Reproductive potential and seedling establishment of the invasive alien tree Schinus molle (Anacardiaceae) in South Africa

Schinus molle (Peruvian pepper tree) was introduced to South Africa more than 150 years ago and was widely planted, mainly along roads. Only in the last two decades has the species become naturalized and invasive in some parts of its new range, notably in semi‐arid savannas. Research is being undertaken to predict its potential for further invasion in South Africa. We studied production, dispersal and predation of seeds, seed banks, and seedling establishment in relation to land uses at three sites, namely ungrazed savanna once used as a military training ground; a savanna grazed by native game; and an ungrazed mine dump. We found that seed production and seed rain density of S. molle varied greatly between study sites, but was high at all sites (384 864–1 233 690 seeds per tree per year; 3877–9477 seeds per square metre per year). We found seeds dispersed to distances of up to 320 m from female trees, and most seeds were deposited within 50 m of putative source trees. Annual seed rain density below canopies of Acacia tortillis, the dominant native tree at all sites, was significantly lower in grazed savanna. The quality of seed rain was much reduced by endophagous predators. Seed survival in the soil was low, with no survival recorded beyond 1 year. Propagule pressure to drive the rate of recruitment: densities of seedlings and sapling densities were higher in ungrazed savanna and the ungrazed mine dump than in grazed savanna, as reflected by large numbers of young individuals, but adult : seedling ratios did not differ between savanna sites. Frequent and abundant seed production, together with effective dispersal of viable S. molle seed by birds to suitable establishment sites below trees of other species to overcome predation effects, facilitates invasion. Disturbance enhances invasion, probably by reducing competition from native plants.     

Sexual and Asexual Processes in Protoperidinium steidingerae Balech (Dinophyceae), with Observations on Life-History Stages of Protoperidinium depressum (Bailey) Balech (Dinophyceae)

ABSTRACT. A suite of morphological, histological, and molecular techniques was used to reveal for the first time division, sexuality, mandatory dormancy period of hypnozygotes, and identity of life-history stages of any Protoperidinium spp. In both Protoperidinium steidingerae and Protoperidinium depressum , asexual division occurred by eleutheroschisis within a temporary cyst, yielding two daughter cells. Daughter cells were initially round and one-half to two-thirds the size of parent cells then rapidly increased in size, forming horns before separating. Gamete production and fusion was constitutive in clonal and non-clonal cultures, indicating that both species may be homothallic. Gametes were isogamous, approximately half the size and lacking the pink pigmentation of the vegetative cells, and were never observed to feed. Gamete fusion resulted in a planozygote with two longitudinal flagella. Planozygotes of P. steidingerae formed hypnozygotes. The fate of planozygotes of P. depressum is unknown. Hypnozygotes of P. steidingerae had a mandatory dormancy period of ca. 70 days. Germination resulted in planomeiocytes with two longitudinal flagella. Nuclear cyclosis occurred in the planozygotes of P. depressum , but in the planomeiocytes of P. steidingerae . The plate tabulation and gross morphology of gametes of P. steidingerae and P. depressum differed markedly from those of vegetative cells. Thus, misidentification of morphologically distinct life-history stages and incomplete examination of thecal plate morphology in field specimens has likely led to taxonomic confusion of Protoperidinium spp. in previous studies.     

Shrub expansion stimulates soil C and N storage along a coastal soil chronosequence

Expansion of woody vegetation in grasslands is a worldwide phenomenon with implications for C and N cycling at local, regional and global scales. Although woody encroachment is often accompanied by increased annual net primary production (ANPP) and increased inputs of litter, mesic ecosystems may become sources for C after woody encroachment because stimulation of soil CO₂ efflux releases stored soil carbon. Our objective was to determine if young, sandy soils on a barrier island became a sink for C after encroachment of the nitrogen‐fixing shrub Morella cerifera, or if associated stimulation of soil CO₂ efflux mitigated increased litterfall. We monitored variations in litterfall in shrub thickets across a chronosequence of shrub expansion and compared those data to previous measurements of ANPP in adjacent grasslands. In the final year, we quantified standing litter C and N pools in shrub thickets and soil organic matter (SOM), soil organic carbon (SOC), soil total nitrogen (TN) and soil CO₂ efflux in shrub thickets and adjacent grasslands. Heavy litterfall resulted in a dense litter layer storing an average of 809 g C m^?2 and 36 g N m^?2. Although soil CO₂ efflux was stimulated by shrub encroachment in younger soils, soil CO₂ efflux did not vary between shrub thickets and grasslands in the oldest soils and increases in CO₂ efflux in shrub thickets did not offset contributions of increased litterfall to SOC. SOC was 3.6–9.8 times higher beneath shrub thickets than in grassland soils and soil TN was 2.5–7.7 times higher under shrub thickets. Accumulation rates of soil and litter C were highest in the youngest thicket at 101 g m^?2 yr^?1 and declined with increasing thicket age. Expansion of shrubs on barrier islands, which have low levels of soil carbon and high potential for ANPP, has the potential to significantly increase ecosystem C sequestration.     

