Patterns of divergence in the olive sunbird Cyanomitra olivacea (Aves: Nectariniidae) across the African rainforest–savanna ecotone

In the debate over modes of vertebrate diversification in tropical rainforests, two competing hypotheses of speciation predominate: those that emphasize the role of geographical isolation during glacial periods and those that stress the role of ecology and diversifying selection across ecotones or environmental gradients. To investigate the relative roles of selection versus isolation in refugia, we contrasted genetic and morphologic divergence of the olive sunbird (Cyanomitra olivacea) at 18 sites (approximately 200 individuals) across the forest–savanna ecotone of Central Africa in a region considered to have harboured three hypothesized refugia during glacial periods. Habitats were characterized using bioclimatic and satellite remote‐sensing data. We found relatively high levels of gene flow between ecotone and forest populations and between refugia. Consistent with a pattern of divergence‐with‐gene‐flow, we found morphological characters to be significantly divergent across the gradient [forest versus ecotone (mean ± SD): wing length 60.47 ± 1.81 mm versus 62.18 ± 1.35 mm; tarsus length 15.51 ± 0.82 mm versus 16.00 ± 0.57 mm; upper mandible length 21.77 ± 1.09 mm versus 23.19 ± 0.98 mm, respectively]. Within‐habitat comparisons across forest and ecotone sites showed no significant differences in morphology. The results show that divergence in morphological traits is tied to environmental variables across the gradient and is occurring despite gene flow. The pattern of divergence‐with‐gene‐flow found is similar to that described for other rainforest species across the gradient. These results suggest that neither refugia, nor isolation‐by‐distance have played a major role in divergence in the olive sunbird, although ecological differences along the forest and savanna ecotone may impose significant selection pressures on the phenotype and potentially be important in diversification. © 2011 The Linnean Society of London, Biological Journal of the Linnean Society, 2011, 103 , 821–835.     

Development of a new piosphere in arid chenopod shrubland grazed by sheep. 2. Changes to the vegetation

The initial development of a piosphere created by stocking a new watering trough with ca. 200 sheep at a near-pristine site in arid chenopod shrubland near Whyalla, South Australia, was studied. The following variables were monitored for up to 8 years using fenced plots as controls:shrub mortality; forage biomass and defoliation of the dominant shrubs and short-lived grasses; linear dimensions of Rhagodia ulicina; the density of short-lived species; and the invasion of exotics. Patterns in these variables were looked for which reflected the attenuation of stocking pressure with distance from water; that is, ‘piosphere patterns’. Piosphere patterns were detected for many variables. Those with values increasing towards the trough were mortality of the main forage shrub Atriplex vesicaria. the density of three short-lived taxa, viz. the bassias (Sclerolaena obliquicuspis, S. patenticuspis. Maireana sclerolaenoides), Tetragonia tetragonoides, and annual Zygophyllum spp. (Z. crenatum. Z. ovatum), and growth of short-lived grass species when sheep stocking pressure was low. Variables with values decreasing towards the trough were grass biomass, percentage of A. vesicaria individuals in flower, the percentage foliation of A. vesicaria and of the forage shrub Maireana sedifolia, and shrub forage biomass of A. vesicaria and M. sedifolia. The rate at which these patterns were registered varied. After only 3 months, a piosphere pattern was evident for grass biomass. Marrubium vulgare, an introduced weed, invaded the trough site within the first 6 months. Almost no A. vesicaria shrubs had died after 2 years, but after 8 years there was a marked piosphere pattern in their mortality. The piosphere patterns in forage biomass and defoliation of A. vesicaria and M. sedifolia became more pronounced with time. Some variables did not exhibit a piosphere pattern, such as the dimensions of the shrub R. ulicina and the densities of successive cohorts of the forb Erodium spp., even though there was an overall effect of grazing in reducing their values. There was no mortality of two dominant shrubs, M. sedifolia and R. ulicina, during the first 8 years.     

Regulation of maturation-promoting factor by protein kinase C in Chaetopterus oocytes

Summary

We present the results of a variety of studies showing that activation of protein kinase C (PKC) in oocytes of Chaetopterus pergamentaceus results in germinal vesicle breakdown (GVBD). Phorbol esters and diacylglycerol can initiate a morphologically normal GVBD accompanied by a spectrum of associated biochemical processes, including increased protein phosphorylation, a shift in protein synthesis and activation of a protein kinase, maturation promoting factor (MPF). MPF activation is essential for GVBD in response to phorbol esters. In addition, inhibitors of PKC can block naturally-induced GVBD. We also present evidence that PKC can phosphorylate p34^cde2, the catalytic subunit of MPF and that phosphorylation by PKC increases the histone H1 kinase activity of immunoprecipitated MPF. Immunoblot studies show that Chaetopterus oocyte p34^cdc2 is not tyrosine phosphorylated prior to the initiation of GVBD, indicating that activation of MPF at GVBD in this species does not require p80^cdc25, the activator of MPF at mitosis. These results suggest that PKC is an essential regulator of GVBD which can directly phosphorylate and regulate p34^cdc2. Since PKC is the intracellular receptor for and is directly activated by tumor-promoters, tumor promotion might involve acceleration of the cell cycle through modification of the enzymatic activity of MPF by PKC.     

