Geographic variations in Helleborus foetidus elaiosome lipid composition: implications for dispersal by ants

Summary. Geographic variations in the correspondence between diaspore phenotypes and disperser behavior are thought to determine the evolution of plant-animal dispersal mutualisms. Helleborus foetidus is a widely distributed plant in Western Europe, which seeds bear a lipid rich elaiosome attracting ant dispersers. Laboratory cross-tests were conducted to check the correspondence between diaspore phenotypes and ant preference in two localities of the Iberian Peninsula, Caurel and Cazorla, separated by 750 km. Diaspores from Caurel were systematically preferred to those from Cazorla by Formica lugubris (the major disperser at Caurel), and Aphaenogatser iberica and Camponotus cruentatus (both major dispersers at Cazorla). Further bioassays conducted on A. iberica only showed that differences in elaiosome traits were sufficient to explain ant preference. Separation of the lipid fractions composing the elaiosome revealed that triglycerides, diglycerides and free fatty acids were all dominated by oleic acid. The elaiosomes from Caurel contained relatively more free oleic acid but were less concentrated in linoleyl-containing triglycerides, free palmitic acid and free linoleic acid than those from Cazorla. The three lipid fractions were attractive to ants but dummies soaked with the free fatty acids extracted from Caurel were preferred to those from Cazorla. Taken together, these results reinforce the idea that oleic acid is a major releaser of seed collection by ants and suggest that geographic variations in free fatty acid composition affect the probability of diaspore removal by ants which in turn potentially determine plant demography.     

Sparse regression for analyzing the development of foliar nutrient concentrations in coniferous trees

Analyzing and predicting the development of foliar nutrient concentrations are important and challenging tasks in environmental monitoring. This article presents how linear sparse regression models can be used to represent the relations between different foliar nutrient concentration measurements of coniferous trees in consecutive years. In the experiments the models proved to be capable of providing relatively good and reliable predictions of the development of foliage with a considerably small number of regressors. Two methods for estimating sparse models were compared to more conventional linear regression models. Differences in the prediction accuracies between the sparse and full models were minor, but the sparse models were found to highlight important dependencies between the nutrient measurements better than the other regression models. The use of sparse models is, therefore, advantageous in the analysis and interpretation of the development of foliar nutrient concentrations.     

Megabenthic decapod crustacean assemblages on the Galician continental shelf and upper slope (north-west Spain)

The structure of megabenthic decapod crustacean assemblages on the Galician (north-west Spain) continental shelf (100 to 200 depth) and upper slope (200 to 500 m) was analyzed based on surveys carried out in autumn and spring, from 1980 to 1987. Forty species belonging to 19 families were caught. The portunid crab Polybius henslowii, a species with pelagic phases, was the most abundant species, but displayed strong spatial and temporal fluctuations. Other dominant species were the Norway lobster Nephrops norvegicus, the portunid Liocarcinus depurator, the galatheids Munida intermedia and M. sarsi, and the shrimps Solenocera membranacea, Plesionika heterocarpus, Pasiphaea sivado and Dichelopandalus bonnieri. Total abundance and biomass (average values excluding Polybius henslowii = 255 individuals and 2.06 kg/30 min tow) and species richness and diversity, H′ (6.85 species and H′ = 1.45 per tow) displayed a significant positive correlation with depth, and strong interannual fluctuations. The factors determining community organization were depth and, to a lesser extent, spatial structure. There was clear evidence of bathymetric zonation, differentiating between species characteristic of the slope (D. bonnieri and Pasiphaea sivado), shelf-slope edge (Macropipus tuberculatus, Pontophilus spinosus, Munida sarsi, S. membranacea, Processa spp.) and shelf (L. depurator, Macropodia tenuirostris, Paguridae and Chlorotocus crassicornis). The spatial zonation was related to changes in oceanography and sediment along the continental margin. Goneplax rhomboides, N. norvegicus, C. crassicornis and Alpheus glaber are benthic species which generally exhibit burrowing behaviour, and they were found mainly in the southern area where there are fine sediments due to the outwelling from the Rías Baixas. Different benthopelagic shrimps (Pontophilus spinosus, Plesionika heterocarpus,Processa spp. and Pasiphaea sivado) were typical of the zone just north of Fisterra, characterized by a convergence of water masses bringing about an increase in productivity due to upwelling. The benthic anomuran and brachyuran crabs Munida intermedia, M.␣sarsi, L.␣depurator and Macropipus tuberculatus were characteristic of the northwestern zone between Fisterra and Estaca, where the infauna reaches high biomass despite coarser sediments with a lower concentration of organic material than in the southern area. Lastly, both the Paguridae and Macropodia tenuirostris were species typically found in the waters in the northern shelf. Based on interannual changes in assemblage structure, two periods could be distinguished: between 1980 and 1984, when Polybius henslowii, D. bonnieri and Pasiphaea sivado had abundance peaks; and another period from 1985 to 1987 when L. depurator, Munida intermedia, M.␣sarsi and Macropipus tuberculatus increased in abundance. Received: 21 May 1996 / Accepted: 9 August 1996     

