Genetic diversity, mutagenesis and dispersal of Antarctic mosses – a review of progress with molecular studies

Abstract

In investigating the extent of genetic diversity in Antarctic mosses the RAPD technique has proven especially useN in demonstrating that these mosses exhibit extensive genetic variation (levels being similar to those in temperate regions), and that within-colony variation is apparently caused not only by immigration and establishment of propagules from elsewhere, but also by mutagenesis. Dispersal of these mosses can also be followed using the RAPD technique; both short-distance dlspersal by wind or water (depending on the moss species) and longer distance dispersal by wind across the ice cap has been demonstrated. Relationships with temperate mosses of the same species are being investigated to determine the origins of Antarctic populations. Genetic technology is also facilitating the taxonomic identification of moss specimens which cannot be identified morphologically due to phenotypic plasticity in Antarctica. Together, these genetic studies are starting to provide information of fundamental scientific importance for understanding the evolution, origins and dispersal mechanisms of Antarctic mosses, and their response to climate change.

Genetic variation of mtCOII gene sequences in the collembolan Isotoma klovstadi from Victoria Land, Antarctica: evidence for population differentiation

“…Genetic drift should cause ®xation of alleles and, therefore, a reduction of genetic variability (Futuyma 1998), but the clonal mode of transmission of mitochondrial DNA may counteract this reduction of variability. However, increased mutation rates, due to the higher levels of UV-B radiation detected in Antarctica (Kennedy 1995;Skotnicki et al 2000), may explain higher levels of variability. If we assume that gene¯ow is extremely reduced, then the highest heterogeneity of the populations of Daniell Peninsula and Football Saddle may be explained by the original presence of a higher number of haplotypes which have survived after the interruption of gene¯ow.…”

“…For these reasons, Antarctic Collembola represent a suitable model organism to study the evolution of barriers to gene¯ow as a consequence of geographic isolation, and the role that the establishment of genetic dierentiation plays in microspeciation processes (Nei et al 1983). The importance of Antarctic fauna and¯ora in evolutionary studies has been recognised at an international level (Eastman 2000), but studies involving genetic variability and dierentiation of Antarctic species have so far concentrated mainly on marine organisms (Fevolden and Schneppenheim 1989;Brierley and Thorpe 1994;Yokawa 1994;Duhamel et al 1995;Bargelloni et al 2000), nematodes (Courtright et al 2000) and mosses (reviewed in Skotnicki et al 2000), with very little attention dedicated to soil microarthropods (Frati and Carapelli 1999). Ganey (2000) and Medlin et al (2000) reviewed the variety of biochemical and molecular markers that can be used to study population genetics, and how they have provided interesting insights into the structure and evolution of Antarctic species.…”

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

“…In plants, the most extensive spatial work has concerned individual-and population-level genetic variations of mosses, typically from Victoria Land and mostly using random-amplified polymorphic DNA (RAPD; reviewed by Skotnicki et al 2000), which is not without methodological problems (Rogers 2007). In several species, substantial variation occurs within clumps, such that although paired shoots are typically (though not always) identical, the distance between shoots increases with the decrease in relatedness (Selkirk et al 1998;Skotnicki et al 1998aSkotnicki et al ,b, 1999aSkotnicki et al ,b, 2002Skotnicki et al , 2004Dale et al 1999).…”

“…The population-level analyses have also led these authors to suggest that long-distance dispersal is not uncommon, though the very fact that long-distance migrants can be detected suggests that the events might be rare (Rogers 2007). Wind is reputedly the primary agent responsible for dispersal over significant distances (Skotnicki et al 1998b(Skotnicki et al , 2001, while overland water flow during periods of elevated temperatures, when melt water is available, is responsible for local dispersal (Skotnicki et al 2000).…”

Evidence of morphometric differentiation among Antarctic moss populations as a response to local microenvironment

“…In the Antarctic Continent, the harsh climatic conditions include air temperatures below freezing, strong winds, light varying from total darkness to total sunlight and little amount of free water. These conditions are a challenge for Antarctic live forms and the phenotypic plasticity exhibited by bryophytes may represent an alternative strategy over genetic differentiation to enable growth in such a range of environments (Skotnicki et al 2000;Buryová & Shaw 2005).…”