Spiders (Arachnida: Araneae) of a wildlife and cattle savanna ranch in South-Western Zimbabwe

grass-dwelling fauna dominated by Thyene thyenioides (15.29 % of the total abundance). The most abundant functional group was the free-living ground-dwellers ( n = 1809, 77.71 % ), followed by free-living plant-dwellers ( n = 266, 11.43 % ) and orb-web builders ( n = 186, 7.98 % ). The current study contributes to the knowledge of a megadiverse group of predatory arthropods in the region. Conservation implications: Sampling and monitoring of rangelands is essential, as the former aids in the identification of new species not previously recorded, as well as increasing knowledge on the distribution of spider species, which if not adequately conserved could face significant threats to their survival even before their documentation.


Introduction
With roughly 51 000 described species (World Spider Catalog 2023), spiders are found in almost all terrestrial biotopes, are easy to collect, and are essential predators (Turnbull 1973).According to the African Arachnological Database, there are presently 454 species known from Zimbabwe (Dippenaar-Schoeman et al. 2015), representing 0.89% of the global species richness (World Spider Catalog 2023).This is far below the 2253 species recorded from the neighbouring country of South Africa (Foord et al. 2020).In contrast, it is higher than the 250 species from the neighbouring Botswana and 183 from Malawi (Jocqué, Alderweireldt & Dippenaar-Schoeman 2013).Despite that within the Afrotropical region, Zimbabwe is amongst the top 10 countries in terms of the highest spider species richness (Jocqué et al. 2013), its known richness can be regarded as low compared to the rest of the region.Jocqué et al. (2013) suggest that the documented spider species richness of any country more strongly reflects the effort placed on studying its fauna than its size, mainly because countries with approximately similar sizes have recorded very contrasting levels of species richness (Jocqué et al. 2013).
The inclusion of spiders into conservation programmes requires correct and regularly updated checklists (Dippenaar-Schoeman et al. 2015).The latter expedited the inclusion of South African spiders in the National Spatial Biodiversity Assessment (NSBA) in 2010 (Dippenaar-Schoeman et al. 2015) and the subsequent preparation of a National Red List (Foord et al. 2020).However, in Zimbabwe, limited checklists (FitzPatrick 2001) and partial surveys have contributed distribution data on species (Cumming & Wesołowska 2004;Wesołowska & Cumming 2011), which unfortunately have not yet been included in any Government of Zimbabwe National Reports on biodiversity and conservation.Additionally, vast areas of the country are still poorly sampled, thus limiting the knowledge of distribution records and the identification of endemic species.
In order to contribute to spider diversity distribution records within Zimbabwe, spiders were sampled at a mixed wildlife and cattle ranch using pitfall traps and sweep-netting.Sampling was conducted from June 2017 to April 2018.A total of 2328 spiders representing 25 families, 94 genera, and 166 species were recorded.The most species-rich families were Salticidae (33 spp.), followed by the Gnaphosidae (28 spp.) and Lycosidae (20 spp.), while eight families were represented by a single species.Pitfall traps accounted for 1857 individuals overall, with the ground-dwelling fauna dominated by Stenaelurillus guttiger (37.86% of the total abundance).Sweep-nets accounted for 471 individuals overall, with the grass-dwelling fauna dominated by Thyene thyenioides (15.29% of the total abundance).The most abundant functional group was the free-living ground-dwellers (n = 1809, 77.71%), followed by free-living plant-dwellers (n = 266, 11.43%) and orb-web builders (n = 186, 7.98%).The current study contributes to the knowledge of a megadiverse group of predatory arthropods in the region.

