The response of life‐history traits to a new species in the community: a story of Drosophila parasitoids from the Rhône and Saône valleys

In the present study, we investigated the evolution of life‐history traits in the main species of a community, after the arrival of a new competitor. Two parasitoid species, Leptopilina heterotoma and Asobara tabida, are present throughout the Rhône and Saône valleys, whereas a third species, Leptopilina boulardi, is slowly extending its distribution northwards. In the presence of L. boulardi, competing parasitoids experience a higher mortality and lower host availability. Resources should thus be re‐allocated between traits according to these new factors. We compared life‐history traits of populations of L. heterotoma and A. tabida in areas with and without L. boulardi. As predicted by both Price's balanced mortality hypothesis and the theory of life‐history traits, we found that investment in reproduction is higher in southern populations for both native species, coupled with higher travelling abilities. However, only A. tabida paid their higher fecundity by a lower longevity. The absence of a clear trade‐off between these traits in L. heterotoma may be explained by a lower metabolic rate in southern populations. These results highlight the importance of the community change over climate in the evolution of life‐history traits in this parasitoid community. © 2012 The Linnean Society of London, Biological Journal of the Linnean Society, 2012, ?? , ??–??.     

Myrosinase in Raphanus sativus L.

A previous paper reported an investigation of myrosinase inthe seeds, seedlings and the different organs of mature plantsof Sinapis alba. The enzyme distribution was related to thehistological localization of myrosin cells. The present paperreports the situation for Raphanus sativus. Differences in myrosinasepatterns have been found but the two taxa are similar in thatthere is good evidence for the presence of the enzyme in myrosincells and in other non-specialized cells. Key words: Raphanus, Myrosinase, Isoelectric focusing, Myrosin cells     

A comparison of spike and spikelet survival in mainstem and tillers of barley

Initiation and abortion of spikelet primordia on primary tillers and mainstem were compared for plants of spring barley, Maris Mink, sown on two sowing dates during 1983, in plots at the Scottish Crop Research Institute (SCRI) and at Long Ashton Research Station (LARS). Sowing date had no effect on the number of spikelets initiated on either mainstem or surviving tillers and many more spikelets were initiated on equivalent stems at LARS than at SCRI but more spikelets aborted at the former site. The final number of spikelets produced was eventually similar. Spikelet abortion was complete by anthesis and coincided with the period of rapid stem and rachis elongation and with the time over which tiller death occurred. Despite the fact that plants at SCRI produced fewer fertile tillers they outyielded those at LARS because much heavier grains were produced on the mainstem and tiller 1 of plants at the Scottish site. An interval of 2 wk between sowing had only small effects on the components of yield.     

Properties and Possible Physiological Significance of Cell Wall Calcium Binding in Etiolated Pea Epicotyls

Baydoun, E. A-H. and Brett, C. T. 1988. Properties and possiblephysiological significance of cell wall calcium binding in etiolatedpea epicotyls.—J. exp. Bot. 39: 199–208. The binding of ⁴⁵Ca²⁺ ions to cell walls prepared from pea epicotylswas examined in young and old parts of the epicotyl, and wasfound to be considerably greater, on a carbohydrate basis, inthe older, non-growing cells. A similar comparison between light-and dark-grown stems showed greater binding in the dark-grownstems. The polygalacturonase-insensitive component of the bindingcontained at least three types of binding with different affinities,and had an apparent pK of 4.3. The specificity of the bindingfor calcium ions was examined and a considerable degree of specificitywas observed. The specificity of inhibition by calcium of epicotylelongation was similar to the specificity of calcium binding.A specific calcium chelator, EGTA, when present at a concentrationof above 10 mol m^–3, promoted the extension of matureregions of the epicotyl, while inhibiting extension of youngertissue. Key words: Cell wall, calcium, pea epicotyl     

The Influence of Antimicrobial Agents on the Percentage of Tetracycline resistant Bacteria in Faeces of Humans and Animals

The effect of antimicrobial administration on the percentage of tetracycline-resistant facultative and anaerobic bacteria in the intestines of humans and animals was studied. Tetracycline was chosen because it is an antibiotic commonly used both as a feed supplement for animals, and therapeutically for humans and animals. More than 200 faecal specimens of bovine, porcine, equine, canine, feline and human origin were collected into pre-reduced anaerobic media. Ninety-one subjects from groups receiving antimicrobials as feed supplements, therapeutically or with no recent antibiotic exposure were included in the study. Counts of both facultative and anaerobic bacteria were determined from media with and without tetracycline. The percentage of normal faecal specimens harbouring tetracycline-resistant coliforms was 56 for humans. 100 for calves. 100 for pigs. 36 for horses, 90 for dogs and 67 for cats. All samples contained Gram negative anaerobes resistant to tetracycline. Subjects from all species receiving antimicrobials showed higher percentages of tetracycline-resistant coliforms and anaerobes than subjects not receiving antibiotics. Greater increases in the percentage of tetracycline-resistant facultative organisms were noted in subjects which received antibiotics as feed supplements compared with subjects which were given therapeutic doses of antibiotics. Percentages of tetracycline-resistant anaerobes showed the opposite trend with more increase among those subjects receiving therapeutic levels of antimicrobial agents.     

