The Breeding System of Polysphondylium pallidum,a Cellular Slime Mold*

SYNOPSIS. A mating type analysis was performed on 231 isolates of the cellular slime mold, Polysphondylium pallidum found in 61 samples collected in eastern North America between northern Florida and southern Canada. Seventy-eight percent of the isolates belonged to one of 2 mating types; 18% were incapable of mating with any partner; 3% were homothallic; and 1%, consisting of 2 isolates from a Florida sample, belonged to a separate breeding group. It is suggested that the majority of isolates represent a species capable of local genetic adaptation to a niche, the parameters of which undergo considerable variation over space and time.     

Phylogenetic relationships and the larval head of the lower Cyclorrhapha (Diptera)

We examined final‐stage larvae of all currently recognized lower cyclorrhaphan (= Aschiza) families, except Ironomyiidae and Sciadoceridae, and those of the higher cyclorrhaphan (= Schizophora) families Calliphoridae, Conopidae, Lonchaeidae, Muscidae, and Ulidiidae, and compared them with larvae of two out‐group families, Rhagionidae and Dolichopodidae, paying particular attention to structures of the head. A set of 86 morphological characters were analysed phylogenetically. The results show that the lower Cyclorrhapha is paraphyletic in relation to the higher Cyclorrhapha. The monophyly of the Cyclorrhapha is strongly supported. The lower Cyclorrhapha is resolved into two clades, based on the Lonchopteridae. Within the Syrphidae the traditional three‐subfamily system is supported, based on the Microdontinae. Within the lower Cyclorrhapha, the larval head is variable in form and arrangement of components. In Lonchopteridae, the mouth lies at the back of an open trough or furrow, comprising ventrally an elongate labium and laterally the maxilla. This arrangement of components appears to facilitate scooping food in water films. In Platypezoidea there is no furrow, and the dorsolateral lobes bearing the antennae are connected by a dorsal extension of the pseudocephalon. The main food‐gathering structure is the hooked apex of the labium, but in Phoridae the mandibles may also be important. In Eumuscomorpha the mandibles are at the apex of the head skeleton. The pseudocephalon is extended and infolded dorsally to form an oral pocket over the mouth. In the Pipunculidae, and the Microdontinae and Syrphinae of the Syrphidae, ventrally it forms a V‐shaped groove or guide along which the mandibles project. The labium is sclerotized apically, and forms a plate or tapered projection. This arrangement of components facilitates holding, piercing and extracting prey tissues. In Eristalinae the pseudocephalon is attached to the mandibles and is formed into a pair of cirri bearing mandibular lobes that lie either side of the mouth. Furthermore, the epipharynx is produced anteriorly in relation to the hypopharynx, and the labium is attached to the anterior part of the epipharynx to form a cavity or atrium. This arrangement is suited to fragmenting and imbibing solid food in Eristalinae with hooked mandibles, and when the mandibles are reduced and the mandibular lobes are inverted and sclerotized, these structures form a filter for separating fluid‐suspended particulate food. In higher Cyclorrhapha an atrium is present as in Eristalinae, but a connection between the pseudocephalon and the mandibles is absent. Instead, the pseudocephalon is bifurcate dorsally and forms a pair of cephalic lobes that ventrally ensheath each mandible. The surface of the sheath may be coated in cirri and other food‐gathering structures. The cephalic lobes, mandibular sheaths and the head skeleton are maneuverable and retractile to a higher degree than in lower Cyclorrhapha. This arrangement of components facilitates feeding on both solid food, in which the mouthooks may extend from the sheath to break the food up, and particulate and suspended food, in which the food‐gathering structures of the sheath scoop up the food. In many higher Cyclorrhapha, maneuverability is enhanced by a break between the labium and the basal sclerite, to which it is fused in all lower Cyclorrhapha. Intermediate characters and states for the structures of the higher cyclorrhaphan larval head are present in out‐groups, and lower Cyclorrhapha and homologies are discussed. Liquidity of the food is an important factor explaining the structure of the larval head in Cyclorrhapha. © 2008 The Linnean Society of London, Zoological Journal of the Linnean Society, 2008, 153 , 287–323.     

Life history reaction norms to time constraints in a damselfly: differential effects on size and mass

Optimality models predict that, under a time constraint, organisms should accelerate development, and preferably so by increasing growth rate, to keep size at emergence constant. Unfortunately, most tests did neglect genetic constraints and interchanged mass with body size which may explain mixed support for some of the models' predictions. We imposed time constraints on full sibling larvae of the damselfly Enallagma cyathigerum by manipulating day length regimes. Under a time constraint, larval development and growth rate based on size indeed were faster. This made it possible to keep size at emergence constant, despite the shorter development time. Interestingly, under a time constraint, growth rate based on mass was not increased and larvae had a lower mass at emergence. We see two reasons for this difference between body mass and size. First, size is fixed at emergence, while mass can still increase in many insects. Secondly, genetic constraints may have contributed to different responses for size and mass. In general, our results strongly suggest discriminating between size and mass when testing life history responses.  © 2004 The Linnean Society of London, Biological Journal of the Linnean Society , 2004, 83 , 187–196.     

