Habitat Distribution Modeling and Estimating Minimum Viable Area for Population Persistence for Three Arachnids of Conservation Interest in Gauteng Province

Faculty of Science; School of Animal, Plant and Environmental Sciences; MSC Research ReportThree arachnid species, the rock scorpion Hadogenes gunningi, the burrowing scorpion Opistophthalmus pugnax and the baboon spider Harpactira hamiltoni have been identified as species of conservation interest for inclusion in a bioregional systematic conservation planning project by the provincial conservation authority in Gauteng province, South Africa. The systematic conservation planning procedure requires information on the spatial distribution and an estimate of the minimum viable area (MVA) required to support a population for species of conservation interest. The purpose of this report is to provide this information for these three arachnid species. 47 sites were sampled on a regular grid across Gauteng province where data were collected for habitat distribution modeling and density estimation for MVA calculation. Sites were sampled by two field workers. Distance sampling methodology was used for the estimation of density and the genetic algorithm for rule set production (GARP) was used for habitat distribution modeling. Analysis of distance data comprised fitting several alternative models to both continuous and interval data, and data for each field worker were analyzed both separately and pooled. To calculate MVA from estimates of population density a minimum viable population size of 2000 adult individuals was assumed. Based on composite models fitted to continuous data collected by both field workers mean MVA for Opistophthalmus pugnax was 431.57 ha (279.44 ha to 666 ha, 95% confidence interval), while that for Harpactira hamiltoni was 909.09 ha (518.00 ha to 1594.90 ha, 95% confidence interval). Insufficient data were collected for the estimation of population density for Hadogenes gunningi, but based on encounter rate relative to the other two species a subjective estimate of MVA between 380 ha and 570 ha is presented. Habitat distribution modeling was conducted at two grains of predictor variable data. As GARP produces highly variable results models were selected according to the criteria of having less than 5% omission and less than 10% non-prediction. Selected models were stacked and predictions of presence and absence summed for each map pixel across all models. The resultant maps of proportion of positive predictions per pixel were multiplied to obtain a final composite map of probability of occurrence. Accuracy of the coarse, fine and composite maps was assessed using receiver operating characteristic analysis. Mean AUC for models for Hadogenes gunningi were 0.893, 0.857 and 0.886. For Opistophthalmus pugnax and Harpactira hamiltoni mean AUC values were 0.831, 0.790, 0.856 and 0.783, 0.765, 0.805 respectively. Probabilities of occurrence were converted to presence absence at the threshold where false positive and false negative prediction rates were equivalent. Hadogenes gunningi is predicted to occur on most ridges within the province, while Opistophthalmus pugnax and H. hamiltoni are predicted to have a patchy distribution in the southern two thirds of the province. The results presented are a significant improvement on the data previously available for these species and it is recommended that their conservation status be revised in light of the results. Concerns regarding the utility of GARP in conservation planning and suggestions for further research are outlined

Pitfall trapping for surveying trapdoor spiders : the importance of timing, conditions and effort

Trapdoor spiders are challenging to sample using active searching methods because of their cryptic burrowing behavior. This poses problems for ecological studies and for gathering the data needed for conservation assessments. Pitfall trapping provides an alternative method that targets adult males as they wander from their burrows in search of females. Using pitfall trapping requires considerations of the timing of sampling within the year, the effects of environmental conditions on spider activity, and sampling effort required for a high probability of detecting species that are present at a sample site. To investigate these factors, pitfall-trapping surveys were conducted at several localities in Gauteng Province, South Africa. The results showed that trapdoor spider activity occurs in all seasons. Each species has a discrete period of activity ranging from a few weeks to several months in duration. Some species are active at different times of the year at different localities. Statistical analysis showed soil moisture as the only significant predictor of activity from amongst seven environmental variables, and the survey results indicate that trapdoor spiders are active under wet conditions following rainfall. Between two and seven nights of trapping are required for a high probability of detecting all species present and active at a site, using the trap design employed for this study with ten trap arrays per site. Trapping must be repeated at regular intervals throughout the year in order to obtain a near complete inventory of the species assemblage. The number of species collected ranged from two to eight per site, with most sites having six or eight species. Pitfall trapping yielded 1.2 3.0 times the number of species obtained by active searching at sites where both methods were employed. Guidelines for planning pitfall-trapping surveys of trapdoor spiders are presented and future research directions are discussed.Funds for pitfall trapping equipment were provided by the Diamond Route and E. Oppenheimer & Son, with the assistance of Duncan MacFadyen. Funds for subsistence and travel were provided by the Gauteng Department of Agriculture and Rural Development.http://www.americanarachnology.org/JOA_online.htmlhb2016Zoology and Entomolog

