A review of the genus Johnstonia Quatrefages, 1866 (Polychaeta, Maldanidae), with a description of a new species from Trinidad, West Indies

In the interests of nomenclatural stability it is proposed that Johnstonia Quatrefages. 1866 (Polychaeta, Maldanidae) be conserved relative to its senior homonym Johnstonia Quatrefages, 1849 (Polychaeta, Nereidae) and its coexistent junior homonym Johnstonia Basir, 1956 (Nematoda, Thelastomatidae). Type material of all species previously assigned to Johnstonia Quatrefages, 1866 is re-examined and a new species from Trinidad described. All three valid species ( J. clymenoides Quatrefages, 1866; J. knysna Day. 1955; J. duplicata sp. n.) are described and figured in detail. An unnamed fourth species is known only from fragments collected off West Africa, and Johnstonia gracilis Kinberg, 1867 is newly synonymised with Euclymene oerstedii (Claparède. 1863).     

CONIFEROUS TREES ASSOCIATED WITH INTERDUNE DEPOSITS IN THE JURASSIC NAVAJO SANDSTONE FORMATION, UTAH, USA

Abstract:  The Lower Jurassic Navajo Sandstone Formation of south-west USA represents one of the largest erg deposits ever to have developed on Earth. Here, we report the widespread occurrence of silicified conifer stumps and trunks within interdune deposits near Moab, south-east Utah. Where present as (par)autochthonous assemblages, trees are associated with the deposits of spring-fed carbonate lakes. A few stumps preserved in growth position are rooted in aeolian sandstone immediately below the lake deposits, and evidently established on interdune soils in response to a rising water table. Following at least several decades of growth, trees were killed as the water table continued to rise forming shallow lakes containing ostracodes. Where present as allochthonous assemblages, randomly orientated tree trunks are associated with massive sandstone beds interpreted as fluidized mass flow deposits. These may have formed when dune slip-faces collapsed during occasional heavy downpours of rain, destroying stands of trees. The occurrence of large conifers over a wide area of the Navajo Sandstone Formation in south-east Utah may record long-lived pluvial episodes during which the dune field stabilized, or reflect the erg-margin position of the localities.     

Nectar usage in a southern Arizona hawkmoth community

Abstract.  1. Hawkmoths (Sphingidae) are important plant associates at two life-history stages: larvae are herbivorous, whereas adults are nectar feeders and often pollinators. The diversity and identities of plants used for nectar is poorly known, however.
2. This study takes a community-level approach to hawkmoth nectar plant usage in a semi-arid grassland habitat in southern Arizona, U.S.A.
3. Pollen carried on the proboscis was identified from over 700 individuals of 14 hawkmoth species attracted to lights over a 2-year period.
4. Two plant species dominated pollen loads, suggesting that hawkmoths use these species extensively as nectar sources: Datura wrightii (Solanaceae), a classic hawkmoth-pollinated plant, and Agave palmeri (Agavaceae), which is known to be used extensively by bats. Field surveys indicate that both species are relatively rare in the flowering community. Little or no pollen was present on the moths from the most common plant species in flower during the study.
5. The dominance of Agave in pollen loads suggests that this typically bat-pollinated species may be subsidising pollinator populations of the hawkmoth-pollinated flora.
6. Three groups of hawkmoths within this community are identified based on larval diets (reported in the literature) and adult diets (documented here): those that, at a given site, heavily exploit the same plant species at both life-history stages ( Manduca sexta and M. quinquemaculata ); those that have broad local associations at both life-history stages ( Hyles lineata ); and those that exhibit narrow but non-overlapping local associations at the two life-history stages (all other hawkmoths at this site).     

Differential Effects of the Parental Photothermal Environment on Development of Dormancy in Caryopses of Aegilops Kotschyi

Aegilops Kotschyi Boiss. plants produce three florets per spikelet(of which the terminal floret is commonly sterile) and exhibitphysiological heterocarpy in the two caryopses which developin each spikelet. Germinability of the basal caryopsis, butnot of the upper one, was subject to environmental influencesto which the parent plant was exposed during its development.Basal caryopses produced by plants grown at low temperature,or in 16-h photoperiods, were more dormant than when producedby plants grown at higher temperature, or in 8-h photo-periods.Germinability of the upper caryopses was equally high in allcases and independent of the parental environment. The photoperiodeffects on germinability were exerted after anthesis. Matureweight of both basal and upper caryopses was higher when producedon plants grown at low temperature, or transferred from 16-hto 8-h photopenods at emergence of the flag leaf     

