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.     

Inhibition of gastric acid secretion in rat stomach by PACAP is mediated by secretin, somatostatin, and PGE(2)

Pituitary adenylate cyclase-activating polypeptide (PACAP), existing in two variants, PACAP-27 and PACAP-38, is found in the enteric nervous system and regulates function of the digestive system. However, the regulatory mechanism of PACAP on gastric acid secretion has not been well elucidated. We investigated the inhibitory action of PACAP-27 on acid secretion and its mechanism in isolated vascularly perfused rat stomach. PACAP-27 in four graded doses (5, 10, 20, and 50 microg/h) was vascularly infused to determine its effect on basal and pentagastrin (50 ng/h)-stimulated acid secretion. To study the inhibitory mechanism of PACAP-27 on acid secretion, a rabbit antisecretin serum, antisomatostatin serum, or indomethacin was administered. Concentrations of secretin, somatostatin, PGE(2), and histamine in portal venous effluent were measured by RIA. PACAP-27 dose-dependently inhibited both basal and pentagastrin-stimulated acid secretion. PACAP-27 at 10 microg/h significantly increased concentrations of secretin, somatostatin, and PGE(2) in basal or pentagastrin-stimulated state. The inhibitory effect of PACAP-27 on pentagastrin-stimulated acid secretion was reversed 33% by an antisecretin serum, 80.0% by an antisomatostatin serum, and 46.1% by indomethacin. The antisecretin serum partially reduced PACAP-27-induced local release of somatostatin and PGE(2). PACAP-27 at 10 microg/h elevated histamine level in portal venous effluent, which was further increased by antisomatostatin serum. However, antisomatostatin serum did not significantly increase acid secretion. It is concluded that PACAP-27 inhibits both basal and pentagastrin-stimulated gastric acid secretion. The effect of PACAP-27 is mediated by local release of secretin, somatostatin, and PGE(2) in isolated perfused rat stomach. The increase in somatostatin and PGE(2) levels in portal venous effluent is, in part, attributable to local action of the endogenous secretin.     

The diversity of beetle assemblages in different habitat types in Sabah, Malaysia

The diversity of beetle assemblages in different habitat types (primary forest, logged forest, acacia plantation and oil palm plantation) in Sabah, Malaysia was investigated using three different methods based on habitat levels (Winkler sampling, flight-interception-trapping and mist-blowing). The overall diversity was extremely high, with 1711 species recorded from only 8028 individuals and 81 families (115 family and subfamily groups). Different degrees of environmental changes had varying effects on the beetle species richness and abundance, with oil palm plantation assemblage being most severely affected, followed by acacia plantation and then logged forest. A few species became numerically dominant in the oil palm plantation. In terms of beetle species composition, the acacia fauna showed much similarity with the logged forest fauna, and the oil palm fauna was very different from the rest. The effects of environmental variables (number of plant species, sapling and tree densities, amount of leaf litter, ground cover, canopy cover, soil pH and compaction) on the beetle assemblage were also investigated. Leaf litter correlated with species richness, abundance and composition of subterranean beetles. Plant species richness, tree and sapling densities correlated with species richness, abundance and composition of understorey beetles while ground cover correlated only with the species richness and abundance of these beetles. Canopy cover correlated only with arboreal beetles. In trophic structure, predators represented more than 40% of the species and individuals. Environmental changes affected the trophic structure with proportionally more herbivores (abundance) but fewer predators (species richness and abundance) in the oil palm plantation. Biodiversity, conservation and practical aspects of pest management were also highlighted in this study.     

