A new burnetiamorph (Therapsida: Biarmosuchia) from the Lower Beaufort Group of South Africa

The basal clade Burnetiamorpha is known from only two specimens representing two genera, Proburnetia from the Severodvinskian horizon of the Vyatka River Basin in the Kotelnich district of Russia, and Burnetia from the Dicynodon Assemblage Zone of the Beaufort Group of South Africa. Both genera are of Late Tatarian (Late Permian) age. This paper describes the cranial morphology of a new genus of burnetiamorph, Bullacephalus , from the Late Permian Tapinocephalus Assemblage Zone of the Beaufort Group of South Africa. It is known from a relatively complete skull and lower jaw and is the best preserved burnetiamorph yet discovered. Apart from being the oldest member of the clade, Bullacephalus is also morphologically the least derived and provides new evidence on the phylogeny of this poorly understood group of basal therapsids.     

Stem deformity inPinus radiata plantations in south-eastern Australia

Plantations of radiata pine (P. radiata D.Don) on soils previously under legume based pastures have a high incidence of stem deformity compared with forest soils. A comparison of soil properties and tree nutrition of 5 to 7 year-old radiata pine on former pastures in the first part of the study showed that stem deformity was strongly correlated with mineralisation of soil N and in particular with nitrification. Other soil properties that have changed as a result of pasture improvement, e.g. pH, available P and Mn, were only partially correlated with stem deformity. In the second part of the study, the role of N availability and other soil properties in the expression of deformity was further investigated in a separate field experiment on soils formerly under native eucalypt forest, tobacco cropping, and improved pasture. Young radiata pine plantings were treated with lime, phosphorus, and nitrogen applied as urea and sodium nitrate. Liming increased soil pH by around 1.5 units, raised exchangeable Ca²⁺ and decreased available Mn. Soil mineral N content was only marginally affected by liming. Superphosphate increased soil available P and raised levels of P in foliage. Changes in soil pH, availability of P, Mn, and B did not affect growth or stem deformity at any of the sites. In contrast, application of N fertilisers at 200 and 600 kg N ha^-1 increased mineral N content and stimulated nitrification, particularly at the forest site. The high rate of N fertiliser increased basal area at the forest site by 45%, but also raised the level of stem deformity from 12% to 56%. At the tobacco and pasture sites, this treatment did not increase growth and did not significantly raise stem deformity above the already high basic level of deformity (63%). Implications of stem deformity in young plantations of radiata pine on potential utilisation later in the rotation are discussed.     

Distance‐driven species turnover in Bornean rainforests: homogeneity and heterogeneity in primary and post‐logging forests

Selective logging is practiced extensively within tropical rainforests of south‐east Asia, and its impact on local biodiversity is well documented. Little is known, however, about the impact of selective logging on patterns of spatial heterogeneity of species. We set out to test the hypothesis that selective logging will lead to a homogenization of the associated faunal assemblages, using moths (Lepidoptera) as our subject taxa. Large‐scale transects were established within primary and post‐logging lowland mixed dipterocarp rainforests around the Danum Valley Conservation Area and surroundings, Sabah, Malaysia (4°50′N–5°00′N and 117°35′E–117°45′E). Five study sites were located within each habitat with geometrically increasing inter‐site distances. Macro‐moths plus Pyraloidea were sampled by light trapping in 2007 and 2008. Vegetation state was also measured at each site. A clear distance–decay relationship (decreasing assemblage similarity with increasing geographic distances) was observed in primary forest but was absent in the post‐logging forest. Large, comparable numbers of macro‐moth species were found in both primary and post‐logging forests. There were no significant differences in moth assemblage composition between primary and post‐logging forests. There are important structural differences between primary and post‐logging forests reflected in the moth assemblages. A two‐stage hypothesis combining both neutral and niche concepts is probably the most parsimonious explanation of these results. First, the composition of the moth assemblage is almost certainly determined locally by the variety of plant–hosts available to larvae, with the plants representing important niche dimensions for the moth species. Second the turnover (or lack of same) in the underlying plant assemblage probably reflects clumping and, in turn, dispersal capacity of the commoner plants in each forest type. Although the impact of selective logging may be subtle, this study suggests that selective logging results in the spatial homogenization of macro‐moth assemblages.     

