Molecular phylogeny of treecreepers (Certhia) detects hidden diversity†

We sequenced a part of the mitochondrial cytochrome-b gene from the seven treecreeper species, including 18 subspecies, to reconstruct the phylogeny of the genus Certhia . Species status of all seven species could be affirmed. Certhia discolor , C. himalayana , C . nipalensis , and C . tianquanensis , the species with relatively small distribution ranges in southeast Asia and simple territorial song, are found at the base of all phylogenetic trees, although without good support. A comparatively recent sister species of C. tianquanensis is C. nipalensis , replacing C. discolor as closest relative. Certhia familiaris , C. brachydactyla and C. americana form a derived set of species (again only weak support). The closest relative of C. americana is C. brachydactyla . The C. familiaris subtree is deeply split into two well-defined population groups: a Eurasian group including populations in northern China (Qinling range northward and all Eurasia) and a Sino-Himalayan group (Himalayas and China excluding northern China). In accordance with acoustic characters, the three subspecies hodgsoni , mandellii and khamensis of the Sino-Himalayan group are combined and elevated to species rank: Certhia hodgsoni . Certhia discolor manipurensis is deeply split from nominate discolor as well, and is also promoted to species level. Within C. brachydactyla (western palearctic) and within C. hodgsoni (Himalayas, China) several populations form well-supported separate lineages that diverged quite recently and represent subspecies level. In all other species, molecular–genetic and vocal characters support traditional species delimitation.     

Half-Life of sRNA from Primary Roots of Zea mays. A Contribution to the Cytokinin Production

Roots produce cytokinins, which could be generated from the catabolism of transfer RNA. To prove such a hypothesis, the half-life of sRNA from primary roots of corn was measured. The shortest half-life was estimated to be 3 days. Depending on growth, cells at the root tips are “moving” out of the growing region and become differentiated cells. Therefore the highest label at the root tip during the pulse incubation is moving backwards during the chase incubation. Prolonged chase increases the half-life of sRNA successively, possibly due to decreasing metabolic activities of the originally labeled cells.     

Declines in breeding site fidelity in an increasing population of White Storks Ciconia ciconia

Following a steep decline, White Stork Ciconia ciconia populations in Germany are currently increasing, allowing us to examine potential density‐dependent effects on breeding dispersal. Our data suggest that the proportion of breeding dispersers has increased over time, indicating a density‐dependent component in nest‐site fidelity that may be linked to increased competition.     

Vacuolar Na/K Exchange, its Occurrence in Root Cells of Hordeum, Atriplex and Zea and its Significance for K/Na Discrimination in Roots

Using excised low-salt roots of barley and Atriplex hortenslsthe transport of endogenous potassium through the xylem vesselswas studied It was enhanced by nitrate and additionally by sodiumions which apparently replaced vacuolar potassium which wasthen available in the symplasm of root cells for transport tothe shoot Vacuolar Na/K exchange also has been investigatedby measurements of longitudinal ion profiles in single rootsof both species. In Atriplex roots a change in the externalsolution from K⁺ to Na⁺ induced an exchange of vacuolar K⁺ forNa⁺, in particular in the subapical root tissues and led toincreased K⁺ transport and loss of K⁺ from the cortex. In inverseexperiments a change from Na⁺ to K⁺ did not induce an exchangeof vacuolar Na⁺; merely in meristematic tissues Na⁺—apparentlyfrom the cytoplasm—was extruded in exchange for K⁺. Inroots of barley seedlings without caryopsis, as in excised roots,a massive exchange of K⁺ for Na⁺ was observed in the continuouspresence of external 1.0 mM Na and 0.2 mM K. This exchange alsowas attributed to the vacuole and was most pronounced in theyoung subapical tissues. It did not occur, however, in the correspondingtissues in roots of fully intact barley seedlings. In these,the young tissues retained a relatively high K/Na ratio alsoin their vacuoles. Similarly, contrasting results were obtainedwith intact and excised roots of Zea mays L. Based on theseresults a scheme of the events that lead to selective cationuptake in intact barley roots is proposed. In this scheme acrucial factor of selectivity is sufficient phloem recirculationof K⁺ by the aid of which K⁺ rich cortical cells are formednear the root tip. When matured these cells are suggested tomaintain a high cytoplasmic K/Na ratio due to K⁺ dependent sodiumextrusion at the plasmalemma and due to recovery of vacuolarK⁺ by Na/K exchange across the tonoplast. Key words: Potassium/Sodium selectivity, Vacuolar exchange, Xylem transport, Hordeum, Zea, Atriplex     

