Affinities in C3Cyperus lineages (Cyperaceae) revealed using molecular phylogenetic data and carbon isotope analysis

Maximum likelihood and Bayesian analyses of nrDNA (ETS1f) and plastid DNA (rpl32‐trnL, trnH‐psbA) sequence data are presented for ‘C₃Cyperus’ (Cyperaceae). The term ‘C₃Cyperus’ indicates all species of Cyperus s.l. that use C₃ photosynthesis linked with eucyperoid vegetative anatomy. Sampling comprises 77 specimens of 61 different taxa, representing nearly all previously recognized subdivisions of C₃Cyperus and the segregate genera Courtoisina, Kyllingiella and Oxycaryum. According to our results, the Cyperus clade is divided in six well‐supported clades. The first of these clades (clade 1) forms three subclades largely corresponding to Cyperus sections Haspani, Incurvi and Diffusi. Clade 2 comprises the entirely New World C. section Luzuloidei sensu Denton (1978). Clade 3 is a highly diverse clade including two subclades: clade 3a, C. sections Pseudanosporum and Anosporum plus the segregate genera Courtoisina and Oxycaryum; and clade 3b, C. section Fusci. Clade 4 corresponds to C. section Alternifolii and clade 5 to C. section Leucocephali plus the segregate genus Kyllingiella. The sixth clade is a well‐supported monophyletic clade encompassing all C₄Cyperus s.l. species (‘C₄Cyperus’). This study establishes a phylogenetic framework for future studies. © 2011 The Linnean Society of London, Botanical Journal of the Linnean Society, 2011, 167 , 19–46.     

Isolation and characterization of microsatellite markers in Pterocarpus officinalis Jacq.

The leguminous Pterocarpus officinalis Jacq. is one of the dominant freshwater wetland tree species in the Caribbean basin. Anthromorphic factors threaten to reduce its population. In order to investigate the genetic diversity and structure of this species, we developed eight pairs of primers for nuclear microsatellites. One hundred ninety‐one individuals were analysed within nine Caribbean and continental populations. These loci were polymorphic in all the populations, with four to 20 alleles per locus. Significant Hardy–Weinberg deviation was detected and was interpreted as a result of Wahlund effect. These loci constitute a powerful tool to investigate the genetic patterns within populations of the swamp species P. officinalis.     

Total metal burdens in the freshwater amphipod Gammarus fasciatus: contribution of various body parts and influence of gut contents

1. The distribution of trace metals among body parts of the freshwater amphipod Gammarus fasciatus was investigated and the effect of depuration on the total body burden was assessed.
2. Concentrations of Cr, Fe, Mn and Ni were one order of magnitude higher in the gut contents than in the various body parts, accounting for 40–72% of the total body burdens of amphipods. Depuration caused a decrease of total metal concentrations of 35–88%.
3. Levels of Cd and Cu were higher in the hepatopancreas than in other body parts, whereas levels of Zn were relatively constant throughout the body. For Cd, Cu and Zn, depuration had no effect on mean body concentrations.
4. For Pb, an important fraction of the total body burden was associated with the exoskeleton; depuration caused a decrease in Pb body concentrations.
5. Regression between amphipod metal concentrations before and after depuration is a potential tool for correcting for the effect of gut contents. This correcting method was found to be promising for Cd, Cu, Mn and Zn, with R ² varying between 0.66 and 0.98. It was less efficient for Cr, Fe and Pb, and was useless for Ni.     

