Testing alternative models for the conservation of koalas in fragmented rural-urban landscapes

Predicting the various responses of different species to changes in landscape structure is a formidable challenge to landscape ecology. Based on expert knowledge and landscape ecological theory, we develop five competing a priori models for predicting the presence/absence of the Koala (Phascolarctos cinereus) in Noosa Shire, south-east Queensland (Australia). A priori predictions were nested within three levels of ecological organization: in situ (site level) habitat (< 1 ha), patch level (100 ha) and landscape level (100-1000 ha). To test the models, Koala surveys and habitat surveys (n = 245) were conducted across the habitat mosaic. After taking into account tree species preferences, the patch and landscape context, and the neighbourhood effect of adjacent present sites, we applied logistic regression and hierarchical partitioning analyses to rank the alternative models and the explanatory variables. The strongest support was for a multilevel model, with Koala presence best predicted by the proportion of the landscape occupied by high quality habitat, the neighbourhood effect, the mean nearest neighbour distance between forest patches, the density of forest patches and the density of sealed roads. When tested against independent data (n = 105) using a receiver operator characteristic curve, the multilevel model performed moderately well. The study is consistent with recent assertions that habitat loss is the major driver of population decline, however, landscape configuration and roads have an important effect that needs to be incorporated into Koala conservation strategies.

The importance of forest area and configuration relative to local habitat factors for conserving forest mammals: A case study of koalas in Queensland, Australia

The loss and fragmentation of forest habitats by human land use are recognised as important factors influencing the decline of forest-dependent fauna. Mammal species that are dependent upon forest habitats are particularly sensitive to habitat loss and fragmentation because they have highly specific habitat requirements, and in many cases have limited ability to move through and utilise the land use matrix. We addressed this problem using a case study of the koala (Phascolarctos cinereus) surveyed in a fragmented rural-urban landscape in southeast Queensland, Australia. We applied a logistic modelling and hierarchical partitioning analysis to determine the importance of forest area and its configuration relative to site (local) and patch-level habitat variables. After taking into account spatial auto-correlation and the year of survey, we found koala occurrence increased with the area of all forest habitats, habitat patch size and the proportion of primary Eucalyptus tree species; and decreased with mean nearest neighbour distance between forest patches, the density of forest patches, and the density of sealed roads. The difference between the effect of habitat area and configuration was not as strong as theory predicts, with the configuration of remnant forest becoming increasingly important as the area of forest habitat declines. We conclude that the area of forest, its configuration across the landscape, as well as the land use matrix, are important determinants of koala occurrence, and that habitat configuration should not be overlooked in the conservation of forest-dependent mammals, such as the koala. We highlight the implications of these findings for koala conservation. (c) 2006 Elsevier Ltd. All rights reserved.

Do predators aggregate in response to pest density in agroecosystems? Assessing within-field spatial patterns

1. The spatial heterogeneity of predator populations is an important component of ecological theories pertaining to predator-prey dynamics. Most studies within agricultural fields show spatial correlation (positive or negative) between mean predator numbers and prey abundance across a whole field over time but generally ignore the within-field spatial dimension. We used explicit spatial mapping to determine if generalist predators aggregated within a soybean field, the size of these aggregations and if predator aggregation was associated with pest aggregation, plant damage and predation rate. 2. The study was conducted at Gatton in the Lockyer Valley, 90 km west of Brisbane, Australia. Intensive sampling grids were used to investigate within-field spatial patterns. The first row of each grid was located in a lucerne field (10 m from interface) and the remaining rows were in an adjacent soybean field. At each point on the grid the abundance of foliage-dwelling and ground-dwelling pests and predators was measured, predation rates [using sentinel Helicoverpa armigera (Hubner) egg cards] and plant damage were estimated. Eight grids were sampled across two summer cropping seasons (2000/01, 2001/02). 3. Predators exhibited strong spatial patterning with regions of high and low abundance and activity within what are considered to be uniform soybean fields. Ground-dwelling and foliage-dwelling predators were often aggregated in patches approximately 40 m across. 4. Lycosidae (wolf spiders) displayed aggregation and were consistently more abundant within the lucerne, with a decreasing trap catch with distance from the lucrene/soybean interface. This trend was consistent between subsequent grids in a single field and between fields. 5. The large amount of spatial variability in within-field arthropod abundance (pests and predators) and activity (egg predation and plant damage) indicates that whole field averages were misleading. This result has serious implications for sampling of arthropod abundance and pest management decision-making based on scouting data. 6. There was a great deal of temporal change in the significant spatial patterns observed within a field at each sampling time point during a single season. Predator and pest aggregations observed in these fields were generally not stable for the entire season. 7. Predator aggregation did not correlate consistently with pest aggregation, plant damage or predation rate. Spatial patterns in predator abundance were not associated consistently with any single parameter measured. The most consistent positive association was between foliage-dwelling predators and pests (significant in four of seven grids). Inferring associations between predators and prey based on an intensive one-off sampling grid is difficult, due to the temporal variability in the abundance of each group. 8. Synthesis and applications. This study demonstrated that generalist predator populations are rarely distributed randomly and field edges and adjacent crops can have an influence on within-field predator abundance. This must be considered when estimating arthropod (pest and predator) abundance from a set of samples taken at random locations within a field.

