Macromolecular composition of Palaeozoic scolecodonts: insights into the molecular taphonomy of zoomorphs

Dutta, S., Hartkopf‐Fröder, C., Mann, U., Wilkes, H., Brocke, R. & Bertram, N. 2010: Macromolecular composition of Palaeozoic scolecodonts: insights into the molecular taphonomy of zoomorphs. Lethaia, Vol. 43, pp. 334–343. Biogeochemistry and molecular taphonomy of biopolymers of marine zoomorphs are poorly known. In order to obtain insights into this issue we report on the biogeomacromolecular composition of hand‐picked, well‐preserved scolecodonts of Ordovician, Silurian and Devonian age using micro‐Fourier transform infrared (micro‐FTIR) spectroscopy, Curie point pyrolysis‐gas chromatography‐mass spectrometry (Cupy‐GC‐MS) and tetramethylammonium hydroxide (TMAH)‐assisted thermochemolysis‐GC‐MS. The present study reveals that scolecodonts are composed of both aliphatic and aromatic moieties. The micro‐FTIR spectra of scolecodonts are characterized by aliphatic CH_x (3000–2800 and 1460–1450/cm) and CH₃ (1375/cm) absorptions and aromatic C=C (1560–1610/cm) and CH (3050/cm and 700–900/cm) absorptions. The major pyrolysis products from the scolecodonts include aromatic hydrocarbons such as alkylbenzenes, alkylnaphthalenes and alkylphenols. Aliphatic hydrocarbons are represented by a homologous series of n‐alkenes and n‐alkanes. The compounds released upon thermochemolysis with TMAH are saturated and unsaturated fatty acids (as their methyl esters), n‐alkenes/alkanes and aromatic acids (as their methyl esters). No protein/amino acid‐derived compounds have been recognized in the pyrolysates or in the thermochemolysates, and it is concluded that protein/amino acid‐related compounds, which are commonly found in the jaws of extant polychaetes, were destroyed due to diagenetic processes. Obviously, excellent morphological preservation and low thermal alteration are not paralleled by a similar degree of chemical preservation. □Biogeomacromolecules, micro‐FTIR, pyrolysis‐GC‐MS, scolecodonts, thermochemolysis‐GC‐MS.     

Molecular differentiation between coexisting species of Taraxacum sect. Erythrosperma (Asteraceae) from populations in south-east and west Germany

The present study focuses on the genetic differentiation between six coexisting species of Taraxacum sect. Erythrosperma . Twenty-six individuals of T. rubicundum , T. brachyglossum , T. tortilobum , T. lacistophyllum , T. parnassicum and T. scanicum were sampled at 14 locations in south-east (Bavaria) and west Germany (Eifel). Using random amplified polymorphic DNA (RAPD) analysis 139 fragments were amplified. Nineteen of these were found to be species specific. The level of polymorphic bands within the different Taraxacum species varied between 0% and 15.8%. An analysis of molecular variance (AMOVA) revealed strong differentiation between the investigated species: 14.3% of the molecular variance were found within the species, while 85.7% of the genetic variability was observed between the species. However, a geographical differentiation between the different regions could not be observed. All analysed species were clearly separated from each other in a cluster analysis using the neighbour joining technique. The observed strong genetic differentiation between the Taraxacum species clearly supports the agamospecies concept of Taraxacum sect. Erythrosperma , which is at present mainly based on morphological and cytological criteria  © 2004 The Linnean Society of London, Botanical Journal of the Linnean Society , 2004, 145 , 109–117.     

中国横断山地区蓝藻型肺衣属地衣的三个新种

在形态和化学研究的基础上,结合分子生物学研究方法（ITS片段）,对中国横断山地区的830号与蓝细菌共生的肺衣属标本进行了分类学研究,共发现3个新种;其中,横断山肺衣L. hengduanensis的主要特征是具粉芽化裂芽,无脊肺衣L. irrugulosa的网脊不明显,以及宽叶肺衣L. latilobulata的裂片顶端宽且钝圆;3个种在ITS系统发育树上分别形成独立小枝。文中提供了中国肺衣属中与蓝细菌共生的物种检索表。     

Modelling the role of agriculture for the 20th century global terrestrial carbon balance

In order to better assess the role of agriculture within the global climate‐vegetation system, we present a model of the managed planetary land surface, Lund–Potsdam–Jena managed Land (LPJmL), which simulates biophysical and biogeochemical processes as well as productivity and yield of the most important crops worldwide, using a concept of crop functional types (CFTs). Based on the LPJ‐Dynamic Global Vegetation Model, LPJmL simulates the transient changes in carbon and water cycles due to land use, the specific phenology and seasonal CO₂ fluxes of agricultural‐dominated areas, and the production of crops and grazing land. It uses 13 CFTs (11 arable crops and two managed grass types), with specific parameterizations of phenology connected to leaf area development. Carbon is allocated daily towards four carbon pools, one being the yield‐bearing storage organs. Management (irrigation, treatment of residues, intercropping) can be considered in order to capture their effect on productivity, on soil organic carbon and on carbon extracted from the ecosystem. For transient simulations for the 20th century, a global historical land use data set was developed, providing the annual cover fraction of the 13 CFTs, rain‐fed and/or irrigated, within 0.5° grid cells for the period 1901–2000, using published data on land use, crop distributions and irrigated areas. Several key results are compared with observations. The simulated spatial distribution of sowing dates for temperate cereals is comparable with the reported crop calendars. The simulated seasonal canopy development agrees better with satellite observations when actual cropland distribution is taken into account. Simulated yields for temperate cereals and maize compare well with FAO statistics. Monthly carbon fluxes measured at three agricultural sites also compare well with simulations. Global simulations indicate a ∼24% (respectively ∼10%) reduction in global vegetation (respectively soil) carbon due to agriculture, and 6–9 Pg C of yearly harvested biomass in the 1990s. In contrast to simulations of the potential natural vegetation showing the land biosphere to be an increasing carbon sink during the 20th century, LPJmL simulates a net carbon source until the 1970s (due to land use), and a small sink (mostly due to changing climate and CO₂) after 1970. This is comparable with earlier LPJ simulations using a more simple land use scheme, and within the uncertainty range of estimates in the 1980s and 1990s. The fluxes attributed to land use change compare well with Houghton's estimates on the land use related fluxes until the 1970s, but then they begin to diverge, probably due to the different rates of deforestation considered. The simulated impacts of agriculture on the global water cycle for the 1990s are∼5% (respectively∼20%) reduction in transpiration (respectively interception), and∼44% increase in evaporation. Global runoff, which includes a simple irrigation scheme, is practically not affected.     

