Alien Terrestrial Invertebrates in South Africa

Charlene Janion-Scheepers,Charles L Griffiths

doi:10.1007/978-3-030-32394-3_7

Charlene Janion-Scheepers, Charles L Griffiths

Open Access

https://doi.org/10.1007/978-3-030-32394-3_7

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Publication Date: Jan 1, 2020
Citations: 17	License type: CC BY 4.0

Affiliation: Iziko Museums of South Africa, University of Cape Town

Abstract

AbstractAt the time of writing, 466 alien terrestrial invertebrate species have been reported as being established in South Africa. The most diverse groups within this fauna are the insects (330 species; 70.8%), followed by the arachnids (41; 8.8%), annelids (38; 8.2%) and molluscs (33; 7.1%), together accounting for 95.3% of the total. Within the insects, the Hemiptera are the most species-rich group, followed by the Coleoptera. Most of the invasive arachnid species are mites (24 species), many of which are important agricultural pests. The high number of invasive earthworm taxa (38 species) is of concern, given the impacts that alien earthworms have elsewhere in the world. The majority of alien invertebrates were accidentally introduced as contaminants or stowaways, and although exact dates of arrival of most of these remain unknown, many were present over 100 years ago. Also included in the fauna are 95 species of biological control agents that were almost all deliberately introduced and have contributed significantly to the control of 34 invasive plant species (as well as to the control of a few invasive invertebrates). Of the plant species that have been subjected to biological control, 14 are now considered to be under complete control. Most biological control agents are recent introductions and their rates of release are increasing. The most severe economic impacts of accidentally introduced species are as pest species on crops and these can cause considerable losses. These species mostly establish in agricultural habitats dominated by alien plants, or in disturbed and urbanised areas, although some have established in native vegetation. The cryptic nature of many alien invertebrates makes early detection difficult and many probably remained unreported, perhaps decades after their arrival. Regional taxonomic expertise is lacking for many invertebrate groups, so that even native taxa are poorly described. The wider ecological impacts of most alien terrestrial invertebrates remain very poorly known.

Highlights

The majority of alien invertebrates were accidentally introduced as contaminants or stowaways, and exact dates of arrival of most of these remain unknown, many were present over 100 years ago
Dinocampus coccinellae and the fungus Hesperomyces virescens, can perhaps be used as biological control agents, but their impact on native species needs to be tested (Minnaar et al 2014; Haelewaters et al 2016, 2017)
The negative effects of invasive earthworms on ecosystems elsewhere are clear (Hendrix et al 2008; Ferlian et al 2018), and their impact on soil biodiversity and health need to be better understood in South Africa

Summary

Introduction

In the global invasion literature published between 1980 and 2006, plants were the subject of 44% of studies and vertebrates 15%, while invertebrates were the subject of 36% of publications, despite their considerably greater diversity in terms of both native and introduced species. The dates of introduction of most regional alien terrestrial invertebrates remain unknown, many are known to have been introduced more than 100 years ago (Picker and Griffiths 2011). Increased trade and importation of plants caused a progressive increase in the number of alien terrestrial invertebrates introduced into South Africa (Picker and Griffiths 2017).

Results

Conclusion