Biogeography

Biogeography is the science that describes and aims to predict species distribution patterns. For Antarctic terrestrial biology there are clear declines in species richness from northern regions to southern colder ones. However, there is large variation across regional and local scales, so scale matters when interpreting species patterns.

Continental

under construction

Regional

Antarctic ice free regions are separated by extensive glaciers or ocean, which makes it hard for small invertebrates like springtails and mites to cross from one region to another. Mosses, lichens and algae can be dispersed by wind across seawater and glaciers and establish on new locations.

Antarctic terrestrial habitats are surrounded by glaciers and ocean, making it hard for organisms to migrate to other regions

Mountain peaks surrounded by glaciers are island refuges for terrestrial biota.

Antarctic terrestrial habitats are surrounded by glaciers and ocean, making it hard for organisms to migrate to other regions

Local

At a local scale (m - km) species patterns are primarily driven by water and nutrient availability. Water is scarce in Antarctica as most of it is locked in ice, and therefore, inaccessible for use by plants and animals. Most plant life in Antarctica can be found thriving near melt streams and snow fields, especially mosses often depend on such water sources for survival and growth and therefore grow nearby readily available water sources. Lichens are more hardy and often relay on humidity in the air. Nevertheless, lichens do not grow everywhere, as some species are vulnerable to snow cover and avoid growing in areas with a thick winter snow pack. Other lichens thrive on bare rock but are easily out-competed by taller lichens.

Moss communities thrive where there is frequent or persistent water available.

Terrestrial algae (Prasiola crispa) can lie dormant for long periods and is quickly re-activated when liquid water becomes available.

Moss communities can be very small. Much of Antarctic vegetation consists of very many tiny patches of moss and lichen communities

Lichen fell-fields support extensive fields of various lichen species. Mostly on dry and wind exposed habitats

Terrestrial algae (Prasiola crispa) can form extensive fields under the right conditions, but can quickly disappear under dry and windy conditions

Landscape filled with moss communities (Byers Peninsula - Livingston Island)

Species interactions

Terrestrial animals are dependent on the plant life for food, but plants also provide shelter against harsh weather conditions. Mosses typically grow in wet places, but can also retain a lot of water for long periods, so any animal that is vulnerable to drought will benefit from living within a moss habitat. Springtails typically thrive very well among mosses and can reach densities of up to 1 million individuals per square meter of moss. Similarly, the algal mats crated by Prasiola crispa can support high numbers of springtails due to the microclimate but also because the algal mat is used as a food source by springtails.

The mites living in Antarctica have a thick outer shell and are well suited to cope with dry conditions. This is probably one of the reasons why they thrive well among lichen fell fields, where they consumer algae, lichens or prey upon other animals.

Not all Antarctic terrestrial animals are associated with plant life and instead are more often found underneath rocks, where they find shelter against dehydration, frost and UV light. They most likely feed on microbial mats or algal growth at the rock edge.

Nutrients

Antarctic vegetation is highly enriched in nutrients nearby penguin colonies but not all species thrive under such severe nutrient loadings and moss and lichen diversity and biomass peaks at some distance from bird and seal aggregations. The nutrient enrichment of the mosses and lichens also affects the associated animals with higher species numbers and abundance, as they provide a more nutritious food source, compared to areas outside the influence of penguins and seals. Penguins and seals are an important nutrient factor from the sea to land and create biodiversity hotspots of terrestrial biota.

Springtail and mite abundance and species richness is enhanced by the nutrient input from penguins and elephant seals

Most lichens and mosses cannot thrive near penguin colonies due to high nitrogen loading, but orange coloured lichens like Xanthoria benefit from the additional nutrients.

Want to know more...

A selection of resources on Antarctic Biogeography

Convey, P., Chown, S. L., Clarke, A., Barnes, D. K. A., Bokhorst, S., Cummings, V., Ducklow, H. W., Frati, F., Green, T. G. A., Gordon, S., Griffiths, H. J., Howard-Williams, C., Huiskes, A. H. L., Laybourn-Parry, J., Lyons, W. B., McMinn, A., Morley, S. A., Peck, L. S., Quesada, A., Robinson, S. A., Schiaparelli, S. and Wall, D. H. 2014. The spatial structure of Antarctic biodiversity. Ecological Monographs, 84, 203-244.

Convey, P. and Biersma, E. M. (2024). Antarctic Ecosystems. Encyclopedia of Biodiversity S. S.M. Oxford, Elsevier. 1: 133-148.

Bokhorst, S., Convey, P. and Aerts, R. 2019. Nitrogen inputs by marine vertebrates drive abundance and richness in Antarctic terrestrial ecosystems. Current Biology, 29, 1721-1727.

Many of the above documents are freely available from the publisher websites, but if not, please feel free to reach out to the authors for a copy