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Poa annua L. in the maritime Antarctic: an overview

Poa annua is the only flowering plant species that has established a breeding population in the maritime Antarctic, through repeated anthropogenic introduction. The first appearance of this species in the Antarctic was observed in 1953. Annual bluegrass inhabits mainly anthropogenic sites, but recently has entered tundra communities. The functioning of P. annua in the Antarctic could not have been possible without adaptations that enable the plants to persist in the specific climatic conditions typical for this zone. Poa annua is highly adaptable to environmental stress and unstable habitats: huge phenotypic and genotypic variability, small size, plastic life cycle (life-history types ranging from annual to perennial forms). The spreading of P. annua in the Antarctic Peninsula region is a classic example of the expansion process following anthropogenic introduction of an invasive species, and illustrates the dangers to Antarctic terrestrial ecosystems that are associated with increasing human traffic.

Diaspores of the introduced species Poa annua L. in soil samples from King George Island (South Shetlands, Antarctica).

Abstract The soil seed bank and seed germination capacity of Poa annua in the vicinity of the Polish Antarctic Station (South Shetlands, Antarctica) were investigated. It was documented that annual bluegrass can reproduce sexually and produce a functional seed bank of close to 5000 seeds/m2 under maritime Antarctic conditions. Comparison of germination between Poa annua and two native plant species revealed that Poa annua seeds can germinate as fast or even faster than native species, and are more vigorous. Our studies show that in the Antarctic Poa annua can successfully reproduce sexually and produce fully developed, viable caryopses that are able to survive the maritime Antarctic winter, not only in a soil bank, but also directly in the previous years inflorescences.

Spatial structure of the soil seed bank of Poa annua L.—alien species in the Antarctica

Poa annua L. (annual bluegrass) is the only non–native flowering plant species that has successfully established a breeding population in the maritime Antarctic and has been shown to maintain a soil seed bank. The characteristic of the spatial structure of the Antarctic population of this species is the formation of distinct dense clumps—tussocks. In the temperate zone the species is only loosely tufted. We focused on the characteristics of seed deposition associated with the tussocks and some aspects of the spatial heterogeneity of the soil seed bank of P. annua in the Antarctic. We wanted to assess the microspatial structure of the soil seed bank of annual bluegrass at Arctowski Station. Therefore we compared the number of seeds deposited underneath and in the vicinity of P. annua clumps. Our results indicate that P. annua in the Antarctic maintains a soil seed bank comparable to species typical for the polar tundra. The microspatial structure of P. annua soil seed bank in the Antarctic is highly associated with the presence of tussocks. Seeds are deposited underneath the tussock rather than in the vicinity of the clump. Our results also indicate that seeds are able to survive the Antarctic winter and readily germinate under optimal conditions.

Response of Poa annua to extreme conditions: comparison of morphological traits between populations from cold and temperate climate conditions

Poa annua is an expansive species that has developed a stable breeding population on the west shore of Admiralty Bay, King George Island (Antarctica). We investigated whether the colonization success of this species in extreme climatic conditions is associated with morphological variability. We compared the differences in 12 traits among P. annua populations thriving in Admiralty Bay, Tatra Mountains and Warsaw. Our expectations that plants occurring in maritime Antarctic and mountain conditions should exhibit similar morphological characteristics were not confirmed. Comparison of individual morphometric traits indicated high variability within as well as between the studied populations. Plants from the Admiralty Bay population differed significantly from plants from the Warsaw and Tatra populations in 9 of the 12 studied traits. We discovered more similarities between the Polish populations (Warsaw and Tatra) than between the populations from harsh environments (maritime Antarctic and Tatra). The Tatra population exhibited intermediate morphological characteristics in relation to plants from the other two studied populations. In parallel, the climatic conditions expressed in mean monthly air temperature were intermediate in the Tatra location. Four traits analyzed by other authors in the sub-Antarctic populations and by us in the maritime Antarctic population were consistently lower than for the Tatra and Warsaw populations. This finding is in accordance with our working hypothesis (i.e., plants growing in harsh cold conditions exhibit similar morphological characteristics). Our results might suggest that the morphological response to environmental stress of plants occurring in mountain and polar conditions may be similar.

Encroachment of forest species into operating and abandoned railway areas in north-eastern Poland

Abstract Floristic investigations concerning vascular plants, supplemented by a determination of the basic soil parameters and concentration of four heavy metals (Cu, Zn, Mn, Fe), were carried out in 12 railway areas located in north-eastern Poland (eight located on tracks withdrawn from use, four located on operating tracks). The vegetation types of the areas in the immediate vicinity of the selected sites differed (forest, grassland or meadow, ruderal). The soil samples exhibited considerable uniformity with respect to their pH values, and, although the nutrient levels varied, the concentration of the latter did not seem to be a factor limiting plant growth. The concentration of heavy metals did not hinder plant growth. Although the chemical features of the soil were within limits that did not make plant growth difficult, the process of plant regeneration proceeded differently, depending on the accessibility of diaspores from the surrounding areas. The decreasing rate of therophytes, especially aliens, manifested a stage of succession on abandoned tracks. In the case of ground flora, gradual “preparation” of the habitat (shadow factor on the track) was very important. The degree of advancement of forest regeneration on abandoned tracks was more strongly evidenced by the constant return of ground flora species, and not by trees as was commonly thought.

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)

Abstract 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 Fus 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.

