Status of the South American tuberous legume Pachyrhizus tuberosus (Lam.) Spreng.: Field observations, taxonomic analysis, linguistic studies and agronomic data on the diversity of the South American Pachyrhizus tuberosus (Lam.) Spreng. complex with special reference to the identification of two new cultivar groups from Ecuador and Peru

The tuberous legume Pachyrhizus tuberosus is found in cultivation sporadically throughout the tropical lowlands of South America. As a result of field studies conducted in Bolivia, Ecuador, Peru and Venezuela, three distinct cultivar groups have been identified. Rare references presenting further evidence in support of this grouping, and yielding information on the cultivation history, are reviewed. The differences in morphology, agricultural practices, tuberous root quality and uses have been studied, as has the linguistic evidence of the origin and domestication processes. The herbarium and live material have been subjected to multivariate analyses in order to establish which easily observable phenotypic characters can be used in the identification of the three cultivar groups. This paper reports on the analysis of 23 morphological characteristics from 31 P. tuberosus cultivar records. The considerable potential of this cultivar/landrace complex and the possibilities of establishing in situ conservation initiatives are discussed. This revised version was published online in August 2006 with corrections to the Cover Date.     

Uptake of Amino Acids by Barley Leaf Slices: Kinetics, Specificity, and Energetics

Uptake of ¹⁴C-labelled _L-lysine. _L-arginine, _L-glutamic acid, _L-aspartic acid, and glycine was studied in 0.75 mm wide barley (Hordeum vulgare L. cv. Lise) leaf slices. After an initial period (10 min) of rapid accumulation amino acid uptake proceeded at a steady, lower rate for several hours. Uptake was stimulated by 10^?4M Ca^?2+ ions. Uptake was strongly _pH dependent with the following optima: aspartic acid _pH 3.5. glutamic acid _pH 4.1. glycine _pH 5.8, lysine _pH 6–7, and arginine _pH 5–8 (a broad plateau). The optimal temperature was about 30°C. and the temperature coefficient in the range 0–20gGC was 2.3–2.5. Concentration-dependence data gave uptake isotherms which appeared to be multiphasic for all the amino acids used. The amino acids inhibited each other in a competitive fashion, indicating that they were all transported by a single carrier system. Uptake of lysinc was strongly inhibited by 10^?4M 2.4-dinitrophenol. Lysine uptake was not stimulated by light under aerobic conditions. However, it was much reduced in the dark under anaerobic conditions. This reduction was almost compensated for by light. The light-stimulation of uptake under anaerobic conditions was abolished by 10^?5M 3-(3,4-dichlorophenyl) 1.1-dimethylurea.     

Two multiplex sets of eight and five microsatellite markers for the European corn borer,Ostrinia nubilalis Hübner (Lepidoptera: Crambidae)

Primer sequence and polymorphism data are presented for 13 microsatellite loci isolated from the European corn borer moth, Ostrinia nubilalis, as part of a project to construct a linkage map for the two pheromone strains. Experimental conditions are described for polymerase chain reaction (PCR) multiplexing, which allows genotyping in two electrophoresis runs of eight and five markers each. In a sample of 27 individuals coming from one European locality, the number of alleles per locus ranged from one to 12, and gene diversity from 0 to 0.859. Seven loci showed a deficit of heterozygotes. Eleven loci cross‐amplify in the related Ostrinia furnacalis.     

Strong correspondence between gillnet catch per unit effort and hydroacoustically derived fish biomass in stratified lakes

1. Sampling of lake fish assemblages is a challenging task in fish science, and the information obtained strongly depends on the choice of sampling gear. The use of more than one sampling technique is generally preferred in order to achieve a comprehensive view on fish assemblage structure. Therefore, the knowledge of whether catches between fishing gears are comparable is crucial. 2. We compared catches in benthic multi‐mesh gillnets with fish biomass estimates obtained by vertical hydroacoustics in 18 European lakes strongly varying in morphometry and trophic status. Separate analyses were conducted for different depth strata and for several fish length thresholds to account for depth‐ and size‐selective gillnet catches. 3. Gillnet catches and hydroacoustically obtained fish biomass estimates were significantly correlated. The strength of correlations was independent of the fish length thresholds applied, but varied across different depth strata of the lakes, with the strongest correlations occurring in the shallow strata. 4. The results support the applicability of vertical hydroacoustics for the quantification of fish biomass in stratified lakes. Survey designs combining hydroacoustics with limited gillnetting at sampling dates shortly one after the other, the latter for the purpose of inventory sampling only, are a cost‐effective strategy for sampling fish assemblages in lakes. However, gillnet sampling does not provide reliable fish density estimates in very deep lakes with separate, pelagic‐dwelling fish assemblages.     

Patterns of natural mortality in stream‐living brown trout (Salmo trutta)

1. We tested the hypothesis that lifetime mortality patterns and their corresponding rates and causal factors differ among populations of stream‐living salmonids. To this end, we examined the lifetime mortality patterns of several successive cohorts of two stream‐living brown trout (Salmo trutta) populations in Spain and Denmark. 2. In the southern population, we observed a consistent two‐phase pattern, in which mortality was negligible during the first half of the lifetime and severe during the rest of the lifetime. In contrast, the northern population demonstrated a three‐phase pattern with an earlier phase varying from negligible to severe, followed by a second stage of weak mortality, and lastly by a third life stage of severe mortality. 3. Despite substantial differences in the mortality patterns between the two populations, the combined effect of recruitment (as a proxy of the density‐dependent processes occurring during the lifetime) and mean body mass (as a proxy of growth experienced by individuals in a given cohort) explained c. 89% of the total lifetime mortality rates across cohorts and populations. 4. A comparison with other published data on populations of stream‐living brown trout within its native range highlighted lifetime mortality patterns of one, two, three and four phases, but also suggested that common patterns may occur in populations that experience similar individual growth and population density.     