Lichens as indicators of a perturbation/stability gradient in the Asperillo dunes, SW spain

In the asperillo dune system, Southwest Spain, lichen vegetation covering the dune sand, has a low species diversity but is an important component of the perennial vegetation, providing stability, nutrients, and moisture to the soil layer. The Asperillo dunes harbour (1) natural ecosystems, (2) disturbed systems affected by forestry activities where the natural vegetation is eliminated, and (3) pine forest resulting from afforestation withPinus pinea since the end of the 1940s where the composition and abundance of the lichen flora has been drastically changed. Our hypothesis was that the lichen species composition and distribution are influenced by the type and period of human intervention. To test this hypothesis a 1.2 km × 1.1 km area, which includes zones with different degrees of conservation and perturbation, consisting of five different habitats, was selected: well preservedJuniperus woodland,Pinus pinea plantations with dense scrub, dense scrub,P. pinea plantations cleared from scrub, and pioneer scrub in recent pine afforestation. In each area, randomly located 5m × 5 m homogeneous plots were sampled. In each plot the cover of shrub and lichen species was recorded. The first results show that lichen cover is higher in the most preserved areas,Cladonia mediterranea being the dominant species under theJuniperus phoenicea canopy. The lichen community changes in composition and abundance depending on the time elapsed since the last perturbation.     

Sequestration of pyrrolizidine alkaloids by larvae ofTellervo zoilus (Lepidoptera: Ithomiinae) and their role in the chemical protection of adults against the spiderNephila maculata (Araneidae)

Summary Life stages of the primitive Australian ithomiine butterflyTellervo zoilus and its larval hostplant, the apocynaceous vineParsonsia straminea, were quantitatively assayed for pyrrolizidine alkaloids (PAs). PAs were found in all stages, mainly as N-oxides, being most concentrated in larvae and freshly-emerged adults. Although adults feed at various confirmed PA sources this probably does not compensate for losses, as wild-caught adults had considerably lower concentrations of PAs. The main alkaloid present in both freshly-emerged adults and in leaves of the host-plant was lycopsamine (1b), stored by butterflies in the N-oxide form. Its presence in higher proportion, in relation to intermedine (1a), in larvae, pupae and adults ofTellervo in relation to the host-plants suggests the inversion of intermedine to lycopsamine by the insects. No 14-member ring macrocyclic PAs were detected in either food-plant or butterflies. Several other PAs were found in wild-caught adults reflecting visits to other PA sources. PAs were also found in high concentrations in freshly-emerged individuals of the danaineEuploea core bred onParsonsia straminea. Wild-caughtDanaus affinis had high PA levels acquired from adult feeding. Freshly emergedEuploea raised onIschnocarpus frutescens andDanaus raised onIschnostemma carnosum (both PA-free) were preyed on by the orb weaving spiderNephila maculata, and showed no PAs. In all cases where PAs were present, most butterflies were liberated, usually cut out of the web unharmed, byNephila. The spider's response was not closely linked to PA concentration, however, and may also depend on hunger levels and previous experience with PA-containing butterflies. All control and other non-PA containing butterflies were consumed although rejection of some body parts of freshly-emergedDanaus affinis suggests that compounds other than PAs may be involved.     

