Extensive Lower Cretaceous (Albian) methane seepage on Ellef Ringnes Island, Canadian High Arctic

During field mapping of Ellef Ringnes Island, Canadian Arctic Archipelago, 139 isolated Lower Cretaceous methane seep deposits were found from 75 field sites. Stable isotopes of the carbonates have values of δ13C= -47‰ to -35‰ and δ18O= -4.0‰ to +0.7‰. Isoprenoids in organics from one of the seeps are significantly depleted in 13C, with the most negative δ13C of = -118 ‰ and -113 ‰ for PMI and phytane/crocetane, respectively. These values indicate an origin through methane oxidation, consistent with biomarkers that are characteristic for anaerobic methanotrophic archaea within the seep deposits, accompanied by terminally-branched fatty acids sourced by sulphate-reducing bacteria, showing similar 13C values (-92‰). The seep deposits contain a moderate diversity macrofaunal assemblage containing ammonites, bivalves, gastropods, scaphopods, ‘vestimentiferan’ worm tubes and brachiopods. The assemblage is dominated numerically by species that probably had chemosymbionts. The seep deposits formed in the subsurface with strong redox zones, in an otherwise normal marine setting, characterised by oxic waters at high paleolatitudes. While geographically widespread, over an area of ~10,000 km2, seep deposits on Ellef Ringnes Island occur in a narrow stratigraphic horizon, suggesting a large release of biogenic methane occurred over a brief period of time. This gas release was coincident with a transition from a cold to warm climate during the latest Early Albian, and we hypothetize that this may relate to gas hydrate release

Significant differential gene duplication without ancestral tetraploidy in a genus of mexican fish

A comparison of the protein products of 20–25 structural gene loci among the known species of the goodeid fish genus Skiffia suggests that at least 4 loci (16–20%) have undergone species-specific duplications (or, in 1 case, apparent loss) during the evolution of the genus. The species are clearly diploids, and the data therefore indicate that even a large proportion of differentially duplicated loci within a group of related fish species is not critical evidence of common tetraploid ancestry. Differential duplication of structural gene loci may be an important component of the genetic differences that separate congeneric conventional diploid species.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/42725/1/18_2005_Article_BF01953797.pd

Early Cretaceous methane seepage system and associated carbonates, biota and geochemistry, Sverdrup Basin, Ellef Ringnes Island, Nunavut

Over one hundred carbonate deposits, interpreted as having formed at methane seepage sites in the Sverdrup Basin have been discovered on Ellef Ringnes Island, Canadian Arctic. The deposits, up to 2.7 metres tall and 60 metres wide, are found within the lower member of the Lower Cretaceous Christopher Formation, a silty marine shale. The carbonates have complex and heterogeneous structures typical of seep carbonates, including banded botryoidal and clotted textures as well as void filling sparite. Stable carbon isotopes show highly 13C-depleted values, as low as δ13CVPDB = -53‰, indicative of authigenic carbonate precipitation via the anaerobic oxidation of biogenic methane. Abundant and well-preserved fauna include multiple species of bivalves, worm tubes, ammonites and gastropods. Methane seepage is calculated to have lasted ~500,000 years and was brought about by a tensional stress regime as well as salt diapirism related faulting

Data from: The purging of deleterious mutations in simple and complex mating environments

There is a general expectation that sexual selection should align with natural selection to aid the purging of deleterious mutations, yet experiments comparing purging under monogamy vs. polygamy have provided mixed results. Recent studies suggest that this may be because the simplified mating environments used in these studies reduces the benefit of sexual selection through males and hampers natural selection through females by increasing costs associated with sexual conflict. To test the effect of the physical mating environment on purging, we use experimental evolution in Drosophila melanogaster to track the frequency of four separate deleterious mutations in replicate populations that experience polygamy under either a simple or structurally complex mating arena while controlling for arena size. Consistent with past results suggesting a greater net benefit of polygamy in a complex environment, two of the mutations were purged significantly faster in this environment. The other two mutations showed no significant difference between environments

Mutant allele and homozygote mutant genotype frequencies from experimental populations

This file contains data on mutant allele frequencies and homozygote mutant genotype frequencies at various time points (generations) in independent, replicate populations experimentally evolving in either a complex or simple mating environment. Each row corresponds to a frequency estimate from a particular population in a given generation. Columns are: mutant: the mutation in question; population: an arbitrary ID number given to each replicate population (6 populations per mutation, 3 in each treatment); treatment: simple vs. complex mating treatment; generation: the generation in which the given frequency was estimated; type: whether the frequency is that of the mutant allele (as estimate from a set of test crosses) or the mutant homozygote genotype; frequency - the frequency estimate expressed as a proportion

Table S1. Initial geneotype and allele frequencies. from The purging of deleterious mutations in simple and complex mating environments

Initial genotype and allele frequencies in replicate experimental populations of each mutation upon their foundin

Figure S1. Pictures of the simple complex mating arenas. from The purging of deleterious mutations in simple and complex mating environments

Overhead views of the simple and complex mating arenas with the lids removed and inverted