Phylogeny and Historical Ecology of Rhodocoma (Restionaceae) from the Cape Floristic Region

A macroevolutionary analysis of macroecological relationships in Rhodocoma revealed a complex history of rapid ecological divergence, as well as genetic isolation via shifts in flowering times. The rate and extent of divergence observed among even the youngest of species pairs indicated that the selective forces driving these processes are strong enough to effect substantial amounts of ecological change in relatively short periods of time, and are potentially important factors promoting the origin and persistence of species diversity not only in Rhodocoma, but also the African Restionaceae as a whole. These results also suggest that the rate and extent of ecological differentiation can vary between lineages, and this may be a consequence of variations in the intensities of selective regimes or phylogenetic constraints that different lineages experience. Investigation into the nature of this differentiation revealed that much of it has occurred along altitudinal gradients, but in tandem with substantial shifts in other ecological parameters such as rainfall and fire survival. This multidimensionality of ecological differentiation increases the number of possible combinations of ecological parameters and may allow for a more precise partitioning of niche space

Leadership in Sport Organizations

First paragraph: The ability to lead, inspire and motivate people is an important human characteristic. Indeed, it has been suggested that leadership is vital for effective organizational and societal functioning (Antonakis, Cianciolo, & Sternberg, 2004), with great or poor organizational, military, or sport performances frequently credited to great leadership or lack thereof. Therefore, it is not surprising that leadership has become one of the most studied topics within the social sciences (Antonakis et al., 2004). Leadership has been studied from a number of different perspectives (e.g., trait, behavioural, contingency, relational, skeptic, information-processing based approaches) which has resulted in a large number of different theories and models of leadership. Indeed, as long ago as 1971, Fiedler (1971) stated that, “there are almost as many definitions of leadership as there are theories of leadership - and there almost as many theories of leadership as there are psychologists working in the field” (p. 1)

Functional immunoglobulin transgenes guide ordered B-cell differentiation in Rag-1-deficient mice

We have examined the regulatory role of the individual components of the immunoglobulin antigen receptor in B-cell development by transgenic complementation of Rag-1 deficient (Rag-1⁻) mice. Complementation with a membrane µ heavy chain (µHC) gene allows progression of developmentally arrested Rag-1⁻ pro-B-cells to the small pre-B cell stage, whereas the introduction of independently integrated µHC and κ light chain (κLC) transgenes promotes the appearance of peripheral lymphocytes which, however, remain unresponsive to external stimuli. Complete reconstitution of the B-cell lineage and the emergence of functionally nature Rag-1⁻ peripheral B cells is achieved by the introduction of cointegrated heavy and light chain transgenes encoding an anti-H-2^k antibody. This experimental system demonstrates the competence of the µHC and κLC to direct and regulate the sequential stages of B-cell differentiation, defines the time at which negative selection of self-reactive B cells occurs, and shows that elimination of these cells occurs equally well in the absence of Rag-1 as in its presence. These data also support the hypothesis that Rag-1 directly participates in the V(D)J recombination process

Non-equilibrium dynamics and floral trait interactions shape extant angiosperm diversity.

Why are some traits and trait combinations exceptionally common across the tree of life, whereas others are vanishingly rare? The distribution of trait diversity across a clade at any time depends on the ancestral state of the clade, the rate at which new phenotypes evolve, the differences in speciation and extinction rates across lineages, and whether an equilibrium has been reached. Here we examine the role of transition rates, differential diversification (speciation minus extinction) and non-equilibrium dynamics on the evolutionary history of angiosperms, a clade well known for the abundance of some trait combinations and the rarity of others. Our analysis reveals that three character states (corolla present, bilateral symmetry, reduced stamen number) act synergistically as a key innovation, doubling diversification rates for lineages in which this combination occurs. However, this combination is currently less common than predicted at equilibrium because the individual characters evolve infrequently. Simulations suggest that angiosperms will remain far from the equilibrium frequencies of character states well into the future. Such non-equilibrium dynamics may be common when major innovations evolve rarely, allowing lineages with ancestral forms to persist, and even outnumber those with diversification-enhancing states, for tens of millions of years

Impairment of organ-specific T cell negative selection by diabetes susceptibility genes: genomic analysis by mRNA profiling

BACKGROUND T cells in the thymus undergo opposing positive and negative selection processes so that the only T cells entering circulation are those bearing a T cell receptor (TCR) with a low affinity for self. The mechanism differentiating negative from positive selection is poorly understood, despite the fact that inherited defects in negative selection underlie organ-specific autoimmune disease in AIRE-deficient people and the non-obese diabetic (NOD) mouse strain RESULTS Here we use homogeneous populations of T cells undergoing either positive or negative selection in vivo together with genome-wide transcription profiling on microarrays to identify the gene expression differences underlying negative selection to an Aire-dependent organ-specific antigen, including the upregulation of a genomic cluster in the cytogenetic band 2F. Analysis of defective negative selection in the autoimmune-prone NOD strain demonstrates a global impairment in the induction of the negative selection response gene set, but little difference in positive selection response genes. Combining expression differences with genetic linkage data, we identify differentially expressed candidate genes, including Bim, Bnip3, Smox, Pdrg1, Id1, Pdcd1, Ly6c, Pdia3, Trim30 and Trim12. CONCLUSION The data provide a molecular map of the negative selection response in vivo and, by analysis of deviations from this pathway in the autoimmune susceptible NOD strain, suggest that susceptibility arises from small expression differences in genes acting at multiple points in the pathway between the TCR and cell death.This work was supported by grants from the NHMRC and the Juvenile Diabetes Research Foundation

The role of discharge variability in determining alluvial stratigraphy

We illustrate the potential for using physics-based modeling to link alluvial stratigraphy to large river morphology and dynamics. Model simulations, validated using ground penetrating radar data from the Río Paraná, Argentina, demonstrate a strong relationship between bar-scale set thickness and channel depth, which applies across a wide range of river patterns and bar types. We show that hydrologic regime, indexed by discharge variability and flood duration, exerts a first-order influence on morphodynamics and hence bar set thickness, and that planform morphology alone may be a misleading variable for interpreting deposits. Indeed, our results illustrate that rivers evolving under contrasting hydrologic regimes may have very similar morphology, yet be characterized by marked differences in stratigraphy. This realization represents an important limitation on the application of established theory that links river topography to alluvial deposits, and highlights the need to obtain field evidence of discharge variability when developing paleoenvironmental reconstructions. Model simulations demonstrate the potential for deriving such evidence using metrics of paleocurrent variance