A phylogenetic mixture model for detecting pattern-heterogeneity in gene sequence or character-state data

We describe a general likelihood-based 'mixture model' for inferring phylogenetic trees from gene-sequence or other character-state data. The model accommodates cases in which different sites in the alignment evolve in qualitatively distinct ways, but does not require prior knowledge of these patterns or partitioning of the data. We call this qualitative variability in the pattern of evolution across sites "pattern-heterogeneity" to distinguish it from both a homogenous process of evolution and from one characterized principally by differences in rates of evolution. We present studies to show that the model correctly retrieves the signals of pattern-heterogeneity from simulated gene-sequence data, and we apply the method to protein-coding genes and to a ribosomal 12S data set. The mixture model outperforms conventional partitioning in both these data sets. We implement the mixture model such that it can simultaneously detect rate- and pattern-heterogeneity. The model simplifies to a homogeneous model or a rate- variability model as special cases, and therefore always performs at least as well as these two approaches, and often considerably improves upon them. We make the model available within a Bayesian Markov-chain Monte Carlo framework for phylogenetic inference, as an easy-to-use computer program.

Floral ontogeny in Polygalaceae and its bearing on the homologies of keeled flowers in Fabales

Keeled flowers are characteristic of many species of Polygalaceae (tribe Polygaleae), in which there is often a distinctive crest located at the abaxial petal. This study of floral ontogeny across the entire family highlights potential suites of characters that relate to the evolution of keeled and crested flowers. One character suite encompasses interconnected transformations of the lateral perianth organs acting as an evolutionary module: bracteoles, lateral sepals (with delayed initiation and petaloid appearance), and lateral petals (suppressed or lost). The plastochron between initiation of the lateral sepals and that of the other sepals is relatively long in the tribe Polygaleae, in which the calyx is usually heteromorphic. By contrast, in the petal whorl, the difference between a zygomorphic and an actinomorphic corolla involves organ suppression rather than heterochrony. Four primary androecial patterns are identified in the family, and the gynoecium ranges between syncarpous‐bicarpellate and multicarpellate. Stigma diversity is based on two primary morphological types: one in which the papillate stigmatic surfaces lie close together, the other in which they are physically separated. The floral ontogeny of Polygalaceae is considered alongside comparative data available for other members of the order Fabales, and hypotheses to account for the similarities and differences between keeled flowers are discussed.

Simultaneous bridge-localized and mixed-valence character in diruthenium radical cations featuring diethynylaromatic bridging ligands

A series of bimetallic ruthenium complexes [{Ru(dppe)Cp*}2(μ-C≡CArC≡C)] featuring diethynylaromatic bridging ligands (Ar = 1,4-phenylene, 1,4-naphthylene, 9,10-anthrylene) have been prepared and some representative molecular structures determined. A combination of UV–vis–NIR and IR spectroelectrochemical methods and density functional theory (DFT) have been used to demonstrate that one-electron oxidation of compounds [{Ru(dppe)Cp*}2(μ-C≡CArC≡C)](HC≡CArC≡CH = 1,4-diethynylbenzene; 1,4-diethynyl-2,5-dimethoxybenzene; 1,4-diethynylnaphthalene; 9,10-diethynylanthracene) yields solutions containing radical cations that exhibit characteristics of both oxidation of the diethynylaromatic portion of the bridge, and a mixed-valence state. The simultaneous population of bridge-oxidized and mixed-valence states is likely related to a number of factors, including orientation of the plane of the aromatic portion of the bridging ligand with respect to the metal d-orbitals of appropriate π-symmetry.

