Phenological fate of plant-acquired pyrrolizidine alkaloids in the polyphagous arctiid Estigmene acrea

Summary. The alkaloid profiles of the life history stages of the highly polyphagous arctiid Estigmene acrea were established. As larvae individuals had free choice between a plain diet (alkaloid-free) and a diet that was supplemented with Crotalaria-pumila powder with a known content and composition of pyrrolizidine alkaloids (PAs). Idiosyncratic retronecine esters (insect PAs) accounted for approximately half of the PAs recovered from the larvae. These alkaloids were synthesized by the larvae through esterification of dietary supinidine yielding the estigmines, and esterification of retronecine yielding the creatonotines. The retronecine is derived from insect-mediated degradation of the sequestered pumilines (macrocyclic PAs of the monocrotaline type). With one exception, the PA profiles established for larvae were found almost unaltered in all life-stages as well as larval exuviae and pupal cocoons. The exception is the males, which in comparison to pupae and adult females, showed a significantly decreased quantity of the creatonotines and pumilines. These data support the idea that the creatonotines are direct precursors of the PA-derived male courtship pheromone, hydroxydanaidal. Crosses of PA-free males with PA-containing females and vice versa confirmed an efficient trans-mission of PAs from males to females and then from females to eggs. In single cases a male bestowed almost his total PA load to the female, and a female her total load to the eggs. The results are discussed with respect to pheromone formation, PA transmission between life-stages, and the defensive role of PAs against predators and parasitoids     

Characterization of cation-pi interactions in aqueous solution using deuterium nuclear magnetic resonance spectroscopy

Chemical interactions of aromatic organic contaminants control their fate, transport, and toxicity in the environment. Recent molecular modeling studies have suggested that strong interactions can occur between the pi electrons of aromatic molecules and metal cations in aqueous solutions and/or on mineral surfaces, and that such interactions may be important in some environmental systems. However, spectroscopic evidence for these so-called cation-pi interactions has been extremely limited to date. In this paper, cation-pi interactions in aqueous salt solutions were characterized via 2H nuclear magnetic resonance (NMR) spin-lattice relaxation times (T1) and calculations of molecular correlation times (tau(c)) for a series of perdeuterated (d6-benzene) benzene-cation complexes. The T1 values for d6-benzene decreased with increasing concentrations of LiCl, NaCl, KCl, RbCl, CsCl, and AgNO3, with the largest effects observed in the AgNO3 and CsCl solutions. Upon normalizing tau(c) values by solution viscosity effects, an overall affinity trend of Ag+ > Cs+ > K+ > Rb+ > Na+ > Li+ was derived for the d6-benzene-cation complexes. The ability of Ag+ to complex d6-benzene was significantly reduced upon addition of NH3, which strongly coordinates Ag+ at high pH. Results with d6-benzene, d8-naphthalene, d2-dichloromethane, and d12-cyclohexane in 0.1 M methanolic salt solutions confirmed that spin-lattice relaxation rates are characterizing cation-pi interactions. The relatively strong cation-pi bonding observed between Ag+ and aromatic hydrocarbons probably results from covalent interactions between the aromatic pi electrons and the d orbitals of Ag+, in addition to the normal electrostatic interaction.     

Cation-pi bonding: a new perspective on the sorption of polycyclic aromatic hydrocarbons to mineral surfaces

Recent molecular modeling and spectroscopic studies have suggested that relatively strong interactions can occur between aromatic pi donors and metal cations in aqueous solutions. The objective of this study was to characterize potential cation-pi interactions between pi donors and exchangeable cations accumulated at mineral surfaces via both spectroscopic and batch sorption methods. Quadrupolar splitting in deuterium nuclear magnetic resonance ((2)H NMR) spectroscopy for d(2)-dichloromethane, d(6)-benzene, and d(8)-toluene (C(6)D(5)- moiety) in aqueous suspensions of a Na-saturated reference montmorillonite unambiguously indicated the ordering of solute molecules with respect to the clay surface. The half line broadening (Delta nu(1/2)) of (2)H NMR of d(6)-benzene in montmorillonite suspensions showed that soft exchangeable cations generally resulted in more benzene sorption compared with harder cations (e.g., Ag(+) > Cs(+) > Na(+) > Mg(2+), Ba(2+)). In batch sorption experiments, saturating minerals (e.g., porous silica gels, kaolinite, vermiculite, montmorillonite) with a soft transition metal or softer base cations generally increased the polycyclic aromatic hydrocarbon (PAH) sorption relative to harder cations (e.g., Ag(+) > Cs(+) > K(+) > Na(+); Ba(2+) > Mg(2+)). Sorption of phenanthrene to Ag(+)-saturated montmorillonite was much stronger compared with 1,2,4,5-tetrachlorobenzene, a coplanar non-pi donor having slightly higher hydrophobicity. In addition, a strong positive correlation was found between the cation-dependent sorption and surface charge density of the minerals (e.g., vermiculite, montmorillonite > silica gels, kaolinite). These results, coupled with the observations in (2)H NMR experiments with montmorillonite, strongly suggest that cation-pi bonding forms between PAHs and exchangeable cations at mineral surfaces and affects PAH sorption to hydrated mineral surfaces.     