Evolution of alternative sex-determining mechanisms in teleost fishes

We compiled information from the literature on the taxonomic distributions in extant teleost fishes of alternative sex-determination systems: male-heterogametic (XY) gonochorism, female-heterogametic (ZW) gonochorism, hermaphroditism, unisexuality, and environmental dependency. Then, using recently published molecular phylogenies based on whole-genomic or partial mitochondrial DNA sequences, we inferred the histories and evolutionary transitions between these reproductive modes by employing maximum parsimony and maximum likelihood methods of phylogenetic character mapping. Across a broad teleost phylogeny involving 25 taxonomic orders, a highly patchy distribution of different sex-determination mechanisms was uncovered, implying numerous transitions between alternative modes, but this heterogeneity also precluded definitive statements about ancestral states for most clades. Closer inspection of family-level and genus-level phylogenies within each of four orders further bolstered the conclusion that shifts in sex-determining modes are evolutionarily frequent and involve a variety of distinct ancestral-descendant pathways. For possible reasons discussed herein, the evolutionary lability of sex-determining modes in fishes contrasts strikingly with the evolutionary conservatism of sex determination within both mammals and birds. © 2006 The Linnean Society of London, Biological Journal of the Linnean Society , 2006, 87 , 83–93.     

Female ornaments in the Pied Flycatcher Ficedula hypoleuca: associations with age, health and reproductive success

Female ornamentation has received little attention in studies of sexual selection. Traditionally, female ornaments have been explained as a genetically correlated response to selection in males. However, recent findings suggest that female ornaments may be adaptive. Southern populations of Pied Flycatchers Ficedula hypoleuca are suited for studies of female ornamentation because, in addition to the white wing patch, some females also express the white forehead patch characteristic of males. We thus addressed the associations of these two ornaments with female age and with some health and breeding parameters in a Spanish population of Pied Flycatchers. Female ornament expression was not associated with haemoparasite prevalences, clutch size or parental provisioning effort. However, females expressing the white forehead patch raised more fledglings, and females with larger wing patches bred earlier, had higher number of hatchlings and showed increased levels of total serum immunoglobulins. Thus, these two unrelated epigamic ornaments may indicate some aspects of female quality. Further experimental studies could test the possibility that these plumage traits might function as signals to the males or might be used during female–female aggressive encounters in competition for nest-sites and mates.     

Depression of Nitrate and Ammonium Transport in Barley Plants with Diminished Sulphate Status. Evidence of Co-regulation of Nitrogen and Sulphate Intake

When barley plants were grown in a solution with nitrate asthe sole N-source but deprived of sulphate (–Splants)for 1 to 5 d, the capacity for sulphate transport by the rootsincreased very markedly; subsequent measurement of influx using³⁵S-labelled showed increases of > 10-fold compared to plants continuously supplied with sulphate (+S plants).There were only small effects on plant growth over a 5 d periodand yet the influx of , labelled with the short-lived tracer ¹³N, was diminished by approximately 30%.By contrast, the influx of phosphate was little affected bysulphate-deprivation. When a sulphate supply was restored to– S plants, the sulphate influx was quickly repressedover the subsequent 24 h and the nitrate influx was restoredto >90% of the value in +S plants. When plants were grown in a solution with a mixed nitrate andammonium supply and deprived of sulphate for 1 d or 5 d thedepression of nitrate influx was more strongly marked (up to55% depression). The influx of ammonium was also depressed after5 d of sulphate-deprivation, but not at 1 d, nor where the concentrationof ammonium in the uptake solution was lowered to 20 mmol m^–3or less. Additional measurements with ¹⁵N-labelled nitrate and ammoniumover longer periods were used to determine net uptake. Net uptakeof nitrate was depressed to a similar extent to efflux, butnet ammonium uptake was depressed only in unbuffered uptakesolution where the pH decreased to pH 4.9 during the uptakeperiod. The ¹⁵N-tracer experiments showed that the translocationof label to the shoot, from both nitrate and ammonium, was depressedto a greater extent than net uptake in –S plants. Thedepression of nitrate influx, caused by 5 d of sulphate deprivation,could be relieved almost completely by providing plants with1.0 mol m^–3 L-methionine during the day prior to influxmeasurement. This treatment substantially decreased sulphateand potassium (⁸⁶Rb-labelled) influx in both +S and –Splants, but greatly increased total S-status of the plants.This methionine treatment had no effect on ammonium influx ornet uptake in – S plants but increased influx significantlyin +S ones. When plants were grown with sulphate but deprived of nitratefor 4 d there was a marked depression of the sulphate influx(by 48–65%) but a smaller effect on phosphate influx (21–37%of +N). The results are discussed in relation to the effects of sulphate-deprivationon growth rate and the root: shoot weight ratio. It is concludedthat the effects on influx and net uptake of nitrogen are moresevere than could be accounted for by these factors. The decreasedtranslocation of either nitrate, or the products of nitrateand ammonium assimilation from the roots, is suggested as areason for the depression of influx. The restoration of nitrateinflux and net uptake by methionine suggests that, for thision at least, a shortage of S-amino acids within the plant maylead to the accumulation of inhibitory concentrations of non-Samino acids in the transport pool. Key words: ¹³N, sulphate, nitrate, ammonium, ion-uptake, barley     

