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1 Previous studies of Antarctic clonal moss populations using RAPD markers have reported extraordinarily high levels of genetic variation. This has been claimed to reflect somatic mutation, possibly resulting from elevated UV-B radiation. 2 Our study used microsatellite markers to compare the genetic variation present within continental Antarctic,...
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... contrast to published expectations however we found little evidence of clonality in any of our samples. The ratio of G O to G E was close to unity for most populations except those from the Southern Ocean islands, which had significantly lower estimates of G O :G E than all other regions (F 4,18 =5.1048, P=0.0063, Fig. 3). Multilocus genotype frequencies were never significantly different to values expected under conditions of sexual reproduction and random mating, except for a single population from the Southern Ocean islands (Île Guillou, P<0.01). We also estimated multilocus genotypic diversity for all samples within each region to increase the ...
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... The lowest ITS haplotypic diversity within B. argenteum worldwide was observed in Antarctica, as in the cosmopolitan moss Ceratodon purpureus Hedw (Brid.) (Clarke et al. 2008. Although the hypothesis of lower mutation rates in Antarctic B. argenteum populations cannot be ruled out (Hills et al. 2010), such a low regional genetic diversity can also be interpreted in terms of the sterile condition of B. argenteum in Antarctica (Ochyra et al. 2008), either due to the regional absence of one of the sexes in this dioicous species, and/or inhibition of sex expression due to prevailing cold and dry conditions (Longton 1988). ...
Since the onset of glaciation following the Oligocene (30–28 Ma), the prevalence of increasingly cold conditions has shaped the evolution of the Antarctic biota. Two hypotheses, postglacial recruitment from extra-regional locations and in situ persistence, have been proposed to explain the biogeography of the contemporary species-poor terrestrial Antarctic biota. Bryophytes, which form a major group of the Antarctic flora, exhibit a strong, inherent ability to survive cold conditions but also have high long-distance dispersal capacities, which are compatible with both hypotheses. Here, we test these hypotheses by means of population genetic and phylogeographic analyses of the cosmopolitan moss Bryum argenteum. We find evidence for at least three independent colonisation events of the species in Antarctica. Ancestral area reconstruction coupled with molecular dating suggests colonisation times of the different Antarctic clades ranging from four million years for the oldest lineage to half a million years for the youngest lineage. This suggests multiple colonisation events of Antarctica by this species during several glacial cycles within the Pleistocene, Pliocene and possibly late Miocene. This is the first study to demonstrate in situ persistence of bryophytes in Antarctica throughout previous glaciations.
... Mosses have been the subject of several genetic studies in the Antarctic and sub-Antarctic. These studies have been based on haplotype frequencies of allozymes (the dominant vegetative stage of mosses is haploid; e.g., Adam et al., 1997;Selkirk et al., 1997), random amplified polymorphic DNA markers (RAPDs; e.g., Seppelt et al., 1996;Adam et al., 1997;Skotnicki et al., 1997Skotnicki et al., , 1998aSkotnicki et al., , b, 1999Skotnicki et al., , 2000Skotnicki et al., , 2001Skotnicki et al., , 2002Skotnicki et al., , 2004Selkirk et al., 1997Selkirk et al., , 1998, DNA sequencing, particularly of the internal transcribed spacer regions (ITS1 and ITS2) of the nuclear rRNA encoding multigene family (e.g., Skotnicki et al., 2002Skotnicki et al., , 2004Skotnicki et al., , 2005, and by genotyping of microsatellites (Clarke et al., 2008. Some of these studies have not sampled large numbers of individual moss colonies across study sites, and RAPD analyses have been criticized generally for experimental artefacts, lack of reproducibility and the fact that the inheritance of loci is unknown (e.g., Hadrys et al., 1992;Grosberg et al., 1996). ...
