Palaeoecology and diversity of endosymbionts in Palaeozoic marine invertebrates: Trace fossil evidence

Endosymbionts are organisms that live within the growing skeleton of a live host organism, producing a cavity called a bioclaustration. The endosymbiont lives inside the bioclaustration, which it forms by locally inhibiting the normal skeletal growth of the host, a behaviour given the new ethological category, impedichnia. As trace fossils, bioclaustrations are direct evidence of past symbioses and are first recognized from the Late Ordovician (Caradoc). Bioclaustrations have a wide geographic distribution and occur in various skeletal marine invertebrates, including tabulate and rugose corals, calcareous sponges, bryozoans, brachiopods, and crinoids. Ten bioclaustration ichnogenera are recognized and occur preferentially in particular host taxa, suggesting host-specificity among Palaeozoic endosymbionts. The diversity of bioclaustrations increased during the Silurian and reached a climax by the late Middle Devonian (Givetian). A collapse in bioclaustration diversity and abundance during the Late Devonian is most significant among endosymbionts of host coral and calcareous sponge taxa that were in decline leading up to the Frasnian-Famennian mass extinction.     

Mating patterns and determinants of individual reproductive success in brown trout (Salmo trutta) revealed by parentage analysis of an entire stream living population

Reproductive success and its determinants are difficult to infer for wild populations of species with no parental care where behavioural observations are difficult or impossible. In this study, we characterized the breeding system and provide estimates of individual reproductive success under natural conditions for an exhaustively sampled stream‐resident brown trout (Salmo trutta) population. We inferred parentage using a full probability Bayesian model that combines genetic (microsatellite) with phenotypic data. By augmenting the potential parents file with inferred parental genotypes from sib‐ship analysis in cases where large families had unsampled parents, we could make more precise inference on variance of family size. We observed both polygamous and monogamous matings and large reproductive skew for both sexes, particularly in males. Correspondingly, we found evidence for sexual selection on body size for both sexes. We show that the mating system of brown trout has the potential to be very flexible and we conjecture that environmental uncertainty could be driving the evolution and perhaps select for the maintenance of plasticity of the mating system in this species.     

Macro-alga population shows low but significant heterogeneity in developmental instability with no detectable association with individual fitness

We studied among-individual variation in developmental instability (DI) and fitness-related parameters in 80 individual plants of Fucus vesiculosus (Phaeophyta). To minimize differential environmental effects, plants were sampled from one environmentally homogenous population. DI was measured as fluctuating asymmetry (FA) of four bilaterally symmetric traits (branch length, receptacle length and width, and bladder width) for an average total of 30 structures per individual. FA levels varied significantly among individual plants, consistent with a coefficient of variation of 0.12 for organism-wide DI or 0.13–0.21 for trait-specific DI. These values are lower than estimates for other organisms, suggesting that the genetic heterogeneity in DI was low. The data provide some evidence for organism-wide DI, but simulations show that organism-wide and trait-specific variation cannot be conclusively separated. Growth rate of branch tips was determined experimentally, demonstrating significant variation among individuals. FA was not significantly correlated with growth rate or with morphological variables associated with fecundity, age, size, and health. At the same time, the signs of all the correlation coefficients were consistent with the expectation of a negative relationship between DI and fitness. The simulations indicated that the correlation between FA and the underlying DI was comparatively strong (high hypothetical repeatability), implying that the lack of significant associations between FA and fitness variables reflected a weak relationship between DI and these fitness parameters. This weak relationship may be related to the low amount of DI variation in the study population.  © 2007 The Linnean Society of London, Biological Journal of the Linnean Society , 2007, 92 , 277–286.     

Distribution patterns and dispersal strategies of Galiciales

In Caliciales both passive and active spore dispersal occurs. A review of the distribution of 162 species is given. Species with small spores have wider distribution than species with large spores, irrespective of dispersal strategy. In antitropical species there is only rarely a differentiation between Northern and Southern Hemisphere populations. It is concluded that in several small-spored genera long-distance dispersal has been instrumental in dispersing the species and range extensions have been much more frequent than in large-spored species for which vicariance explanations are more appropriate. Comparisons with bryophyte distributions show differences in dispersal strategies and distribution patterns.     

