The ecology of Cenomanian lithistid sponge frameworks, Regensburg area, Germany

Upper Jurassic‐Lower Cretaceous sponge biostromes and bafflestone mounds were common and widespread in European temperate to tropical marine environments. They declined markedly during the Late Cretaceous. Most sponge frameworks were paucispecific and ecologically simple, with only basic levels of succession or tiering. The occurrence of ecologically complex, lithistid sponge biostromes and mounds in the Cenomanian Quadersandstein Member, Regensburger Grünsandstein of the Saal Quarry, Bavaria, is therefore of special significance. These are ecologically the most complex sponge frameworks yet reported from the Cretaceous. Their size, morphology and ecological organization compare favorably with shallow‐water, sponge‐dominated frameworks in modern seas. The Saal Quarry sponge frameworks are generally associated with firmgrounds and condensed intervals in the transgressive systems tract of the Cenomanian‐Turonian, tectonoeustatic supercycle UZA‐2. The lowest sponge frameworks are up to 1 m high bafflestone mounds consisting of large, irregular, sheet‐ and mound‐like recumbent sponges overlain by diverse, cylindrical, pyriform, upward‐branching forms of Jerea and Siphonia. These biostromes overlie a condensed interval or firmground which locally contains small, in situ pyriform sponges (Jerea pyriformis Lamouroux) as well as Middle Cenomanian Inoceramus etheridgei Woods. The upper sponge frameworks consist of bafflestone mounds up to 4.4 m wide and 1.3 m high, composed of six lithistid sponge morphotypes, possibly representing several species of Jerea and Siphonia. The occurrence of Rotalipora cushmanni in strata overlying the upper sponge framework indicates a Late Cenomanian age. Morphotypes preserve internal sponge morphologies and partially dissolved spicules surrounded by a diagenetic halo of silicified, pelletoid grainstone and/or packstone. Silica cements were derived from spicule dissolution. Different combinations of these morphotypes dominate three to four successional stages of sponge framework growth, and show vertical ecological tiering within communities. This ecological zonation is consistent among frameworks, and is partially or wholly repeated between storm‐related disturbance events.     

Are smaller subspecies of common brushtail possums more omnivorous than larger ones?

Body size is often associated with a dietary divergence within taxonomically related groups so that large animals are often folivorous, while smaller species shift progressively towards omnivory or carnivory. This trend may be influenced by allometric constrains which result in relatively high energetic requirements, but low gut capacities in small animals, compared to their large counterparts. The common brushtail possum (Trichosurus vulpecula, Phalangeridae) has six subspecies ranging widely in weight (1–4 kg). They are not strictly folivorous, but supplement their diet with more nutritious, non‐foliar foods. We predicted that T. vulpecula subspecies diverged in diet in association with body size, with smaller subspecies consuming higher proportions of non‐foliar foods. We assessed this with a review and a meta‐analysis of previous Australian studies. We also investigated the previously unquantified diet of T. v. hypoleucus at three sites in the northern jarrah forest of Western Australia. Results from the meta‐analysis and the review supported our prediction. However, the large variability in the data highlighted their limitations and those of the techniques commonly used to quantify the diet of T. vulpecula. Nonetheless, small subspecies of T. vulpecula appear to consume higher proportions of non‐foliar foods. These results should encourage further research into the body size/diet relationship within T. vulpecula and other possum species. Results from the dietary study of T. v. hypoleucus emphasized their omnivorous diet, which was dominated by foliage and flowers and smaller proportions of invertebrates, seeds and fruits. The common brushtail possum is seldom an exclusive arboreal folivore, but rather ranges from folivory to omnivory.     

Global decomposition experiment shows soil animal impacts on decomposition are climate‐dependent

Climate and litter quality are primary drivers of terrestrial decomposition and, based on evidence from multisite experiments at regional and global scales, are universally factored into global decomposition models. In contrast, soil animals are considered key regulators of decomposition at local scales but their role at larger scales is unresolved. Soil animals are consequently excluded from global models of organic mineralization processes. Incomplete assessment of the roles of soil animals stems from the difficulties of manipulating invertebrate animals experimentally across large geographic gradients. This is compounded by deficient or inconsistent taxonomy. We report a global decomposition experiment to assess the importance of soil animals in C mineralization, in which a common grass litter substrate was exposed to natural decomposition in either control or reduced animal treatments across 30 sites distributed from 43°S to 68°N on six continents. Animals in the mesofaunal size range were recovered from the litter by Tullgren extraction and identified to common specifications, mostly at the ordinal level. The design of the trials enabled faunal contribution to be evaluated against abiotic parameters between sites. Soil animals increase decomposition rates in temperate and wet tropical climates, but have neutral effects where temperature or moisture constrain biological activity. Our findings highlight that faunal influences on decomposition are dependent on prevailing climatic conditions. We conclude that (1) inclusion of soil animals will improve the predictive capabilities of region‐ or biome‐scale decomposition models, (2) soil animal influences on decomposition are important at the regional scale when attempting to predict global change scenarios, and (3) the statistical relationship between decomposition rates and climate, at the global scale, is robust against changes in soil faunal abundance and diversity.     

