Interaction between herbivore defense and microbial signaling: bacterial quorum-sensing compounds weaken JA-mediated herbivore resistance in Nicotiana attenuata

Bacteria play important roles in plant–herbivore interactions and communicate with each other with chemical signals, often N-acylhomoserine lactones (AHL). Plant responses to these signals may influence resistance to microbial attack, but the effects of these signals on herbivore defense are unstudied. To determine whether AHL influence jasmonate (JA)-mediated herbivore resistance in Nicotiana attenuata, we treated wild-type (WT) and JA-deficient genotypes (antisense expression of NaLOX3) with N-hexanoyl-dl-homoserine lactone (C6-HSL) and measured the performance of Manduca sexta larvae. Larval mass gain on C6-HSL-treated WT plants was equivalent to that on non-treated NaLOX3-silenced plants, but significantly 4.1-fold larger than on untreated WT plants. Mass gain was unaffected by C6-HSL treatment of NaLOX3-silenced plants. Microarray analysis of the plants elicited with C6-HSL and JA inducing fatty acid–amino acid conjugates revealed a down-regulation of a proteinase inhibitor in the C6-HSL-treated WT plants. The results therefore suggest that the increased performance of M. sexta was due to direct or indirect effect of C6-HSL on JA-mediated defenses.     

Large-sample-size assessment of socioeconomic predictors of community-level resource management occurrence

Community-level resource management efforts are cornerstones in ensuring sustainable use of natural resources. Yet, understanding how community characteristics influence management practices remains contested. With a sample size of ≥725 communities, we assessed the effects of key community (i.e., socioeconomic) characteristics (human population size and density, market integration, and modernization) on the probability of occurrence of fisheries management practices, including gear, species, and spatial restrictions. The study was based in Solomon Islands, a Pacific Island country with a population that is highly dependent on coastal fisheries. People primarily dwell in small communities adjacent to the coastline dispersed across 6 island provinces and numerous smaller islands. We used nationally collected data in binomial logistic regression models to examine the likelihood of management occurrence, given socioeconomic context of communities. In contrast to prevailing views, we identified a positive and statistically significant association between both human population size and market integration and all 3 management practices. Human population density, however, had a statistically significant negative association and modernization a varied and limited association with occurrence of all management practices. Our method offers a way to remotely predict the occurrence of resource management practices based on key socioeconomic characteristics. It could be used to improve understanding of why some communities conduct natural resource management activities when statistical patterns suggest they are not likely to and thus improve understanding of how some communities of people beat the odds despite limited market access and high population density.     

Impact of Land Use on Soluble Organic Nitrogen in Soil

Although it has been hypothesized that soluble organic nitrogen (SON) plays a central role in regulating productivity in some terrestrial ecosystems, the factors controlling the size of the SON pool in soil remain poorly understood. Therefore our principal aim in this work was to assess the impact of seven different land use systems (rough and managed grassland, deciduous and coniferous woodland, heathland, wetland and tilled land) on the size of the SON and inorganic N (NO ₃ ^– , NH ₄ ⁺ ) pools in the surface soil layer (0–15 cm). After extraction with deionised water, we found that in most cases the size of the water extractable organic N (WEON) pool was similar in size to the inorganic N pool. In contrast, the KCl extractable organic N (KClEON) pool constituted the dominant form of soluble N in soils under all land uses, perhaps indicating that significant amounts were held on the soil exchange phase. In contrast to inorganic N, which varied significantly with land use, the size of the KClEON and WEON pool was similar for all land uses with the exception of KClEON in tilled land, where significantly lower amounts were observed. We conclude that SON constitutes an important soil N pool in a broad range of land uses, and that its role in microbial N assimilation, plant nutrition and ecosystem responses to atmospheric N deposition warrants further attention. SAFRD, University of Newcastle, Newcastle-upon-Tyne, NE1 7RU, U.K.     

Spatiotemporal changes and fragmentation of mangroves and its effects on fish diversity in Ca Mau Province (Vietnam)

Mangroves are important economically and ecologically, however mangrove cover has declined dramatically leading to habitat fragmentation and biodiversity loss. Information on mangrove cover change, fragmentation and impacts on fish diversity is poorly understood. The aims of this study are to detect spatiotemporal changes and mangrove status, examine fragmentation changes and associated effects on fish diversity. Landsat images in1989, 2000, and 2013 were used to classify mangrove cover in Ca Mau Province (Vietnam) and validated against high resolution Pleiades imagery. Fragmentation changes in mangrove cover were examined using series of landscape metrics evaluated against fish diversity indices (Simpson’s index, Jaccard’s coefficient and relative abundance). Results show that mangrove cover has declined 24.6% in the province. Currently, high and moderately dense mangroves distribute in southern half of the region while the low density mangroves occurs in the northern half. Over the 24 year study periods, the number of patches and edge density has increased 58% and 53.9%, respectively, while the mean patch size and mean patch edge has decreased 52.3% and 26.6%. Fish diversity in the more highly fragmented mangrove area was 1.78 times lower than the less fragmented mangrove. The study illustrates the applicability of using Landsat satellite imagery for use in mangrove fragmentation studies as well as the impact of fragmentation.     

