however, take many forms and may ultimately be recognised as being the most
significant impacts of many alien terrestrial invertebrates. Here we illustrate the
diversity and complexity of ecosystem effects that can occur by profiling six important regional alien terrestrial invertebrates: the Varroa Mite (Box 7.1), the Acacia Gall
Wasp (Box 7.2), the White Garden Snail (Box 7.3), the Harlequin Lady Beetle (Box
7.4), the European Wasp (Box 7.5) and the Argentine Ant (Box 7.6).
7.6 Risk Assessment
Several traits associated with alien terrestrial invertebrates can be used to make
informative decisions or risk assessments regarding preventing, detecting, controlling or managing invertebrate introductions (Kumschick et al. 2016). Important
features include life-history traits, such as those related to reproduction
(e.g. sexual or parthenogenetic, number of eggs produced), overwintering strategy,
dispersal, and thermal tolerance. Several physiological studies using Collembola
(springtails) as model organisms have indicated that invasive species are generally
more tolerant of warmer, drier conditions than native species (Chown et al. 2007;
Slabber et al. 2007; Janion et al. 2010; Janion-Scheepers et al. 2018). Research on
the importance of physiological traits on the invasiveness of invertebrates include
studies on the phenotypic plasticity and local adaptation of Drosophila (Gibert et al.
2016) and Ceratitis flies (Nyamukondiwa et al. 2013; Weldon et al. 2018). Understanding these traits may shed some light on how to better manage or prevent the
introduction of invasive species (Karsten et al. 2016), especially pest species, which
are predicted to change in distribution with climate change (Bebber et al. 2013; Pecl
et al. 2017). In the case of the dominant South African invasive invertebrate groups,
such as the Hemiptera and Coleoptera, some of these traits may also be important,
but data on ‘invasiveness’ traits in these groups are lacking.
7.7 Conclusion and Research Gaps
The ecological impacts of most alien terrestrial invertebrates in South Africa are
poorly known, even for those within taxonomically well-known groups. Indeed, a
recent survey of all soil biota suggested that for most groups of soil invertebrates in
South Africa, the impact of introduced species on the local biota and ecosystem
functioning remain unknown (Janion-Scheepers et al. 2016). 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. This group is taxonomically well known, and a useful
key exists to distinguish between South African and introduced earthworm species
(Plisko and Nxele 2015).
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C. Janion-Scheepers and C. L. Griffiths
significant impacts of many alien terrestrial invertebrates. Here we illustrate the
diversity and complexity of ecosystem effects that can occur by profiling six important regional alien terrestrial invertebrates: the Varroa Mite (Box 7.1), the Acacia Gall
Wasp (Box 7.2), the White Garden Snail (Box 7.3), the Harlequin Lady Beetle (Box
7.4), the European Wasp (Box 7.5) and the Argentine Ant (Box 7.6).
7.6 Risk Assessment
Several traits associated with alien terrestrial invertebrates can be used to make
informative decisions or risk assessments regarding preventing, detecting, controlling or managing invertebrate introductions (Kumschick et al. 2016). Important
features include life-history traits, such as those related to reproduction
(e.g. sexual or parthenogenetic, number of eggs produced), overwintering strategy,
dispersal, and thermal tolerance. Several physiological studies using Collembola
(springtails) as model organisms have indicated that invasive species are generally
more tolerant of warmer, drier conditions than native species (Chown et al. 2007;
Slabber et al. 2007; Janion et al. 2010; Janion-Scheepers et al. 2018). Research on
the importance of physiological traits on the invasiveness of invertebrates include
studies on the phenotypic plasticity and local adaptation of Drosophila (Gibert et al.
2016) and Ceratitis flies (Nyamukondiwa et al. 2013; Weldon et al. 2018). Understanding these traits may shed some light on how to better manage or prevent the
introduction of invasive species (Karsten et al. 2016), especially pest species, which
are predicted to change in distribution with climate change (Bebber et al. 2013; Pecl
et al. 2017). In the case of the dominant South African invasive invertebrate groups,
such as the Hemiptera and Coleoptera, some of these traits may also be important,
but data on ‘invasiveness’ traits in these groups are lacking.
7.7 Conclusion and Research Gaps
The ecological impacts of most alien terrestrial invertebrates in South Africa are
poorly known, even for those within taxonomically well-known groups. Indeed, a
recent survey of all soil biota suggested that for most groups of soil invertebrates in
South Africa, the impact of introduced species on the local biota and ecosystem
functioning remain unknown (Janion-Scheepers et al. 2016). 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. This group is taxonomically well known, and a useful
key exists to distinguish between South African and introduced earthworm species
(Plisko and Nxele 2015).
200
C. Janion-Scheepers and C. L. Griffiths