Persistence and vulnerability of island endemic birds.

This thesis investigates the dynamic relationship between the processes of extinction on islands and the traits of oceanic island endemic birds associated with persistence and vulnerability. This is explored using the comparative method and a data set of all birds endemic to oceanic islands. Two case studies are then presented to examine the resilience of the island endemic birds of Principe and Boné de Joquei in the Gulf of Guinea. When comparing closely related oceanic island and mainland birds, clutch size is lower on islands and, within islands it continues to decline as the distribution area of a species decreases. Small birds (<27 cm in body length) tend to get larger, and there is a trend for sexual size dimorphism to increase on oceanic islands. Recent extinction rates are lower on islands that have been exposed to humans for a long period of time. The birds on such islands are also less threatened by the introduction of exotics. A long period of exposure to humans also reduces the probability that the remaining species are flightless, ground-nesting, or non-forest- restricted endemics. When comparing island and mainland species that have similar areas of distribution, there is no significant difference in extinction risk. However, island birds are more threatened by introduced species. On oceanic islands, flightless birds, ground-nesting birds, birds with larger body size, and habitat specialists are associated with a greater risk of extinction than other birds. Sexually selected traits such as sexual body size dimorphism and dichromatism are not associated with elevated extinction risk. The resilience of the island endemic birds on Principe appears to be associated with a unique land use history and evolutionary exposure to predators, competitors and disease. Finally, a state of super abundance may be essential for the long-term persistence of endemic birds on small remote oceanic islands.Open acces

Cyclic AMP-specific phosphodiesterase, PDE8A1, is activated by protein kinase A-mediated phosphorylation

The cyclic AMP-specific phosphodiesterase PDE8 has been shown to play a pivotal role in important processes such as steroidogenesis, T cell adhesion, regulation of heart beat and chemotaxis. However, no information exists on how the activity of this enzyme is regulated. We show that under elevated cAMP conditions, PKA acts to phosphorylate PDE8A on serine 359 and this action serves to enhance the activity of the enzyme. This is the first indication that PDE8 activity can be modulated by a kinase, and we propose that this mechanism forms a feedback loop that results in the restoration of basal cAMP levels. (C) 2012 Federation of European Biochemical Societies. Published by Elsevier B. V. All rights reserve

Variations of radiocarbon in tree rings: southern hemisphere offset preliminary results

The Queen's University of Belfast, Northern Ireland and University of Waikato, Hamilton, New Zealand radiocarbon laboratories have undertaken a series of high-precision measurements on decadal samples of dendrochronologically dated oak (Quercus patrea) and cedar (Libocedrus bidwillii) from Great Britain and New Zealand, respectively. The results show a real atmospheric offset of 3.4 ± 0.6% (27.2 ± 4.7 ¹⁴C yr) between the two locations for the interval AD 1725 to AD 1885, with the Southern Hemisphere being depleted in ¹⁴C. This result is less than the value currently used to correct Southern Hemisphere calibrations, possibly indicating a gradient in Δ¹⁴C within the Southern Hemisphere

The ABC transporter gene family of Caenorhabditis elegans has implications for the evolutionary dynamics of multidrug resistance in eukaryotes

BACKGROUND: Many drugs of natural origin are hydrophobic and can pass through cell membranes. Hydrophobic molecules must be susceptible to active efflux systems if they are to be maintained at lower concentrations in cells than in their environment. Multi-drug resistance (MDR), often mediated by intrinsic membrane proteins that couple energy to drug efflux, provides this function. All eukaryotic genomes encode several gene families capable of encoding MDR functions, among which the ABC transporters are the largest. The number of candidate MDR genes means that study of the drug-resistance properties of an organism cannot be effectively carried out without taking a genomic perspective. RESULTS: We have annotated sequences for all 60 ABC transporters from the Caenorhabditis elegans genome, and performed a phylogenetic analysis of these along with the 49 human, 30 yeast, and 57 fly ABC transporters currently available in GenBank. Classification according to a unified nomenclature is presented. Comparison between genomes reveals much gene duplication and loss, and surprisingly little orthology among analogous genes. Proteins capable of conferring MDR are found in several distinct subfamilies and are likely to have arisen independently multiple times. CONCLUSIONS: ABC transporter evolution fits a pattern expected from a process termed 'dynamic-coherence'. This is an unusual result for such a highly conserved gene family as this one, present in all domains of cellular life. Mechanistically, this may result from the broad substrate specificity of some ABC proteins, which both reduces selection against gene loss, and leads to the facile sorting of functions among paralogs following gene duplication

Towards a radiocarbon calibration for oxygen isotope stage 3 using New Zealand kauri (Agathis australis)

It is well known that radiocarbon years do not directly equate to calendar time. As a result, considerable effort has been devoted to generating a decadally resolved calibration curve for the Holocene and latter part of the last termination. A calibration curve that can be unambiguously attributed to changes in atmospheric ¹⁴C content has not, however, been generated beyond 26 kyr cal BP, despite the urgent need to rigorously test climatic, environmental, and archaeological models. Here, we discuss the potential of New Zealand kauri (Agathis australis) to define the structure of the ¹⁴C calibration curve using annually resolved tree rings and thereby provide an absolute measure of atmospheric ¹⁴C. We report bidecadally sampled ¹⁴C measurements obtained from a floating 1050-yr chronology, demonstrating repeatable ¹⁴C measurements near the present limits of the dating method. The results indicate that considerable scope exists for a high-resolution ¹⁴C calibration curve back through OIS-3 using subfossil wood from this source