Specialization for hawkmoth and long-proboscid fly pollination in Zaluzianskya section Nycterinia (Scrophulariaceae)

The evolution of pollination systems has been investigated in Zaluzianskya section Nycterinia (Scrophulariaceae), a group characterized by very long-tubed flowers (up to 60 mm) that open either only at night (19 species) or during the day (one species). Field observations of three species: Z. natalensis , Z. elongata and Z. pulvinata , revealed that their flowers are pollinated shortly after dusk by hawkmoths. Further observations showed that Z. microsiphon , the sole species to have flowers that open only during the day, is pollinated exclusively by long-proboscid flies belonging to the family Nemestrinidae. A phylogenetic analysis of Z. sect. Nycterinia based on morphological characters indicates that Z. microsiphon evolved within a clade of night-flowering species. The shift from hawkmoth to long-proboscid fly pollination in Zaluzianskya was probably facilitated because long corolla tubes, white petals and dilute nectar in hawkmoth-pollinated flowers are pre-adaptations for pollination by long-proboscid flies. However, the autapomorphic features of Z. microsiphon , such as zygomorphy, diurnal flower anthesis and lack of scent, can be regarded as adaptations for long-proboscid fly pollination. Breeding system experiments on Z. natalensis and Z. microsiphon revealed the existence of genetic self-incompatibility. © 2002 The Linnean Society of London, Botanical Journal of the Linnean Society , 138 , 17–27.     

Development and characterization of microsatellite loci in the endangered oyster mussel Epioblasma capsaeformis (Bivalvia: Unionidae)

Primers for 10 polymorphic microsatellite loci were developed and characterized for the endangered oyster mussel Epioblasma capsaeformis from the Clinch River, Tennessee. Microsatellite loci also were tested in four other populations or species. Amplification was successful for most loci in these closely related endangered species or populations; therefore, a high level of flanking sequence similarity was inferred for this group of species and populations. Allelic diversity ranged from nine to 20 alleles/locus, and averaged 13.6/locus. This study demonstrated the feasibility of using polymerase chain reaction (PCR) primers to amplify microsatellite loci across freshwater mussel species to conduct population genetics studies.     

The dissipation of excess excitation energy in British plant species

The reversible dissipation of excitation energy in higher plants is believed to protect against light-induced damage to the photosynthetic apparatus. This dissipation is measured as the non-photochemical quenching of chlorophyll fluorescence. A method is described whereby the saturated capacity for rapidly reversible non-photochemical quenching can be compared between plant species. This method was applied to 22 common British plant species whose habitat was quantified using an index that describes shade tolerance. An association was found between occurrence in open habitats and a high capacity for non-photochemical quenching. It was found that, whilst this capacity was species dependent, it did not depend upon the conditions under which the plant was grown. The possible role of zeaxanthin as a determinant of quenching capacity was examined by measuring the contents of xanthophyll cycle carotenoids for each species. Comparing species, no correlation was seen between the saturated level of non-photochemical quenching and zeaxanthin content expressed relative to either total carotenoid or to chlorophyll. When zeaxanthin was expressed relative to the amount of xanthophyll cycle intermediates (zeaxanthin, antheraxanthin and violaxanthin), a weak correlation was seen.     

Influence of urethane and of hydrostatic pressure on the growth of bacteriophages T2, T5, T6, and T7

