Brood raiding and the population dynamics of founding and incipient colonies of the fire ant, Solenopsis invicta

Abstract. 1. One of the first activities of minim workers in incipient fire ant nests is mutual brood raiding, the amalgamation of nests through the reciprocal stealing of brood and defection of workers.
2. Discrete mating flights created cohorts of incipient colonies. About 25% of founding nests survived the claustral period of 16–48 days (depending on season). Early incipient colony mortality was 5–6% per day. Over 60% of this mortality was accounted for through brood raiding. Most colonies raided when each cohort first became active, and many raided more than once. Raid size (number of nests, duration, distance) tended to increase during the summer as colonies grew through raiding. After the raiding period, nest mortality rate dropped 3–10-fold. Only 1–3% of founding nests were still alive at this time.
3. Queens from losing or failed nests tended to abandon their nests and attempted to enter successful ones, often following raiding trails to do so. This emigration was at least as successful as non-emigration in ultimately achieving the status of reproductrix of a successful nest (about 4%).
4. Brood raiding is a dominant process in early population dynamics, probably accounting for most of the early nest mortality. Its effect is to change the venue and unit of competition from nest-against-nest to a shifting aggregation of queens, workers and brood involving entire local populations. Nest thinning is thus very rapid, and the boost to the size of winning nests very large, allowing raiding colonies to win the competition for territory, and to achieve the early colony maturity so important to this, and other, weedy species. The importance of winning brood raids may also have driven increased minim production through the evolution of pleometrosis.     

阔叶树的叶形曲线方程：—适于叶面积计算的数学模型

树木的叶形可以看作一个平面几何图形。这种几何图形可用解析方程给予表达,我们把这种解析方程称为叶形曲线方程。由于叶形是一个左右对称,而上下不对称的图形,也就是说叶的最宽处绝大多数不在叶的中部,少数在     

Membrane and cytoplasmic resistivity properties of normal and sickle red blood cells

The cytoplasmic resistivities and membrane breakdown potentials of normal (AA), sickle-cell-trait (AS), and sickle (SS) red blood cells have been measured by the biophysical methodology of resistive pulse spectroscopy over a range of osmolalities. At isotonicity, the average membrane breakdown potentials are virtually identical for the three types of cells occurring at about 1150 V/cm. Average isotonic cytoplasmic resistivities are somewhat higher for the SS cells (166.7±7.49 ohm-cm) compared to the AA (147.6±1.98 ohm-cm) or AS cells (148.7±1.79 ohm-cm). As medium osmolality is varied, the differences in resistive properties become enlarged, especially at very low and very high osmolalities. At high osmolalities, both types of sickle cells show a large increase in internal resistivity compared to the normals; at low osmolality, the SS samples exhibit a distinctly different membrane breakdown characteristic, decreasing in this parameter, whereas the other two groups increase. Of the 15 SS samples tested, three displayed much higher cytoplasmic resistivities at isotonicity: 218.2±5.25 ohm-cm, compared to an average of 153.5±3.46 ohm-cm for the other 12. The relationship between these high resistivities and the subfraction of irreversibly sickled cells in the sample is discussed.     

Construction of a cosmid library of Spirulina platensis as an approach to DNA physical mapping

Abstract A Spirulina platensis gene library has been constructed using cosmid vector pMMB34. The cosmid bank was controlled for its random gene distribution by colony hybridization. Genes were identified using either homologous or heterologous probes of genes involved in photosynthesis (large and small subunit of d -ribulose 1,5-bisphosphate carboxylase, 32 kDa thylakoid protein, α, β subunits of C-phycocyanin) and protein synthesis (elongation factors EF-Tu, EF-G).     

Pollenfertility and seed formation in theOrnithogalum umbellatum/angustifolium complex (Liliaceae/Scilloideae)

The pollen fertility and seed formation of six species of theOrnithogalum umbellatum/angustifolium complex and of seven related species were studied. Four types of pollen grains could be recognized. The pollen fertility varied greatly in this complex and is not related to the ploidy level. The seed formation ofO. umbellatum showed an adaptation to a subcontinental-Mediterranean climate, that ofO. angustifolium to an Atlantic climate. In both cases raindrops seem to be important for pollination, in view of the absence of insect pollinators. After open pollination 113 seedlings were obtained in four species. Their chromosome numbers were determined. Nearly all the cultivated seedlings were aneuploid, which points to a positive selection of euploids in nature, because aneuploid individuals are rare in the wild.Biosystematic Studies on theOrnithogalum umbellatum/angustifolium Complex III.—Previous parts of this series are Part I: Taxonomy. Proceeding Kon. Ned. Acad. Wet. series C,85 (4), 563–574 (1982) andvan Raamsdonk (1984).     