Adenocarcinoma of colon differentiating as dome epithelium of gut-associated lymphoid tissue

Aims: An early adenocarcinoma of the ascending colon was confined to a mass of gut-associated lymphoid tissue (GALT). The first description of an adenocarcinoma of colon differentiating as dome epithelium is presented. Methods and results: A plaque-like carcinoma was identified opposite the ileocaecal valve in an asymptomatic 56-year-old man with a family history of colorectal cancer. Malignant epithelium was confined to a mass of GALT filling but limited to the submucosa, Characterization of the neoplasm was undertaken by means of mucin histochemistry, immunohistochemistry, electron microscopy and assessment of DNA microsatellite instability status. The malignant epithelium comprised well differentiated columnar cells with a microvillous brush border and expressing MUC1, but no goblet cells or expression of MUC2. The demonstration of focal clusters of intraepithelial B-lymphocytes supported the presence of functioning M-cells within the malignant neoplasm. The cancer was DNA microsatellite stable despite the finding of tumour infiltrating lymphocytes. Conclusions: There is evidence for the origin of colorectal neoplasia from dome epithelium in both experimental models and microreconstruction studies of early adenomas in nonpolypotic human colorectal mucose, It is suggested that the lymphocyte-rich subset of colorectal cancer that expresses MUC1 but not MUC2 may be differentiating as dome epithelium of gut-associated lymphoid tissue.

Substance P preferentially inhibits large conductance nicotinic ACh receptor channels in rat intracardiac ganglion neurons

The effects of substance P (SP) on nicotinic acetylcholine (ACh)-evoked currents were investigated in parasympathetic neurons dissociated from neonatal rat intracardiac ganglia using standard whole cell, perforated patch, and outside-out recording configurations of the patch-clamp technique. Focal application of SP onto the soma reversibly decreased the peak amplitude of the ACh-evoked current with half-maximal inhibition occurring at 45 mu M and complete block at 300 mu M SP. Whole cell current-voltage (I-V) relationships obtained in the absence and presence of SP indicate that the block of ACh-evoked currents by SP is voltage independent. The rate of decay of ACh-evoked currents was increased sixfold in the presence of SP (100 mu M), suggesting that SP may increase the rate of receptor desensitization. SP-induced inhibition of ACh-evoked currents was observed following cell dialysis and in the presence of either 1 mM 8-Br-cAMP, a membrane-permeant cAMP analogue, 5 mu M H-7, a protein kinase C inhibitor, or 2 mM intracellular AMP-PNP, a nonhydrolyzable ATP analogue. These data suggest that a diffusible cytosolic second messenger is unlikely to mediate SP inhibition of neuronal nicotinic ACh receptor (nAChR) channels. Activation of nAChR channels in outside-out membrane patches by either ACh (3 mu M) or cytisine (3 mu M) indicates the presence of at least three distinct conductances (20, 35, and 47 pS) in rat intracardiac neurons. In the presence of 3 mu M SP, the large conductance nAChR channels are preferentially inhibited. The open probabilities of the large conductance classes activated by either ACh or cytisine were reversibly decreased by 10- to 30-fold in the presence of SP. The single-channel conductances were unchanged, and mean apparent channel open times for the large conductance nAChR channels only were slightly decreased by SP. Given that individual parasympathetic neurons of rat intracardiac ganglia express a heterogeneous population of nAChR subunits represented by the different conductance levels, SP appears to preferentially inhibit those combinations of nAChR subunits that form the large conductance nAChR channels. Since ACh is the principal neurotransmitter of extrinsic (vagal) innervation of the mammalian heart, SP may play an important role in modulating autonomic control of the heart.

Bryophyte propagule banks in a feldmark on subantarctic Macquarie Island

Subantarctic Macquarie Island has substantial areas of feldmark on its plateau above 200 m altitude. Samples of the substrate (5.5 cm in depth) from bare areas of feldmark contained viable propagules of bryophyte species found at adjacent and distant sites on the island. In laboratory conditions propagules of 15 bryophyte taxa germinated, allowing interpretation of reasons for bare patches in feldmark: bryophytes were successful at colonizing stable ground but when surface movement was present, burial and/or damage of propagules and young plants prevented colonization. Spherical moss polsters found in cryoturbatic areas in feldmark, however, represent a growth form that can tolerate surface movement. A conceptual model illustrating processes associated with colonization dynamics of bryophytes on feldmark terraces is presented. Ten of the 15 germinated taxa were nonlocal taxa which currently grow in plant communities at lower and hence warmer altitudes on Macquarie Island. The presence of viable propagules of these taxa provide an immediate and constant potential for dramatic vegetation change with climate change.

3D protein structure matching by patch signatures

For determining functionality dependencies between two proteins, both represented as 3D structures, it is an essential condition that they have one or more matching structural regions called patches. As 3D structures for proteins are large, complex and constantly evolving, it is computationally expensive and very time-consuming to identify possible locations and sizes of patches for a given protein against a large protein database. In this paper, we address a vector space based representation for protein structures, where a patch is formed by the vectors within the region. Based on our previews work, a compact representation of the patch named patch signature is applied here. A similarity measure of two patches is then derived based on their signatures. To achieve fast patch matching in large protein databases, a match-and-expand strategy is proposed. Given a query patch, a set of small k-sized matching patches, called candidate patches, is generated in match stage. The candidate patches are further filtered by enlarging k in expand stage. Our extensive experimental results demonstrate encouraging performances with respect to this biologically critical but previously computationally prohibitive problem.