Spatial and temporal variability across life's hierarchies in the terrestrial Antarctic

Abstract

Antarctica and its surrounding islands lie at one extreme of global variation in diversity. Typically, these regions are characterized as being species poor and having simple food webs. Here, we show that terrestrial systems in the region are nonetheless characterized by substantial spatial and temporal variations at virtually all of the levels of the genealogical and ecological hierarchies which have been thoroughly investigated. Spatial variation at the individual and population levels has been documented in a variety of genetic studies, and in mosses it appears that UV-B radiation might be responsible for within-clump mutagenesis. At the species level, modern molecular methods have revealed considerable endemism of the Antarctic biota, questioning ideas that small organisms are likely to be ubiquitous and the taxa to which they belong species poor. At the biogeographic level, much of the relatively small ice-free area of Antarctica remains unsurveyed making analyses difficult. Nonetheless, it is clear that a major biogeographic discontinuity separates the Antarctic Peninsula and continental Antarctica, here named the 'Gressitt Line'. Across the Southern Ocean islands, patterns are clearer, and energy availability is an important correlate of indigenous and exotic species richness, while human visitor numbers explain much of the variation in the latter too. Temporal variation at the individual level has much to do with phenotypic plasticity, and considerable lifehistory and physiological plasticity seems to be a characteristic of Antarctic terrestrial species. Environmental unpredictability is an important driver of this trait and has significantly influenced life histories across the region and probably throughout much of the temperate Southern Hemisphere. Rapid climate change-related alterations in the range and abundance of several Antarctic and subAntarctic populations have taken place over the past several decades. In many sub-Antarctic locations, these have been exacerbated by direct and indirect effects of invasive alien species. Interactions between climate change and invasion seem set to become one of the most significant conservation problems in the Antarctic. We conclude that despite the substantial body of work on the terrestrial biodiversity of the Antarctic, investigations of interactions between hierarchical levels remain scarce. Moreover, little of the available information is being integrated into terrestrial conservation planning, which lags far behind in this region by comparison with most others.

Microbiology of Eutrophic (Ornithogenic and Hydrocarbon-Contaminated) Soil

“…With mean annual temperatures ranging from 0 to -12°C and mean annual precipitation of 200-1,000 mm water equivalent (Balks et al 2013), these 'coastal oases' are exceedingly warm and wet in an Antarctic context. The biology of the Peninsula is also significantly different from that of the interior of the continent, as few invertebrate and plant species found here are shared with other regions of Antarctica (Chown and Convey 2007). The greater availability of water in coastal soils allows significant organic matter buildup, with nutrients generally not limiting plant growth (Balks et al 2013).…”

Geothermal activity helps life survive glacial cycles

“…This pattern of diversity is entirely unexpected for the continent. Past work has typically focused on species-energy or latitudinal gradient relationships, frequently noting that they break down for the continent or that local microclimatic conditions determine diversity patterns (42)(43)(44)(45)(46). Importantly, because the sample units used here have a 100-km radius around either geothermal or nongeothermal sites, the outcomes do not reflect the current effects of heated ground at the geothermal sites.…”

“…This separation was considered necessary because the distinction between biodiversity on the Antarctic Peninsula and biodiversity in continental areas has long been recognized (35,42). For broad "geothermal vs. nongeothermal" analyses (see below), data were also analyzed for both regions together, but for the "distance from nearest geothermal," models were only fitted on a regional basis because doing so was considered more appropriate to assess gradients.…”

Biological invasions in terrestrial Antarctica: what is the current status and can we respond?

“…Even within the McMurdo Dry Valleys of southern Victoria Land, by far the most extensive area of ice-free ground within the continent, studies of microbial and arthropod communities report signals of isolation and divergence within valleys and catchments (McGaughran et al 2008(McGaughran et al , 2010Chan et al 2013). Isolation, high levels of endemism and a general lack of inter-species competition within many native terrestrial Antarctic communities may make them particularly vulnerable to the impacts of invasive species (Chown and Convey 2007;.…”

“…Broady and Weinstein 1998;Hodgson et al 2010). The majority of areas of exposed terrestrial ground are isolated, small and island-like (Bergstrom and Chown 1999;Arnold et al 2003;Hughes et al 2006), factors that are important in driving the evolutionary isolation, divergence and high levels of regional endemism that appear to characterise Antarctic biota (Chown and Convey 2007;Pugh and Convey 2008). Even within the McMurdo Dry Valleys of southern Victoria Land, by far the most extensive area of ice-free ground within the continent, studies of microbial and arthropod communities report signals of isolation and divergence within valleys and catchments (McGaughran et al 2008(McGaughran et al , 2010Chan et al 2013).…”