1. Context

1. The French Polar Institute in Antarctic and subantarctic islands

Within the latitudinal belt 45-54°S, the Southern Ocean contains a number of dots of land, almost all of which are volcanic in origin. These subantarctic islands are remote, and host low plant and invertebrate diversities. These fascinating islands are characterized by impoverished terrestrial ecosystems with highly reduced or absent functional redundancy.

2. Program IPEV 136 'Subanteco'

3. Scientific context (Program IPEV 136 'Subanteco')

Subantarctic islands have much reduced floral and invertebrate diversity and typically do not include many taxonomic and functional groups familiar from lower latitudes. Their native terrestrial faunas comprise primarily arthropods (mites, springtails, spiders, beetles, flies and moths), tardigrades, nematodes, rotifers, enchytraeids, earthworms and molluscs. There are no large invertebrate predators, and, originally, predation represented an insignificant ecological pressure on indigenous communities. While detritivores appear to numerically dominate these invertebrate communities, decay processes are slow. There are no native land mammals, reptiles or amphibians on French subantarctic islands, and only two non-marine birds. ‘Megaherbs’, often endemic to particular subantarctic islands, are a dominant feature of many plants communities, whose evolution is linked with the absence of native vertebrate herbivores. The number of native flowering plants is 17 at Ile de la Possession (147 km²) in Archipel Crozet (about 355 km² in total), 22 at Iles Kerguelen (7200 km²) (Van der Putten et al. 2010), 17 at Ile Amsterdam (55 km²) including the tree Phylica arborea, and 10 at Ile Saint-Paul (7 km²).

The physical remoteness and climatic constraints of the French subantarctic islands (Archipel Crozet, Iles Kerguelen, Iles Amsterdam and Saint-Paul Amsterdam have long hindered human visitations. Since the recent establishment of permanent stations in the mid XXth century (1950 at Amsterdam, 1951 at Iles Kerguelen, 1964 at Crozet), the number of visiting ships and visitors landing significantly increased. There resulted in an increase in the number of introduced plant species (cultivated species non-included), which is very similar at Archipel Crozet (59), at Iles Kerguelen (69), and at Ile Amsterdam (56) according to the last published reviews (Frenot et al. 2001; 2005). Comparatively to the plants, the number of invasive invertebrates is lower (from 15 to 30 depending on the island). For the mammals, nine species were deliberately or inadvertently introduced at the French southern islands (Chapuis et al. 1994), and established wild populations.

Alien species have mainly been introduced to the Kerguelen Islands by ship, with most introductions occurring at the research station. In addition, these islands are not situated along major commerce routes, are inhabited by a limited number of people each year (at most 100), do not have any industry and have very limited means of terrestrial transportation that would facilitate quick and regular exchanges between geographically distant points for an alien species (Lebouvier et al. 2011). As a result, it is reasonably straightforward to detect the arrival and establishment of alien species, and monitor consequences on species interactions.

In this context, our main goals are to: 1/ complement our knowledge of the native subantarctic biodiversity, 2/ provide a picture of ecosystem modification over the past 40 years under both invasion and climate change pressures, 3/ unravel key characteristics of successful invaders (plasticity, genetics selection, unsaturated ecosystems) and, using a food web approach, achieving a better functional understanding of the impact of alien species within unsaturated ecosystems, 4/ predict the future dynamics of invasion, and mitigate their impacts.

References:

Chapuis J-L, Bousses P, Barnaud G (1994). Alien mammals, impact and management in the French Subantarctic Islands. Biol. Conserv 67, 97-104.

Frenot Y, Gloaguen JC, Massé L, Lebouvier M (2001) Human activities, ecosystem disturbance and plant invasions in sub—Antarctic Crozet, Kerguelen and Amsterdam Islands. Biol Conserv 101, 33–50.

Frenot Y, Chown SL, Whinam J, Selkirk PM, Convey P, Skotnicki M, Bergstrom DM (2005) Biological invasions in the Antarctic: extent, impacts and implications. Biol Rev 80, 45–72.

Lebouvier M, Laparie M, Hullé M, Marais A, Cozic Y, Lalouette L, Vernon P, Candresse T, Frenot Y, Renault D (2011) The significance of the sub-Antarctic Kerguelen Islands for the assessment of the vulnerability of native communities to climate change, alien insect invasions and plant viruses. Biol Invasions 13, 1195-1208.