years, an additional resupply voyage was required to supply the base). While visits to
Prince Edward Island are permitted only every 4 years (Department of Environmental Affairs Directorate: Antarctica and Islands 2010), more than 4 years may pass
without a visit.
The new base, and the new research and supply vessel, the S.A. Agulhas II
(completed in 2012), house more people than did the old base and research vessel.
Therefore, the numbers of people that arrive at, and overwinter on, the island
annually has increased, which is likely to increase the opportunities for the introduction of new species (McGeoch et al. 2015).
Improved policy brought about by better awareness of the problem of invasions
has resulted in lowered rates of introduction of terrestrial species to the islands,
especially to the more frequently visited and inhabited Marion Island (Greve et al.
2017), and the eradication of some invasive species (Cooper et al. 1992; Bester et al.
2002), with efforts for the eradication of four localised alien plant species ongoing
(DEA: Natural Resources Management Programme et al. 2012). However, despite
strict biosecurity regulations, which include, amongst others, no tourism, a ban on
fresh food or other biological material such as untreated wood, regulated checks on
field equipment and containers, and the disinfection of footwear (Department of
Environmental Affairs Directorate: Antarctica and Islands 2010), the success of
these policies depend on awareness, buy-in and cooperation from the community
that travels to the islands, and the effectiveness of policy implementation (McGeoch
et al. 2015).
It has long been suggested that climate change will exacerbate the extent and
impact of biological invasions (Dukes and Mooney 1999; Walther et al. 2002;
Daehler 2003). This is also evident on the PEIs, where rapid climate change has
been shown to benefit a number of invasive terrestrial taxa, including M. musculus,
which have shown range expansions and increases in density over the past 20 years
(McClelland et al. 2018), and several alien plant species, which have expanded their
ranges up altitudinal slopes (Chown et al. 2012; le Roux et al. 2013a).
There is also evidence that climate change may benefit invaders into the future,
often more so than native species. Physiological experiments on invertebrates such
as springtails have shown that, for certain thermal traits, invasive alien species have
higher phenotypic plasticity than the native species (Chown et al. 2007; Slabber et al.
2007; Janion et al. 2010). Also, invasive species survive longer under drier conditions when acclimated at warmer temperatures, whilst native species do not. Manipulative field experiments corroborate these findings: the abundance of alien species
is higher under drier, warmer conditions (McGeoch et al. 2006). This could result in
the displacement of native species by the abundant invasive species (Terauds et al.
2011), although the impacts on functional roles remains poorly understood. Finally,
an increase in the frequency of low temperature events due to an increase in freezethaw cycles as a result of less snow and more clear-sky nights (Smith and Steenkamp
1990), are expected to alter the abundances and distribution of invertebrates species
(Chown and Froneman 2008); this could indirectly affect assemblage-level function
(Janion et al. 2009).
For plants, trait studies indicate that the leaves of invasive species on Marion
Island have poorer defence mechanisms (including lower frost tolerance) than native
218
M. Greve et al.
Prince Edward Island are permitted only every 4 years (Department of Environmental Affairs Directorate: Antarctica and Islands 2010), more than 4 years may pass
without a visit.
The new base, and the new research and supply vessel, the S.A. Agulhas II
(completed in 2012), house more people than did the old base and research vessel.
Therefore, the numbers of people that arrive at, and overwinter on, the island
annually has increased, which is likely to increase the opportunities for the introduction of new species (McGeoch et al. 2015).
Improved policy brought about by better awareness of the problem of invasions
has resulted in lowered rates of introduction of terrestrial species to the islands,
especially to the more frequently visited and inhabited Marion Island (Greve et al.
2017), and the eradication of some invasive species (Cooper et al. 1992; Bester et al.
2002), with efforts for the eradication of four localised alien plant species ongoing
(DEA: Natural Resources Management Programme et al. 2012). However, despite
strict biosecurity regulations, which include, amongst others, no tourism, a ban on
fresh food or other biological material such as untreated wood, regulated checks on
field equipment and containers, and the disinfection of footwear (Department of
Environmental Affairs Directorate: Antarctica and Islands 2010), the success of
these policies depend on awareness, buy-in and cooperation from the community
that travels to the islands, and the effectiveness of policy implementation (McGeoch
et al. 2015).
It has long been suggested that climate change will exacerbate the extent and
impact of biological invasions (Dukes and Mooney 1999; Walther et al. 2002;
Daehler 2003). This is also evident on the PEIs, where rapid climate change has
been shown to benefit a number of invasive terrestrial taxa, including M. musculus,
which have shown range expansions and increases in density over the past 20 years
(McClelland et al. 2018), and several alien plant species, which have expanded their
ranges up altitudinal slopes (Chown et al. 2012; le Roux et al. 2013a).
There is also evidence that climate change may benefit invaders into the future,
often more so than native species. Physiological experiments on invertebrates such
as springtails have shown that, for certain thermal traits, invasive alien species have
higher phenotypic plasticity than the native species (Chown et al. 2007; Slabber et al.
2007; Janion et al. 2010). Also, invasive species survive longer under drier conditions when acclimated at warmer temperatures, whilst native species do not. Manipulative field experiments corroborate these findings: the abundance of alien species
is higher under drier, warmer conditions (McGeoch et al. 2006). This could result in
the displacement of native species by the abundant invasive species (Terauds et al.
2011), although the impacts on functional roles remains poorly understood. Finally,
an increase in the frequency of low temperature events due to an increase in freezethaw cycles as a result of less snow and more clear-sky nights (Smith and Steenkamp
1990), are expected to alter the abundances and distribution of invertebrates species
(Chown and Froneman 2008); this could indirectly affect assemblage-level function
(Janion et al. 2009).
For plants, trait studies indicate that the leaves of invasive species on Marion
Island have poorer defence mechanisms (including lower frost tolerance) than native
218
M. Greve et al.