The rules of engagement: how to defend against combinations of predators

Studies of inducible defenses have traditionally examined prey responses to one predator at a time. However, prey in nature encounter combinations of predators that should force them to produce phenotypic compromises. We examined how snails (Helisoma trivolvis) alter their phenotype in the presence of three different predator species that were presented alone and in pairwise combinations. When snails were exposed to each predator alone, they formed predator-specific defenses that reflected the differences in each predator’s foraging mode. When snails were exposed to pairwise combinations of predators, their phenotype was dependent on their ability to detect each predator, the risk posed by each predator, and the effectiveness of a given defense against each predator. Consequently, responses to combined predators were typically biased towards one of the predators in the pair. This suggests that prey facing combined predators do not form simple intermediate defenses and, as a result, may experience enhanced mortality risk when they encounter natural predator regimes.     

Congruence of Morphological and Molecular Phylogenies

When phylogenetic trees constructed from morphological and molecular evidence disagree (i.e. are incongruent) it has been suggested that the differences are spurious or that the molecular results should be preferred a priori. Comparing trees can increase confidence (congruence), or demonstrate that at least one tree is incorrect (incongruence). Statistical analyses of 181 molecular and 49 morphological trees shows that incongruence is greater between than within the morphological and molecular partitions, and this difference is significant for the molecular partition. Because the level of incongruence between a pair of trees gives a minimum bound on how much error is present in the two trees, our results indicate that the level of error may be underestimated by congruence within partitions. Thus comparisons between morphological and molecular trees are particularly useful for detecting this incongruence (spurious or otherwise). Molecular trees have higher average congruence than morphological trees, but the difference is not significant, and both within- and between-partition incongruence is much lower than expected by chance alone. Our results suggest that both molecular and morphological trees are, in general, useful approximations of a common underlying phylogeny and thus, when molecules and morphology clash, molecular phylogenies should not be considered more reliable a priori.     

Acorn dispersal estimated by radio-tracking

Bird-dispersed seeds are difficult to track, especially in the case of long-distance dispersal events. To estimate the oak dispersal distance and the seed shadow generated by the European jay (Garrulus glandarius), we inserted radio-transmitters in 239 acorns, placed them in bird-feeders and then located them by radio-tracking. Using this methodology we located the exact caching site of 94 Quercus ilex and 54 Q. suber acorns and determined the caching habitat characteristics (vegetation type, distance, spatial distribution). The results show that: (1) there is no differences in the dispersal distance distribution between the different acorn species or sizes, (2) dispersal distances range from approximately 3 m up to approximately 550 m (mean = 68.6 m; median = 49.2 m), (3) recently abandoned fields and forest tracks were the sites preferred by jays to cache acorns, whereas fields and shrublands were avoided and (4) seed shadows showed acorn aggregation zones (i.e. clusters of caches) close to the feeder as well as isolated caches at longer distances. The results also suggest that radio-transmitters are a cheap and reliable way to determine seed shadows and quantify both seed dispersal and post-dispersal seed predation for medium to large seeds.     

Pollination biology of a disjunct population of the endangered sandhills endemic <Emphasis Type="Italic">Penstemon haydenii</Emphasis> S. Wats. (Scrophulariaceae) in Wyoming,USA

We studied the breeding system and flower visitors of the endangered plant, Penstemon haydenii, at several south-central Wyoming, USA occurrences. In agreement with earlier studies of the species 300 km to the east in Nebraska, we found Wyoming plants to be self-incompatible and pollinator-dependent for sexual reproduction. Flower visitors were several species of native bees in the families Apidae (particularly bumblebees), Halictidae (small sweat bees), and Megachilidae (especially in the genus Osmia); and the masarid wasp Pseudomasaris vespoides. Especially important was Osmia brevis, an abundant megachilid bee, and one of only two species (the sweat bee Lasioglossum (Dialictus) pruinosum was the other) present at all five sites. As in Nebraska, fruit set did not differ between our experimental cross-pollination treatment and an open-pollinated control. However, unlike Nebraska, open-pollinated treatments in Wyoming produced significantly fewer seeds per fruit than the experimental out-crossing treatment. We discuss several possible explanations for seed limitation: (1) a scarcity of pollinators early in the flowering season; (2) resource competition for developing ovules on open-pollinated inflorescences but not on experimental inflorescences; (3) the deposition of self pollen through intra-inflorescence and intra-genet pollinator movements; (4) few S-alleles and mating types in the Wyoming metapopulation compared to the Nebraska metapopulation, from which it likely derives.     