Cryptic diversity of South African trapdoor spiders : three new species of Stasimopus Simon, 1892 (Mygalomorphae, Ctenizidae), and redescription of Stasimopus robertsi Hewitt, 1910

Three new species of Stasimopus Simon, 1892, are described from the Gauteng and North West provinces of South Africa. They are readily distinguished from all other known Stasimopus species by the presence of spinules in the tarsal scopulae on the first two pairs of legs of adult males. The only described species recorded in the vicinity, Stasimopus robertsi Hewitt, 1910, which appears to be endemic to northern Gauteng Province, is redescribed. The four species are comprehensively illustrated, a key to identify the adult males from those of other new species in the region is provided, and their conservation status discussed. Available evidence suggests that many Stasimopus species remain to be discovered and described, but significant effort will be required to obtain adult males, considered important for accurate species delimitation in the genus.Funds for pitfall trapping equipment were provided by the Oppenheimer family and E. Oppenheimer & Son, with the assistance of Duncan MacFadyen. Funds for other costs associated with fieldwork were provided by the Gauteng Department of Agriculture and Rural Development, Government of the Republic of South Africa. Fieldwork was funded in part by National Science Foundation grants EAR 0228699 and DEB 0228699 to the second author.http://digitallibrary.amnh.org/dspace/handle/2246/9am2013ab201

Assessing the taxonomic resolution of southern African trapdoor spiders (Araneae: Ctenizidae; Cyrtaucheniidae; Idiopidae) and implications for their conservation

Taxonomic classifications simultaneously represent hypotheses of taxon identity and relationships to taxonomists, and real, unchanging entities to users of taxonomic information. Taxonomic changes, while representing scientific progress, can be a source of frustration for users. A method for assessing confidence in the taxonomy of a group of organisms would assist users of the taxonomy. A method is presented for determining the degree of development of a taxonomy, a concept termed ‘taxonomic resolution’. The method was applied to six groups of southern African mygalomorph trapdoor spiders, namely Stasimopus Simon 1892 (Ctenizidae Thorell 1877), Ancylotrypa Simon 1889 (Cyrtaucheniidae Simon 1889), four genera of Idiopidae Simon 1889 assessed as a single group, Galeosoma Purcell 1903, the families Migidae Simon 1889 and Microstigmatidae Roewer 1942, and the burrowing scorpion genus Opistophthalmus C. L. Koch 1837 (Scorpionidae Latreille 1802). The method was based on the assumption that species delimitation in a group of organisms, the taxonomy of which is based on morphological characters, depends on whether the sample of material examined is adequate for assessing variation in those characters. Five assessment criteria were identified and scored for a group of species using the taxonomic literature. Estimates of the number of species remaining to be discovered and described in each group were also included in the assessment. The results obtained for the trapdoor spiders ranged from 15 to 29%, indicating a potentially significant degree of uncertainty in the taxonomy. Results for Migidae and Microstigmatidae were 51 and 78% respectively, whereas the result for Opistophthalmus was 93%. The applied value of a measure of taxonomic resolution, the limitations of the method, and a strategy for developing a more generally applicable method are discussed.National Science Foundation DEB grants 0228699 and 0413453.http://www.springerlink.com/content/0960-3115/ab201

Cryptic diversity of South African trapdoor spiders : three new species of Stasimopus Simon, 1892 (Mygalomorphae, Ctenizidae), and redescription of Stasimopus robertsi Hewitt, 1910

Three new species of Stasimopus Simon, 1892, are described from the Gauteng and North West provinces of South Africa. They are readily distinguished from all other known Stasimopus species by the presence of spinules in the tarsal scopulae on the first two pairs of legs of adult males. The only described species recorded in the vicinity, Stasimopus robertsi Hewitt, 1910, which appears to be endemic to northern Gauteng Province, is redescribed. The four species are comprehensively illustrated, a key to identify the adult males from those of other new species in the region is provided, and their conservation status discussed. Available evidence suggests that many Stasimopus species remain to be discovered and described, but significant effort will be required to obtain adult males, considered important for accurate species delimitation in the genus.Funds for pitfall trapping equipment were provided by the Oppenheimer family and E. Oppenheimer & Son, with the assistance of Duncan MacFadyen. Funds for other costs associated with fieldwork were provided by the Gauteng Department of Agriculture and Rural Development, Government of the Republic of South Africa. Fieldwork was funded in part by National Science Foundation grants EAR 0228699 and DEB 0228699 to the second author.http://digitallibrary.amnh.org/dspace/handle/2246/9am2013ab201