Soil and plants contamination with selected heavy metals in the area of a railway junction / Zanieczyszczenie gleby i roślin wybranymi metalami ciężkimi na terenie węzła kolejowego

Abstract Heavy metal (As, Mn, Ni, Sn, Ti) concentrations were determined in soil and plant samples collected in different areas of the railway junction Iława Główna, Poland. Soil and plant samples were collected in four functional parts of the junction, i.e. the loading ramp, main track within the platform area, rolling stock cleaning bay and the railway siding. Four plant species occurring in relatively higher abundance were selected for heavy metals analysis, although in the loading ramp and platform areas only one species could be collected in the amount which makes chemical analysis possible. The selected species included three perennials (Daucus carota, Pastinaca sativa and Taraxacum officinale) and one annual plant (Sonchus oleraceus). The entire area of the railway junction showed elevated concentrations of heavy metals when compared to the control level. It was most pronounced for the platform area and railway siding. The concentration of arsenic, manganese and nickel in plants growing in these parts of the junction exceeded the toxic level. The highest contamination of soil and plants found in the platform area suggested advanced emission process of the analyzed metals from wheel and track abrasion. Literature review showed that the concentration of the investigated metals in soil was generally higher than that found in centers of cities and along traffic roads proving that the railway is an important linear source of soil contamination W pracy przedstawiono wyniki badań dotyczące zawartości wybranych metali ciężkich (As, Mn, Ni, Sn, Ti) w glebie i roślinach na obszarze węzła kolejowego Iława Główna. Próby gleby i roślin pobierano w czterech częściach węzła, a mianowicie na rampie załadowczej, torowisku głównym, myjni i bocznicy kolejowej. Na całym obszarze węzła kolejowego stwierdzono podwyższone stężenia metali ciężkich w porównaniu z terenem kontrolnym. Najwyższe stężenia stwierdzano na torowisku głównym i bocznicy kolejowej. Stężenie arsenu, manganu i niklu w roślinach występujących na tym obszarze przekracza poziom toksyczny. Najwyższe zanieczyszczenie gleby i roślin stwierdzane na torowisku wskazuje na występowanie procesów emisji metali spowodowanych ścieraniem kół i szyn. Porównanie z danymi literaturowymi wskazuje, że stężenie badanych metali w glebie jest większe niż w glebach centów miast i wzdłuż drogowych szlaków komunikacyjnych, co dowodzi, że linie kolejowe stanowią istotne liniowe źródło zanieczyszczenia gleby

What affects the probability of biological invasions in Antarctica? Using an expanded conceptual framework to anticipate the risk of alien species expansion

Successful alien species invasion depends on many factors studied mostly in post invasion habitats, and subsequently summarized in frameworks tailored to describe the studied invasion. We used an existing expanded framework with three groups of contributing factors: habitat invisibility, system context and species invasiveness, to analyze the probability of alien species invasions in terrestrial communities of Maritime Antarctic in the future. We focused on the first two factor groups. We tested if the expanded framework could be used under a different scenario. We chose Point Thomas Oasis on King George Island to perform our analysis. Strong geographical barrier, low potential bioclimatic suitability and resource availability associated with habitat invasibility significantly reduce the likelihood of biological invasion in Antarctica. An almost full enemy release (low pressure of consumers), the high patchiness of the habitat, and the prevalence of open gaps also associated with habitat invasibility increase the possibility of invasion. The dynamics of functional connectivity, propagule pressure and spatio-temporal patterns of propagule arrival associated with human activity and climate change belonging to the system context contribute to an increase in the threat of invasions. Due to the still low land transport activity migration pathways are limited and will reduce the spread of alien terrestrial organisms by land. An effective way of preventing invasions in Antarctica seems to lie in reducing propagule pressure and eliminating alien populations as early as possible. The expanded conceptual framework opens up wider possibilities in analyzing invasions taking place in different systems and with multiple taxa.

Plastic biomass allocation as a trait increasing the invasiveness of annual bluegrass (Poa annua L.) in Antarctica

The plasticity of functional traits promotes invasiveness of a species. Biomass allocation, as one of these traits, is responsible for resource acquisition, and its plastic modifications can be of adaptive value in new environments before any genetic adaptations may occur. Our aim was to compare in situ biomass allocation in aboveground and belowground organs in an Antarctic and a Polish population of annual bluegrass (Poa annua), the only alien plant species successfully invading Antarctica. The Antarctic population was characterised by three times lower aboveground biomass, more compact plant growth habit and higher fraction of biomass allocated into belowground organs than in the Polish population. The differences between populations are probably a result of adaptation to local conditions. The modifications of the studied traits in the Antarctic population are most likely a response to extreme atmospheric and edaphic conditions and enable the species to survive and spread in this hostile environment. Our results are in accordance with the balanced growth hypothesis. At the same time, these trait values enhance species performance under Antarctic conditions making P. annua a potential threat to local plant communities under altering climate changes and growing human impact scenario.

Psychronectria hyperantarctica, gen. nov., comb. nov., epitypification and phylogenetic position of an Antarctic bryophilous ascomycete

ABSTRACT The holotype of Thyronectria hyperantarctica was re-examined, redescribed, and compared with new collections of an Antarctic bryophilous ascomycete from a similar area. Because the condition of type material was insufficient for molecular studies, the authors designated an epitype from newly collected material with a high degree of morphological similarity to the holotype and paratype material. Phylogenetic analysis of the epitype revealed that its closest phylogenetic affinity was with the family Tilachlidiaceae and it formed a monophyletic group in this lineage within other collections of the species. Therefore, the new monotypic genus Psychronectria is described to accommodate Thyronectria hyperantarctica. The fungus is superficially similar to Thyronectria species in Nectriaceae, but the ascospores differ in color, size, and type of septation.