Cynipid galls: insect-induced modifications of plant development create novel plant organs

Cynipid gall formation is achieved by an insect–plant interaction whereby cynipid gallwasps redirect host‐plant development to form novel structures to protect and nourish the developing larvae. Work was carried out to investigate the molecular mechanisms involved in this interaction, and extend the understanding of plant tissue development. Cytological changes of the inner‐gall tissue throughout the development of several gall species was investigated and the developmental stages of gall formation defined, to reveal two different patterns of development followed by the galls tested. Fluorescent in situ hybridization demonstrated many of the inner‐gall cells to be polytenized. Comparisons between inner‐gall and non‐gall tissue protein signatures by Schönrogge et al. (Plant, Cell and Environment 23, 215–222, 2000) have demonstrated the variation between gall and non‐gall protein signatures, and identified a number of inner‐gall proteins. Further analysis of one of these inner‐gall proteins involved in lipid synthesis, putative biotin carboxyl carrier protein (BCCP), revealed differential expression throughout development, and showed this expression to be concentrated in the inner‐gall tissue in all the gall species tested.     

Genetic variability in intergenic spacers of ribosomal DNA in Pisolithus isolates associated with pine, eucalyptus and Afzelia in lowland Kenyan forests

Basidiocarps of Pisolithus associated with indigenous ( Afzelia quanzensis Welw.) and introduced ( Pinus caribaea Mor. and Eucalyptus camaldulensis Dehnh.) hosts in the lowland forests of the Coast Province of Kenya are morphologically distinct. Genetic variability among 52 Pisolithus basidiocarps, collected beneath the various host plants, was examined based on sequence polymorphism within the internal transcribed spacer (ITS) and intergenic spacer (IGS1) of ribosomal DNA genes. Variability in ITS and IGS1 sequences indicated that the three host-associated morphotypes were genetically different. Consensus trees generated by bootstrap analysis of sequence data of Pisolithus isolates from Australia and Kenya are polyphyletic and strongly suggest that the three different morphotypes/genotypes present in Kenya represent separate biological species. In addition, our data indicate that little genetic exchange occurs in silva between these species.     

Effects of over-winter fumigation with sulphur and nitrogen dioxides on biochemical parameters and spring growth in red spruce (Picea rubens Sarg.)

Abstract. Red spruce ( Picea rubens Sarg.) seedlings were overwintered in two controlled environment chambers designed to simulate sub-zero winter conditions. One of the chambers was fumigated throughout the 5-month period with low concentrations of SO₂+ NO₂. Extracts of extracellular fluid from trees in this treatment revealed accumulations of sulphite and nitrite, but not of sulphate or nitrate. Analysis of the chloroplast membrane lipid monogalactosyl diglyceride (MGDG) indicated a large increase in fatty acid saturation in both treatments during mid-winter, with a subsequent recovery to earlier levels. Although at the end of the experiment the MGDG of polluted trees contained significantly less linolenic acid, there was no overall treatment effect on fatty, acid content. In the following spring, there was some indication that flushing of leader buds began earlier and proceeded at a slower rate in polluted trees compared to controls, but no other growth parameters were affected by the winter treatment. The absorption of SO₂ and NO₂ and the accumulation of their products during dormancy is discussed as a potential mechanism for metabolic disruption, resulting in changes to seasonal responses which could be critical to the survival of the plant.     

History of a Late Carboniferous phylloid algal bank complex in northeastern New Mexico

The growth history of a phylloid algal biohermal complex of Late Carboniferous (Westphalian) age, outcropping within the La Pasada Formation in northeastern New Mexico, U.S.A., is described in relationship to paleogeography, biostratigraphy, and microfacies associations. This phylloid algal biohermal complex occurs within typical Late Paleozoic cyclical sediments, in a paleogeographic setting along a narrow shelf margin bordering a deep geosynclinal trough to the northwest. Fusulinid foraminifers suggest that the bioherm is of Middle Pennsylvanian (lower Des Moines) age, whereas the overlying sediments are of middle Des Moines age. Both field and petrographic evidence suggest that the bioherm grew upward from relatively shallow water depths, into extremely shallow water where it probably was subaerially exposed. Biohermal growth appears to have been initiated on a 'hard-ground' surface on which lithified clasts and abundant clusters of robust linoproductid brachiopods served as a foundation. Four major microfacies have been identified from the biohermal complex. These are: (I) phylloid algal wackestones-packstones (mound proper), (2) marly limestones (sediments laterally adjacent to and overlying mound), (3) pelletal-foraminiferal wackestone (partially capping the mound), and (4) crinoidal packstones-grainstones (post-mound). Comparison is made with other surface and subsurface occurrences of phylloid algal complexes of similar age in the southwestern United States.     

Zinc-induced Vacuolation in Root Meristematic Cells of Cereals

In the absence of Zn, vacuolar volume fractions of root meristematiccells of Secale cereale L. cv. K2, Triticum aestivum L. cv.Chinese Spring and Oryza sativa L. cv. IR34 were 5.64 x 10^–2,2.17 x 10^–2 and 1.63 x 10^–2 µm³ vacuole µm^–3tissue, respectively. A 4-d exposure to a subtoxic concentrationof zine (0.2 µg Zn cm^–3) induced a 2.93-fold anda 6.78-fold increase in the total vacuolar volume fraction inOryza and Triticum, respectively, whereas no significant increasewas observed for Secale. It is proposed that this Zn-inducedvacuolation represents a compartmentalization mechanism. Theinitial total vacuolar volume fraction in Secale was greaterthan that for Oryza and Triticum and this may enable compartmentalizationof the metal soon after the onset of treatment so reducing itscytotoxic effects. These findings are similar to those observedin contrasting cultivars of Festuca rubra L. Triticum aestivum L, Secale cereale L, Oryza sativa L, zinc, root meristem, vacuolation