... Despite the concerns noted above, RAPD data do reveal marked geographic association of clusters of related sequences at a range of spatial scales from the intercontinental to hundreds of kilometres within Antarctica (Skotnicki et al., 1998a(Skotnicki et al., , 2004. This is consistent with microsatellite Seppelt et al.,1996Seppelt et al., (1999; Skotnicki et al.,1997;1999;Selkirk et al.,1998 data for Ceratodon purpureus, where significant genetic differentiation has been detected amongst populations globally, and particularly between populations located on Southern Ocean Islands or within the maritime Antarctic (Clarke et al., 2008). These populations are separated by up to 2000 km and presumably dispersal is restricted by large distances of unsuitable habitat or ocean separating them. ...
... Likewise, Sarconeurum glaciale demonstrated limited genetic differentiation between populations with up to 75 km separation . These studies appear to be more consistent with studies based on microsatellite genotyping of Ceratodon purpureum in Windmill Islands, East Antarctica, where although overall genetic variance amongst populations in this region is high (20%; Clarke et al., 2008), suggesting that dispersal is restricted, the existence of common genotypes across sites separated by up to 15 km are evidence that occasional long-distance dispersal takes place . Genetic variation in Antarctic populations of Ceratodon purpureus on Windmill Islands, based on microsatellite genotyping, was lower than in populations from non-polar locations. ...
... This within-clump variation has been suggested to be equal to or higher than that of sexually reproducing species, and has been attributed to high rates of somatic mutation possibly related to UV-B exposure (Skotnicki et al., 2000(Skotnicki et al., , 2002. However, a number of recent studies have failed to support this interpretation (see Robinson et al., 2003;Rogers, 2007;Stevens et al., 2007;Clarke et al., 2008). If real, such a source of genetic variation would be important, as most mosses on the Antarctic continent reproduce vegetatively -sporophyte maturation is rare, but not absent, and increases northwards along the Peninsula and to the sub-Antarctic (Smith & Convey, 2002). ...
... Patterns of variation in mosses also suggest substantially different colonization histories, with some sites showing evidence of multiple colonization events and little subsequent spread, and others indicating a single colonization and either substantial subsequent spread or pronounced antiquity of the population (e.g., Selkirk et al., 1997;Clarke et al., 2008). However, the very fact that long-distance migrants can be detected suggests that the events might be rare (Rogers, 2007). ...
IntroductionVariation across spaceVariation through timeConclusions and implicationsAcknowledgmentsReferences
... If effective, this process should apply to all loci in a similar manner and may have contributed to the general trend across all loci. However, microsatellites are polymorphic due to slippage mutation of the DNA polymerase and UV radiation seems not necessarily to affect this process [39,40]. Second, human disturbance is much stronger at lower elevations. ...
The distribution of genetic diversity among plant populations growing along elevational gradients can be affected by neutral as well as selective processes. Molecular markers used to study these patterns usually target neutral processes only, but may also be affected by selection. In this study, the effects of elevation and successional stage on genetic diversity of a dominant tree species were investigated controlling for neutrality of the microsatellite loci used.
Diversity and differentiation among 24 populations of Castanopsis eyrei from different elevations (251-920 m) and successional stages were analysed by eight microsatellite loci. We found that one of the loci (Ccu97H18) strongly deviated from a neutral model of differentiation among populations due to either divergent selection or hitchhiking with an unknown selected locus. The analysis showed that C. eyrei populations had a high level of genetic diversity within populations (A(R) = 7.6, H(E) = 0.82). Genetic variation increased with elevation for both the putatively selected locus Ccu97H18 and the neutral loci. At locus Ccu97H18 one allele was dominant at low elevations, which was replaced at higher elevations by an increasing number of other alleles. The level of genetic differentiation at neutral loci was similar to that of other Fagaceae species (F(ST) = 0.032, = 0.15). Population differentiation followed a model of isolation by distance but additionally, strongly significant isolation by elevation was found, both for neutral loci and the putatively selected locus.
The results indicate higher gene flow among similar elevational levels than across different elevational levels and suggest a selective influence of elevation on the distribution of genetic diversity in C. eyrei. The study underlines the importance to check the selective neutrality of marker loci in analyses of population structure.