Detecting deterrence from patrol data

The threat posed to protected areas by the illegal killing of wildlife is countered principally by ranger patrols that aim to detect and deter potential offenders. Deterring poaching is a fundamental conservation objective, but its achievement is difficult to identify, especially when the prime source of information comes in the form of the patrols’ own records, which inevitably contain biases. The most common metric of deterrence is a plot of illegal activities detected per unit of patrol effort (CPUE) against patrol effort (CPUE-E). We devised a simple, mechanistic model of law breaking and law enforcement in which we simulated deterrence alongside exogenous changes in the frequency of offences under different temporal patterns of enforcement effort. The CPUE-E plots were not reliable indicators of deterrence. However, plots of change in CPUE over change in effort (ΔCPUE-ΔE) reliably identified deterrence, regardless of the temporal distribution of effort or any exogenous change in illegal activity levels as long as the time lag between patrol effort and subsequent behavioral change among offenders was approximately known. The ΔCPUE-ΔE plots offered a robust, simple metric for monitoring patrol effectiveness; were no more conceptually complicated than the basic CPUE-E plots; and required no specialist knowledge or software to produce. Our findings demonstrate the need to account for temporal autocorrelation in patrol data and to consider appropriate (and poaching-activity-specific) intervals for aggregation. They also reveal important gaps in understanding of deterrence in this context, especially the mechanisms by which it occurs. In practical applications, we recommend the use of ΔCPUE-ΔE plots in preference to other basic metrics and advise that deterrence should be suspected only if there is a clear negative slope. Distinct types of illegal activity should not be grouped together for analysis, especially if the signs of their occurrence have different persistence times in the environment.     

Reproduction in short-beaked common dolphins (<Emphasis Type="Italic">Delphinus delphis</Emphasis>) from the western North Atlantic

A single population of short-beaked common dolphins (Delphinus delphis Linnaeus) occurs in the western North Atlantic from Florida to Newfoundland. Dolphins killed in a swordfish driftnet fishery between 1989 and 1998 provided samples for the present study. These were combined with additional observations from carcasses collected from stranding programs. Samples were examined from 74 female and 161 male short-beaked common dolphins. A highly significant male bias in the sex ratio of both the bycatch and stranding samples suggests that sex-based habitat partitioning or school segregation occurs in this population. Age was estimated from decalcified thin sections of teeth and testis and ovarian samples were examined both macro- and microscopically. Analyses showed that reproduction was both seasonal and synchronized. Females reached sexual maturation at approximately age eight; males matured at 9.5 years. Conception occurred during July and August (mean day 24 July). Gestation was estimated to last just under a year, so most females gave birth during July and August (mean day 15 July). Annual pregnancy rate was estimated to be between 25 and 33%. Males undergo a fivefold seasonal increase in testes mass and a twofold increase in seminiferous tubule diameter. Peak sperm production potential was observed in July. At the end of the breeding season testis size and activity decreased after August. Male dolphins in this population are hypothesized to engage in some form of sperm competition.     

Identifying natural and anthropogenic sources of metals in urban and rural soils using GIS-based data,PCA, and spatial interpolation

Determining sources of neurotoxic metals in rural and urban soils is important for mitigating human exposure. Surface soil from four areas with significant clusters of mental retardation and developmental delay (MR/DD) in children, and one control site were analyzed for nine metals and characterized by soil type, climate, ecological region, land use and industrial facilities using readily available GIS-based data. Kriging, principal component analysis (PCA) and cluster analysis (CA) were used to identify commonalities of metal distribution. Three MR/DD areas (one rural and two urban) had similar soil types and significantly higher soil metal concentrations. PCA and CA results suggested that Ba, Be and Mn were consistently from natural sources; Pb and Hg from anthropogenic sources; and As, Cr, Cu, and Ni from both sources. Arsenic had low commonality estimates, was highly associated with a third PCA factor, and had a complex distribution, complicating mitigation strategies to minimize concentrations and exposures.     

Correlates of female choice in resource-defending antelope

Summary Where males offer their mates assistance in rearing offspring as well as access to defended resources, female mate choice should be influenced by both male phenotype and resource quality. In contrast, where there is no paternal care the relative importance of choice for male and territory traits is less well understood. We looked at female distribution across male territories in order to assess mate choice criteria in puku Kobus vardoni, and topi Damaliscus lunatus, two antelope where males defend resources but are not involved in parental care. In both species female distribution was correlated with male phenotype as well as the quality of forage and risk of predation on different territories. Male and territory characteristics were intercorrelated, but statistical analysis revealed that male traits, forage quality and predation risk were all significant, independent predictors of female choice in both study species. This is the first demonstration that female choice in mammals might be simultaneously influenced by male phenotype as well as the quality of defended resources.Correspondence to: A. Balmford