What lies beneath: South Africa’s megadiversity of soil biota Part II

By Dr. Charlene Janion-Scheepers & SERG members

This is the second in a three-part blog series highlighting the rich soil biodiversity found in South Africa.

 

If you think about South Africa the first thing that may come to mind is Table Mountain and the well-known Kruger National Park. However, the country has an extraordinary diversity of mammals, birds, reptiles, amphibians and plants.  And don’t forget about the famous “Big Five”. But have you ever wondered about what lies beneath the soil and makes up the mysterious “Not-so-Big Five”?

Following the formation of the Soil Ecosystem Research Group in 2011 (read our first blog here), we set out to understand the current known diversity of soil biota in South Africa. We collated all current knowledge available for each soil biota group, including historic information of the field in South Africa, data on the current known number of species, distribution data, collection techniques and the locality of the major museum collections (for groups discussed see Fig. 1).

The results confirmed that the soil biota of South Africa is very diverse, but poorly sampled. Most groups are following the global trend of showing an increase in species descriptions, but for some groups, such as protozoans, proturans and tardigrades, data are lacking with no local taxonomic expertise available. Groups such as spiders, ants, earthworms, mites, nematodes and gastropods are reasonably well known due to long standing research programs and excellent effort by the taxonomists. For other groups, knowledge is more fragmented, but increasing due to international research collaborations (such as for springtails), but also due to the development of advanced technologies (such as for fungi).

Fig. 1. Soil groups discussed in this review. (a) Fungi (Aspergillus clavatus)—M. Truter, (b) Nematoda—M. Marais, (c) Protozoa—Flickr user: Picturepest*, (d) Enchytraeidae—WikiCommons user: Cherus*, (e) Tardigrada—R. Goldstein & V. Madden*, (f) Acari (Tectocepheus velatus)—L. Coetzee, (g) Microcoryphia—B. Marlin*, (h) Diplura—A. Murray*, (i) Protura—A. Murray*, (j) Collembola (Isotomurus maculatus)—C. Janion-Scheepers, (k) Oligochaeta—S. Shepherd*, (l) Amphipoda (Talitroides topitotumbest) C. Griffiths, (m) Gastropoda (Achatina imaculata)—D. Herbert, (n) Gastropoda (Chlamydephorus sexangulus)—D. Herbert (o) Isopoda (Porcellio scaber)—C. Griffiths, (p) Diplopoda (Centrobolus sp.)—M. Hamer, (q) Idiopidae (Galeosoma planiscutatum)—P. Webb, (r) Opiliones—L. Lotz, (s) Scorpiones (Opisthacanthus sp.) eating Chilopoda—J. Measey, (t) Pseudocorpiones—L. Deharveng, (u) Scarabaeinae (Scarabaeus cupreus)—Scarab Research Group, University of Pretoria, (v) Termitoidae (Hodotermes mossambicus)—J. Mitchell, (w) Formicidae (Camponotus sp.)—B. Braschler, (x1) Hepialidae (Eudalaca ammon)—R. Schutte, (x2) Gryllotalpidae (Gryllotalpa africana)—M. Picker/C. Griffiths, (x3/x4) Apidae (Anthophora braunsiana, and their nests)—A. Weaving, (y1) Scincidae (Scolotes gronovii)—J. Measey, (y2) Cape mole rat (Georychus capensis)—J. Measey. Photographs contributed by authors unless otherwise indicated (* licenced under creative commons licence).

 

What was even more astounding was that more than half of all the species known for most groups are endemic to South Africa. This number if probably much higher than current estimates, as the number of species descriptions is still steadily increasing. For some this endemicity is extraordinary high for some groups, such as isopods (95%), opiliones (92%), bristletails (95%), earthworms (84%), gastropods (80%) and tardigrades (89%). For many soil insect species endemicity is probably much higher than the current estimate. Several groups contain a large percentage of the globally described species. For example, 6.4% of the world’s nematode species, 7.7% earthworms, 10.2% Embioptera and 8.4% dung beetles are found in South Africa. For many of these groups, as is the case worldwide, are in need of taxonomic revision and detailed field sampling. While sampling has been relatively comprehensive in some areas (Fig. 2), the Nama-Karoo, Northern Cape and Eastern Cape Provinces are all poorly sampled. Natural soils in biodiversity hotspots, such as the Fynbos Biome, are also understudied.

Fig. 2: The distribution of soil fauna in South Africa.

 

In summary, while we’ve learned that we already know an amazing amount about the animals and other organisms that live in our soils, we realised that what we don’t know is even greater. Read our paper here.

 

In our next blog we will discuss some future research directions and sampling strategies, while also focusing on some threats that face soil biota in South Africa and ways we can mitigate these.

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