To breed or not to breed: a seabird's response to extreme climatic events

Intermittent breeding is an important life-history strategy that has rarely been quantified in the wild and for which drivers remain unclear. It may be the result of a trade-off between survival and reproduction, with individuals skipping breeding when breeding conditions are below a certain threshold. Heterogeneity in individual quality can also lead to heterogeneity in intermittent breeding. We modelled survival, recruitment and breeding probability of the red-footed booby (Sula sula), using a 19 year mark–recapture dataset involving more than 11 000 birds. We showed that skipping breeding was more likely in El-Niño years, correlated with an increase in the local sea surface temperature, supporting the hypothesis that it may be partly an adaptive strategy of birds to face the trade-off between survival and reproduction owing to environmental constraints. We also showed that the age-specific probability of first breeding attempt was synchronized among different age-classes and higher in El-Niño years. This result suggested that pre-breeders may benefit from lowered competition with experienced breeders in years of high skipping probabilities.     

Microdot technology for individual marking of small arthropods

• 1 Individual mark–release–recapture is an important method for gathering data on insect movement, although it is limited by the constraints of tagging small insects with individual information.
• 2 Microdots, originally developed for covert security applications, are small polymer discs (diameter 0.5 mm) bearing up to 26 characters of information and have the potential as an alternative to the larger bee tags. In the present study, we test microdots for the individual marking of a 9‐mm parasitoid wasp.
• 3 We individually marked 505 wasps. The recapture rate was 24% of individuals over 189 recapture events, for which 84% retained legible microdot labels. Movement was in the range 0–161 m with a mean displacement 21.2 ± 2.7 m. A captive survival experiment showed no difference in lifespan between marked and unmarked wasps.
• 4 The present study shows that microdots can provide an effective, durable, low‐cost method for individually tagging small insects. The technique offers new opportunities by greatly expanding the capability for individually marking small insects, shifting the minimum size below that of bee tags, which is the only other manufactured option for individualized miniature marking.

     

Cultivation shapes genetic novelty in a globally important invader

Acacia saligna is a species complex that has become invasive in a number of countries worldwide where it has caused substantial environmental and economic impacts. Understanding genetic and other factors contributing to its success may allow managers to limit future invasions of closely related species. We used three molecular markers to compare the introduced range (South Africa) to the native range (Western Australia). Nuclear markers showed that invasive populations are divergent from native populations and most closely related to a cultivated population in Western Australia. We also found incongruence between nuclear and chloroplast data that, together with the long history of cultivation of the species, suggest that introgressive hybridization (coupled with chloroplast capture) may have occurred within A. saligna. While we could not definitively prove introgression, the genetic distance between cultivated and native A. saligna populations was comparable to known interspecific divergences among other Acacia species. Therefore, cultivation, multiple large‐scale introductions and possibly introgressive hybridization have rapidly given rise to the divergent genetic entity present in South Africa. This may explain the known global variation in invasiveness and inaccuracy of native bioclimatic models in predicting potential distributions.     

Identification and quantification of peptides and proteins secreted from prostate epithelial cells by unbiased liquid chromatography tandem mass spectrometry using goodness of fit and analysis of variance

The proteins secreted by prostate cancer cells (PC3(AR)6) were separated by strong anion exchange chromatography, digested with trypsin and analyzed by unbiased liquid chromatography tandem mass spectrometry with an ion trap. The spectra were matched to peptides within proteins using a goodness of fit algorithm that showed a low false positive rate. The parent ions for MS/MS were randomly and independently sampled from a log-normal population and therefore could be analyzed by ANOVA. Normal distribution analysis confirmed that the parent and fragment ion intensity distributions were sampled over 99.9% of their range that was above the background noise. Arranging the ion intensity data with the identified peptide and protein sequences in structured query language (SQL) permitted the quantification of ion intensity across treatments, proteins and peptides. The intensity of 101,905 fragment ions from 1421 peptide precursors of 583 peptides from 233 proteins separated over 11 sample treatments were computed together in one ANOVA model using the statistical analysis system (SAS) prior to Tukey-Kramer honestly significant difference (HSD) testing. Thus complex mixtures of proteins were identified and quantified with a high degree of confidence using an ion trap without isotopic labels, multivariate analysis or comparing chromatographic retention times.     