The Amphipod Functional Model and Its Bearing upon Systematics and Phylogeny

The peculiar habitus of Amphipods with lateral compression, deep coxal plates 1-4, broad bases of peraeopods 5-7, and enlarged pleura (epimeral plates) of abdominal segments 1-3 is seen as a functional system closely dependent upon the currents produced by the incessant beating of the pleopods. The derivation and position of branchiae and oostegites is discussed. The morphology of more or less aberrant groups, including the suborders Caprellidea and Ingolfiellidea, and its correlations with the mode of life and the basic functional model is analyzed. The possible bearing of the functional model system upon the position of the Amphipoda among the Peracarida is briefly dealt with.     

Range limits,large‐scale biogeographic variation,and localized evolutionary dynamics in a polymorphic damselfly

Studies of heritable colour polymorphisms allow investigators to track the genetic dynamics of natural populations. By comparing polymorphic populations over large geographic areas and across generations, issues about both morph stability and evolutionary dynamics can be addressed, increasing our understanding of the potential mechanisms maintaining genetic polymorphisms. In the present study, we investigated population morph frequencies in a sex‐limited heritable colour polymorphic damselfly (Ischnura elegans, Vander Linden), with three discrete female morphs. We compared the frequencies of these three female morphs in 120 different populations from ten European countries at differing latitudes and longitudes. There were pronounced differences in morph frequencies both across the entire European biogeographic range, as well as at a smaller scale within regions. We also found considerable between‐population variation at the local scale within regions, particularly at the edges of the range of this species. We discuss these findings in the context of recent models of adaptive population divergence along the range of a species. This polymorphism is thus highly dynamic, with stable morph frequencies at the core of the species range but fluctuating morph dynamics at the range limits. We finish with a discussion of how local interactions and climatic factors can be expected to have a strong influence on the biogeographic patterns in this species and other sexually selected polymorphisms. © 2011 The Linnean Society of London, Biological Journal of the Linnean Society, 2011, 102 , 775–785.     

Ciliates as engineers of phototrophic biofilms

1. Phototrophic biofilms consist of a matrix of phototrophs, non‐photosynthetic bacteria and extracellular polymeric substances (EPS) which is spatially structured. Despite widespread exploitation of algae and bacteria within phototrophic biofilms, for example by protozoans, the ‘engineering’ effects of these ciliates on the spatial heterogeneity of phototrophic biofilms are poorly studied. 2. We studied the potential engineering effects of two ciliates, Urostyla sp. and Paramecium bursaria, on the spatial heterogeneity of synthetic multispecies biofilms. Biomass of phototrophic organisms, EPS and bacteria was analysed three dimensionally using confocal laser scanning microscopy. Spatial heterogeneity and cover of the phototrophs, bacteria and EPS were determined at several depths within the biofilm. 3. Ciliate species did not interfere with the overall development of phototrophic microorganisms, because the thickness of the biofilm was equal whether the ciliates were present or not, even though their abundance did affect spatial heterogeneity of biofilm components. When Urostyla was present, it reduced aggregation in EPS and bacteria and increased EPS biovolume. This implies a local facilitating effect of ciliates on photosynthetic activity. Biofilms to which Paramecium was added did not differ from controls in terms of phototrophs, EPS cover and biovolume. Nevertheless, ciliates affected the spatial heterogeneity of these components as phototrophs and EPS became more evenly distributed. 4. This study shows that ecosystem engineering by organisms does not only occur at large spatial scales, as in grasslands and estuaries, but also plays a role at the microscopic scale of biofilms. This effect on spatial heterogeneity was not driven by substantial exploitation of biofilm components, but via the subtle engineering effects of ciliates.     

Low levels of ribosomal RNA partly account for the very high photosynthetic phosphorus‐use efficiency of Proteaceae species

Proteaceae species in south‐western Australia occur on phosphorus‐ (P) impoverished soils. Their leaves contain very low P levels, but have relatively high rates of photosynthesis. We measured ribosomal RNA (rRNA) abundance, soluble protein, activities of several enzymes and glucose 6‐phosphate (Glc6P) levels in expanding and mature leaves of six Proteaceae species in their natural habitat. The results were compared with those for Arabidopsis thaliana. Compared with A. thaliana, immature leaves of Proteaceae species contained very low levels of rRNA, especially plastidic rRNA. Proteaceae species showed slow development of the photosynthetic apparatus (‘delayed greening’), with young leaves having very low levels of chlorophyll and Calvin–Benson cycle enzymes. In mature leaves, soluble protein and Calvin–Benson cycle enzyme activities were low, but Glc6P levels were similar to those in A. thaliana. We propose that low ribosome abundance contributes to the high P efficiency of these Proteaceae species in three ways: (1) less P is invested in ribosomes; (2) the rate of growth and, hence, demand for P is low; and (3) the especially low plastidic ribosome abundance in young leaves delays formation of the photosynthetic machinery, spreading investment of P in rRNA. Although Calvin–Benson cycle enzyme activities are low, Glc6P levels are maintained, allowing their effective use.