Self, role and character: developing a professional identity as a drama teacher

The paper reports on research into what may have influenced trainees on four post-graduate teacher training courses in England to become specialist drama teachers rather than pursue careers in the world of professional entertainment. In doing so it raises questions regarding the value of considering teaching as a performing art. The paper goes on to explore how drama trainees regard an understanding of performance, and an ability to both use and demonstrate performance techniques, as integral to their role as subject specialists. The subsequent discussion examines how a drama teacher’s professional identity may be seen as being made up of the three inter-connected elements, self, role and character. Thus, while all teaching may be considered to involve some elements of performativity , this paper suggests that, for the drama specialist, an understanding of what constitutes ‘performance’ has a particular importance. One conclusion drawn from the research is that recognising the place of performance in their practice may result in experienced teachers of drama regarding themselves as artists whose art is teaching drama; another is that recognising the different ways in which adopting a role may involve performance could be of value to all teachers and teacher educators.

Superfast non-linear diffusion: capillary transport in particulate porous media

The migration of liquids in porous media, such as sand, has been commonly considered at high saturation levels with liquid pathways at pore dimensions. In this letter we reveal a low saturation regime observed in our experiments with droplets of extremely low volatility liquids deposited on sand. In this regime the liquid is mostly found within the grain surface roughness and in the capillary bridges formed at the contacts between the grains. The bridges act as variable-volume reservoirs and the flow is driven by the capillary pressure arising at the wetting front according to the roughness length scales. We propose that this migration (spreading) is the result of interplay between the bridge volume adjustment to this pressure distribution and viscous losses of a creeping flow within the roughness. The net macroscopic result is a special case of non-linear diffusion described by a superfast diffusion equation (SFDE) for saturation with distinctive mathematical character. We obtain solutions to a moving boundary problem defined by SFDE that robustly convey a time power law of spreading as seen in our experiments.

(Re)enchanting geography? The nature of being critical and the character of critique in human geography

Enchantment is a term frequently used by human geographers to express delight, wonder or that which cannot be simply explained. However, it is a concept that has yet to be subject to sustained critique, specifically how it can be used to progress geographic thought and praxis. This paper makes sense of, and space for, the unintelligibility of enchantment in order to encourage a less repressed, more cheerful way of engaging with the geographies of the world. We track back through our disciplinary heritage to explore how geographers have employed enchantment as a force through which the world inspires affective attachment. We review the terrain of the debate surrounding recent geographical engagements with enchantment, focusing on the nature of being critical and the character of critique in human geography, offering a new ‘enchanted’ stance to our geographical endeavours. We argue that the moment of enchantment has not passed with the current challenging climate; if anything, it is more pressing.

Mapania multiflora, a distinctive new species of Cyperaceae (Mapanioideae) from Borneo

Mapania multiflora is described and illustrated. It is vegetatively similar to taxa with broad leaves and pseudopetioles, such as M. cuspidata. However, it is reproductively similar to sect. Thoractostachyum with a paniculate inflorescence and furrowed fruit. The DNA is similar to M. bancana in sect. Thoractostachyum, in the three sampled cpDNA regions: atpH-F, trnL-F and psbA-trnH. However, it is identical to none of these due to its unique combination of vegetative, reproductive and molecular characteristics.

Late-Holocene changes in character and behaviour of land-terminating glaciers on James Ross Island, Antarctica

Virtually no information is available on the response of land-terminating Antarctic Peninsula glaciers to climate change on a centennial timescale. This paper analyses the topography, geomorphology and sedimentology of prominent moraines on James Ross Island, Antarctica, to determine geometric changes and to interpret glacier behaviour. The moraines are very likely due to a late-Holocene phase of advance and featured (1) shearing and thrusting within the snout, (2) shearing and deformation of basal sediment, (3) more supraglacial debris than at present and (4) short distances of sediment transport. Retreat of ∼100 m and thinning of 15–20 m has produced a loss of 0.1 km3 of ice. The pattern of surface lowering is asymmetric. These geometrical changes are suggested most simply to be due to a net negative mass balance caused by a drier climate. Comparisons of the moraines with the current glaciological surface structure of the glaciers permits speculation of a transition from a polythermal to a cold-based thermal regime. Small land-terminating glaciers in the northern Antarctic Peninsula region could be cooling despite a warming climate.