The high value of logged tropical forests: lessons from northern Borneo

The carbon storage and conservation value of old-growth tropical forests is clear, but the value of logged forest is less certain. Here we analyse >100,000 observations of individuals from 11 taxonomic groups and >2,500 species, covering up to 19?years of post-logging regeneration, and quantify the impacts of logging on carbon storage and biodiversity within lowland dipterocarp forests of Sabah, Borneo. We estimate that forests lost ca. 53% of above-ground biomass as a result of logging but despite this high level of degradation, logged forest retained considerable conservation value: floral species richness was higher in logged forest than in primary forest and whilst faunal species richness was typically lower in logged forest, in most cases the difference between habitats was no greater than ca. 10%. Moreover, in most studies >90% of species recorded in primary forest were also present in logged forest, including species of conservation concern. During recovery, logged forest accumulated carbon at five times the rate of natural forest (1.4 and 0.28?Mg?C?ha^?1?year^?1, respectively). We conclude that allowing the continued regeneration of extensive areas of Borneo??s forest that have already been logged, and are at risk of conversion to other land uses, would provide a significant carbon store that is likely to increase over time. Protecting intact forest is critical for biodiversity conservation and climate change mitigation, but the contribution of logged forest to these twin goals should not be overlooked.     

Asymmetric boundary shifts of tropical montane Lepidoptera over four decades of climate warming

Aim To estimate whether species have shifted at equal rates at their leading edges (cool boundaries) and trailing edges (warm boundaries) in response to climate change. We provide the first such evidence for tropical insects, here examining elevation shifts for the upper and lower boundaries shifts of montane moths. Threats to species on tropical mountains are considered. Location Mount Kinabalu, Sabah, Malaysia. Methods We surveyed Lepidoptera (Geometridae) on Mount Kinabalu in 2007, 42 years after the previous surveys in 1965. Changes in species upper and lower boundaries, elevational extents and range areas were assessed. We randomly subsampled the data to ensure comparable datasets between years. Estimated shifts were compared for endemic versus more widespread species, and for species that reached their range limits at different elevations. Results Species that reached their upper limits at 2500–2700 m (n= 28 species, 20% of those considered) retreated at both their lower and upper boundaries, and hence showed substantial average range contractions (?300 m in elevational extent and ?45 km² in estimated range area). These declines may be associated with changes in cloud cover and the presence of ecological barriers (geological and vegetation transitions) which impede uphill movement. Other than this group, most species (n= 109, 80% of the species considered) expanded their upper boundaries upwards (by an average of 152 m) more than they retreated at their lower boundaries (77 m). Main conclusions Without constraints, leading margins shifted uphill faster than trailing margins retreated, such that many species increased their elevational extents. However, this did not result in increases in range area because the area of land available declines with increasing elevation. Species close to a major ecological/geological transition zone on the mountain flank declined in their range areas. Extinction risk may increase long before species reach the summit, even when undisturbed habitats are available.     

Dose-dependent differential upregulation of CCN1/Cyr61 and CCN3/NOV by the gap junction protein Connexin43 in glioma cells

Gap junctions form channels that allow exchange of materials between cells and are composed of transmembrane protein subunits called connexins. While connexins are believed to mediate cellular signaling by permitting intercellular communication to occur, there is also increasing evidence that suggest connexins may mediate growth control via a junction-independent mechanism. Connexin43 (Cx43) is the most abundant gap junction protein found in astrocytes, and gliomas exhibit reduced Cx43 expression. We have previously observed that restoration of Cx43 levels in glioma cells led to increased expression of CCN3 (NOV) proteins. We now report that overexpression of Cx43 in C6-glioma cells (C6-Cx43) also upregulates the expression of CCN1 (Cyr61). Both CCN1 and CCN3 belong to the Cyr61/Connective tissue growth factor/Nephroblastoma-overexpressed (CCN) family of secretory proteins. The CCN proteins are tightly associated with the extracellular matrix and have important roles in cell proliferation and migration. CCN1 promotes growth in glioma cells, as shown by the increased proliferation rate of CCN1-overexpressing C6 cells. In addition to its effect on cell growth, CCN1 also increased the motility of glioma cells in the presence of extracellular substrates such as fibronectin. Gliomas expressing high levels of Cx43 preferentially upregulated CCN3 which resulted in reduced growth rate. CCN3 could also be observed in Cx43 gap junction plaques in confluent C6-Cx43H culture at the stationary phase of their growth. Our results suggest that the dissimilar growth characteristics between high and low Cx43 expressors may be due to differential regulation of CCN3 by varying levels of Cx43.