Root exudation (net efflux of amino acids) may increase rhizodeposition under elevated CO2

Increases in atmospheric CO₂ concentration ([CO₂]) can lead to global climate change and theoretically could enhance carbon (C) deposition in soil, but data on this complex issue are contradictory. One approach for clarifying the diverse forces influencing plant‐derived C in the rhizosphere involves defining how elevated [CO₂] alters the fundamental process of C transfer from plant roots to the soil. We examine here how a step increase in [CO₂] affects the innate influx and efflux components of root exudation in axenic plants, as one foundation for understanding how climate change may affect rhizodeposition. Increasing [CO₂] from 425 to 850 μmol mol^?1 during short‐term trials enhanced shoot and root dry weight (P<0.01) of annual rye grass (Lolium multiflorum Lam.) and medic (Medicago truncatula L.) but had no effect on growth of maize (Zea mays L.). Root amino‐acid flux in the same plants changed only in maize, which increased the efflux rate (nmol g root fresh weight^?1 h^?1) of six amino acids (arginine, alanine, proline, tyrosine, lysine and leucine) significantly (P<0.05) under elevated [CO₂]. None of the three plant species altered the steady‐state concentration of 16 amino acids released into a hydroponic solution with changing [CO₂], apparently because amino‐acid influx rates, measured at 2.5 μm , consistently exceeded efflux rates. Indeed, plants recovered amino acids at rates 94–374% higher than they were lost from roots regardless of [CO₂]. These results indicate that, in theory, any effect of [CO₂] doubling on amino‐acid efflux can be offset by innately higher rates of influx. In practice, however, higher rates of amino‐acid cycling (i.e., efflux+influx) for each root segment (in C₄ maize) or from more root tissue (in the two C₃ species) should increase root exudation by plants exposed to elevated [CO₂] as additional amino acids would be adsorbed to soil particles or be taken up by soil microorganisms.     

Effects of carbaryl and cyhexatin on survival and reproductive behaviour of Cydia pomonella (Lepidoptera: Tortricidae)

The effects of carbaryl, an insecticide and an abscission agent, and cyhexatin, an acaricide, on the survival, reproductive behaviour and subsequent egg hatch and larval migration of the codling moth, Cydia pomonella L., were investigated under laboratory conditions. Dilution series starting with the concentration recommended for high volume application in the field were evenly sprayed in plastic cups. Depending on the concentration used, both pesticides resulted in high adult mortality, males being more susceptible. Although the total number of the eggs laid by C. pomonella females was significantly reduced in most treatments, the females exposed to different residues of carbaryl laid significantly more eggs during the first 24 h of exposure. This was not the case for cyhexatin. While in all treatments almost 50% of the eggs were laid on the side of the cups, the spatial distribution of the eggs laid under the lid and on the floor was concentration dependent. With one exception, continuous exposure of the moths to carbaryl significantly reduced the number of spermatophores per female. Less than one spermatophore per female was transferred at the highest four concentrations of carbaryl and the highest three concentrations of cyhexatin; whereas, the number of spermatophores per female amounted to about four per female for the other treatments. In contrast to carbaryl, which exhibited a high ovicidal effect at all concentrations, the ovicidal activity of cyhexatin was low. This was manifested in a high rate of egg hatch and the extent of embryonic development in most of the treatments. Furthermore, while carbaryl killed the newly-hatched larvae at all concentrations, cyhexatin acted as a larvicide at the highest two concentrations only.     

结瘤因子和苏芸金菌素对干旱胁迫下燕麦产量及其保护酶活性的影响

结瘤因子(LCO)和苏芸金菌素(TH17)在逆境环境下对作物生长具有重要调节作用。该试验在盆栽条件下,以‘坝莜3号’燕麦品种为材料,分别在苗期、拔节期和抽穗期进行干旱胁迫并叶面喷施浓度为0.01 μmol/L的LCO和TH17,比较燕麦产量、叶片渗透调节物质和几种保护酶活性的变化情况。结果显示:(1)与喷施清水对照（CK）相比,正常水分条件下喷施LCO和TH17能促进燕麦生长,提高产量;在干旱胁迫下(SS)喷施LCO和TH17能减轻燕麦株高、穗长、穗粒数、生物产量、单株粒重以及干物质积累速率的降低幅度,且在苗期喷施LCO和TH17燕麦单穗粒重增加幅度最高,分别较干旱胁迫对照（SS_CK）提高61.25%和65.00%。(2)干旱胁迫下,LCO和TH17使游离脯氨酸含量增加最多的时期是拔节期,分别较SS_CK增加27.19%和41.00%;可溶性总糖在抽穗期提高幅度最大,分别较SS_CK高61.43%和112.54%;可溶性蛋白在苗期提高幅度最大,且分别较SS_CK提高9.58%和13.80%。(3)干旱胁迫下,LCO和TH17使SOD和POD活性增加幅度最大的时期均是抽穗期,CAT活性则是在拔节期增加幅度最大。(4)干旱胁迫下,在苗期LCO和TH17使燕麦叶片相对电导率和MDA含量降低幅度最大,分别较SS_CK降低17.61%、36.67%和43.43%、30.28%。研究表明,在苗期喷施LCO和TH17使燕麦产量提高幅度最高;干旱条件下,不同时期喷施LCO和TH17能提高燕麦自身渗透调节能力、抗氧化保护酶活性和增强细胞膜的稳定性,从而使其更好地适应干旱条件。     