Shifts in elemental composition,methylmercury content and δ15N ratio during growth of a High Arctic copepod

1. We examined how ontogenetic development in a calanoid copepod from the High Arctic, Limnocalanus macrurus, influenced its elemental composition (carbon, nitrogen, phosphorus), methylmercury (MeHg) content and stable nitrogen and carbon isotope ratios in populations from nine lakes. 2. Population structure explained 33–83% of among‐lake variation in the C, N and P composition of the biomass. Biomass dominated by early‐stage copepodites had a greater P content, which declined in more mature populations, as indicated by significant changes in % P and the molar N/P ratio. Carbon and lipid contents increased with the proportion of adult biomass. Copepod populations sampled in warmer waters had a greater proportion of adult biomass, and water temperature was the most significant environmental variable explaining elemental composition. 3. A δ¹⁵N enrichment of 3.3 ± 1.0‰ was associated with copepodite development. Gut contents of L. macrurus showed no evidence of animal (invertebrate) prey, indicating no change in trophic position. 4. Unexpectedly, MeHg concentration was negatively correlated with the proportion of adult biomass. However, this trend was not significant after correcting MeHg concentration to non‐lipid dry mass, suggesting a lipid dilution effect in more mature copepods. Lake surface area, rather than ontogeny, best explained MeHg concentrations in L. macrurus. 5. Ontogenetic influences on chemical constituents of this common Arctic copepod, particularly δ¹⁵N ratios and uncorrected MeHg concentrations, highlight the relevance of developmental processes for studies of food webs and mercury in species‐poor High Arctic lakes.     

Spatial pattern of ovule maturation in the inflorescence of Echium vulgare: demography, resource allocation and the constraints of architecture

Many of the flowers produeed bv a plant fail to mature seeds despite effective pollination. The role of inflorescence architecture governing patterns of abortion in plants has been underestimated. 1 he inflorescence of Echium vulgare L. comprises a raceme bearing lateral inflorescences, each of which is cymosc. Within each cyme, there is a correlation between the proximity of a flower to the main axis and its order of flowering; and (lie probability of it maturing seeds. These findings appear to result from a decrease in the availability of maternal resources as the flowering period progresses. No relationship could be shown between the position of the cyme on the main inflorescence and the number of seeds set per flower although position was correlated with the length of the cyme, the number of (lowers and the length of the subtending bract. The mctamcric units of E. vulgare appear to function largely independently in their assimilation of resources. Larger cymes not only bear more flowers, but also draw on a larger area of photosynthetic tissue for resources. This hypothesis is supported by the removal of the bract or of part of the cyme at the onset of flowering; cymes without bracts mature fewer ovules than controls while decapitated cymes mature a greater proportion of ovules.     

UNCOUPLING OF OOCYTE-FOLLICLE CELLS TRIGGERS REINITIATION OF MEIOSIS IN AMPHIBIAN OOCYTES

Reinitiation of meiosis has been triggered in vitro in oocytes of the anouran Xenopus laevis and the urodeles Pleurodeles waltlii and Ambystoma mexicanum by enzymatic, mechanical or manual defolliculation, without addition of hormone. By measuring changes in the membrane resistance and time constants, we also demonstrate the existence of an electrical polarized coupling between the oocyte and its follicle and show that progesterone breaks it definitively within the first two hours. These results are discussed in relation to mammalian maturation.     

Dynamic Aspects of Antigen Binding to B Cells in Immune Induction

Antigens either immunize B lymphocytes direct, or must be aided by such cells as T cells or macrophages. This is chiefly caused by the physical structure of the antigen's macromolecular “carrier”.     