Human tRNA genes function as chromatin insulators

Insulators help separate active chromatin domains from silenced ones. In yeast, gene promoters act as insulators to block the spread of Sir and HP1 mediated silencing while in metazoans most insulators are multipartite autonomous entities. tDNAs are repetitive sequences dispersed throughout the human genome and we now show that some of these tDNAs can function as insulators in human cells. Using computational methods, we identified putative human tDNA insulators. Using silencer blocking, transgene protection and repressor blocking assays we show that some of these tDNA-containing fragments can function as barrier insulators in human cells. We find that these elements also have the ability to block enhancers from activating RNA pol II transcribed promoters. Characterization of a putative tDNA insulator in human cells reveals that the site possesses chromatin signatures similar to those observed at other better-characterized eukaryotic insulators. Enhanced 4C analysis demonstrates that the tDNA insulator makes long-range chromatin contacts with other tDNAs and ETC sites but not with intervening or flanking RNA pol II transcribed genes.     

Paleoreconstruction of estuarine sediments reveal human‐induced weakening of coastal carbon sinks

Human activities in coastal areas frequently cause loss of benthic macrophytes (e.g. seagrasses) and concomitant increases in microalgal production through eutrophication. Whether such changes translate into shifts in the composition of sediment detritus is largely unknown, yet such changes could impact the role these ecosystems play in sequestrating CO₂. We reconstructed the sedimentary records of cores taken from two sites within Botany Bay, Sydney – the site of European settlement of Australia – to look for human‐induced changes in dominant sources of detritus in this estuary. Cores covered a period from the present day back to the middle Holocene (~6000 years) according to ²¹⁰Pb profiles and radiocarbon (¹⁴C) dating. Depositional histories at both sites could not be characterized by a linear sedimentation rate; sedimentation rates in the last 30–50 years were considerably higher than during the rest of the Holocene. C : N ratios declined and began to exhibit a microalgal source signature from around the time of European settlement, which could be explained by increased nutrient flows into the Bay caused by anthropogenic activity. Analysis of stable isotopic ratios of ¹²C/¹³C showed that the relative contribution of seagrass and C₃ terrestrial plants (mangroves, saltmarsh) to detritus declined around the time of rapid industrial expansion (~1950s), coinciding with an increase in the contribution of microalgal sources. We conclude that the relative contribution of microalgae to detritus has increased within Botany Bay, and that this shift is the sign of increased industrialization and concomitant eutrophication. Given the lower carbon burial efficiencies of microalgae (~0.1%) relative to seagrasses and C₃ terrestrial plants (up to 10%), such changes represent a substantial weakening of the carbon sink potential of Botany Bay – this occurrence is likely to be common to human‐impacted estuaries, and has consequences for the role these systems play in helping to mitigate climate change.     

Population Ecology of the Eastern Box Turtle in a Fragmented Landscape

Abstract: In the mid-Atlantic region, urban sprawl and development have resulted in habitat alterations and fragmentation; however, the effects on eastern box turtle (Terrapene carolina carolina) populations are unclear. To investigate the status of eastern box turtle populations in a fragmented landscape, we used mark—recapture and radiotelemetry to estimate population density, sex ratio, age structure, and survival on 4 study areas with differing degrees of isolation and human disturbance in northern New Castle County, Delaware, USA. We estimated adult population densities ranging from 0.81 turtles/ha to 3.62 turtles/ha among our 4 study areas. Sex ratios were male-biased at 2 study areas and balanced at 2 study areas. Proportion of juveniles ranged from 0% to 31%. Estimated annual survival rate ranged from 0.813 to 0.977. Mortality of radiotagged and marked turtles was primarily due to natural causes, but mowing was the primary cause of human-induced mortality. We found evidence of population decline at one study area due to low survival and recruitment. Human disturbances, isolation, and habitat composition appear to have the greatest influence on the box turtle populations we studied. To minimize mortality from human disturbance, we suggest planting crops adjacent to forest habitat that require no mowing or mowing at a height ≥15 cm. (JOURNAL OF WILDLIFE MANAGEMENT 72(3):745–753; 2008)