Leaf gas exchange and nitrogen dynamics of N2-fixing, field-grown Alnus glutinosa under elevated atmospheric CO2

Few studies have investigated the effects of elevated CO₂ on the physiology of symbiotic N₂-fixing trees. Tree species grown in low N soils at elevated CO₂ generally show a decline in photosynthetic capacity over time relative to ambient CO₂ controls. This negative adjustment may be due to a reallocation of leaf N away from the photosynthetic apparatus, allowing for more efficient use of limiting N. We investigated the effect of twice ambient CO₂ on net CO₂ assimilation (A), photosynthetic capacity, leaf dark respiration, and leaf N content of N2-fixing Alnus glutinosa (black alder) grown in field open top chambers in a low N soil for 160 d. At growth CO₂, A was always greater in elevated compared to ambient CO₂ plants. Late season A vs. internal leaf p(CO₂) response curves indicated no negative adjustment of photosynthesis in elevated CO₂ plants. Rather, elevated CO₂ plants had 16% greater maximum rate of CO₂ fixation by Rubisco. Leaf dark respiration was greater at elevated CO₂ on an area basis, but unaffected by CO₂ on a mass or N basis. In elevated CO₂ plants, leaf N content (μg N cm^?2) increased 50% between Julian Date 208 and 264. Leaf N content showed little seasonal change in ambient CO₂ plants. A single point acetylene reduction assay of detached, nodulated root segments indicated a 46% increase in specific nitrogenase activity in elevated compared to ambient CO₂ plants. Our results suggest that N₂-fixing trees will be able to maintain high A with minimal negative adjustment of photosynthetic capacity following prolonged exposure to elevated CO₂ on N-poor soils.     

Recolonization by benthic invertebrates after experimental disturbance in a Swiss prealpine river

1. Although the crucial point of disturbance experiments in streams is the extent to which they can simulate an actual spate, this aspect has been widely neglected in the design of such studies. Similarly, the influence of the specific hydrological disturbance regime of a stream on its benthic community has received much theoretical attention in recent years, but hypotheses have rarely been tested in the field. 2. Our field experiment compared the structure of the benthic invertebrate community in the prealpine River Necker in north-eastern Switzerland with predictions of the patch dynamics concept about the faunal composition of frequently disturbed streams. We also compared the resistance and resilience of the invertebrates between two sites in the River Necker. A similar substratum composition at both sites, but higher shear stress values both at baseflow and bankfull discharge at site 2, implied a higher disturbance frequency at the latter site. Five patches of stream bed of ≈ 9 m² were disturbed by kicking and raking at each site, while five similar areas served as controls. From each plot, six Surber samples were taken: the first immediately after the disturbance, and the following five 1, 3, 6, 10 and 30 days later. 3. Resilience of the total benthic invertebrate fauna was high. The total number of individuals recovered to undisturbed densities within 30 days at site 1 and 6 days at site 2. Taxon richness recovered within 3 days. In accordance with theory, taxa with high recolonization rates made up a major percentage of the total number of individuals, especially in disturbed plots. However, this percentage was lower at site 2 in spite of the higher disturbance frequency at this site. Rhithrogena spp., Leuctra spp. and the Simuliidae recovered faster to undisturbed densities at site 2. In contrast, absolute recolonization rates of these taxa were higher at site 1, where total invertebrate densities were more than twice as high as at site 2. 4. Our results suggest that the time since the last disturbance should be considered as an important factor in studies of benthic invertebrate communities in prealpine rivers, because disturbances can alter the community structure. In frequently disturbed streams, very short sampling intervals may be needed to detect differences in taxon-specific colonization rates. The specific hydrological disturbance regime of such streams is also important, because even within-stream differences in the resilience of the benthic invertebrate community are possible.     

Universal primers for a large cryptically simple cpDNA microsatellite region in Aristolochia (Aristolochiaceae)

We provide a new and valuable marker to study species relationships and population genetics in order to trace evolutionary, ecological, and conservational aspects in the genus Aristolochia. Universal primers for amplification and subsequent sequencing of a chloroplast microsatellite locus inside the trnK intron are presented. Utility of the primers has been tested in 32 species representing all clades of Aristolochia, including population studies within the A. pallida complex, A. clusii and A. rotunda. The microsatellite region is characterized as a (A_nT_m)_k repeat of 22–438 bp containing a combination of different repeats arranged as ‘cryptically simple’.