Ionic Interactions of Petiole and Lamina During the Life of a Leaf of Castor Bean (Ricinus communis L.) Under Moderately Saline Conditions

Ion (K⁺, Na⁺, Mg²⁺, Ca²⁺ and Cl) flows and partitioning in thepetiole and lamina of leaf 6 of castor bean {Ricinus communisL.) plants growing in the presence of a mean of 71 mol m^–3NaCl were described by an empirical modelling technique. Thiscombined data on changes in ion contents of petiole and lamina,ion: carbon molar ratios of phloem bleeding sap and pressure-inducedxylem exudates of the leaf with previously described informationon the economies of C and N in identical leaf material. Datawere expressed as daily exchanges of ions in xylem and phloem,or depicted as models of ion balance and transport activityof petiole and lamina during four consecutive phases of leaflife. The early import phase was characterized by high intakeof K and Mg through phloem, and of Ca mainly through xylem,but only limited intake of Na and Cl. The next phase up to fullleaf expansion showed similar relative differences in xylemintake between ions and the onset of rapid phloem export fromthe lamina of K and Mg, some export of Na and Cl but scarcelyany of Ca. The next mature phase, marked by maximal photosynthesisand transpiration by the leaf, showed high xylem intake of allions in xylem. This was more than matched by phloem export ofMg and K, but by only fractional re-export of Na and Cl andagain very limited cycling through the leaf of Ca. The finalpre-senescence phase exhibited similar behaviour, but with generallygreater contribution to phloem transport from mobilization ofion reserves of the lamina. The petiole retained particularlylarge amounts of Na and Cl in its early growth, thereby protectingthe lamina from excessive entry of salt, but these petiolarpools, together with those or other nutrient ions, were laterpartially mobilized to the lamina via the xylem stream. Datawere discussed in relation to the relatively high salt toleranceexhibited by the species. Key words: Ricinus communis, xylem and phloem transport, ion balance, K+ economy, Na+ exclusion, NaCl-stress, salt tolerance, leaf development     

Cation and Chloride Partitioning through Xylem and Phloem within the Whole Plant of Ricinus communis L. under Conditions of Salt Stress

Uptake and partitioning through the xylem and phloem of K⁺,Na⁺, Mg²⁺ , Ca²⁺ and Cl^– were studied over a 9 d intervalduring late vegetative growth of castor bean (Ricinus communisL.) plants exposed to a mean salinity stress of 128 mol m^–3NaCl. Empirically based models of flow and utilization of eachion within the whole plant were constructed using informationon ion increments of plant parts, molar ratios of ions to carbonin phloem sap sampled from petioles and stem internodes andpreviously derived information on carbon flow between plantsparts in xylem and phloem in identical plant material. Salientfeatures of the plant budget for K⁺ were prominent depositionin leaves, high mobility of K⁺ in phloem, high rates of cyclingthrough leaves and downward translocation of K⁺ providing theroot with a large excess of K⁺ . Corresponding data for Na⁺showed marked retention in the root, lateral uptake from xylemby hypocotyl, stem internodes and petioles leading to low intakeby young leaf laminae and substantial cycling from older leavesback to the root. The partitioning of the anionic componentof NaCl salinity, Cl^–, contrasted to that of Na⁺ in thatit was not substantially retained in the root, but depositedmore or less uniformly in stem, petiole and leaf lamina tissues.The flow pattern for Mg²⁺ showed relatively even depositionthrough the plant but some preferential uptake by young leaves,generally lesser export than import by leaf laminae, and a returnflow of Mg²⁺ from shoot to root considerably less than the recordedincrement of the root. Ca²⁺ partitioning contrasted with thatof the other ions in showing extremely poor phloem mobility,leading to progressive preferential accumulation in leaf laminaeand negligible cycling of the element through leaves or root.Features of the response of Ricinus to salinity shown in thepresent study were discussed with data from similar modellingstudies on white lupin (Lupinus albus L.) and barley (Hordeumvulgare L.) Key words: Ricinus communis L, potassium, sodium, chloride, calcium, magnesium, phloem, xylem, transport, partitioning, salinity     