Effects of monovalent cations on red cell shape and size

Human erythrocytes were incubated in isotonic solutions of different monovalent cations. The apparent size of the red cells measured on scanning electron microscopic pictures decreases in the order Li⁺>Na⁺=K⁺>Rb⁺. These differences in size are abolished after pretreatment with trypsin, which removes a large part of the charges associated with membrane glycoproteins. Shape alterations are also observed. Normal biconcave shapes are visible after Na⁺ or K⁺ incubation, whereas Li⁺ leads to flabby, flattened cells with a certain tendency to crenation, and Rb⁺ causes more pronounced biconcavity with a certain tendency to cupping. The overall effects of pretreatment with trypsin are similar to those of Li⁺. Our results provide evidence that the electrostatic repulsion of glycoproteins and other charged membrane components may play an essential role in maintaining red cell shape.     

Factors to consider in performing survival studies with insect cells

Summary Insect cell lines are not well-suited to colony formation in liquid medium following low-density cell plating. The present studies demonstrate that the time of addition of fetal bovine serum to the culture medium and the number of γ-irradiated feeder cells added to each plate are important factors in developing a useful colony formation assay. TN-368 lepidopteran and WR69-DM-1 dipteran cell lines were used for these experiments. Both cell types display increased plating efficiencies if serum is added to the medium one or more days prior to plating as compared to adding serum immediately before plating. Growth curves obtained by seeding cells at higher densities also indicate that cell growth is slightly better if serum is added one or more days before seeding. These findings are especially important for survival and toxicity studies because the results demonstrate that even seemingly minor factors involved in cell survival assays may benefit treated cells to a greater degree than untreated control cells, thus providing an erroneous assessment of cell survival. This work was supported by USPHS grant R01-CA34158, awarded by the National Cancer Institute, DHHS, Bethesda, MD.     

Outer membrane proteins of gentamicin induced small colony variants of Pseudomonas aeruginosa

Small colony variants (SCVs) of Pseudomonas aeruginosa NCTC 6750 (WT) were repeatedly isolated in an in vitro kinetic model after exposure to gentamicin (GM). There were minor differences biochemically and in phage and serotyping between the wild type (WT) strain and SCVs. Changes in outer membrane protein profiles were found. SCVs were more resistant to polymixin and to a range of aminoglycosides (except kanamycin), but were more susceptible to a range of other antibiotics (hydrophilic and hydrophobic) with differing modes of action.     

Body shape and differences between species

The variation of body shape among prosimians is reviewed. Special emphasis is placed on the selective advantages, that is the mechanical reasons, to which variants of the locomotor apparatus can be traced back. There are differences found in the cheiridia, but at present they cannot be explained in terms of mechanics; there is nearly no knowledge about the mechanical meaning of their diversity. Myological characteristics of taxa can be explained mechanically, but this has not yet been done. Well known are variations of body proportions. These discriminate higher taxa, and are largely coincident with the often-used locomotor categories. In spite of this, there are only few sound arguments about the real biomechanic value of characteristic proportions for a given locomotor mode. What is known on this field, is reviewed. Progress can be made only, if the mechanical conditions, set by postural behavior and locomotion, are understood completely. The subtle distinctions between lower taxonomic units can normally be identified only on the basis of detailed and quantified analyses of movements on one hand, and of biometrics on the other. In the few cases in which such studies have been made, the differences of morphology fit to the mechanical requirements of locomotion which also differ only in quantitative details.     

Shape analysis of two sympatric coral species: Implications for taxonomy and evolution

Fourier shape analysis of Pleurodictyum americanum and P. dividua , favositid tabulate corals, from the Middle Devonian Hamilton Group of New York State, indicates that colony growth form is variable within species between environments, but that the range of variability in growth form is static through time. Pleurpdictyum dividua displays a columnar morphotype; however, P. dividua and P. americanum cannot be discriminated from one another based on colony shape alone. A major prediction of the punctuated equilibrium model of evolution is morphological stasis throughout the duration of a species. Harmonic means of assemblages of P. americanum show no persistent temporal trends. The range of harmonic means present among the oldest assemblages (Centerfield Limestone) are comparable to those among the youngest assemblages (Windom Shale) and to those in the intervening intervals. Character stasis in colony growth form lasted throughout a 2.5-3.5 my interval. In tabulate corals, where reproductive modes such as fragmentation have not been demonstrated, growth form may be useful in interpreting ancient environments. In addition, the tempo of evolution of growth form can be analyzed when sufficient morphological data are available from a wide distribution of environments. Thus, Fourier shape analysis of growth form provides a powerful tool for paleontologists to interpret the ecology and evolution of colonial marine animals.