INVERTEBRATES-

SUMMARY REPORT 2019

1. INTRODUCTION

Oana Nature Reserve (South Namibia) is a mountainous semi-desert habitat, with 50km Orange River frontage, spanning over 45,000 hectares (110,000 acres). Due to its remoteness, ruggedness and previous hunting/farmland use, the area is heavily understudied. The unique topography creates a mosaic of different habitat types within the area, including gravel and sandy plains to basalt hills, quarts outcrops and numerous dry river beds following the topography of the land. Rainfall is limited in the region and water bodies are scarce, with some artificial watering holes scattered through-out the area. This report provides a summary of activities carried out between September and October 2019 (19.09.19-10.10.2019), within a scope of invertebrate research, carried out by Mr Mark Pajak (invertebrate specialist), who has visited Oana Nature Reserve. This reports presents a list of taxa recorded, with notes on the insect diversity at the reserve, study limitations, as well as recommendations and potential areas for investigation. 2. METHODS Insect sampling was carried out at a variety of locations within short driving distance from Oana Basecamp (Latitude - 28.812458 Longitude 18.955156). The basecamp itself provided a convenient collecting location due to the bright camp lights used at night and also water, food and shelter provided during the day which acted to attract insects. The data collection methods included:

. Small pitfall traps- constructed by cutting 1 litre plastic water bottles in half and burying them in groups in the sand. These were left in situ and checked daily. . Vegetation sampling- using a 46cm diameter heavy duty sweep net. . Water traps- containers with water and a few drops of detergent to collect flying insects. . Aerial traps- despite being constructed, these were not suitable due to the powerful and unpredictable wind causing their breakage . Ad hoc observations and photographs- collected and recorded from other members of the team, in order to get as big a picture as possible of the diversity of invertebrates at the reserve. . Night time searches- carried out using a UV torch, particularly targeting scorpions

Where insects could not be identified to species and released, they were killed using ethyl acetate and pinned for identification at a later stage.

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3. FINDINGS

3.1 Invertebrate diversity summary

In total 95 invertebrate observations were recorded during the study between 19.09.19-10.10.2019, covering 87 different invertebrate taxa spanning across 21 orders of insects, , molluscs and chilopods. The most diverse invertebrate orders recorded were , beetles and true flies. The relative diversity between various invertebrate groups recorded is presented in the Fig.1

Whilst no scorpions were found during the collecting period, several species have been see at the camp at other times.

Figure.1 Number of different invertebrate taxa recorded during the survey

3.2 Family breakdown

For each of the more abundant and diverse invertebrate groups, the breakdown of families recorded within them was recorded. Within the true spiders, orb weavers, wall spiders and cellar spiders were most diverse. For beetles, darkling beetles, ground beetles and weevils were predominant. For true flies, robberflies, beeflies and hoverflies were the most diverse families, whilst ants were the most diverse family of the hymenoptera.

3.3 Locality breakdown

Oana basecamp and the Orange river valley were areas where the most species were recorded during the sampling period, however collecting efforts were made at other localities as well (Fig. 2)

Figure 2. Number of invertebrate taxa recorded at each locality.

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3.4 Collecting methods The majority of invertebrates were recorded during active searching and sweep netting, however a range of other sapling methods was applied (Fig.3)

Figure. 3 Collecting methods and number of invertebrate species recorded.

4. DISCUSSION The full list of invertebrate species present at Oana Nature Reserve is far from complete. More species are expected to be found, if further collecting efforts are made across other areas in the reserve and over a wider timeframe. Taking into consideration the vastness of the area, the temperature extremities, the elusiveness of diurnal invertebrates and limited timeframe of the study- these have likely restricted the diversity of species recorded at Oana. Furthermore, the seasonality and extremity of weather conditions could mean insect activity for some groups is restricted to narrow periods of activity which would be missed during single collecting event. Despite the limitations of the study, the diversity of insects found indicates a rich desert biodiversity, and a complex ecosystem for predators, parasites, parasitoids and commensal species; showing adaptations to the extreme daytime heat and specific relationships with mammals and plants, using dead stems, burrows and soil for nest construction and shelter.

Invertebrates are known to provide food for mammals e.g. the main predators of the huntsman ( arenicola) are gerbils Gerbillurus paeba, G. tytonis and DesmodUlus auricularis (Henschel 1990). At the same time, mammals can also be food for invertebrates i.e. mites were seen parasitising the ears of rodents, whilst ticks were seen walking free around a waterhole at Oana. The ability of larger creatures to dig burrows creates microhabitats for invertebrates - spider webs were seen hanging over burrow entrances on several occasions. The ubiquity of termite holes across vast areas indicates lots of subterranean activity and such terraforming is affecting soil composition and nutrients, which in turn may affect plant diversity.

