Rhodotorula psychrophila sp. nov., Rhodotorula psychrophenolica sp. nov. and Rhodotorula glacialis sp. nov., novel psychrophilic basidiomycetous yeast species isolated from alpine environments.
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Three novel psychrophilic species of the genus Rhodotorula are described. Rhodotorula psychrophila sp. nov. (type strain PB19(T)=CBS 10440(T)=DSM 18768(T)), Rhodotorula psychrophenolica sp. nov. (type strain AG21(T)=CBS 10438(T)=DSM 18767(T)) and Rhodotorula glacialis sp. nov. (type strain A19(T)=CBS 10436(T)=DSM 18766(T)) were isolated from soil collected from an alpine railway area, from mud in the thawing zone of a glacier foot and from glacier cryoconite, respectively. All three species have been assigned to the genus Rhodotorula on the basis of molecular sequence data and physiological and morphological properties. Rhodotorula psychrophila is not able to grow at temperatures above 15 degrees C. Rhodotorula psychrophenolica and Rhodotorula glacialis degrade high concentrations of phenol (up to 12.5 and 5 mM, respectively) as the sole carbon source at 10 degrees C. Sequence analyses of the 26S rDNA D1/D2 regions indicated that the novel species are phylogenetically related and belong to a clade that includes other psychrophilic yeasts. (+info)
Tracing the effects of the Little Ice Age in the tropical lowlands of eastern Mesoamerica.
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The causes of late-Holocene centennial to millennial scale climatic variability and the impact that such variability had on tropical ecosystems are still poorly understood. Here, we present a high-resolution, multiproxy record from lowland eastern Mesoamerica, studied to reconstruct climate and vegetation history during the last 2,000 years, in particular to evaluate the response of tropical vegetation to the cooling event of the Little Ice Age (LIA). Our data provide evidence that the densest tropical forest cover and the deepest lake of the last two millennia were coeval with the LIA, with two deep lake phases that follow the Sporer and Maunder minima in solar activity. The high tropical pollen accumulation rates limit LIA's winter cooling to a maximum of 2 degrees C. Tropical vegetation expansion during the LIA is best explained by a reduction in the extent of the dry season as a consequence of increased meridional flow leading to higher winter precipitation. These results highlight the importance of seasonal responses to climatic variability, a factor that could be of relevance when evaluating the impact of recent climate change. (+info)
Diffusion-controlled metabolism for long-term survival of single isolated microorganisms trapped within ice crystals.
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Two known habitats for microbial metabolism in ice are surfaces of mineral grains and liquid veins along three-grain boundaries. We propose a third, more general, habitat in which a microbe frozen in ice can metabolize by redox reactions with dissolved small molecules such as CO(2), O(2), N(2), CO, and CH(4) diffusing through the ice lattice. We show that there is an adequate supply of diffusing molecules throughout deep glacial ice to sustain metabolism for >10(5) yr. Using scanning fluorimetry to map proteins (a proxy for cells) and F420 (a proxy for methanogens) in ice cores, we find isolated spikes of fluorescence with intensity consistent with as few as one microbial cell in a volume of 0.16 microl with the protein mapper and in 1.9 microl with the methanogen mapper. With such precise localization, it should be possible to extract single cells for molecular identification. (+info)
Genome-wide effects of postglacial colonization in Arabidopsis lyrata.
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The perennial outcrossing Arabidopsis lyrata is becoming a plant model species for molecular ecology and evolution. However, its evolutionary history, and especially the impact of the climatic oscillations of the Pleistocene on its genetic diversity and population structure, is not well known. We analyzed the broad-scale population structure of the species based on microsatellite variation at 22 loci. A wide sample in Europe revealed that glaciations and postglacial colonization have caused high divergence and high variation in variability between populations. Colonization from Central Europe to Iceland and Scandinavia was associated with a strong decrease of genetic diversity from South to North. On the other hand, the Russian population included in our data set may originate from a different refugium probably located more to the East. These genome-wide patterns must be taken into account in studies aiming at elucidating the genetic basis of local adaptation. As shown by sequence data, most of the loci used in this study do not evolve like typical microsatellite loci and show variable levels of homoplasy: this mode of evolution makes these markers less suitable to investigate the between-continent divergence and more generally the worldwide evolution of the species. Finally, a strong negative correlation was detected between levels of within-population diversity and indices of differentiation such as F(ST). We discuss the causes of this correlation as well as the potential bias it induces on the quantification and interpretation of population structure. (+info)
Glacial vicariance in Eurasia: mitochondrial DNA evidence from Scots pine for a complex heritage involving genetically distinct refugia at mid-northern latitudes and in Asia Minor.
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BACKGROUND: At the last glacial maximum, Fennoscandia was covered by an ice sheet while the tundra occupied most of the rest of northern Eurasia. More or less disjunct refugial populations of plants were dispersed in southern Europe, often trapped between mountain ranges and seas. Genetic and paleobotanical evidences indicate that these populations have contributed much to Holocene recolonization of more northern latitudes. Less supportive evidence has been found for the existence of glacial populations located closer to the ice margin. Scots pine (Pinus sylvestris L.) is a nordic conifer with a wide natural range covering much of Eurasia. Fractures in its extant genetic structure might be indicative of glacial vicariance and how different refugia contributed to the current distribution at the continental level. The population structure of Scots pine was investigated on much of its Eurasian natural range using maternally inherited mitochondrial DNA polymorphisms. RESULTS: A novel polymorphic region of the Scots pine mitochondrial genome has been identified, the intron 1 of nad7, with three variants caused by insertions-deletions. From 986 trees distributed among 54 populations, four distinct multi-locus mitochondrial haplotypes (mitotypes) were detected based on the three nad7 intron 1 haplotypes and two previously reported size variants for nad1 intron B/C. Population differentiation was high (GST = 0.657) and the distribution of the mitotypes was geographically highly structured, suggesting at least four genetically distinct ancestral lineages. A cosmopolitan lineage was widely distributed in much of Europe throughout eastern Asia. A previously reported lineage limited to the Iberian Peninsula was confirmed. A new geographically restricted lineage was found confined to Asia Minor. A new lineage was restricted to more northern latitudes in northeastern Europe and the Baltic region. CONCLUSION: The contribution of the various ancestral lineages to the current distribution of Scots pine was asymmetric and extant endemism reflected the presence of large geographic barriers to migration. The results suggest a complex biogeographical history with glacial refugia shared with temperate plant species in southern European Peninsulas and Asia Minor, and a genetically distinct glacial population located more North. These results confirm recent observations for cold tolerant species about the possible existence of refugial populations at mid-northern latitudes contributing significantly to the recolonization of northern Europe. Thus, Eurasian populations of nordic plant species might not be as genetically homogenous as assumed by simply considering them as offsets of glacial populations located in southern peninsulas. As such, they might have evolved distinctive genetic adaptations during glacial vicariance, worth evaluating and considering for conservation. (+info)
Climate change and postglacial human dispersals in southeast Asia.
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