Cretaceous/Paleogene Floral Turnover in Patagonia: Drop in Diversity,Low Extinction,and a Classopollis Spike

Nearly all data regarding land-plant turnover across the Cretaceous/Paleogene boundary come from western North America, relatively close to the Chicxulub, Mexico impact site. Here, we present a palynological analysis of a section in Patagonia that shows a marked fall in diversity and abundance of nearly all plant groups across the K/Pg interval. Minimum diversity occurs during the earliest Danian, but only a few palynomorphs show true extinctions. The low extinction rate is similar to previous observations from New Zealand. The differing responses between the Southern and Northern hemispheres could be related to the attenuation of damage with increased distance from the impact site, to hemispheric differences in extinction severity, or to both effects. Legacy effects of the terminal Cretaceous event also provide a plausible, partial explanation for the fact that Paleocene and Eocene macrofloras from Patagonia are among the most diverse known globally. Also of great interest, earliest Danian assemblages are dominated by the gymnosperm palynomorphs Classopollis of the extinct Mesozoic conifer family Cheirolepidiaceae. The expansion of Classopollis after the boundary in Patagonia is another example of typically Mesozoic plant lineages surviving into the Cenozoic in southern Gondwanan areas, and this greatly supports previous hypotheses of high latitude southern regions as biodiversity refugia during the end-Cretaceous global crisis.     

Assessing the impact of the CPU power-saving modes on the task-parallel solution of sparse linear systems

We investigate the benefits that an energy-aware implementation of the runtime in charge of the concurrent execution of ILUPACK—a sophisticated preconditioned iterative solver for sparse linear systems—produces on the time-power-energy balance of the application. Furthermore, to connect the experimental results with the theory, we propose several simple yet accurate power models that capture the variations of average power that result from the introduction of the energy-aware strategies as well as the impact of the P-states into ILUPACK’s runtime, at high accuracy, on two distinct platforms based on multicore technology from AMD and Intel.     

Cloning and expression analysis of goldfish (Carassius auratus L.) prominin

The integral membrane protein known as prominin was first identified on the apical surface of mouse neural epithelial cells as well as on the surface of human haematopoietic progenitor cells. This report describes a prominin-like sequence and expression analysis of the prominin in the goldfish. The predicted amino acid sequence for goldfish prominin shares all of the hallmark structural characteristics of the prominin family, however the relatedness assessed using the percent amino acid identity indicated that goldfish prominin cannot be placed into the current mammalian dichotomy of type 1 or 2. The real time PCR analyses indicated that prominin was broadly expressed in different tissues with particularly high levels observed in the kidney and gill of the goldfish. Goldfish prominin was also found to be differentially expressed in subpopulations of in vitro-derived goldfish macrophages, with the highest expression observed in progenitor cells.     

Positive selection is a general phenomenon in the evolution of abalone sperm lysin

Lysin is a 16kDa acrosomal protein used by abalone sperm to create a hole in the egg vitelline envelope (VE). The interaction of lysin with the VE is species-selective and is one step in the multistep fertilization process that restricts heterospecific (cross-species) fertilization. For this reason, the evolution of lysin could play a role in establishing prezygotic reproductive isolation between species. Previously, we sequenced sperm lysin cDNAs from seven California abalone species and showed that positive Darwinian selection promotes their divergence. In this paper an additional 13 lysin sequences are presented representing species from Japan, Taiwan, Australia, New Zealand, South Africa, and Europe. The total of 20 sequences represents the most extensive analysis of a fertilization protein to date. The phylogenetic analysis divides the sequences into two major clades, one composed of species from the northern Pacific (California and Japan) and the other composed of species from other parts of the world. Analysis of nucleotide substitution demonstrates that positive selection is a general process in the evolution of this fertilization protein. Analysis of nucleotide and codon usage bias shows that neither parameter can account for the robust data supporting positive selection. The selection pressure responsible for the positive selection on lysin remains unknown.