Paedomorphosis of ammonoids as a result of sealevel fluctuations in the Late Devonian Wocklumeria Stufe

A remarkable diversification of several independent ammonoid lineages with high evolutionary rates occurred in the Late Devonian Wocklumeria Stufe. Many speciation events led to paedomorphic ammonoids that display a striking range of conch shapes, sculpture, and ornamentation. In the goniatite family Prionoceratidae, the transition from normal Mimimitoceras species to paedomorphic Balvia species provides an example of rapid size decrease combined with an early character developmental offset arising from progenesis. Adults of early Balvia species largely have the preadult ancestral morphology of Mimimitoceras , but later evolving species acquire distinct conch and ornamentation types. Progenetic ammonoid species also appeared within the clymeniid family Kosmoclymeniidae and probably in the Glatzielliidae. In the clymeniid family Parawocklumeriidae, evolution is characterized by the extension of tri-segmented and triangularly coiled whorls found only in juveniles of earlier species, to the adults of later species. This is interpreted as resulting from neoteny. The distribution of paedomorphic ammonoids in the Late Devonian Wocklumeria Stufe is closely correlated to relative sealevel changes. The regressive trend in the lower two-thirds of the Wocklumeria Stufe is interpreted as the cause of a diversification of the pelagic habitat during unstable conditions, and as an extrinsic factor inducing heterochronic change. Some ammonoids reacted by rapid maturation and faster reproductive rates, giving the opportunity to exploit a wider range of niches. The apparent consequence was the formation of several allopatric species. □ Ammonoidea, Late Devonian, evolution, heterochrony, sealevel changes.     

Half-life of tRNA Containing N6(Δ2-isopentenyl)adenosine in Lactobacillus acidophilus ATCC 4963

tRNA containing N⁶-(Δ²-isopentenyl)adenosine may be precursors for the plant hormone cytokinin. To discriminate between tRNA containing and not containing cytokinin nucleotides, double labelling experiments were made by the use of [2¹⁴C]-mevalonic acid and [³H-methyl]-methionine. At a generation cycle of 2 h for Lactobacillus acidophilus ATCC 4963, the half-lives of tRNA labelled with [³H-methyl]-methionine and [2-¹⁴C]-mevalonic acid are similar, namely 3 h. Isopentenylation of tRNA could be measured to be maximally 1:10.     

Ultraviolet radiation and consumer effects on a field-grown intertidal macroalgal assemblage in Antarctica

Ultraviolet radiation (UVR) research on marine macroalgae has hithero focussed on physiological effects at the organism level, while little is known on the impact of UV radiation on macroalgal assemblages and even less on interactive effects with other community drivers, e.g. consumers. Field experiments on macrobenthos are scarce, particularly in the Antarctic region. Therefore, the effects of UVR and consumers (mainly limpets were excluded) on early successional stages of a hard bottom macroalgal community on King George Island, Antarctica, were studied. In a two‐factorial design experimental units [(1) ambient radiation, 280–700 nm; (2) ambient minus UVB, 320–700 nm and (3) ambient minus UVR, 400–700 nm vs. consumer–no consumer] were installed between November 2004 and March 2005 (n= 4 plus controls). Dry mass, species richness, diversity and composition of macroalgal assemblages developing on ceramic tiles were followed. Consumers significantly suppressed green algal recruits and total algal biomass but increased macroalgal richness and diversity. Both UVA and UVB radiation negatively affected macroalgal succession. UVR decreased the density of Monostroma hariotii germlings in the first 10 weeks of the experiment, whereas the density of red algal recruits was significantly depressed by UVR at the end of the study. After 106 days macroalgal diversity was significantly higher in UV depleted than in UV‐exposed assemblages. Furthermore, species richness was significantly lower in the UV treatments and species composition differed significantly between the UV‐depleted and the UV‐exposed treatment. Marine macroalgae are very important primary producers in coastal ecosystems, serving as food for herbivores and as habitat for many organisms. Both, UVR and consumers significantly shape macroalgal succession in the Antarctic intertidal. Consumers, particularly limpets can mediate negative effects of ambient UVR on richness and diversity till a certain level. UVB radiation in general and an increase of this short wavelength due to stratospheric ozone depletion in particular may have the potential to affect the zonation, composition and diversity of Antarctic intertidal seaweeds altering trophic interactions in this system.