New collection records for Theraphosidae (Araneae, Mygalomorphae) in Angola, with the description of a remarkable new species of Ceratogyrus

During 2015 and 2016 several baboon spider specimens (Araneae: Theraphosidae) were collected in central Angola during surveys undertaken for the Okavango Wilderness Project. These collections represent range and habitat extensions for Pterinochilus Pocock, 1897, Ceratogyrus Pocock, 1897 and Phoneyusa Karsch, 1884. The new species Ceratogyrus attonitifer sp. n. is described from female specimens and the distribution of genera mapped. Central and eastern Angola is severely under sampled for theraphosid spiders, with every species collected during the survey either being potentially new to science or representing a significant range extension for the genus.The National Geographic Okavango Wilderness Project, the KwaZulu-Natal Museum and the University of Pretoria.https://africaninvertebrates.pensoft.netam2020Zoology and Entomolog

An assessment of rehabilitation success in an African grassland using ants as bioindicators

Many studies that evaluate rehabilitation make use of invertebrate bioindicators. Invertebrates, especially ants, make useful indicators as they are sensitive to environmental change. We compared ant assemblages in rehabilitated and control sites in the Rietvlei Nature Reserve, a protected area important for grassland conservation in South Africa. Pitfall traps were used to sample ant assemblages at six control sites and six rehabilitated sites. In addition, environmental and vegetation surveys were conducted at each site. We found that the ant assemblages differed significantly between the control and rehabilitated sites, although there was considerable overlap; the control sites supported a greater species density and higher abundance of ants than the rehabilitated sites. In total, 36 ant species were collected (control sites: 34 species; rehabilitated sites: 26 species). The environmental survey revealed that percentages of bare ground and coarse sand, as well as soil pH, differed significantly between the control and rehabilitated sites. The control and rehabilitated sites also supported significantly different plant assemblages. Three indicator ant species were identified for the control sites: Crematogaster rectinota, Crematogaster amita and Monomorium fastidium. No indicator species were identified for the rehabilitated sites. These results suggest that recovery from the previous agricultural use of the area is still incomplete and highlights the lack of research examining the success of rehabilitation in the grassland biome. CONSERVATION IMPLICATIONS : The present study illustrates the need for further research on rehabilitation techniques utilised in the grassland biome. This is of value as the remainder of South African grasslands are considered critically endangered.The National Research Foundationhttp://www.koedoe.co.zaam2016Plant ScienceZoology and Entomolog

An assessment of rehabilitation success in an African grassland using ants as bioindicators

Many studies that evaluate rehabilitation make use of invertebrate bioindicators. Invertebrates, especially ants, make useful indicators as they are sensitive to environmental change. We compared ant assemblages in rehabilitated and control sites in the Rietvlei Nature Reserve, a protected area important for grassland conservation in South Africa. Pitfall traps were used to sample ant assemblages at six control sites and six rehabilitated sites. In addition, environmental and vegetation surveys were conducted at each site. We found that the ant assemblages differed significantly between the control and rehabilitated sites, although there was considerable overlap; the control sites supported a greater species density and higher abundance of ants than the rehabilitated sites. In total, 36 ant species were collected (control sites: 34 species; rehabilitated sites: 26 species). The environmental survey revealed that percentages of bare ground and coarse sand, as well as soil pH, differed significantly between the control and rehabilitated sites. The control and rehabilitated sites also supported significantly different plant assemblages. Three indicator ant species were identified for the control sites: Crematogaster rectinota, Crematogaster amita and Monomorium fastidium. No indicator species were identified for the rehabilitated sites. These results suggest that recovery from the previous agricultural use of the area is still incomplete and highlights the lack of research examining the success of rehabilitation in the grassland biome. CONSERVATION IMPLICATIONS : The present study illustrates the need for further research on rehabilitation techniques utilised in the grassland biome. This is of value as the remainder of South African grasslands are considered critically endangered.The National Research Foundationhttp://www.koedoe.co.zaam2016Plant ScienceZoology and Entomolog