturbance (transformed savannah vs pristine savannah) and season on the diversity of four groups of surface-active arthropods (ants, beetles, millipedes and spiders) in the savannah biome in Mpumalanga province. The objectives of the study were to determine 1) whether flightless arthropod assemblages differ between disturbed and pristine savannah, and 2) whether functional guilds of flightless arthropod assemblages differ between summer and winter. Field sampling using pitfall traps was done to collect the surface-active arthropods in pristine and disturbed savannah during summer and winter. All samples were sorted into morphospecies and identified into family or genus where possible and then assigned into functional guilds. Functional guilds were allocated based on the feeding habits of the surface-active arthropods, resulting in three distinct functional guilds (detritivores, herbivores and carnivores) being identified. Surface-active arthropods with diverse feeding habits were lumped to form a fourth functional guild, the “diverse functional guild”. I found significant differences in the species composition of ants, beetles and spiders between disturbed and pristine savannahs. The species richness and abundance of ants was significantly greater in the disturbed than pristine savannah, while beetles and spiders had similar species richness and abundance between the two habitat types. The number of unique species of the surface-active arthropods in the disturbed savannah were two times more than those in the pristine savannah. The species richness and composition of all functional guilds of the surface-active arthropods differed between summer and winter, with greater species richness in summer than in winter. Herbivorous and carnivorous arthropods had significantly higher abundance in summer than in winter, while the abundance of detritivores and the “diverse functional guild” was similar between the two seasons. This study shows that different vegetation types support different compositions of surface-active arthropods and that there may be a positive relationship between vegetation structure and the assemblages of surface-active arthropods in the savannah. Furthermore, the study highlights a potentially positive relationship between the assemblages of herbivorous and carnivorous arthropods. I recommend that it may be essential to consider both disturbed and pristine habitat types in the conservation of surface-active arthropods, especially in South Africa where most of the land is outside of formal conservation areas. This assertion is supported by the greater number of unique species of surface-active arthropods found in the disturbed than in the pristine savannah. My study provides relevant baseline information because little is known about the assemblages of surface-active arthropods in savannah landscapes dominated by croplands. Furthermore, my study gives some insight on how the assemblages of surface-active arthropods may respond to disturbance in the savannah.Item Genetic analyses of a Southern African millipede (Bicoxidens Attems 1928)(2014) Tinago, Tawanda.; Mwabvu, Tarombera.; Macdonald, Angus Hector Harold.Bicoxidens Attems, 1928 is an afrotropical millipede in the family Spirostreptidae which constitutes nine species. Based on the analysis of the male copulatory organs known as gonopods, Bicoxidens is monophyletic. However, gonopod morphology is central to millipede taxonomy, examination of gonopod morphology alone may not elucidate hidden genetic diversity thereby underestimating species richness in Bicoxidens. Analysis of genetic data as an additional source of taxonomic data has been noted to reveal genetic variation and flagged hidden species within millipedes. Hence there is a need to revise the morphological species definitions and phylogeny of Bicoxidens using both mitochondrial and nuclear DNA sequences. Furthermore, low vagility and habitat discontinuity may limit gene flow among Bicoxidens populations resulting differentiation and high genetic variation. In this regard, the sequences of the mitochondrial cytochrome oxidase 1 (COI) and 16S rRNA genes were used to delimit species, unravel hidden species and test the monophyly of Bicoxidens. In addition, the phylogeography and population genetic structure of B. flavicollis was investigated based on COI and 16S rRNA sequences. Genetic distances were computed using COI. Phylogenetic inferences were done based on Maximum likelihood and Bayesian inference analyses of the COI and 16S rRNA sequences individually and with the combined data set (COI+16S rRNA). The phylogeography and population genetic structure of B. flavicollis was inferred based on genetic diversity indices, population genetic differentiation estimate PhiPT, haplotype network analyses and maximum likelihood analyses of both COI and 16S rRNA. Bayesian population structure analyses was done using the COI data set only. Furthermore, Mantel’s isolation by distance among B. flavicollis specimens was tested. Interspecific genetic distances (> 0.075) based on the Juke-Cantor model supported the morphological species definitions in Bicoxidens. However, high intraspecific sequence differences in B. flavicollis (> 0.14), B. friendi (0.084) and B. brincki (> 0.188) suggest the presence of cryptic species. The possible presence of cryptic species was supported by the phylogenic analyses which recovered a paraphyletic Bicoxidens