Amazonian peatlands: an ignored C sink and potential source

In tropical lowlands, peatlands are commonly reported from Southeast Asia, and especially Indonesian tropical peatlands are known as considerable C sinks and sources. In contrast, Amazonia has been clearly understudied in this context. In this study, based on field observations from 17 wetland sites in Peruvian lowland Amazonia, we report 0–5.9 m thick peat deposits from 16 sites. Only one of the studied sites did not contain any kind of peat deposit (considering pure peat and clayey peat). Historic yearly peat and C accumulation rates, based on radiocarbon dating of peat samples from five sites, varied from 0.94 ± 0.99 to 4.88 ± 1.65 mm, and from 26 ± 3 to 195 ± 70 g C m⁻², respectively. The long-term apparent peat and C accumulation rates varied from 1.69 ± 0.03 to 2.56 ± 0.12 mm yr⁻¹, and from 39 ± 10 to 85 ± 30 g C m⁻² yr⁻¹, respectively. These accumulation rates are comparable to those determined in the Indonesian tropical peatlands. Under altered conditions, Indonesian peatlands can release globally relevant amounts of C to the atmosphere. Considering the estimated total area of Amazonian peatlands (150 000 km²) close to that of the Indonesian ones (200 728 km²) as well as several factors threatening the Amazonian peatlands, we suggest that the total C stocks and fluxes associated with Amazonian peatlands may be of global significance.     

Phytogenic biosynthesis and emission of methyl acetate

Acetylation of plant metabolites fundamentally changes their volatility, solubility and activity as semiochemicals. Here we present a new technique termed dynamic ¹³C‐pulse chasing to track the fate of C_1–3 carbon atoms of pyruvate into the biosynthesis and emission of methyl acetate (MA) and CO₂. ¹³C‐labelling of MA and CO₂ branch emissions respond within minutes to changes in ¹³C‐positionally labelled pyruvate solutions fed through the transpiration stream. Strong ¹³C‐labelling of MA emissions occurred only under pyruvate‐2‐¹³C and pyruvate‐2,3‐¹³C feeding, but not pyruvate‐1‐¹³C feeding. In contrast, strong ¹³CO₂ emissions were only observed under pyruvate‐1‐¹³C feeding. These results demonstrate that MA (and other volatile and non‐volatile metabolites) derive from the C_2,3 atoms of pyruvate while the C₁ atom undergoes decarboxylation. The latter is a non‐mitochondrial source of CO₂ in the light generally not considered in studies of CO₂ sources and sinks. Within a tropical rainforest mesocosm, we also observed atmospheric concentrations of MA up to 0.6 ppbv that tracked light and temperature conditions. Moreover, signals partially attributed to MA were observed in ambient air within and above a tropical rainforest in the Amazon. Our study highlights the potential importance of acetyl coenzyme A (CoA) biosynthesis as a source of acetate esters and CO₂ to the atmosphere.     

Endogenous Growth Substances in Normal and Dwarf Mutants of Cortland and Golden Delicious Apple Shoots

Endogenous growth substances in the shoots of dwarf mutants of Cortland (Cortland 65–6 and Cortland 65–7) and Golden Delicious (Golden Auvil Spur and Yellow Spur) were investigated in relation to dwarfism. The shoots were extracted at three stages of growth, namely: 1) rapid elongation growth, 2) formation of terminal bud, and 3) cessation of cambial growth. The growth substances were partially separated by thin layer chromatography and bioassayed using the Avena first internode and Lepidium seed germination tests. Shoot extracts from the normal Cortland and Golden Delicious plants contained higher levels of auxins at all stages of growth than those from dwarf mutants. Growth-promoting activity was found in two zones on chromatograms developed with isopropanol: ammonia: water (10:1:1 v/v/v):R_f 0.4 to 0.5 and R_f 0.8 to 0.9. The Lepidium seed germination test showed the presence of a highly inhibitory zone between R_f 0.3 and 0.4 in the extracts of dwarf and normal plants. However, the peak of germination inhibition activity was sharp for dwarf mutants and less for extracts of normal growing plants at 3 stages of growth. The inhibitory substance(s) was further purified on TLC plates by successive separations in different solvent systems. Two substances which inhibited the Lepidium seed germination were found, one close to the R_f value of synthetic abscisic acid and the other appeared to be similar to xanthoxin in R_f value, biological activity and UV absorption spectra.