Sex differences in the drivers of reproductive skew in a cooperative breeder

Many cooperatively breeding societies are characterized by high reproductive skew, such that some socially dominant individuals breed, while socially subordinate individuals provide help. Inbreeding avoidance serves as a source of reproductive skew in many high‐skew societies, but few empirical studies have examined sources of skew operating alongside inbreeding avoidance or compared individual attempts to reproduce (reproductive competition) with individual reproductive success. Here, we use long‐term genetic and observational data to examine factors affecting reproductive skew in the high‐skew cooperatively breeding southern pied babbler (Turdoides bicolor). When subordinates can breed, skew remains high, suggesting factors additional to inbreeding avoidance drive skew. Subordinate females are more likely to compete to breed when older or when ecological constraints on dispersal are high, but heavy subordinate females are more likely to successfully breed. Subordinate males are more likely to compete when they are older, during high ecological constraints, or when they are related to the dominant male, but only the presence of within‐group unrelated subordinate females predicts subordinate male breeding success. Reproductive skew is not driven by reproductive effort, but by forces such as intrinsic physical limitations and intrasexual conflict (for females) or female mate choice, male mate‐guarding and potentially reproductive restraint (for males). Ecological conditions or “outside options” affect the occurrence of reproductive conflict, supporting predictions of recent synthetic skew models. Inbreeding avoidance together with competition for access to reproduction may generate high skew in animal societies, and disparate processes may be operating to maintain male vs. female reproductive skew in the same species.     

The stereospecificity of hydrogen abstraction by uridine diphosphoglucose dehydrogenase

UDP-glucose dehydrogenase catalyzes the incorporation of tritium into UDP-glucose (UDPG) in the presence of UDP-α-D-gluco-hexodialdose (UDP-Glc-6-CHO) and [B-³H]-NADH. The ³H is located exclusively at C-6 of the glucose moiety of UDPG and at least 79% of it is in the pro-R position. It is concluded that UDPG dehydrogenase catalyzes the abstraction of the pro-R hydrogen at C-6 of the glucose moiety of the substrate as the first step in the conversion of UDPG to UDP-glucuronic acid. The apparent lack of complete stereospecificity has been shown to result from a hitherto undetected reversible redox reaction prior to the release of UDP-glucuronic acid by the enzyme.     

Reduction of Technetium by Desulfovibrio desulfuricans: Biocatalyst Characterization and Use in a Flowthrough Bioreactor

Resting cells of Desulfovibrio desulfuricans coupled the oxidation of a range of electron donors to Tc(VII) reduction. The reduced technetium was precipitated as an insoluble low-valence oxide. The optimum electron donor for the biotransformation was hydrogen, although rapid rates of reduction were also supported when formate or pyruvate was supplied to the cells. Technetium reduction was less efficient when the growth substrates lactate and ethanol were supplied as electron donors, while glycerol, succinate, acetate, and methanol supported negligible reduction. Enzyme activity was stable for several weeks and was insensitive to oxygen. Transmission electron microscopy showed that the radionuclide was precipitated at the periphery of the cell. Cells poisoned with Cu(II), which is selective for periplasmic but not cytoplasmic hydrogenases, were unable to reduce Tc(VII), a result consistent with the involvement of a periplasmic hydrogenase in Tc(VII) reduction. Resting cells, immobilized in a flowthrough membrane bioreactor and supplied with Tc(VII)-supplemented solution, accumulated substantial quantities of the radionuclide when formate was supplied as the electron donor, indicating the potential of this organism as a biocatalyst to treat Tc-contaminated wastewaters.     

Mammalian Rho GTPases: new insights into their functions from in vivo studies

Rho GTPases are key regulators of cytoskeletal dynamics and affect many cellular processes, including cell polarity, migration, vesicle trafficking and cytokinesis. These proteins are conserved from plants and yeast to mammals, and function by interacting with and stimulating various downstream targets, including actin nucleators, protein kinases and phospholipases. The roles of Rho GTPases have been extensively studied in different mammalian cell types using mainly dominant negative and constitutively active mutants. The recent availability of knockout mice for several members of the Rho family reveals new information about their roles in signalling to the cytoskeleton and in development.     

The cost of being alone: the fate of floaters in a population of cooperatively breeding pied babblers Turdoides bicolor

The occurrence of group-living behaviour has often been explained by the benefits individuals receive through cooperation; including increased reproductive output, vigilance against predators, and load-lightening behaviour. However, to fully understand the benefits of group-living, it is important to quantify the costs of living alone. Here, we look at the fate of floaters (individuals who have no fixed territory and remain alone for extended periods) in a population of cooperatively breeding pied babblers Turdoides bicolor . We found that individuals spent less time foraging and more time vigilant for predators when found as a floater compared to when they were in a group. Consequently, they suffered a continuous loss of body mass, with long-term floaters suffering the highest losses. This had a long-term effect: floaters that eventually did regain a position in a group usually entered as helpers, in contrast to dispersers, who usually entered a new group as breeders. This high cost of living alone highlights the benefits of group-living and may help to understand patterns of delayed dispersal in some social species.