phylogram with B. flavicollis, B. brincki and B. friendi exhibiting divergent lineages. Bicoxidens flavicollis populations exhibited high genetic diversity and strong population differentiation which suggests restricted gene flow. Haplotype network and Maximum likelihood analyses revealed limited sharing of haplotypes and cryptic species in populations at Mazowe and Nyanga, respectively. Bicoxidens flavicollis populations were grouped in two four genetic clusters. Isolation by distance was insignificant among B. flavicollis specimens. The results support the utility of both COI and 16S rRNA in species delimitation in Bicoxidens. There is a growing body of evidence which also suggests presence of hidden species in B. flavicollis, B brincki and B friendi. Furthermore effort to uncover more hidden species should be made to elucidate the species richness before conservation strategies can be implemented.Item Genetic diversity of populations of a Southern African millipede, Bicoxidens flavicollis (Diplopoda, Spirostreptida, Spirostreptidae)(2018) Gounden, Yevette.; Zishiri, Oliver Tendayi.; Mwabvu, Tarombera.The African millipede genus Bicoxidens is endemic to Southern Africa, inhabiting a variety of regions ranging from woodlands to forests. Nine species are known within the genus but Bicoxidens flavicollis is the most dominant and wide spread species found across Zimbabwe. Bicoxidens flavicollis individuals have been found to express phenotypic variation in several morphological traits. The most commonly observed body colours are brown and black. In the Eastern Highlands of Zimbabwe body colour ranges from orange- yellow to black, individuals from North East of Harare have a green-black appearance and a range in size (75–110 mm). There is disparity in body size which has been noted with individuals ranging from medium to large and displaying variation in the number of body rings. Although much morphological variation has been observed within this species, characterization based on gonopod morphology alone cannot distinguish or define variation between phenotypically distinct individuals. Morphological classification has been found to be too inclusive and hiding significant genetic variation. Taxa must be re-assessed with the implementation of DNA molecular methods to identify the variation between individuals. This study aimed to detect genetic divergence of B. flavicollis due to isolation by distance of populations across Zimbabwe. The mitochondrial DNA 16S and 12S rRNA genes were used to detect levels of genetic variation as mitochondrial markers express high variability making them suitable for phylogenetic studies. Sequence analysis of the 16S rRNA gene resulted in the generation of 22 haplotypes, derived from 42 sequences with strong haplotype diversity (Hd > 0.9). Analysis of Molecular Variance (AMOVA) analysis determined that variation among the populations was significantly greater (> 80 %) than the variation occurring within populations (< 12 %). A high fixation index (FST = 0.88229) indicated a high level of population genetic differentiation. With analysis of the 16S rRNA gene, B. flavicollis individuals demonstrated both distinctive phylogeographic diversity and genetic similarity for specific regions within Zimbabwe. Phylogenetic analyses using the 12S rRNA gene provided evidence of a more distinct genetic structure between localities. Nineteen haplotypes were derived from 19 sequences, which indicated a genetically distinct population structure (Hd = 1.000). The AMOVA analysis demonstrated that variation among the populations was greater (> 60 %) than the variation occurring within populations (< 40 %), although both were quite high. A low fixation index (FST = 0.37466) suggests a predominantly homozygous population structure. Both genes indicated distinctly structured populations, whilst the 16S rRNA also suggested the existence of closely clustered populations based on PCoA analyses, which is further supported by the presence of admixed haplotypes. The results are significant for B. flavicollis as a genetically diverse species. The findings of this study can be considered for future comparative research within the genus Bicoxidens or against other geographically distant genera. Additional markers such as those of nuclear origin, can be used along with mitochondrial markers to investigate and identify more diplopods which exhibit this level of genetic divergence although belonging to a single species. Acquired knowledge and understanding from phylogeographic studies will provide researchers with greater taxonomic awareness.Item Revision of the taxonomy and distribution of the African millipede genera Bicoxidens, Spirostreptus, Plagiotaphrus and Archispirostreptus (Diplopoda, Spirostreptida, Spirostreptidae)(2010) Mwabvu, Tarombera.; Slotow, Robert Hugh.No abstract available.Item A revision of the taxonomy and phylogenetic background of the South African genus Kazimierzus Plisko, 2006 (Oligochaeta: Kazimierzidae)(2018) Nxele, Thembeka Clara.; Zishiri, Oliver Tendayi.; Plisko, Jadwiga Danuta.; Mwabvu, Tarombera.Species identity and distribution information is important in conservation and monitoring of biodiversity. Megadrile fauna is very diverse in Southern Africa with most of the fauna demonstrating high levels of endemism, closely related species often separated by subtle morphological characters. Natural and various fertile biotopes of South