Native and Alien Antarctic Grasses as a Habitat for Fungi.

Biological invasions are now seen as one of the main threats to the Antarctic ecosystem. An example of such an invasion is the recent colonization of the H. Arctowski Polish Antarctic Station area by the non-native grass Poa annua. This site was previously occupied only by native plants like the Antarctic hair grass Deschampsia antarctica. To adapt successfully to new conditions, plants interact with soil microorganisms, including fungi. The aim of this study was to determine how the newly introduced grass P. annua established an interaction with fungi compared to resident grass D. antarctica. We found that fungal diversity in D. antarctica roots was significantly higher compared with P. annua roots. D. antarctica managed a biodiverse microbiome because of its ability to recruit fungal biocontrol agents from the soil, thus maintaining a beneficial nature of the endophyte community. P. annua relied on a set of specific fungal taxa, which likely modulated its cold response, increasing its competitiveness in Antarctic conditions. Cultivated endophytic fungi displayed strong chitinolysis, pointing towards their role as phytopathogenic fungi, nematode, and insect antagonists. This is the first study to compare the root mycobiomes of both grass species by direct culture-independent techniques as well as culture-based methods.

Root-Associated Bacteria Community Characteristics of Antarctic Plants: Deschampsia antarctica and Colobanthus quitensis-a Comparison.

Colobanthus quitensis (Kunth) Bartl. and Deschampsia antarctica Desv. are the only Magnoliophyta to naturally colonize the Antarctic region. The reason for their sole presence in Antarctica is still debated as there is no definitive consensus on how only two unrelated flowering plants managed to establish breeding populations in this part of the world. In this study, we have explored and compared the rhizosphere and root-endosphere dwelling microbial community of C. quitensis and D. antarctica specimens sampled in maritime Antarctica from sites displaying contrasting edaphic characteristics. Bacterial phylogenetic diversity (high-throughput 16S rRNA gene fragment targeted sequencing) and microbial metabolic activity (Biolog EcoPlates) with a geochemical soil background were assessed. Gathered data showed that the microbiome of C. quitensis root system was mostly site-dependent, displaying different characteristics in each of the examined locations. This plant tolerated an active bacterial community only in severe conditions (salt stress and nutrient deprivation), while in other more favorable circumstances, it restricted microbial activity, with a possibility of microbivory-based nutrient acquisition. The microbial communities of D. antarctica showed a high degree of similarity between samples within a particular rhizocompartment. The grass' endosphere was significantly enriched in plant beneficial taxa of the family Rhizobiaceae, which displayed obligatory endophyte characteristics, suggesting that at least part of this community is transmitted vertically. Ultimately, the ecological success of C. quitensis and D. antarctica in Antarctica might be largely attributed to their associations and management of root-associated microbiota.

Bacterial Communities Associated with Poa annua Roots in Central European (Poland) and Antarctic Settings (King George Island).

Poa annua (annual bluegrass) is one of the most ubiquitous grass species in the world. In isolated regions of maritime Antarctica, it has become an invasive organism threatening native tundra communities. In this study, we have explored and compared the rhizosphere and root-endosphere dwelling microbial community of P. annua specimens of maritime Antarctic and Central European origin in terms of bacterial phylogenetic diversity and microbial metabolic activity with a geochemical soil background. Our results show that the rhizospheric bacterial community was unique for each sampling site, yet the endosphere communities were similar to each other. However, key plant-associated bacterial taxa such as the Rhizobiaceae family were poorly represented in Antarctic samples, probably due to high salinity and heavy metal concentrations in the soil. Metabolic activity in the Antarctic material was considerably lower than in Central European samples. Antarctic root endosphere showed unusually high numbers of certain opportunistic bacterial groups, which proliferated due to low competition conditions. Thirteen bacterial families were recognized in this study to form a core microbiome of the P. annua root endosphere. The most numerous were the Flavobacteriaceae, suspected to be major contributors to the ecological success of annual bluegrass, especially in harsh, Antarctic conditions.

Is Antarctica under threat of alien species invasion?

The last decade has seen a rapid development of scientific, logistic and tourist activities, especially in the Antarctic region with the mildest climatic conditions: the Antarctic Peninsula. This region is also exhibiting rapid regional warming and all of the already diagnosed alien species in the Antarctic Treaty Area were found within the Antarctic Peninsula. Identifying potential invasive species that can threaten this pristine area of the Earth helps us to take specific preventive actions. This article is a commentary on Hughes et al., 26, 2702-2716.

How much of the invader's genetic variability can slip between our fingers? A case study of secondary dispersal of Poa annua on King George Island (Antarctica).

We studied an invasion of Poa annua on King George Island (Maritime Antarctic). The remoteness of this location, its geographic isolation, and its limited human traffic provided an opportunity to trace the history of an invasion of the species. Poa annua was recorded for the first time at H. Arctowski Polish Antarctic Station in the austral summer of 1985/6. In 2008/9, the species was observed in a new locality at the Ecology Glacier Forefield (1.5 km from "Arctowski"). We used AFLP to analyze the genetic differences among three populations of P. annua: the two mentioned above (Station and Forefield) and the putative origin of the introduction, Warsaw (Poland). There was 38% genetic variance among the populations. Pairwise ФPT was 0.498 between the Forefield and Warsaw populations and 0.283 between Warsaw and Station. There were 15 unique bands in the Warsaw population (frequency from 6% to 100%) and one in the Station/Forefield populations (which appears in all analyzed individuals from both populations). The Δ(K) parameter indicated two groups of samples: Warsaw/Station and Forefield. As indicated by Fu's Fs statistics and an analysis of mismatch distribution, the Forefield population underwent a bottleneck and/or founder effect. The Forefield population was likely introduced by secondary dispersal from the Station population.