Spiders (Arachnida: Araneae) of a wildlife and cattle savanna ranch in South-Western Zimbabwe
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Therefore, there is a need to document more species distributions within Zimbabwe.Furthermore, the augmentation of spider biodiversity information, particularly species richness, can also be applied through activities that include the examination of unidentified material in museums and increasing awareness through engagement with the public (Dippenaar-Schoeman et al. 2015).Such activities encourage interest and research on invertebrates, such as spiders.
As part of the PhD study of the first author, spiders were sampled in several biotypes as part of two kraaling impact studies.Sampling proceeded over a period of approximately 1 year, using mainly two methods (pitfall traps and sweep netting).Detailed information on the response of spiders to short-duration kraaling has been published (Sebata et al. 2022), and this article provides an annotated checklist of the spiders sampled at the Debshan Ranch.

Materials and methods
The study was conducted at a mixed cattle and wildlife ranch called Debshan (29º 15ʹ E, 19º 35ʹ S), located 100 km north-east of Bulawayo along the Bulawayo-Harare road in the Insiza district, Matabeleland North Province.Rainfall falls between October and April, with an annual average of 639 mm (Dunham et al. 2003).Average daily humidity is 55% and the annual average temperature is 18°C, with the hottest month being October (average 21°C) and the coldest being July (average 12.4°C).The ranch lies at an elevation of between 1230 m and 1414 m above sea level (Dunham et al. 2003).
The landscape of the ranch is moderately undulating, with coarse-grained, yellowish-brown loamy sands.Some sections have ultramafic or mafic rocks that that give rise to productive red and dark brown clayey soils (Robertson 2013).The soils support floral types that are normally dispersed in a chain-like pattern (Dunham et al. 2003) Spider sampling was conducted from June 2017 to April 2018 utilising pitfall traps and sweep netting following the sampling design reported in Sebata (2020), which was part of a PhD study on the kraaling impact on spider diversity that focused on only ground-dwelling and grass-dwelling spiders.At the end of the collecting period, the contents were collected and emptied into plastic bottles with 70% ethanol for sorting in the laboratory.All adult specimens were sorted to morphospecies and identified to species level, where possible.Voucher specimens were deposited in the Arachnology collection of the Natural History Museum in Bulawayo, Zimbabwe.

Ethical considerations
This article does not contain any experimental studies with human or animal participants, and informed consent is not applicable.

Results and discussion
A total of 2328 spiders representing 25 families, 94 genera, and 166 species were recorded during the study (Table 1).
The dominant ground-dwelling families at Debshan Ranch are also fairly similar to those found in earlier studies in African grasslands (Haddad et al. 2015) and savannas (Haddad 2022) 70; 14.86%); however, Oxyopidae (n = 5; 0.12%) was not as common in this study as in other savanna biotypes (Foord et al. 2002(Foord et al. , 2016)).In order to enhance their chances of survival within their ideal habitats, some grass-dwelling species have evolved elongate, pale bodies, while grounddwelling species are cryptically coloured (Dippenaar-Schoeman et al. 2013), for example, in Salticidae (Haddad & Wesolowska 2011).

Conclusion
This study contributes to our knowledge of the geographical distribution of Zimbabwean spiders.The baseline information on the spider assemblages of Debshan Ranch provides a list of 166 species.However, in order to improve on the distributions and the diversity of the spider fauna, inventories should be conducted in all floral biomes in the country, using not only pitfall traps and sweep nets, but a variety of active search methods, that is, hand collecting, beating sheets amongst others.This will ensure that all spider taxa, including those in trees and bushes (left out in the sampling design of this study) are also included.This will allow researchers to determine the species that are endemic and threatened.

TABLE 1 :
Family composition of the spider fauna collected from Debshan Ranch, Zimbabwe.

TABLE 2 :
Checklist of the spiders caught on previously kraaled sites and their surrounding vegetation from June 2017 to April 2018 at Debshan Ranch, Shanghani, Zimbabwe.
Relative proportion of each functional group sampled by pitfall trapping and sweep-netting in the Miombo woodlands at Debshan Ranch, Zimbabwe from June 2017 till April 2018.Classification of spiders into functional groups was adapted from Foord et al. (2011).