Hotspots and richness pattern of grasshopper species in cultural landscapes

The success of the hotspot approach for biodiversity conservation depends on the spatial scale and the indicator species used. In this study, we investigated grasshopper species richness in Switzerland at a 1 ha resolution including a total of 111 species. We compared the representativeness of common and of endangered grasshopper species for the overall grasshopper species richness and we assessed the efficiency of the hotspot approach for grasshopper conservation. The pattern of overall grasshopper species richness was well represented by both the number of common and the number of endangered grasshopper species. For evaluating the efficiency of different hotspot approaches for conservation, we compared hotspots of common species, hotspots of endangered species (rarity hotspots), and hotspots of all grasshopper species (richness hotspots). Among these hotspot types, richness hotspots not only featured most common grasshopper species, but they even contained more endangered species than the rarity hotspots. The combination of rarity hotspots and hotspots of common species featured more species than the other combinations of hotspot types. However, the gain of combining two hotspot types compared to the single-hotspot approach was low (max. 3 species). About 24% of the species were not contained in any of the hotspots. These grasshopper species require species-specific action plans. As rarity hotspots were located in areas that are rather strongly affected by landscape change, species richness in rarity hotspots may decrease in the future. We conclude that, for grasshoppers, the hotspot approach on the 1 ha scale can be an effective way to conserve a high proportion of species richness.     

Generation and maintenance of suspension cultures from cotyledons and their organogenic potential of two mangrove species, Sonneratia alba and S. caseolaris

Liquid cultures were successfully generated from cotyledons of two Sonneratia species, S. alba and S. caseolaris in Murashige and Skoog (MS) medium containing 0.1 μmol L⁻¹ 2,4-dichlorophenoxyacetic acid (2,4-D). Adventitious roots differentiated from cotyledons of S. alba. Proliferated cells were subcultured and a large volume of suspension cells was subsequently established in 100-mL flasks. All the cytokinins tested inhibited cell proliferation. After three years of culture, the potential to differentiate was tested as indicated by greening of the cells. Greening occurred when suspension cells were transferred to solid MS medium with and without 0.1 μmol L⁻¹ 2,4-D. Greening was stimulated by low concentrations of the weak auxins indolebutyric acid (IBA) and naphthaleneacetic acid (NAA) while 2,4-D stimulated late-stage greening. Abscisic acid (ABA) inhibited greening. Gibberellic acid (GA₃) at 1.0 μmol L⁻¹ stimulated callus greening and was not inhibitory even when tested at high concentrations. Cytokinins were inhibitory in combination with 0.1 μmol L⁻¹ of either IBA or NAA. The cause of different effects of plant hormones on growth and differentiation was discussed. Small-scale liquid media and 24-well culture plates of solid media methods developed in this paper are suitable for the optimization of hormonal conditions for cell proliferation and differentiation.     