Midpoint attractors and species richness: Modelling the interaction between environmental drivers and geometric constraints

We introduce a novel framework for conceptualising, quantifying and unifying discordant patterns of species richness along geographical gradients. While not itself explicitly mechanistic, this approach offers a path towards understanding mechanisms. In this study, we focused on the diverse patterns of species richness on mountainsides. We conjectured that elevational range midpoints of species may be drawn towards a single midpoint attractor – a unimodal gradient of environmental favourability. The midpoint attractor interacts with geometric constraints imposed by sea level and the mountaintop to produce taxon‐specific patterns of species richness. We developed a Bayesian simulation model to estimate the location and strength of the midpoint attractor from species occurrence data sampled along mountainsides. We also constructed midpoint predictor models to test whether environmental variables could directly account for the observed patterns of species range midpoints. We challenged these models with 16 elevational data sets, comprising 4500 species of insects, vertebrates and plants. The midpoint predictor models generally failed to predict the pattern of species midpoints. In contrast, the midpoint attractor model closely reproduced empirical spatial patterns of species richness and range midpoints. Gradients of environmental favourability, subject to geometric constraints, may parsimoniously account for elevational and other patterns of species richness.     

Lianas as a food resource for herbivorous insects: a comparison with trees

Woody climbers or, ‘lianas’, are one of the features that characterise rainforests. They contribute substantially to plant diversity and leaf biomass which makes them a potentially important food source for herbivores. Here, we focus on insect herbivores, folivores in particular, to show how disparities in the quantitative and qualitative availability of leaves between lianas and trees may differentially influence insect folivory and the herbivore communities themselves. We develop a conceptual model and show that lianas in general have lower structural and chemical defences, a greater nutritional profile and a preferable phenology in comparison with trees, which, contrary to our expectations, has led to assemblages of more‐specialised insects. The impacts this has on higher trophic levels and broader ecological networks, however, are poorly known. We show through a study of four tropical floras from different biogeographic realms that lianas are likely to be a target for a wide range of insect herbivore taxa as they are a phylogenetically diverse group and increase diversity of higher taxa at local scales. This, in combination with their highly palatable leaves, may also make them a suitable temporary food source for insects during times when preferred host plants are scarce. This phenomenon has been observed in mammalian herbivores but awaits investigation in insects as does the effects this may have on survival and fitness. Apparent recent increases in liana abundances in some forests, likely due to climate change, makes understanding their role in supporting and maintaining biodiversity an increasingly important and necessary challenge. Since trees or saplings have usually been the subject of studies on insect herbivory, major knowledge gaps remain about the ways in which lianas contribute to, support and maintain the ecosystems in which they exist. We use our conceptual model to guide future research directions and express the necessity for caution when extrapolating explanations of herbivory derived from data on trees to growth forms with fundamentally different ecologies.     

Crescentic glomerulonephritis--a manifestation of a nephritogenic Th1 response?

Crescentic glomerulonephritis (GN) is the histopathological correlate of the clinical syndrome of rapidly progressive glomerulonephritis. Glomerular crescent formation complicates proliferative forms of GN and indicates severe disease with a poor renal prognosis. In the past 10 years evidence from experimental models of GN and from human disease has accumulated suggesting that crescentic glomerulonephritis is a manifestation of a delayed type hypersensitivity (DTH)-like response to nephritogenic antigens. The elucidation of T helper 1 (Th1) and Th2 subsets in mice and in humans has led to the hypothesis that crescentic GN is a manifestation of a Th1 predominant DTH mediated immune response. Recent experiments performed mainly in a murine model of crescentic glomerulonephritis have tested this hypothesis. Crescent formation in this model is substantially interleukin (IL)-12 and interferon-gamma (IFN-gamma) dependent. Administration of IL-12, deletion of endogenous IL-4 or IL-10 results in enhanced disease, while administration of exogenous IL-4 and/or IL-10 reduces crescentic injury. These findings, together with the available evidence from human studies (examining the pattern of immune effectors in glomeruli, data on cytokine production by peripheral blood mononuclear cells and case reports of the induction of proliferative and/or crescentic GN by administration of IFN-gamma or IL-2) suggest that human crescentic GN is manifestation of a Th1 mediated DTH-like nephritogenic immune response.