Attached vermiform gastropods in Carboniferous marginal marine stromatolites and biostromes

Tubiform fossils conventionally referred to Serpula cf. advena Salter and species of Spirorbis Lamarck from the British Lower Limestone Shales and Border Group (Lower Carboniferous) are re-examined. They occur in peritidal carbonate environments of schizohaline aspect. These fossils superficially resemble calcareous polychaete tubes but have skeletal characters, including molluscan wall structure, numerous internal septa, and protoconch, which indicate that they represent a new group of substrate-attached, disjunctly coiled gastropods. They resemble archaeogastropods in internal morphology of the skeleton but show parallels in external form and occurrence with the extant Vermetidae. There are two principal modes of occurrence: (1) erect tubes forming intertidal biostromes associated with non-skeletal algal laminites, and (2) prostrate discoidal tubes encrusting subtidal skeletal stromatolites or occasionally forming larger irregular bioherms. These biostromes and bioherms are comparable in structure to Recent vermetid reef developments.     

The Plastic Growth Responses of Three Agamospecies of Dandelion to Two Levels of Nutrient

The ability of a genotype to produce different phenotypes inresponse to variable environments is a crucial aspect of lifehistory strategies as it determines the shape of the fitnessset for the population. Apomictic dandelions generate littlegenetic variation between parent and offspring and plasticityis the main strategy in the face of environmental variability.The plastic response of three coexisiting dandelions has beenmeasured over two nutrient regimes. Cyclical growth patternsare species specific and in some cases independent of nutrientlevels. Differences between the agamospecies are greater athigh nutrient levels and the agamospecies appear to produceonly one phenotype at low nutrient levels. Taraxacum, plasticity, phenotypes, nutrient level     

The first record of gynodioecy in a species of Gnidia (Thymelaeaceae) from South Africa

Sexual polymorphism was studied in the shrub Gnidia wikstroemiana (Thunb.) Meisn. from the semiarid Nama Karoo Biome, South Africa. The populations comprised plants bearing either female flowers, or hermaphrodite flowers with variable female function. In two populations, female plants accounted for 36–37% of the flowering plants. Female flowers were smaller and their stamens were reduced to staminodes, but their styles were significantly longer than those of hermaphrodite flowers. Energy investment in flowers and fruits for females and hermaphrodites was measured using bomb calorimetry. Females produce a greater number of less costly flowers than hermaphrodites, and invest less energy per unit in production of flowers and inflorescences. In contrast, females invest more energy per unit in production of fruits and infructescences than hermaphrodites. Females overall invest 7.3% more energy in reproduction than hermaphrodites. Female flowers were obligate out-crossers (xenogamous), with 35% of nonmanipulated, open-pollinated flowers setting fruit, comparable with fruit set among selfed hermaphrodite flowers. The breeding strategy of G. wikstroemiana most closely resembles gynodioecy. This is the first report of sexual dimorphism in Gnidia L. and sub-Saharan Thymelaeaceae.  © 2006 The Linnean Society of London, Botanical Journal of the Linnean Society , 2006, 152 , 219–233.     

Molecular phylogeny of Nitidulidae: assessment of subfamilial and tribal classification and formalization of the family Cybocephalidae (Coleoptera: Cucujoidea)

We present a molecular phylogeny of Nitidulidae based on thirty ingroup taxa representing eight of the ten currently recognized subfamilies. Approximately 10 K base pairs from seven loci (12S, 16S, 18S, 28S, COI, COII and H3) were used for the phylogenetic reconstruction. The phylogeny supports the following main conclusions: (i) Cybocephalidae are formally recognized as a distinct family not closely related to Nitidulidae and its constituent taxa are defined; (ii) Kateretidae are sister to Nitidulidae; (iii) Cryptarchinae are monophyletic and sister to the remaining nitidulid subfamilies; (iv) subfamily Prometopinae stat. res. is reinstated and defined, to accommodate taxa allied to Axyra Erichson, Prometopia Erichson and Megauchenia MacLeay; (v) Amphicrossinae, Carpophilinae and Epuraeinae are shown to be closely related taxa within a well‐supported monophyletic clade; (vi) tribal affinities and respective monophyly within Nitidulinae are poorly resolved by our data and must be more rigorously tested as there was little or no support for prior morphologically based tribes or genus‐level complexes; (vii) Nitidulinae are found to be paraphyletic with respect to Cillaeinae and Meligethinae, suggesting that they should either be subsumed as tribes, or Nitidulinae should be divided into several subfamilies to preserve the status of Cillaeinae and Meligethinae; (viii) Teichostethus Sharp stat. res. is not a synonym of Hebascus Erichson and the former is reinstated as a valid genus. These conclusions and emendations are discussed in detail and presented within a morphological framework.     

On the Metabolism of Tortula ruralis Following Desiccation and Freezing: Respiration and Carbohydrate Oxidation

Recovery from desiccation by Tortula ruralis (Hedw.) Gaertn., Meyer and Scherb was accompanied by an immediate, rapid increase in respiration (measured as oxygen uptake) at 25.5°C or 3.5°C. The respiratory burst was greater on rehydration of moss which had been rapidly desiccated over silica gel than that which had been more slowly desiccated in atmospheres of high relative humidity. No respiration was observed in dry moss. Dried moss which had been placed in liquid nitrogen resumed respiration on rewarming and rehydration but moss which had been frozen in the hydrated state respired to a lesser extent and showed signs of freeze damage. In the initial stages of slow drying a slight increase in respiration was noted, followed by a gradual decrease as drought became more severe. In contrast to observations made on many higher plants under drought stress, this moss did not exhibit any changes in its starch and sugar content during or following desiccation, nor were there any changes in free proline levels. Using (1-¹⁴C)-glucose and (6-¹⁴C)-glucose, the relative activities of the Embden–Meyerhof–Parnas and pentose phosphate pathways in hydrated and rehydrated moss were determined, as were the activities of specific enzymes involved in these pathways. An increased activity of the Embden–Meyerhof–Parnas pathway of glucose oxidation on rehydration of Tortula was observed. The possible significance of this latter observation is outlined.