The presence of humans: several species of pholcidae occur in caves and in close proximity to humans (Huber, B. A. 2005), Several synanthropics are widespread in Africa, namely the giant cellar spider Artema atlanta, which is present at the campsite, however further investigation would be needed to establish which Pholcids are inhabiting the large

4 mammal burrows. The persistence of flies during the hottest time of day attempting to get water and shelter from faces of passers-by, shows that there are specialist adaptations to locating mammals in the day by some flies.

Ants, bees and wasps (Hymenoptera) have diverse requirements and may be important pollinators and, in the case of wasps, predators in the semi-arid to arid areas of southern Africa (Gess and Gess 2014). The complexity of the desert ecosystem is illustrated by the presence of specialist spider hunting wasps of the Pompilidae family - with the spider hunting wasp Hempipepsis present at the campsite. Whilst these only hunt specific spider species for the development of their larvae, three plant families (Apocynaceae, Orchidaceae and Asparagaceae subfamily Scilloideae) are pollinated exclusively by Hemipepsis wasps (Shuttleworth & Johnson 2011).

5. RECOMMENDATIONS

5.1 Literature and equipment

The literature available at the basecamp facilitated a basic identification of specimens and records. Whilst the characteristics of many invertebrate families are fairly simple to recognise in the field, identification to genus and species is much harder and requires up to date literature and keys and access to a binocular microscope. If this is purchased, it would be worthwhile to attempt sourcing keys (if these exist) to the identification of the following families: Spiders: Araneidae, Oecobiidae, Pholcidae, Beetles: Carabidae, Curculionidae, Tenebrionidae, True Flies: Asilidae, Bombyliidae, Syrphidae, Hymenoptera: Formicidae. Moreover, taxonomic experts for these groups should also be approached and focussed collecting efforts in these specific families should be pursued, in order to increase the number of species known to the area, and the potential for new species to be found.

5.2 Data collecting efforts and species list review

It is recommended for the full invertebrate species list (produced from the survey) to be reviewed when literature is available, or with reference to museum collections, in consultation with experts in particular taxonomic groups. Long-term and regular collecting efforts over a wide area, using a diverse range of sampling techniques is required for fully establishing the insect and biodiversity. The complex geology at Oana creates a huge range of different substrate types, shelters and crevices, which in turn may influence invertebrate diversity. Based on that, a potential future invertebrate study could investigate whether the colour and structure of rock types, has an effect on the species composition of specific within reserve.

5.3 Reference collection

The high levels of endemism in Namibia e.g. beetles, and scarcity of published keys to identification of various groups found in the area highlight the need to retain voucher specimens that will allow for re-identification and determination.

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The specimens collected should be stored in a suitable container such as an entomological drawer / cabinet in a dry environment, and organised into families. This collection can be added to with further collecting efforts and will form a useful resource for future visits by entomologists. Provided that each specimen is pinned with accurate geographical information, they may act as vouchers for new species in the future, if they were to be conserved in a museum and were a subject to further study.

5.3.1 Photographs

A photographic database of observations at Oana would be useful, provided that sufficient metadata is recorded, including date and locality. For large, distinctive insects these could be used to generate identifications, however the majority of invertebrates cannot be reliably identified from a photograph due to the range of microscopic features needed to determine the species.

5.3.2 Fluid preservation

A purchase of materials e.g. sealable sample tubes and a supply of 70% iso-propyl alcohol for fluid preservation of soft bodied invertebrates such as spiders is recommended. Collecting specimens is required for identification of species e.g. six eyed sand spiders of the genus Hexopthalma. Within the literature for spiders, specimen colours refer to that of preserved specimens and therefore a reference collection of preserved spiders would be needed to further understand and identify the spiders of Oana.

6. REFERENCES

Henschel, J. R., 1990. The biology of Leucorchestris arenicola (Araneae: Heteropodidae), a burrowing spider oft he Namib dunes. In: Seely, M. K., ed., Namib ecology: 25 years of Namib research, pp. 115-127. Transvaal Museum Monograph No.7, Transvaal Museum, Pretoria. Huber, B.A. (2005) The Pholcid Spiders Of Africa (Araneae: Pholcidae): State Of Knowledge And Directions For Future Research. In African Biodiversity: Molecules, Organisms, Ecosystems. Proc. 5th Intern. Symp. Trop. Biol., Museum Koenig, Bonn (BA Huber, BJ Sinclair, K-H Lampe, eds). Springer Verlag. 2005. Gess, S and Gess F. (2014) Wasps and bees in southern Africa.in SANBI Biodiversity Series 24 Shuttleworth, A. Johnson, S. (2011) The Hemipepsis wasp-pollination system in South Africa: a comparative analysis of trait convergence in a highly specialized plant guild Botanical Journal of the Linnean Society, 2012, 168, 278–299. Galina N. Azarkina & Stefan H. Foord2 (2013) Redescriptions of poorly known species of jumping spiders (Araneae: Salticidae) from South Africa and Namibia. Zootaxa 3686 (2): 165–182

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