Africa have a diverse terrestrial megadrile fauna, but to date, taxonomic and systematic studies of most taxa are incomplete. Such studies are vital as they contribute to the understanding of evolutionary processes and also provide information for conservation. To date, South African indigenous megadrile accredited to three strict indigenous families, Microchaetidae (s.str.), Tritogeniidae and Kazimierzidae, differ morphologically and differ also in their geographical distribution. The representatives of Kazimierzus, the only genus in Kazimierzidae, are known from the Western and South-Western Atlantic coast of South Africa, the area known for endemism in other invertebrate fauna and often associated with diverse flora. Considering these factors Kazimierzus was selected for the present study. The selected 25 Kazimierzus species occur in specific biotopes, their distribution is highly restricted to selected places, and most of them do not overlap. The study aimed to employ integrative taxonomy (morphology and molecular) to carry out a taxonomic revision of this genus and the objectives were1. to evaluate the validity of described species and provide an identification key to all species of Kazimierzus; 2. to determine the distribution of the genus Kazimierzus, in order to provide reliable data on species diversity, geographical distribution in Southern Africa and factors contributing to their distribution limits; this information is vital for conservation planning because earthworms can be used as bio-indicators of soil ecosystem health and 3. to investigate phylogenetic relationships within the genus. Kazimierzus was originally accredited to the family Microchaetidae (s. lato). Family Kazimierzidae was erected to accommodate Kazimierzus species because their morphology and anatomy were found to be different from the Microchaetidae (s. str) and also their geographic distribution confirmed separation from the other families. Four new species were described and a key to all species of Kazimierzus was constructed. DNA was extracted from twelve species and mitochondrial gene fragments (COI) were amplified and sequenced. Bayesian and maximum likelihood were used to determine phylogenetic relationships among species. The results validated the twelve species known currently. Cryptic diversity was observed in K. occidualis with genetic divergence greater than 12 % among populations. Kazimierzus franciscus and K. ljungstroemi have a low genetic variability suggesting close relatedness or probably conspecificity. A group of specimens from Clanwilliam are morphologically identical to K. sophieae but are genetically distinct and may belong to an undescribed taxon. These observations highlighted the importance of integrative taxonomy in earthworms in order to present reliable taxonomic and biogeographic data. A species distribution model was used to predict the distribution patterns of K. hamerae. Potentially new habitats were predicted along the Atlantic Ocean, in the southern part, as well as, in the north-western part of Namibia. The occurrence in Namibia was tested in the south, unfortunately no Kazimierzus specimens were found in the region where sampling was done. In addition, the model demonstrated that precipitation in the driest month is the most relevant predictor in spatial distribution patterns of K. hamerae. Because of the increasing awareness of the importance of earthworms in South Africa, indigenous earthworm species are given English common names. As such, all the species of Kazimierzus were given English common names. It is hoped that using common names may facilitate and increase the use of earthworms in conservation planning and environmental impact assessments. More farmers are showing interest in soil biology and it is hoped that, by giving earthworms English names, their importance and use will increase in the agricultural sector.Item A taxonomic revision of Tritogenia Kinberg, 1867 and Michalakus Plisko, 1996 (Oligochaeta, Tritogeniidae) occurring in KwaZulu-Natal Midlands, South Africa, based on morphological and DNA sequence data.(2014) Nxele, Thembeka Clara.; Mwabvu, Tarombera.; Plisko, Jadwiga Danuta.; Willows-Munro, Sandi.The conservation and monitoring of biodiversity depends on the knowledge of species identity and distribution. Southern Africa has a rich and characteristic megadrile fauna. Most of the fauna show high levels of endemism with closely related species often separated by subtle morphological characters. Grasslands and forests of South Africa have a diverse terrestrial earthworm fauna, but up to date systematic studies of most taxa are incomplete. Such studies are an opportunity to contribute to understanding evolutionary processes and to provide information for conservation. The genera Tritogenia and Michalakus occur in grasslands and forests in north-eastern part of South Africa in the KwaZulu-Natal province. This study investigated the taxonomic validity of the Tritogenia and Michalakus species in the KwaZulu-Natal Midlands. Ten species of Tritogenia and one of Michalakus are known from this region, with species descriptions based on morphological characters. In this study integrative taxonomy is employed, with both morphological and molecular data used to assess the reliability of traditional morphology-based techniques and the relationships among these species. Detailed comparative morphological observations from fresh