Phylogeography of the pelagic fish Seriola lalandi at different scales: confirmation of inter-ocean population structure and evaluation of southern African genetic diversity

The study investigated the global and regional phylogeography of the yellowtail kingfish Seriola lalandi by examining genetic diversity and population genetic structure of this species at inter-and intra-ocean level and on a regional scale. DNA fragments of two mitochondrial genes, cytochrome b (Cytb) and cytochrome c oxidase subunit I (COI) and one nuclear gene, recombination activating gene 1 (RAG1), were sequenced to investigate the global-scale phylogeography of this species. The population genetic structure within the South Pacific, as well as along the South African coastline, was examined further using six microsatellite markers. Three distinct clades were identified for S. lalandi, which correspond with previously described subspecies of the North-East Pacific, North-West Pacific and the Southern Hemisphere. Within the latter, additional divergence was observed between the South Pacific and the South-East Atlantic regions. Divergence estimates were indicative of a Pacific origin for S. lalandi populations, because of Pleistocene vicariant events. Microsatellite analyses revealed overall significant genetic differentiation between South African and South Pacific samples. This corroborates recent findings on the global phylogeography of the species. No population differentiation was observed within South Africa, indicating high levels of gene flow.     

Genomic resources for the spotted ragged-tooth shark Carcharias taurus

Genomic data can be a useful tool in the management and conservation of biodiversity. Here, we report the development of genomic resources for the spotted ragged-tooth shark Carcharias taurus using genome-wide DNA data from Illumina next-generation sequencing. We explored two commonly used genetic marker types: microsatellites and mitochondrial DNA. A total of 4 394 putative microsatellites were identified, of which 10 were tested on 24 individuals and found to have ideal properties for population genetic analyses. Additionally, we reconstructed the first complete mitochondrial genome of a South African spotted ragged-tooth shark, and highlight the most informative gene regions to facilitate future primer design. The data reported here may serve as a resource for future studies and can ultimately be applied in the sustainable conservation and fisheries management of this apex predator.     

Carbon losses in soils previously exposed to elevated atmospheric CO2 in a chaparral ecosystem: Potential implications for a sustained biospheric C sink

Between 1996 and 2001 an experimental set up in a chaparral community near San Diego, CA, examined various plant and ecosystem responses to CO₂ concentrations ranging from 250 to 750 μl l^− 1. These experiments indicated a significant increase in soil C sequestration as CO₂ rose above the ambient levels. In 2003, two years after the cessation of the CO₂ treatments, we returned to this site to examine soil C dynamics with a particular emphasis on stability of specific pools of C. We found that in as little as two years, C content in the surface soils (0–15 cm) of previously CO₂ enriched plots had dropped to levels below those of the ambient and pretreatment soils. In contrast, C retained in response to CO₂ enrichment was more durable in the deeper soil layers (> 25 cm deep) where both organic and inorganic C were on average 26% and 55% greater, respectively, than C content of ambient plots. Using stable isotope tracers, we found that treatment C represented 25% of total soil C and contributed to 55% of soil CO₂ efflux, suggesting that most of treatment C is readily accessible to decomposers. We also found that, C present before CO₂ fumigation was decomposed at a faster rate in the plots that were exposed to elevated CO₂ than in those exposed to ambient CO₂ levels. To our knowledge, this is the first report that allows for a detail accounting of soil C after ceasing CO₂ treatments. Our study provides a unique insight to how stable the accrued soil C is as CO₂ increases in the atmosphere.