Chapter 7
Alien Terrestrial Invertebrates
in South Africa
Charlene Janion-Scheepers and Charles L. Griffiths
Abstract At 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.
C. Janion-Scheepers (*)
Centre for Invasion Biology, Iziko Museums of South Africa, Cape Town, South Africa
e-mail: cjanion@gmail.com
C. L. Griffiths
Centre for Invasion Biology, Department of Biological Sciences, University of Cape Town,
Cape Town, South Africa
© The Author(s) 2020
B. W. van Wilgen et al. (eds.), Biological Invasions in South Africa, Invading
Nature - Springer Series in Invasion Ecology 14,
https://doi.org/10.1007/978-3-030-32394-3_7
185
Alien Terrestrial Invertebrates
in South Africa
Charlene Janion-Scheepers and Charles L. Griffiths
Abstract At 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.
C. Janion-Scheepers (*)
Centre for Invasion Biology, Iziko Museums of South Africa, Cape Town, South Africa
e-mail: cjanion@gmail.com
C. L. Griffiths
Centre for Invasion Biology, Department of Biological Sciences, University of Cape Town,
Cape Town, South Africa
© The Author(s) 2020
B. W. van Wilgen et al. (eds.), Biological Invasions in South Africa, Invading
Nature - Springer Series in Invasion Ecology 14,
https://doi.org/10.1007/978-3-030-32394-3_7
185