Vocal morphology of the Physalaemus pustulosus species group (Leptodactylidae): morphological response to sexual selection for complex calls

Most male frogs in the genus Physalaemus produce a whine-like advertisement call. Male P. pustulosus , however, add chucks to the call. This enhances the attractiveness of the call to females, and has evolved under the influence of sexual selection despite the increased predation risk from the frog-eating bat ( Trachops cirrhosus ). This complex call is unusual, if not unique, among anurans because the two call components overlap in time. Here we investigate the morphological changes responsible for the production of complex calls.
The Physalaemus purtulosus species group consists of four species. Physalaemus pustulosus and P. petersi are sister species, and recently it has been shown that P. petersi produces chucks. Physalaemus coloradorum and P. purtulatus are sister species and neither is known to produce chucks. Two laryngeal characters vary within the species group. Physalaemus pustulosus has a large fibrous mass (FMI), whose vibration is responsible for production of the chuck. This mass is much smaller in the other three species. In P. pustulosus and P. petersi the FMI is anchored dorsally, deep within the bronchial process, the attachment is more extensive in P. pustulosus. Neither P. pustulatus nor P. coloradorum have such a dorsal attachment associated with their FMI. This character is responsible for allowing the FMI to vibrate independently of the vocal cords, that is, for the production of the complex call. Thus the morphological changes responsible for the evolution of this unusual behavioural innovation, the complex call, are gradual, and almost trival, in nature. This study also shows that the primitive condition of the larynx of the P. pustulosus and P. petersi ancestor, was predisposed to the production of complex calls.
We also document ontogenetic and sexually dimorphic patterns in larynx structure.     

Isolation and characterization of polymorphic microsatellite loci in the Hawaiian flycatcher,the elepaio (Chasiempis sandwichensis)

Thirteen polymorphic microsatellite loci were isolated and characterized from two clades of an endemic Hawaiian flycatcher, the elepaio (Chasiempis sandwichensis). Seven dinucleotide repeats and one trinucleotide repeat were cloned from Kauai elepaio; five dinucleotide repeats were cloned from Oahu elepaio. Polymorphism was assessed in a sample of Oahu elepaio (n = 22) revealing two to 16 alleles per locus. Observed heterozygosity ranged from 0.14 to 0.91. However, linkage analysis exposed highly significant linkage disequilibrium between two of the most polymorphic loci. Twelve loci are therefore expected to be useful for investigations of population structure.     

Coexistence of Intraspecies and Interspecies Specific Antigenic Determinants on the Major Structural Polypeptide of Mammalian C-type Viruses

THE report of a shared viral antigen (termed gs-3) among mammalian C-type viruses from four species¹, extending an earlier report of cross reactivity between mouse and cat viral antigens², has far reaching implications in the search for human cancer viruses or their gene products. The report is confirmed both by the data presented here and also by the data obtained by another laboratory³. Our gel diffusion assays using various selected sera against mouse, hamster and cat crude and purified C-type viral antigens indicate that the cross reactive antigenic determinants are specifically present on the major structural polypeptide of C-type viruses. The polypeptide also carries species specific determinants. These conclusions are drawn from complement fixation and gel diffusion tests using six types of antisera (either individual sera or pools) prepared as described in Table 1.     

The Effect of Metabolic Poisons on ATP Level and on Active Phosphate Uptake in Chlorella pyrenoidosa

Influence of light and dark aerobic conditions and of various metabolic poisons [3-(3,4-dichlorophenyl)1,1-dimethylurea (DCMU), 2,4-dinitrophenol (2,4-DNP), carbonyl cyanide-m-chlorophenylhydrazone (m-CCCP), α,α′bis(hexafluoroacetonyl) acetone (1799), N,N′-dicyclohexylcarbodiimide (DCCD), sodium azide, fatty acids] on the active phosphate uptake and on the ATP level has been investigated. Cells in the dark have the same level of ATP as in the light though the phosphate transport is decreased. Similar findings are observed with DCMU. Other poisons used inhibit phosphate uptake and decrease ATP level. However their effect is more drastic on phosphate transport than on the ATP level. There is no good correlation between the ATP level and phosphate transport.     

The Effect of Temperature on the Fatty Acid Composition of Tetrahymena pyriformis WH-14

SYNOPSIS. A reduction in the growth temperature of Tetrahymena pyriformis strain WH-14 from 35 C to 15 C resulted in distinct alterations in the fatty acid composition of the glycerophospholipids. The proportion of normal saturated acids declined from 26 to 19%; palmitoleic acid increased by 6%, and the composition of the polyunsaturated fatty acids increased in 18:2 Δ^6,11(n) and decreased in 18:2 Δ^9,12(n) and 18:3 Δ^6,9,12(n). The unsaturation index (the average number of double bonds/100 molecules) did not change with a shift in temperature.
Two biosynthetic pathways exist in Tetrahymena for the formation of unsaturated fatty acids. The observed changes in fatty acid composition that accompany a lowering of the environmental temperature can be accounted for by a reduction in the accumulation of products of the fatty acid pathway leading to the formation of γ-linolenic acid [16:0(n) → 18:0(n) → 18:1 Δ⁹(n) → 18:2 Δ^9,12(n) → 18:3 Δ^6,9,12(n)] and an increase in the components of the pathway leading to the formation of 18:2 Δ^6,11(n) [16:0(n) → 16:1 Δ⁹(n) → 18:1 Δ¹¹(n) → 18:2 Δ^6,11(n)]. The data suggest that the regulatory mechanism in Tetrahymena differs from that found in some bacteria where a simple substitution of unsaturated fatty acids for saturated fatty acids occurs at low culture temperatures.