Conflict and Impacts of Divers and Anglers in a Marine Park

The New South Wales State Government (Australia) gazetted the Jervis Bay Marine Park (JBMP) in 1998. During the preparation of the draft zoning plan in 2000, societal data on two conflicting park user groups—recreational scuba divers and fishers (anglers)—was collected. While conflict resolution was a plan priority, other factors, such as cumulative environmental impacts of users and protection for the critically endangered grey nurse shark (Carcharias taurus), further complicated planning. Both scuba diving and angling are primary summer activities and are disproportionately concentrated around the headlands of the bay. Furthermore, shore based game-fishing was concentrated on the northern headland, where the conflict was centered. However, when the exact locations of divers and anglers were determined, there was a partial partitioning of the available space, with only a small contested overlap. To resolve conflict and maximize positive environmental outcomes, a sanctuary zone and no-anchoring zone option in the draft zoning plan was sought to formalize this partition. The human dimension data proved valuable in guiding environmental management in this politically volatile situation. A baseline study conducted 11 years previously was also used to gain a limited perspective on change in user numbers. Comparison between study periods indicated dive numbers had remained similar, while the number of dive charter trips was significantly less. The numbers of anglers, for the four months compared, had doubled and tripled. The actual data used to inform management is presented and the limitations of this best available data approach are discussed.     

From the Editor

Editorial Introduction

From the Editor     

Investigation of the phylogenetic relationships between <Emphasis Type="Italic">Diuris fragrantissima</Emphasis> and its closest relatives using AFLPs

This study investigated the genetic relationships between the rare terrestrial orchid Diuris fragrantissima and three closely related purple flowered species using Amplified Fragment Length Polymorphisms. The purple-flowered species were found to form individual phenetic clusters confirming recognition of D. fragrantissima at the rank of species. Levels of genetic variation were lower within D. fragrantissima than within its closest relatives but were higher than expected for severely bottlenecked species. Gene flow was detected among all species (Nm = 2.34) and populations (Nm = 0.65) however low among population gene flow indicates that populations may be at risk of divergence. This study has implications for the conservation of D. fragrantissima.     

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.     

Erratum to: Cuckoldry rates in the Molly Miller (<Emphasis Type="Italic">Scartella cristata</Emphasis>; Blenniidae), a hole-nesting marine fish with alternative reproductive tactics

Microsatellite markers were developed and employed to assess genetic maternity and paternity of embryos in nest-tended clutches of the Molly Miller (Scartella cristata), a marine fish in which alternative reproductive tactics (ARTs) by males were recently described from behavioral and morphological evidence. Genetic data gathered for 1,536 surveyed progeny, from 23 barnacle-nest holes in a single Floridian population, indicate that on average about 5.5 females (range 3–9) contributed to the pool of progeny within a nest. With regard to paternity, the microsatellite data demonstrate that most of the surveyed nests (82.6%) contained at least some embryos that had not been sired by the nest-tending (bourgeois) male, and overall that 12.4% of offspring in the population had been sired via "stolen" fertilizations by other males. These are among the highest values of cuckoldry documented to date in nest-tending fishes, and they support and quantify the notion that the nest-parasitic ART is reproductively quite successful in this species despite what would otherwise seem to be highly defensible nesting sites (the restricted interior space of a barnacle shell). Our estimated cuckoldry rates in this population of the Molly Miller are compared to those previously reported for local populations in other nest-tending fish species, with results discussed in the context of ecological and behavioral variables that may influence relative frequencies of nest parasitism.