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

Molecular variation of Antarctic grass Deschampsia antarctica Desv. from King George Island [Antarctica]

Deschampsia antarctica Desv. plants collected on King George Islands (Antarctica) at two localities that differ in topographic and nutrition conditions exhibited morphological variation that differentiated plants of both locations. The molecular variation characteristic to individuals of both sites was tested using AFLP approach in order to verify whether morphological variation characteristic to the plants resulted from environmental factors or possibly from differences at the DNA level. Four primer pair combinations were used to generate 339 AFLP fragments, 132 of which were polymorphic and allowed evaluation of genetic relationships among D. antarctica individuals. Chi-square test revealed that only 12 signals were discriminative for the plants from both locations. Cluster analysis conducted on these AFLP fragments demonstrated that plants from the location rich in biogenes were more polymorphic than those from poor one. Our data suggest that the phenotypic variation specific to plants of both locations seem to be the result of adaptation to the environmental conditions like soil and moisture rather than reflect genetic differences

Wykorzystanie markerow RAPD do analizy zmian genetycznych zwiazanych z dlugotrwalym przechowywaniem i regeneracja ziarniakow zyta [Secale cereale L.]

Celem pracy była analiza zmian zachodzących na poziomie DNA w wyniku procesu długiego przechowywania ziarniaków żyta i ich późniejszej regeneracji w warunkach polowych w oparciu o markery typu RAPD. W tym celu przeanalizowano trzy populacje żyta 'Dańkowskie Złote', różniące się okresem przechowywania i liczbą cykli kolejnych regeneracji. Izolację DNA z 75 żywych ziarniaków z każdej serii przeprowadzono przy użyciu techniki SDS. Reakcję PCR (Łańcuchowa reakcja polimerazy) prowadzono kolejno w obecności jednego z 5-ciu 10-nukleotydowych starterów. Mieszaninę reakcyjną rozdzielano elektroforetycznie na żelu agarozowym. Uzyskano łącznie dla wszystkich populacji 110 markerów RAPD. Zaobserwowano istotne statystycznie różnice w częstotliwości 50 z nich. Te różnice mogą świadczyć o zmianach w strukturze genetycznej populacji, będących efektem długotrwałego przechowywania i regeneracji ziarniaków.The aim of studies was to analyse the genetic changes in rye seeds induced by natural ageing during long-term storage in a seed bank and after regeneration in field conditions, by means of RAPD markers. In our experiment, the seeds of three populations of different age and two different reproduction cycles of Dańkowskie Złote rye were used. Genomic DNAs were isolated from 75 seeds of each sample. The polymerase chain reaction was accomplished by means of five primers which were ten nucleotides long each. One hundred and ten RAPD markers were shared among the series. Changes in the frequency of fifty markers were statistically significant among the populations. These changes could be attributed to genetic changes related to long-term storage and regeneration of seeds

Genetic structure of declining chinstrap penguin (Pygoscelis antarcticus) populations from South Shetland Islands (Antarctica)

Seabirds and their response to climate perturbations are important bioindicators of changes in Antarctic ecosystems. During 30 years of observations of two chinstrap penguin (Pygoscelis antarcticus) colonies, one on King George Island and the other on Penguin Island (South Shetland Islands, Antarctica), the size of the breeding populations decreased by 84 and 41 %, respectively. We applied analyses of amplified fragment length polymorphisms to study the genetic structure of the two populations and to evaluate the influence of the sudden population decrease. Our data indicate that there were only weak genetic differences between the populations, which were not strong enough to support the hypothesis of population differentiation. Weak genetic differences observed between the two populations seem not to be determined by selection processes. We hypothesize that the very low level of between-population genetic structure can be explained by some extent of genetic drift, which is largely compensated by gene flow. Moreover, the two populations seem to remain in a stationary state. Our results support the hypothesis of limited natal philopatry in chinstrap penguins. The observed decrease in population size is probably caused by migration or a rise in juvenile mortality due to the increasing krill limitation of the marine food web. However, detailed research is required to address this issue