The fossil record of birds from the James Ross Basin, West Antarctica

The fossil record of birds from Antarctica is concentrated in the James Ross Basin, located in north-east of the Antarctic Peninsula. Birds are here represented by an extensive Paleogene record of penguins (Sphenisciformes) and Cretaceous–Paleogene record of Anseriformes, followed by other groups with a minor representation (Procellariiformes, Falconiformes, and Pelagornithidae), and others previously assigned controversially to “Ratites”, Threskiornithidae, Charadriiformes, Gruiformes, Phoenicopteriformes, and Gaviiformes. We provide a complete update of these records, commenting on the importance of some of these remains for the evolution of the major clades.Fil: Acosta Hospitaleche, Carolina Ileana Alicia. Universidad Nacional de La Plata. Facultad de Ciencias Naturales y Museo. División Paleontología Vertebrados; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata; ArgentinaFil: Jadwiszczak, Piotr. University Of Bialystok; PoloniaFil: Clarke, Julia A.. University of Texas at Austin; Estados UnidosFil: Cenizo, Marcos. Museo de Historia Natural de La Pampa, División Paleontología; Argentina. Fundación de Historia Natural Félix de Azara; Argentin

Aneuploids in the shrub birch Betula humilis populations in Poland

Shrub birch (Betula humilis Schrk.) is endangered glacial relict growing in natural and drained fens and transitional mires. At present study we examined karyotypes of 103 individuals of B. humilis, collected in six populations from eastern and northeastern Poland. We found 60% of diploid individuals with 2n = 28. The rest of studied plants were aneuploids with 26, 27, 29, 30 and 31 chromosomes in their karyotypes. High frequencies of aneuploids in Polish populations of B. humilis could be a consequence of: (i) hybridization with congeneric species, (ii) stress resulting from range fragmentation, (iii) karyotype instability of individuals with 2n ≠ 28, or (iv) vegetative reproduction

Identification of the barrier to gene flow between phylogeographic lineages of the common hamster Cricetus cricetus

In anthropogenically disturbed habitats, natural barriers still exist and have to be recognized, as they are important for conservation measures. Areas of phylogeographic breaks within a species are often stabilized in inhospitable regions which act as natural barriers. An area of contact between phylogeographic lineages of the common hamster (Cricetus cricetus) was found in the Małopolska Upland in Poland. A total of 142 common hamsters were captured between 2005 and 2009. All hamsters were genotyped at 17 microsatellite loci and partial sequences of the mitochondrial (mtDNA) control region were obtained. No mixed populations with mtDNA haplotypes of both lineages were found. The distance between marginal populations was about 20 km; no hamsters were found in the area between. A principal components analysis (PCA) was performed on microsatellite data and the greatest change in PC1 scores was found between marginal samples. To define the habitat components responsible for the phylogeographic break, we compared the habitat composition of sites occupied by hamsters with those from which hamsters were absent. We found that hamsters avoided forested areas and sandy soils. The area of the potential barrier was characterized by a high proportion of woodland and unfavorable soils in comparison with neighboring areas inhabited by hamsters. They cannot settle in this area due to their high winter mortality in shallow burrows and high predation in the fields adjacent to forests

A microsatellite study in the Łęgucki Młyn/Popielno hybrid zone reveals no genetic differentiation between two chromosome races of the common shrew (Sorex araneus)

This study investigated a chromosome hybrid zone between two chromosomal races of the common shrew (Sorex araneus). Gene flow and genetic structure of the hybrid zone, located in the northeast of Poland, were studied using seven polymorphic autosomal microsatellite loci (L9, L14, L33, L45, L67, L68, L97) and a Y-linked microsatellite locus (L8Y). Seventy-five animals (46 of the Łęgucki Młyn race and 29 of the Popielno race) from nine different localities were examined and the data were analyzed using hierarchical AMOVA and F-statistic. The studied microsatellite loci and races (divided into nine geographical populations) were characterized by observed heterozygosity (HO), expected heterozygosities within (HS), and between (HT) populations, inbreeding coefficient (FIS), fixation index (FST), and average allelic richness (A). We found that genetic structuring within and between the two chromosome races were weak and non-significant. This finding and unconstrained gene flow between the races indicates a high level of migration within the Łęgucki Młyn/Popielno hybrid zone, suggesting that evolutionarily important genetic structuring does not occur in interracial zones where races which are not genetically distinct come into contact

Where have all the petrels gone? Forty years (1978–2020) of Wilson’s Storm Petrel (Oceanites oceanicus) population dynamics at King George Island (Isla 25 de Mayo, Antarctica) in a changing climate