PHYLOGENY OF PRIMATES AND OTHER EUTHERIAN ORDERS: A CLADISTIC ANALYSIS USING AMINO ACID AND NUCLEOTIDE SEQUENCE DATA

Abstract— Genealogical reconstructions carried out by the parsimony method on protein amino acid and DNA nucleotide sequence data are providing fresh evidence on cladistic branching patterns at taxonomic levels from the classes of Vertebrata and orders of Eutheria to the genera of Hominoidea. Minimum length trees constructed from amino acid sequence data group Mammalia with Archosauria (i.e., Aves plus Crocodilia), Amniota with Amphibia, and Tetrapoda with Teleostei. Within Mammalia, Edentata and Paenungulata (e.g., Proboscidea) appear as the most anciently separated from other eutherians. Another superordinal eutherian clade consists of Artiodactyla, Cetacea, and Perissodactyla. A third consistently contains Primates, Lagomorpha, and Tupaia. The cladistic positions of such orders as Carnivora, Chiroptera, Insectivora, and Rodentia are not well resolved by the currently still sparse body of sequence data. However, recent dramatic progress in the technology of gene cloning and nucleotide sequencing has opened the way for so enlarging the body of sequence data that it should become possible to solve almost any problem concerning the phylogenetic systematice of extant mammals. An example is provided by hominoid genera. Minimum length trees constructed from mitochondrial DNA nucleotide sequence data very strongly group Pan, Homo , and Gorilla into Homininae and then join Homininae and Ponginae (pongo) into Hominidae as the sister family of Hylobatidae (Hylobates). Resolution of the hominine trichotomy into two dichotomous branchings should be forthcoming as kilobase sequencing of nuclear genes progresses.     

Differential requirement for NO during ABA-induced stomatal closure in turgid and wilted leaves

Abscisic acid (ABA)-induced stomatal closure is mediated by a complex, guard cell signalling network involving nitric oxide (NO) as a key intermediate. However, there is a lack of information concerning the role of NO in the ABA-enhanced stomatal closure seen in dehydrated plants. The data herein demonstrate that, while nitrate reductase (NR)1-mediated NO generation is required for the ABA-induced closure of stomata in turgid leaves, it is not required for ABA-enhanced stomatal closure under conditions leading to rapid dehydration. The results also show that NO signalling in the guard cells of turgid leaves requires the ABA-signalling pathway to be both capable of function and active. The alignment of this NO signalling with guard cell Ca²⁺-dependent/independent ABA signalling is discussed. The data also highlight a physiological role for NO signalling in turgid leaves and show that stomatal closure during the light-to-dark transition requires NR1-mediated NO generation and signalling.     

Root–soil friction: quantification provides evidence for measurable benefits for manipulation of root‐tip traits

To penetrate soil, a root requires pressure both to expand the cavity it is to occupy, σ_n, and to overcome root–soil friction, σ_f. Difficulties in estimating these two pressures independently have limited our ability to estimate the coefficient of soil–root friction, μ_sr. We used a rotated penetrometer probe, of similar dimensions to a root, and for the first time entering the soil at a similar rate to a root tip, to estimate σ_n. Separately we measured root penetration resistance (PR) Q_r. Root PR was between two to four times σ_n. We estimated that the coefficient of root–soil friction (μ_sr) was 0.21–0.26, based on the geometry of the root tip. This is slightly larger than the 0.05–0.15 characteristic of boundary lubricants. Scanning electron microscopy showed that turgid border cells lined the root channel, supporting our hypothesis that the lubricant consisted of mucilage sandwiched between border cells and the surface of the root cap and epidermis. This cell–cell lubrication greatly decreased the friction that would otherwise be experienced had the surface of the root proper slid directly past unlubricated soil particles. Because root–soil friction can be a substantial component of root PR, successful manipulation of friction represents a promising opportunity for improving plant performance.