Phylogeny of the gastropod superfamily Cerithioidea using morphology and molecules

The Cerithioidea is an ecologically important superfamily of basal Caenogastropoda with speciose marine, brackish water, and freshwater lineages primarily in tropical, subtropical, and warm temperate regions of the world. They often represent significant components of the communities where they occur and have given rise to several spectacular endemic radiations in rivers and ancient lakes. Earlier attempts to resolve the phylogenetic history of the group have been based on smaller taxon and character subsets with incongruent results. Here the monophyly and phylogeny of the group is evaluated with expanded morphological and molecular (16S, 28S rRNA) data sets. For morphological analyses, 151 characters (shell, operculum, radula, alimentary tract, kidney, nervous system, reproductive anatomy, and sperm ultrastructure) were scored for 47 cerithioideans (representing 17 families) and nine outgroup taxa. To test monophyly of the Cerithioidea, extended molecular data sets of 16S and 28S sequences for 57 and 44 taxa, respectively, were compiled using new and previously published sources. For combined analyses, a pruned molecular data set was combined with the morphological partition. The morphological data were analysed alone using only parsimony; molecular and simultaneous analyses were performed using both parsimony and Bayesian inference. The effect of excluding unconserved regions of the alignments was also explored. All analyses, with the exception of the individual 16S and 28S data sets, support monophyly of the Cerithioidea as currently formulated. Of the 12 families represented by more than one terminal, only two (Planaxidae, Potamididae) are always supported as monophyletic; Batillariidae, Cerithiidae, Pachychilidae, Pleuroceridae, Semisulcospiridae, Thiaridae, and Turritellidae are monophyletic in most but not all topologies. The combination of diverse data sources (morphology, 16S and 28S sequences) and inclusion of unconserved regions of the alignments improved the recovery of monophyletic families. At deeper levels, a consensus is beginning to emerge in the recognition of three main assemblages, but whether these represent clades or grades is still unclear; the resolution of these assemblages and the branching order within them are sensitive to exclusion of unconserved regions and choice of optimality criterion. No clear conclusion is reached with respect to the number of freshwater invasions, with two invasions supported on some topologies and three supported on others. Progress toward a robust and stable resolution of cerithioidean relationships will require (1) strategically coordinated sampling for additional morphological and molecular data; (2) comprehensive anatomical treatments for several poorly documented limnic lineages (e.g. Melanopsidae, Thiaridae) and comparative data for poorly understood organ systems (e.g. renal system); (3) the addition of poorly known, minute, and/or rare marine taxa, to provide novel character combinations, insight into putative homologies, and to help anchor basal nodes and break up long branches. © 2011 The Linnean Society of London, Zoological Journal of the Linnean Society, 2011, 162 , 43–89.     

The Place of "Others" in Hunter-Gatherer Intensification

Archaeologists are interested in understanding the conditions under which hunter-gatherer intensification occurs. Typically, most models assign primacy to population pressure or social relations and address intensification as it occurs among foragers inhabiting arid or temperate environments. In this article, I explore episodes of resource intensification and "deintensification" on the subarctic island of Newfoundland. Correlating periods of resource intensification and "deintensification" with changes in the social landscape, I argue that the presence or absence of "Others" played a significant role in informing hunter-gatherer subsistence strategies and settlement patterns.     

CONSTRUCTION OF SENSORY VOCABULARIES FOR PROFILING FOOD

Sensory profiling laboratories rate products for sets of attributes. Order of tasting and carry-over effects from sample to sample are widely recognized. However, within samples, work investigating the possibility of effects due to the order of rating attributes and attribute to attribute carry-over has not been reported. Individual attributes were classified according to whether their presence in a product was perceived to be desirable or not. For both yoghurt and cheese, sample ratings for each attribute were compared when attributes perceived as desirable preceded those perceived as undesirable and vice-versa. In both stimuli, there was evidence that desirable attributes were biased to a lower value when preceded by undesirable ones. Similarly, negative attributes were biased downwards when preceded by desirable ones. For absolute scores, these effects, albeit small, make randomizing attribute ordering desirable. However, lack of evidence of interactions between samples and attribute ordering suggests comparative differences between samples are unaffected.