Terrestrial biota of the Antarctic
- This page is part of the topic Biota of the Antarctic
Looked at from the perspective of the terrestrial and freshwater biologists and biogeographers, the various bits of land are subdivided for the purposes of this volume into three zones - the ‘continental Antarctic’ (comprising most of the continent), the ‘maritime Antarctic’ (comprising the Antarctic Peninsula and associated islands and archipelagos as well as the South Shetland, South Orkney, and South Sandwich Islands, and Bouvetøya), and the ‘sub-Antarctic’ (those islands that lie in or around the Antarctic Polar Frontal Zone (PFZ).
Levels of terrestrial macro-biodiversity in the Antarctic are strikingly lower than those of the Arctic, although the sub-Antarctic hosts greater diversity than the maritime and continental regions. This is the case even relative to the superficially environmentally extreme and isolated High Arctic Svalbard and Franz Josef archipelagos at around 80°N. In comparison with about 900 species of vascular (higher or flowering) plants in the Arctic, there are only two on the Antarctic continent and up to 40 on any single sub-Antarctic island. Likewise, the Antarctic and sub-Antarctic have no native land mammals, against 48 species in the Arctic. The continuous southwards continental connection of much of the Arctic is an important factor underlying these differences. Despite the apparent ease of access to much of the Arctic, few established alien vascular plants or invertebrates are known from locations such as Svalbard (Rønning, 1996; Coulson 2007), in comparison with the 200 species introduced to the sub-Antarctic by human activity over only the last two centuries or so (Frenot et al., 2005, 2008). It may be the case that species comparable to the many sub-Antarctic ‘aliens’, being cosmopolitan northern hemisphere and boreal ‘weeds’, have had greater opportunity to reach polar latitudes by natural means in the north than the south.
Antarctic and sub-Antarctic floras and faunas are strongly disharmonic, with representatives of many major taxonomic and functional groups familiar from lower latitudes being absent. Sub-Antarctic plant communities do not include woody plants, and are dominated by herbs, graminoids and cushion plants; flowering plants (phanerogams) are barely represented (two species) in the maritime and not at all in the continental Antarctic. Sub-Antarctic floras have developed some particularly unusual elements – ‘megaherbs are a striking element of the flora of many islands, being an important structuring force within habitats, and a major contributor of biomass (Meurk et al., 1994a,b; Mitchell et al., 1999; Fell, 2002; Shaw, 2005; Convey et al., 2006a). These plants present an unusual combination of morphological and life history characteristics (Convey et al., 2006a), and their dominance on sub-Antarctic islands is thought to have been encouraged by a combination of the absence of natural vertebrate herbivores (Meurk et al., 1994a; Mitchell et al., 1999), and possessing adaptive benefits relating to the harvesting and focussing of low light levels and aerosol nutrients (Wardle, 1991; Meurk et al., 1994b). The recent anthropogenic introduction of vertebrate herbivores to most sub-Antarctic islands has led to considerable and negative impacts on megaherb-based communities (Frenot et al., 2005; Shaw et al., 2005; Convey et al., 2006b).
The tables below provide summary information on terrestrial biodiversity in the Antarctic.
|Zone||Flowering plants||Ferns and
Table 1.1 Biodiversity of plant taxa in the three Antarctic biogeographical zones. Note that figures presented are approximate, as it is likely that (i) new species records will be obtained through more directed sampling, (ii) a significant number of unrecognized synonymies are likely to exist and (iii) taxonomic knowledge of some Antarctic groups is incomplete.
|Group||Sub-Antarctic||Maritime Antarctic||Continental Antarctic and|
|Rotifera *||> 59||> 50||13|
|Nematoda *||> 22||28||14|
Table 1.2 Biodiversity of native terrestrial invertebrates in the three Antarctic biogeographical zones. Data obtained from Block, in Laws (1984), Pugh (1993), Pugh and Scott (2002), Pugh et al. (2002), Convey and McInnes (2005), Dartnall (2005), Dartnall et al. (2005), Greenslade (2006), Maslen and Convey (2006). ND - number of representatives of group unknown; * - large changes likely with future research due to current lack of sampling coverage, expertise and/or synonymy.
Representing the animal kingdom, across the Antarctic and sub-Antarctic there are no native land mammals, reptiles or amphibians and very few non-marine birds. Instead, terrestrial faunas are dominated by arthropods, including various insects, arachnids, the microarthropod groups of mites and springtails, enchytraeids, earthworms, tardigrades, nematodes, beetles, flies and moths, with smaller representation of some other insect groups (Gressitt, 1970; Convey, 2007a). Although levels of species diversity are low relative to temperate communities, population densities are often comparable, with tens to hundreds of thousands of individuals per square metre. Few of these invertebrates are thought to be true herbivores, and the decomposition cycle is thought to dominate most terrestrial ecosystems, even in the sub-Antarctic, with the exception of some beetles and moths, although detailed autecological studies are typically lacking (Hogg et al., 2006). However, despite the preponderance of detritivores, decay processes are slow. Carnivores are also present (spiders, beetles on the sub-Antarctic islands, along with predatory microarthropods and other microscopic groups throughout), but predation levels are generally thought to be insignificant (Convey 1996a).
Although microbial biodiversity is dominant in most Antarctic terrestrial and freshwater systems, these communities are generally considered to be relatively simple, with a limited trophic structure (Hogg et al., 2006). Furthermore, only a relatively small proportion, 0.33% (Fox and Cooper, 1994) of the continent’s surface area is ice-free and available for terrestrial biota.
Terrestrial microbial diversity has been explored, although not extensively enough. Data are available particularly from the McMurdo Dry Valleys (Priscu et al., 1998; Gordon et al., 2000; Shravage et al., 2007; Babalola et al., 2009) and endolithic communities (de la Torre et al., 2003; de los Rios et al., 2007), the Pridz Bay area (Smith M. et al., 2000; Taton et al., 2006) and also from the Antarctic Peninsula (Hughes and Lawley, 2003). Terrestrial dark crusts are found throughout Antarctica and are commonly dominated by cyanobacteria (Broady, 1996; Mataloni and Tell, 2002; Adams et al., 2006). Freshwater systems have been sampled in studies of benthic habitats in continental Antarctic lakes (Bowman et al., 2000; Brambilla et al., 2001; Sabbe et al., 2004; Taton et al., 2003, 2006; Van Trappen et al., 2002, 2004, 2005). These studies have revealed a considerable amount of new biodiversity, concerning various eubacterial phyla including cyanobacteria. The diversity and function of the microbial lake communities have been reviewed by Ellis-Evans (1996). Molecular genetic tools allow specialist habitats such as hot mineral soils (Soo et al., 2009), cryoconites (Christner et al., 2003) and droppings of the Adélie penguins (Banks et al., 2009) to be studied in detail. Application of these tools to a diverse range of samples from across Antarctica should reveal more diversity and provide insights into distribution patterns, the forces that drive them, the presence and extent of endemism, and the impact of global change.
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