Identification and Characterization of the Seed Storage Proteins from Alfalfa (Medicago sativa)

The major seed storage proteins in alfalfa are medicagin (alegumin-like globulin), alfin (a vicilin-like globulin) anda family of Lower Molecular Weight albumins (LMW₁₃). These comprise30%, 10% and 20%, respectively, of the total extractable proteinfrom cotyledons of mature seeds. Alfin is a heterogeneous oligomericprotein (Mr 150 kD) composed of polypeptides ranging in sizefrom Mr 50 to 14 kD (₁,-₆; 50, 38, 32, 20, 16 and 14 kD, respectively).Medicagin is also a high molecular weight oligomeric protein,but requires high concentrations of salt for solubilization.It is comprised of a family of individually distinct subunits,each composed of an acidic polypeptide (A₁–A₉; Mr 49 to39 kD) linked via disulphide bond(s) to a basic polypeptide(B₁, B₂, B₃; Mr 24, 23 and 20 kD, respectively). This pairingis highly specific and two families are recognizable on thebasis of the B polypeptide (B₃ or B₁/B₂). Subunits (M_r 50–65kD) are assembled as trimers (8S) or larger oligomers (12S–15S)in mature seeds. The lower molecular weight albumins (LMW₁–₃)are acidic (pl<6), and consist of sets of disulphide-bondedpolypeptides (Mr 15 and 11 kD). Key words: Medicago sativa, seed storage proteins, alfin, medicagin     

Nitrate Reduction in Different Grass Species

Optimal extraction conditions, assay conditions, and levels of nit rate reductase activity (NRA) were determined for eight forage grass species adaptable to growing conditions in western North Dakota. Optimal pH for extraction of the enzyme nitrate reductase (NADH: nitrate oxidoreductase) for these species ranged from 7.0 to 9.5, whereas assay pH was 7.6 in all eight species. Substrate concentrations ranged from 1.0 to 10.0 mM for maximum NRA with higher concentrations (100 mM) significantly inhibiting NRA. The enzyme was NADH₂ (0.1 to 0.2 mM for maximum activity) specific. Enhancement of maximum activity with the addition of cysteine during extraction was species dependent; six species required high cysteine concentrations between 5 mM and 10 mM and one species required only a 2.5 mM concentration. The degree of sulfhydryl protection offered by cysteine also varied. Comparisons were made between in vivo and in vitro assay methods. Ratios of in vitro to in vivo NRA ranged from 2.2. to 10.8. Use of bovine serum albumin as a protein stabilizer during extraction increased the measurable NRA in some species. Applications of nitrate reductase assay techniques to field work will be discussed.     

Chromosome numbers in the tribes Anthemideae and Inuleae (Asteraceae)

Twenty-two chromosome counts of 19 taxa (21 populations) in the tribe Anthemideae and one member (one population) of the tribe Inuleae of the family Asteraceae are reported. The Anthemideae studied belong to the subtribes Artemisiinae (14 Artemisia taxa, and one species each of the genera Dendranthema , Filifolium and Neopallasia ) and Tanacetinae (one species each of the genera Lepidolopha and Tanacetopsis ). From the Inuleae, we studied one Inula species. Five counts are new reports (including two at generic level), six are not consistent with previous counts and the remainder are confirmations of very limited (one to four records) previous data. Most of populations of Anthemideae studied have the basic chromosome number x  = 9, with ploidy levels ranging from 2 x to 10 x . Dysploidy is also present, with two x  = 8 diploid taxa. The species of Inuleae studied is a diploid with x  = 10, also indicating dysploidy, other members of the same genus Inula having basic numbers of x  = 9 or 8.  © 2005 The Linnean Society of London, Botanical Journal of the Linnean Society , 2005, 148 , 77–85.     

From acaveate to caveate: evolution of pollen types in the Rhaponticum group (Asteraceae,Centaureinae) related to extreme conditions

A survey of pollen morphology and ultrastructure within the Rhaponticum group, using both scanning and transmission electron microscopy, revealed two pollen types. Most representatives of the Rhaponticum group exhibited Serratula‐type pollen. The exceptions were the genus Oligochaeta, with Centaurea jacea‐type pollen, and the genus Myopordon, with both types of pollen. Phylogenetic inference within the group indicated that Jacea‐type pollen is derived from Serratula‐type pollen. The fact that Myopordon exhibited a series of pollen types, from Serratula type to Jacea type, suggests that a transition from one form to another has occurred in the genus. Therefore, the factor which has produced this evolutionary tendency should be sought within Myopordon. Jacea‐type pollen is characterized by a decrease in size, ornamentation, the absence of a columellar infratectum and the presence of a cavea. A comparative survey of similar tendencies in other groups, and their correlation with potential functional implications, prompted the hypothesis that the critical factor involved in such evolution of pollen could be habitats with extreme conditions. © 2008 The Linnean Society of London, Botanical Journal of the Linnean Society, 2008, 158 , 499–510.