invasive species have been found in native forest ecosystems (Uys et al. 2010;
Nxele 2012).
The total of 466 established alien terrestrial invertebrates recorded in
South Africa is certainly an underestimate of the number already present. There
are two primary reasons for this. Firstly, established alien species, some of which
may have been present in the region for decades, are regularly being discovered,
and more already-existing invasions will surely continue to be uncovered into the
future. One notable example is the six recently-recorded Australian insects found
associated with Eucalyptus trees by Bush et al. (2016). Many such suitable habitats
(e.g. the numerous species of non-commercial, ornamental plants in urban gardens)
still remain poorly explored, and are likely sites where existing alien terrestrial
invertebrates remain undetected. Secondly, there are many groups for which regional
taxonomic expertise is poor or entirely lacking, and these probably include many
more alien or invasive species than are currently recognised, highlighting the need
for improved foundational taxonomic knowledge in South Africa. This is especially
the case for many groups of soil fauna, which are inconspicuous and understudied
(Janion-Scheepers et al. 2016), but which can easily be introduced and distributed
accidentally through eggs in soil and are thus almost certainly under-reported in the
current lists.
7.3 Dates, Rates and Routes of Introduction
Although 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). Some of the earliest reported invasive invertebrates
in South Africa were two species of flea, first recorded during the 1700s (the
Human Flea Pulex irritans and the Chigoe Flea Tunga penetrans; Picker and
Griffiths 2011). Other early invasive invertebrates recorded include the European
Garden Snail (Cornu aspersum), first detected in 1855, the Sand Earwig (Labidura
riparia) in 1863; the Australian Bug (Icerya purchasi) in 1873 and the Codling
Moth (Cydia pomonella) in 1892. Subsequently, 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). This has been particularly
driven by the proliferation and broadening of international trade since the early
twentieth century (Faulkner et al. 2020, Chap. 12, Sect. 12.2.2) and more recently
by increasing rates of deliberate introduction of agents for the biological control
of plant and animal pest species (Annecke and Moran 1982; Hill et al. 2020,
Chap. 19).
190
C. Janion-Scheepers and C. L. Griffiths
Nxele 2012).
The total of 466 established alien terrestrial invertebrates recorded in
South Africa is certainly an underestimate of the number already present. There
are two primary reasons for this. Firstly, established alien species, some of which
may have been present in the region for decades, are regularly being discovered,
and more already-existing invasions will surely continue to be uncovered into the
future. One notable example is the six recently-recorded Australian insects found
associated with Eucalyptus trees by Bush et al. (2016). Many such suitable habitats
(e.g. the numerous species of non-commercial, ornamental plants in urban gardens)
still remain poorly explored, and are likely sites where existing alien terrestrial
invertebrates remain undetected. Secondly, there are many groups for which regional
taxonomic expertise is poor or entirely lacking, and these probably include many
more alien or invasive species than are currently recognised, highlighting the need
for improved foundational taxonomic knowledge in South Africa. This is especially
the case for many groups of soil fauna, which are inconspicuous and understudied
(Janion-Scheepers et al. 2016), but which can easily be introduced and distributed
accidentally through eggs in soil and are thus almost certainly under-reported in the
current lists.
7.3 Dates, Rates and Routes of Introduction
Although 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). Some of the earliest reported invasive invertebrates
in South Africa were two species of flea, first recorded during the 1700s (the
Human Flea Pulex irritans and the Chigoe Flea Tunga penetrans; Picker and
Griffiths 2011). Other early invasive invertebrates recorded include the European
Garden Snail (Cornu aspersum), first detected in 1855, the Sand Earwig (Labidura
riparia) in 1863; the Australian Bug (Icerya purchasi) in 1873 and the Codling
Moth (Cydia pomonella) in 1892. Subsequently, 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). This has been particularly
driven by the proliferation and broadening of international trade since the early
twentieth century (Faulkner et al. 2020, Chap. 12, Sect. 12.2.2) and more recently
by increasing rates of deliberate introduction of agents for the biological control
of plant and animal pest species (Annecke and Moran 1982; Hill et al. 2020,
Chap. 19).
190
C. Janion-Scheepers and C. L. Griffiths