... However, genomic data that facilitate PCR-based polymorphism screens are now available for several bryophyte species, most notably P. patens (Table 2. While it is unknown whether these loci will similarly be variable in F. hygrometrica, these data suggest that within-and among-population differences may have been missed in the earlier allozyme studies. Similarly, McDaniel and Shaw (2005) and Clarke et al. (2008) report finding considerable DNA sequence and microsatellite diversity, respectively, in several populations of C. purpureus. Interestingly, none of the variation resulted in amino acid substitutions, consistent with the previous allozyme study (Shaw and Beer, 1997). ...
Natural phenotypic variation is widely documented within and among populations of bryophyte species. The tools necessary to identify the molecular genetic basis of this variation are now well developed in a few bryophyte model systems. Here, I review evidence for experimentally verified genetic variation in heavy metal tolerance, mineral nutrition, gametophyte growth and sexual dimorphism in four bryophyte model systems: the mosses Ceratodon purpureus, Funaria hygrometrica, Physcomitrella patens and the liverwort Marchantia polymorpha. Although classical genetic experiments needed to identify the basis of this variation have not been widely utilized among bryophyte researchers, genetic maps have recently been published for C. purpureus and P. patens. Bryophytes are well suited for such studies because a large number of recombinants can be generated with a single cross. Additionally, targeted allele replacement is a powerful technique for testing candidate genes identified by map-based cloning. However, additional techniques, such as association mapping or combining whole-genome expression studies with genetic mapping, may also facilitate testing candidate genes.
The health of several East Antarctic moss-beds is declining as liquid water availability is reduced due to recent environmental changes. Consequently, a noninvasive and spatially explicit method is needed to assess the vigour of mosses spread throughout rocky Antarctic landscapes. Here, we explore the possibility of using near-distance imaging spectroscopy for spatial assessment of moss-bed health. Turf chlorophyll a and b, water content and leaf density were selected as quantitative stress indicators. Reflectance of three dominant Antarctic mosses Bryum pseudotriquetrum, Ceratodon purpureus and Schistidium antarctici was measured during a drought-stress and recovery laboratory experiment and also with an imaging spectrometer outdoors on water-deficient (stressed) and well-watered (unstressed) moss test sites. The stress-indicating moss traits were derived from visible and near infrared turf reflectance using a nonlinear support vector regression. Laboratory estimates of chlorophyll content and leaf density were achieved with the lowest systematic/unsystematic root mean square errors of 38.0/235.2 nmol g(-1) DW and 0.8/1.6 leaves mm(-1) , respectively. Subsequent combination of these indicators retrieved from field hyperspectral images produced small-scale maps indicating relative moss vigour. Once applied and validated on remotely sensed airborne spectral images, this methodology could provide quantitative maps suitable for long-term monitoring of Antarctic moss-bed health.
© 2015 The Authors New Phytologist © 2015 New Phytologist Trust.
Whilst light is essential for photosynthesis and development of plants, both excess photosynthetically active radiation and certain wavelengths (e.g. high energy ultraviolet-B) radiation can be damaging. Plants in general possess a suite of mechanisms that act to either prevent absorption of damaging and excess radiation or to mitigate against the damage that such radiation can cause once it is absorbed. Whilst bryophytes share many of these photoprotective mechanisms with the vascular plants, there are key differences in the photoprotection available to bryophytes. Some of these differences pertain to structural features, such as protective epidermal layers, that are available to vascular plants but not generally to bryophytes. Bryophytes thus have to invest more in cellular level photoprotection than vascular plants. In other respects bryophytes may retain mechanisms found in algal ancestors (e.g. thermal energy dissipation associated with the LHCSR protein) that have been lost during the evolution of vascular plants. Many bryophytes are able to manage light absorption during desiccation and rehydration and freezing and thawing, resulting in potentially novel mechanisms of energy dissipation. Given the high stress environments that many bryophytes inhabit, from hot or frozen deserts to alpine habitats with high incident UV-B radiation, it is unsurprising that they have a suite of photoprotective strategies.
We present a bryological bibliography for 2007-8 - a structured checklist.