Numerous seabird species are experiencing population declines, and this trend is expected to continue or even accelerate in the future. To understand the effects of environmental change on seabird populations, long-term studies are vital, but rare. Here, we present over four decades (1978–2020) of population dynamic and reproductive performance data of Wilson’s Storm Petrels (Oceanites oceanicus) from King George Island (Isla 25 de Mayo), Antarctica. We determined temporal trends in population size, breeding output, and chick growth rates, and related interannual variation in these variables to various environmental variables. Our study revealed a decline of 90% in population size of Wilson’s Storm Petrels in two colonies, and considerable changes in breeding output and chick growth rates. Temporal changes in breeding demographics were linked to interannual environmental variation, either causing changes in food availability (particularly Antarctic krill, Euphausia superba) or in nest burrow accessibility due to snow blocking the entrance. With the expected rise in air and sea surface temperatures, the predicted increases in precipitation over the Antarctic Peninsula will likely lead to increased snowstorm prevalence. Additionally, the rising temperatures will likely reduce food availability due to reduced sea ice cover in the wintering grounds of Antarctic krill, or by changing phyto- and zooplankton community compositions. The ongoing environmental changes may thus lead to a further population decline, or at the very least will not allow the population to recover. Monitoring the population dynamics of Antarctic seabirds is vital to increase our understanding of climate change-induced changes in polar food webs

Phylogenetic Analysis of Pelecaniformes (Aves) Based on Osteological Data: Implications for Waterbird Phylogeny and Fossil Calibration Studies

) were also assessed. The antiquity of these taxa and their purported status as stem members of extant families makes them valuable for studies of higher-level avian diversification. (sister taxon to Phalacrocoracidae). These relationships are invariant when ‘backbone’ constraints based on recent avian phylogenies are imposed.Relationships of extant pelecaniforms inferred from morphology are more congruent with molecular phylogenies than previously assumed, though notable conflicts remain. The phylogenetic position of the Plotopteridae implies that wing-propelled diving evolved independently in plotopterids and penguins, representing a remarkable case of convergent evolution. Despite robust support for the placement of fossil taxa representing key calibration points, the successive outgroup relationships of several “stem fossil + crown family” clades are variable and poorly supported across recent studies of avian phylogeny. Thus, the impact these fossils have on inferred patterns of temporal diversification depends heavily on the resolution of deep nodes in avian phylogeny

Importance of fat reserves in Wilson´s storm petrel chicks

All petrels store large quantities of fat during nesting period. Several hypotheses have offered explanations for the exceptional accumulation of fat by petrels and that stored in smaller amounts by other birds. Fat reserves of Wilson's storm petrel chicks attain 80% of dry mass. Lipid index increases up to value of 2.0 during nesting period . The aim of our study was to explain the role of fat stores in the nestlings. Stable growth of chicks during first three weeks of life suggests that stochastic variation of chick food provisioning arises from unpredictable snow storms rather than fluctuating food availability at the sea. The lack of correlation between body mass and head, tarsal or wing length rejects hypotheses that chicks accumulate lipid in order to increase their rate of intake of a limiting nutrients. Accumulation of excessive lipid reserves may be a consequence of overfeeding of the chicks by their parents. This strategy protects offspring from death during periods of starvation, when nest entrances are covered by snow

Genetic Diversity and Fine-Scale Spatial Genetic Structure of the Endangered Shrub Birch (Betula humilis Schrk.) Populations in Protected and Unprotected Areas

The genetic diversity of natural populations is a key factor in the success of long-term ecosystem protection. We studied the genetic diversity and spatial genetic structure (SGS) in three endangered shrub birch (Betula humilis) populations using seven nuclear microsatellite loci. The highest genetic variation was found in the restored Szuszalewo population in Biebrza National Park, where active prevention of thicket forest succession was recently conducted. The results of bottleneck tests were not statistically significant in each locality, although a genetic indication for population reduction was detected in the Rospuda stand, which is not actively protected. The Bayesian clustering, principal coordinates analysis, and FST estimates revealed the greatest difference between Magdzie Bagno and Rospuda samples. SGS was found in all B. humilis stands; however, it was the strongest in the Rospuda locality, where pollen and seed dispersal was limited by dense clusters of shrub birch ramets scattered among forest and brushwood plants. The weakest SGS, also supported by finding some sibling pairs in distant locations, was observed in the Szuszalewo population. The aforementioned results indicate that the active protection practices may impose an immediate beneficial effect on the restoration and maintenance of the B. humilis populations