Microbial biofilms and the preservation of the Ediacara biota

Laflamme, M., Schiffbauer, J.D., Narbonne, G.M., & Briggs, D.E.G. 2011: Microbial biofilms and the preservation of the Ediacara biota. Lethaia, Vol. 44, pp. 203–213. The terminal Neoproterozoic Ediacaran Period is typified by the Ediacara biota (ca. 579–542 Ma), which includes the first morphologically complex macroscopic organisms. Both the taphonomic setting that promoted the preservation of the soft‐bodied Ediacara biota in coarse‐grained sediments, and the influence of associated microbial coatings on this process, have generated debate. Specimens of Ediacaran discs (Aspidella) from the Fermeuse Formation of Newfoundland, Canada, were analysed using environmental scanning electron microscopy (ESEM) and focused ion beam electron microscopy (FIB‐EM) to determine the relationship between the fossil specimens and the surrounding sediment. The presence of chemically distinct (Al–Mg–Fe–K‐ and to a lesser extent S‐rich), finer‐grained sediment (with organized iron sulphides) surrounding the upper and lower margins of the Ediacaran fossils is consistent with elemental analyses of well preserved bacterial biofilms from other localities. ESEM analyses reveal a contrast in the composition of the sediment bound within the discs, which contains a higher concentration of Al, Ca and K, and the purer Si‐rich sediment that forms the surrounding matrix. This suggests that the coarse grained sediment was incorporated into the organism during life. Ediacaran discs were likely surrounded by a bacterial biofilm or thin microbial mat composed primarily of extracellular polymeric substances (or exopolysaccharide) during life, which added structural stability to these frond holdfasts, and facilitated their fossilization. Microbially mediated preservation in Fermeuse‐style Ediacaran taphonomy provides an explanation for the dominance of Aspidella holdfasts in these settings, and suggests that preservation of Ediacaran fossils in the round may be much more prevalent than previously recognized. We suggest that the overwhelming dominance of circular to bulbous forms such as Aspidella in Ediacaran biotas around the world is a direct result of the interplay between microbial ecology and microbially mediated taphonomy. □Aspidella, Ediacaran preservation, environmental scanning electron microscopy, focused ion beam electron microscopy, palaeoecology, taphonomic bias.     

Effects of coexistence on habitat use and trophic ecology of interacting native and invasive amphipods

1. Invasive species in aquatic systems are major drivers of changes in biodiversity. Amphipods are key species in freshwaters, with invasive amphipods either replacing or coexisting with native species and often damaging local biodiversity. However, the consequences of interactions among native and invasive amphipods for their habitat use and feeding ecology and ecosystem function are not yet well understood. 2. We examined a number of streams in Brittany and Northern Ireland, with native and invasive amphipods, to evaluate the consequences of species interactions for both habitat use and diet. Our field studies centred on testing two proposed models: a cohabitation model without competition between two native species (Gammarus pulex vs Echinogammarus berilloni), and a competition model between an invasive and a native species (Gammarus pulex vs Gammarus duebeni celticus). For these three species, alone and in combination, we assessed their habitat use and feeding patterns, the latter through gut contents and stable C and N isotope analyses of their tissues. 3. When existing as single‐species populations, all three species used stream habitats broadly similarly, although G. pulex was more strongly associated with leaf litter and vegetation compared to pebble substrata than the other species. When G. pulex coexisted with either E. berilloni or G. d. celticus, the latter two changed to using all habitats equally, whereas the former retained its habitat preferences. 4. Similarly, all three species when alone had similar gut contents, with inorganic material predominating, followed by leaf and woody material and more rarely algae and invertebrates. When G. pulex coexisted with E. berilloni, the diet of the latter did not change; however, the frequency of inorganic matter, leaves and wood declined in the gut contents of G. pulex. When G. pulex coexisted with G. d. celticus, the pattern of gut contents did not change in either species. 5. When existing as single‐species populations, G. pulex had a broader range of isotopic signatures, both for δ¹³C and for δ¹⁵N, than the two other species, indicating a more variable diet among individuals. When G. pulex coexisted with either E. berilloni or G. d. celticus, the latter two had similar ranges of δ¹³C and δ¹⁵N, whereas for G. pulex the range was much less for δ¹³C and δ¹⁵N, suggesting a less diverse diet. 6. Our results infer two different modes of coexistence between native and non‐native amphipods. We have shown that the native species, which coexist stably, appear to show interference competition, leading to spatial habitat segregation, whereas competition for food and possible intraguild predation by G. pulex on G. d. celticus would explain why the distribution and density of the latter is affected by G. pulex. However, since all the species have a similar diet and feeding habit, we expect no great overall effect on ecosystem processes as a consequence of species interactions and displacements.