Tritogenia material revealed a synonym (Tritogenia soleata Plisko, 1997 = Tritogenia shawi Plisko & Zicsi 1991). To gain further evidence for species level taxonomy and distribution patterns, a molecular phylogeny was constructed based on mitochondrial genes cytochrome c oxidase subunit I (COI) and 16S rRNA. A total of 146 individuals were sequenced for COI from 22 localities and 43 were sub-sampled for 16S rDNA. In most cases, the morphological and molecular data are congruent. The molecular data revealed that the genus Tritogenia is not monophyletic as previously thought. Michalakus initus Plisko 1996 nests within Tritogenia and this finding is observed in both morphological and molecular data. Tritogenia shawi is a cluster with the outgroup species not with other Midlands Tritogenia species. These findings demonstrate the value of using integrative taxonomy in highlighting/revealing the complexities of earthworm fauna in South Africa. The combined morphological and molecular data, though not well supported, ancestral character state reconstructions are generally in agreement with the morphological data in terms of which characters were useful in phylogeny construction.Item Use of ground-dwelling arthropods as bioindicators of ecological condition in grassland and forest vegetation at eThekwini Municipality in KwaZulu-Natal.(2018) Hlongwane, Zabentungwa Thakasile.; Tsvuura, Zivanai.; Mwabvu, Tarombera.; Munyai, Thinandavha Caswell.Epigaeic arthropods are among the most diverse and abundant group of animals. They are important in the functioning of terrestrial ecosystems. Assemblages of arthropods may be affected by vegetation type, seasonality and disturbances such as alien plant invasion. The aim of this study was to develop a bioindicator tool for monitoring ecological conditions of the KwaZulu-Natal Sandstone Sourveld (KZNSS), which is one of the most threatened grasslands in KwaZulu-Natal. The objectives of this study were to 1) determine species abundance and species richness of ground-dwelling arthropods; 2) determine the effect of season on ground-dwelling arthropods; 3) determine functional diversity of ground-dwelling arthropods; and 4) determine if ground-dwelling arthropods distribution differs in three vegetation types in Tanglewood and Giba Gorge nature reserves in the KwaZulu-Natal Sandstone Sourveld. Ground-dwelling arthropods were sampled during the wet and dry seasons at two sites in each of the nature reserves. At each site, pitfall trap sampling was carried out in three vegetation types, namely intact grassland, riverine or scarp forest and a disturbed grassland vegetation. The disturbed grassland vegetation was an ecotone between grassland and forest dominated by alien invasive plants. Ants, beetles, spiders, terrestrial crustaceans, sand crickets, roaches, termites, millipedes, lacewigs, hemipterans and woodlice were the sampled taxa in both reserves. A total of 6 150 specimens belonging to 60 morpho-species were sampled in Giba Gorge and Tanglewood Nature Reserve. Species abundance and richness varied among reserves as greater epigaeic arthropod abundance was observed in Tanglewood than in Giba Gorge Nature Reserve. However, Giba Gorge was the richer reserve than Tanglewood. Distribution of epigaeic arthropods varied among vegetation types, higher arthropod abundance was recorded in the forest than the disturbed and intact grassland. While higher species richness of epigaeic arthropods was recorded in an intact grassland. Ants were the most abundant and richest taxon at both sites and greater abundance of ants was recorded in the disturbed grassland which shows that ants are opportunistic organisms. Seasonality played an important role in epigaeic arthropod species abundance and richness. Higher abundance and richness was observed in the wet season. This shows that the wet season provides optimum food resources, temperature, soil moisture and diverse vegetation structure which is favourable to epigaeic arthropods. Functional diversity varied across vegetation types. Forest supported a greater abundance of decomposers and predators while the disturbed grassland supported greater abundance of generalists and herbivores. This shows that functional guilds have different food resources and niche requirements and vegetation type plays an important role in functional diversity. Generalist arthropods were more abundant in the dry season unlike the predators, herbivores and decomposers which were more abundant in the wet season. Generalists have broad diets and are able to survive under unfavourable conditions. A terrestrial crustacean, Talitriator africana occurred in all vegetation types but was more abundant in forest. An ant, Pheidole sp.02 (megacephala gp.) was the most widespread species. However, it was more abundant in disturbed grassland. These results suggest that T. africana and Pheidole sp.02 (megacephala gp.) could be useful potential indicators for monitoring ecological conditions in the KwaZulu-Natal Sandstone Sourveld. Forests and grasslands should be conserved because they supported higher numbers of epigaeic arthropods and functional guilds. Arthropods play an important role in the functioning of terrestrial ecosystems. Disturbed grassland should be managed and restored back to a grassland because grasslands play an important role in the functioning of the ecosystem by providing direct and indirect ecosystem services