Search

The article presents a study regarding the sea ice variability in the Antarctic. It states that ice concentrations were calculated using the data from the Scanning Multichannel Microwave Radiometer (SMMR), Special Sensor Microwave Imager (SSMI), and Special Sensor Microwave Imager Sounder (SSMIS). The result of the study shows that highly complex nature of the Arctic climate system was reflected by the regional, seasonal, and monthly sea ice trend variabilities.

The article presents a study regarding the sea ice variability in Antarctic. It states that ice concentrations were calculated using the data from the Scanning Multichannel Microwave Radiometer (SMMR), Special Sensor Microwave Imager (SSMI), and Special Sensor Microwave Imager Sounder (SSMIS). The result of the study shows that global warming was being tied to the decrease of sea ice in the Arctic.

Gradients of nucleotide bias and substitution rates occur in vertebrate mitochondrial genomes due to the asymmetric nature of the replication process. The evolution of these gradients has previously been studied in detail in primates, but not in other vertebrate groups. From the primate study, the strengths of these gradients are known to evolve in ways that can substantially alter the substitution process, but it is unclear how rapidly they evolve over evolutionary time or how different they may be in different lineages or groups of vertebrates. Given the importance of mitochondrial genomes in phylogenetics and molecular evolutionary research, a better understanding of how asymmetric mitochondrial substitution gradients evolve would contribute key insights into how this gradient evolution may mislead evolutionary inferences, and how it may also be incorporated into new evolutionary models. Most snake mitochondrial genomes have an additional interesting feature, 2 nearly identical control regions, which vary among different species in the extent that they are used as origins of replication. Given the expanded sampling of complete snake genomes currently available, together with 2 additional snakes sequenced in this study, we reexamined gradient strength and CR usage in alethinophidian snakes as well as several lizards that possess dual CRs. Our results suggest that nucleotide substitution gradients (and corresponding nucleotide bias) and CR usage is highly labile over the ∼200 m.y. of squamate evolution, and demonstrates greater overall variability than previously shown in primates. The evidence for the existence of such gradients, and their ability to evolve rapidly and converge among unrelated species suggests that gradient dynamics could easily mislead phylogenetic and molecular evolutionary inferences, and argues strongly that these dynamics should be incorporated into phylogenetic models. Copyright © 2010 S. Karger AG, Basel [ABSTRACT FROM AUTHOR]

We used phylogenetic and phylogeographical methods to infer relationships among African ground squirrels of the genus Xerus. Using Bayesian, maximum-parsimony, nested clade and coalescent analyses of cytochrome b sequences, we inferred interspecific relationships, evaluated the specific distinctness of Cape ( Xerus inauris) and mountain ( Xerus princeps) ground squirrels, and tested hypotheses for historical patterns of gene flow within X. inauris. The inferred phylogeny supports the hypothesized existence of an ‘arid corridor’ from the Horn of Africa to the Cape region. Although doubts have been raised regarding the specific distinctness of X. inauris and X. princeps, our analyses show that each represents a distinct well-supported, monophyletic lineage. Xerus inauris includes three major clades, two of which are geographically restricted. The distributions of X. inauris populations are concordant with divergences within and disjunctions between other taxa, which have been interpreted as results of Plio–Pleistocene climate cycles. Nested clade analysis, coalescent analyses, and analyses of genetic structure support allopatric fragmentation as the cause of the deep divergences within this species. [ABSTRACT FROM AUTHOR]