In 0.5 per cent NaCl, nutrient broth at 35 degrees C., urethane in a concentration of 0.4 M stops the reproduction of Escherichia coli, strain B. On dilution with 20 volumes of sterile medium, growth is resumed at its former rate after a short lag. In the one-step growth of T2, 15, T6, or T7, in the same medium at the same temperature, 0.4 M urethane, when added at the time of infection, had no apparent effect on adsorption and caused no decrease in titer throughout the latent period of the control, but completely prevented a rise in titer. If diluted 1:20 with sterile medium prior to a certain critical time in the latent period, however, bacteriophage was liberated at the same time, and in the same amount as in the control. The initial stage of apparent insensitivity to the drug lasts from the time of infection until the approximate critical times of 7 minutes with T7, T2, or T6, or 13 minutes with T5. Under the conditions described, the normal latent periods were 14, 23, 30, and 44 minutes for T7, T2, T6, and T5, respectively. At the critical times referred to above, there begins a stage characterized by complete sensitivity, rather than complete insensitivity, to 0.4 M urethane, in the sense that no active phage is subsequently liberated in continued presence of the drug. The length of this completely sensitive stage, as judged by addition of the drug at successive intervals during the latent period, extends from approximately 7 until 9 minutes after infection with T7, 7 until 15 minutes with T2 or T6, or 13 until 25 minutes with T5. When the urethane is added late in this stage of T2, a decrease in initial titer takes place as judged by assays made 40 minutes after infection, the maximum effect occurring when the drug is added between 14 and 15 minutes after infection. When added subsequently to the completely sensitive stage of each type, i.e. subsequently to 9 minutes after infection with T7, 15 minutes with T2 or T6, or 25 minutes with T5, liberation of the bacteriophage takes place in presence of the drug, but the yield is reduced, the amount of reduction being greater the sooner it is added. The yield increases as addition of the drug is delayed, but it is measurably reduced when added late in the rise period. Macroscopic lysis with T7 is delayed by 0.4 M urethane, when present from the time of infection. The delay is less with increased multiplicities of infection. A similar delay occurs with T6r at a multiplicity of 4. The application of hydrostatic pressures of 7,000 to 9,000 p.s.i. early in the latent period, within 5 to 8 minutes after infection, prevents a yield in each of the four phage types, and if maintained for lengthy periods of time a reduction in initial titer occurs. If released at various times shortly after the latent period, a rise in the titer occurred after a certain interval whose length was characteristic of the phage type. The yield was less the longer the release of pressure was delayed. When the pressure was first applied late in the latent period, large amounts of phage were liberated either under pressure or explosively when pressure was released to make the assays. Hydrostatic pressure at 6,000 p.s.i. had little effect on the rate or amount of macroscopic clearing with T7 in relatively high multiplicity of infection, when applied at the start of lysis, but slowed the rate and reduced the amount of clearing when applied shortly after infection.     

Effect of different manuring and defoliation patterns on broad-leaved dock (Rumex obtusifolius) in grassland

The effects of cutting frequency and cutting height on broad‐leaved dock (Rumex obtusifolius) in Lolium perenne‐based agricultural grassland at two levels of fertiliser input were investigated at North Wyke, Devon, UK. Two micro‐plot field experiments, containing immature dock plants at uniform densities, with a factorial design, were used to compare: (a) ‘organic’ and ‘low‐input’ fertilisation, i.e. cattle slurry only vs slurry plus mineral fertiliser (NPK at 100‐0‐64 kg ha^?1 yr^?1), (b) cutting heights of 5–6 cm vs 10–12 cm, and (c) four harvesting frequencies representative of different grassland management practices (regular 4‐weekly cutting, a ‘hay‐stage’ cutting, and two treatments with ‘silage‐stage’ cutting). Expt 1 was established in 1995 with 13 dock plants m^?2 (from excised dock‐root sections) and Expt 2 established in 1996 with 25 plants m^?2 (as seed‐grown plug plants). Treatments were assessed over the 2 subsequent years to determine treatment effects on total herbage dry matter (DM) yield and dock DM yield, and on in‐situ measures of dock ramets. In both experiments, total DM yield was increased by 1.0–2.01 ha^?1 yr^?1 for treatments receiving NK fertiliser; the proportion of dock was also higher than from slurry‐only treatments. In Expt 1, the dock ramet density, mean dock ramet height, mean leaf length and numbers of dock leaves per m² were also greater on NK fertilised treatments in autumn of yr 1. Height of cut had no consistent effect on dock yield, but dock ramet density and leaf density in autumn were greater on the 5–6 cm than the 10–12 cm cutting treatment, Expt 2 only. In yr 2 of both experiments cutting at 4‐weekly intervals resulted in less dock in the herbage than hay‐stage cutting and, particularly in Expt 1, there were associated differences in leaf density and ramet height in autumn; silage‐stage treatments were intermediate. Results are discussed in relation to requirements for management options where there is a need to avoid or reduce herbicides.     

Relationships between carotenoid composition and growth habit in British plant species

The pigment composition of leaves from a number of different plant species collected from field sites in the region of Sheffield, UK, have been compared using high-performance liquid chromatography. Expression of pigment content per unit leaf area was dominated by variation in the total leaf chlorophyll. Neither chlorophyll per unit area nor the chlorophyll a/b ratio were found to be correlated with the habitat from which the plants originated. When the amounts of different carotenoids were expressed relative to the total carotenoid pool, it was found that whilst neither total carotene (α- +β-carotene) nor neoxanthin correlated with ability to grow in shade, the leaf content of both lutein and the total xanthophyll cycle carotenoids (zeaxanthin, anther-axanthin and violaxanthin) did, with lutein content being high in shade species and xanthophyll cycle intermediates low. There was a strong negative correlation between the relative amounts of each of these groups of carotenoids. The ratio of lutein to xanthophyll cycle carotenoids was strongly correlated to an index of shade tolerance.