Population structure and historical demography of the thorny skate (<Emphasis Type="Italic">Amblyraja radiata</Emphasis>, Rajidae) in the North Atlantic

Population genetic structure of the thorny skate (Amblyraja radiata) was surveyed in >300 individuals sampled from Newfoundland, Iceland, Norway, the Kattegat and the central North Sea. A 290-bp fragment of the mt cytochrome-b gene was first screened by SSCP. Sequences of SSCP haplotypes revealed 34 haplotypes, 14 of which were unique to Iceland, 3 to Newfoundland, 1 to Norway and 3 to the Kattegat. The global F _ST was weak but significant. Removal of the two Kattegat locations, which were the most differentiated, resulted in no significant genetic differentiation. Haplotype diversity was high and evenly distributed across the entire Atlantic (h = 0.8) with the exception of the North Sea (h = 0.48). Statistical parsimony revealed a star-like genealogy with a central widespread haplotype. A subsequent nested clade analysis led to the inference of contiguous expansion with evidence for long distance dispersal between Newfoundland and Iceland. Historical demographic analysis showed that thorny skates have undergone exponential population expansion that started between 1.1 million and 690,000 years ago; and that the Last Glacial Maximum apparently had little effect. These results strongly differ from those of a parallel study of the thornback ray (Raja clavata) in which clear structure and former refugial areas could be identified. Although both species have similar life history traits and overlapping ranges, the continental shelf edge apparently does not present a barrier to migration in A. radiata, as it does for R. clavata.     

Unusual echolocation behavior in a small molossid bat, <Emphasis Type="Italic">Molossops temminckii,</Emphasis> that forages near background clutter

When searching for flying insects, Molossops temminckii uses unusual echolocation calls characterized by upward modulation of frequency vs time (UFM). Call frequency increases asymptotically in the relatively long (∼8 ms) pulses from a starting frequency of ∼40 kHz to a long narrowband tail at ∼50 kHz. When approaching a prey, the bat progressively increases the duration of calls and intersperses in the sequence broadband downwardly frequency-modulated signals with a terminal frequency of about 53 kHz, which totally replaces the UFM signals at the end of the approach phase. The sequence progresses to a capture buzz resembling those from other molossid and vespertilionid bats. The M. temminckii wing morphology is characterized by an average aspect ratio and a high wing loading, suggesting that it is more maneuverable than the typical Molossidae but less than typical Vespertilionidae. M. temminckii regularly forages near clutter, where it needs to pay attention to the background and might face forward and backward masking of signals. We hypothesize that the UFM echolocation signals of M. temminckii represent an adaptation to foraging near background clutter in a not very maneuverable bat needing a broad attention window. The broadband component of the signal might serve for the perception of the background and the narrowband tail for detection and perhaps classification of prey. Bats may solve the signal masking problems by separating emission and echoes in the frequency domain. The echolocation behavior of M. temminckii may shed light on the evolution of the narrowband frequency analysis echolocation systems adopted by some bats foraging within clutter.     

Chemical defense: incorporation of diet-derived pyrrolizidine alkaloid into the integumental scales of a moth (<Emphasis Type="Italic">Utetheisa ornatrix</Emphasis>)

Summary. Evidence is presented that pyrrolizidine alkaloid acquired by Utetheisa ornatrix (Lepidoptera, Arctiidae) as a larva from Crotalaria foodplants is incorporated in part into the scales of the adult. A single forewing of a male or female moth may contain in the order of 6 to 13 g monocrotaline in its scale cover or about 1 to 2% of the moths systemic monocrotaline content. Based on estimates of the number of scales per forewing, the monocrotaline content of individual scales is calculated to be in the order of 0.1 and 0.2 ng monocrotaline per male and female scale, respectively. This amounts to concentrations of about 1 and 3%, values roughly at a par with the average systemic concentration (0.5-0.6%) previously determined for monocrotaline in Utetheisa. It is argued that the presence of pyrrolizidine alkaloid in the moths scale coating could account for the promptness with which adult Utetheisa are rejected by spiders. It is suggested further that chemical impregnation of scales with substances deterrent to predators may be more widespread among insects than generally assumed.     

Effect of surfactants on Fenton's reagent-mediated degradation of Kraft black liquor

One of the limitations of the biodegradation of hydrophobic chemical compounds, like lignins, is their low solubility in the aqueous solution where this process takes place. To resolve this problem, surfactants have been used to improve the solubility of these hydrophobic compounds. In this investigation, we studied the effect of surfactants (anionic, cationic, and non-ionic) on the treatment of Kraft black liquor with Fenton's reagent. In the Fenton reaction, H2O2 (two different concentrations, 10 mM and 20 mM), FeCl2 (1 mM) and surfactant solution (10%) were used. Black liquor degradation was determined by UV/Visible spectrophotometry and by measuring phenolic groups. In the presence of Fenton's reagent, the optimum conditions for the oxidative degradation of black liquor were 10 mM H2O2, 1 microL of 10% solution of anionic surfactant (SDS). The importance of the use of surfactants for preparing black liquor for subsequent Fenton's reagent-mediated degradation was discussed.