Improving heterologous polyketide production in <Emphasis Type="Italic">Escherichia coli</Emphasis> by overexpression of an <Emphasis Type="Italic">S</Emphasis>-adenosylmethionine synthetase gene

An S-adenosylmethionine synthetase gene (metK) from Streptomyces spectabilis was cloned into an expression plasmid under the control of an inducible T7 promoter and introduced into a strain of Escherichia coli (BAP1(pBP130/pBP144)) capable of producing the polyketide product 6-deoxyerythronolide B (6-dEB). The metK coexpression in BAP1(pBP130/pBP144) improved the specific production of 6-dEB from 10.86 to 20.08 mg l⁻¹ . In an effort to probe the reason for this improvement, a series of gene deletion and expression experiments were conducted based on a metK metabolic pathway that branches between propionyl-CoA (a 6-dEB precursor) and autoinducer compounds. The deletion and expression studies suggested that the autoinducer pathway had a larger impact on improved 6-dEB biosynthesis. Supporting these results were experiments demonstrating the positive effect conditioned media (the suspected location of the autoinducer compounds) had on 6-dEB production. Taken together, the results of this study show an increase in heterologous 6-dEB production concomitant with heterologous metK gene expression and suggest that the mechanism for this improvement is linked to native autoinducer compounds.     

Monomer composition and sequence of sodium alginate extracted at pilot plant scale from three commercially important seaweeds from Mexico

The marine waters of the Baja California peninsula (Mexico) are a rich source of brown seaweeds with a great potential for exploitation. For that reason, Sargassum sinicola, Eisenia arborea, and Macrocystis pyrifera collected from different locations were subjected to extraction of sodium alginate using a pilot-plant scale process developed in our facilities. The composition and sequence parameters of the recovered alginate were studied by infrared and nuclear magnetic resonance spectroscopy. The spectral analysis of the products revealed that sodium alginate from S. sinicola contains a greater proportion of guluronate monomers (64%) than that from E. arborea (48%), and M. pyrifera (38%). Computation of the frequencies of diads and triads indicated that the alginate from S. sinicola was constructed by intercalated guluronate-blocks of 14 residues in length. In contrast, the length of the G-block in the alginates from E. arborea and M. pyrifera were 7 and 4 residues, respectively. The results show that S. sinicola, E. arborea, and M. pyrifera are sources of sodium alginate with different mannuronate/guluronate ratios, as well as a varied building-block length. In consequence, aqueous dispersions of sodium alginate from the three studied species are expected to exhibit different physical properties.     

Morphology and Taxonomy of <Emphasis Type="Italic">Apristurus longicephahis</Emphasis> (Lamniformes,Seyliorhinidae)

Data on the individual variation and changes with growth in proportions and morphology are presented for the poorly known Apristurus longicephalus, and compared with those of other species. A. longicephalus is concluded to be a distinct species without synonyms, characterized by its long snout, widely separate nostrils, long caudal fin, short abdomen, very sparse teeth, and low number of monospondylous vertebrae. It is a species of small size, maturing at about 42 cm in total length.     

Protection by pyruvate against glutamate neurotoxicity is mediated by astrocytes through a glutathione-dependent mechanism

Pyruvate, an endogenous metabolite of glycolysis, is an anti-toxicity agent. Recent studies have suggested possible roles for pyruvate in protecting CNS neurons from excitotoxic and metabolic insults. Utilizing cultures derived from embryonic rat cortex, the studies presented in this paper indicate that an astroglia-mediated mechanism is involved in the neuroprotective effects of pyruvate against glutamate toxicity. Glutamate-induced toxicity could be reversed by pyruvate in a mixed culture of cortex cells. Importantly, in pure neuronal cultures from the same tissue, pyruvate failed to protect against glutamate toxicity. Addition of astroglia to the pure neuronal cultures restores the ability of pyruvate to protect neurons from glutamate-induced toxicity. Our results further suggest that pyruvate can induce glia to up-regulate the synthesis of glutathione (GSH), an antioxidant that protects cells from toxins such as free radicals. Taken together, our data suggest that astroglia in mixed cultures are essential for mediating the effects of pyruvate, revealing a novel mechanism by which pyruvate, an important intermediate of tricarboxylic acid cycle in the body, may act to protect neurons from damage during insults such as brain ischemia.