Oviposition response of Simulium reptans (Diptera: Simuliidae) to the presence of conspecific eggs

Abstract.

• 1 The oviposition behaviour of Simulium reptans L. is described from two sites on the River Spey, Scotland. Female aggregations were observed immediately downstream of oviposition sites and were composed mainly of gravid flies (range 60–80%0) together with smaller numbers that were either freshly bloodfed (range 2–17%) or infected with mermithid nematodes (range 0–30%).
• 2 The time from landing on the oviposition sites to the onset of oviposition was recorded. The time in the presence of greater than 1-day-old eggs did not significantly differ from sites with no eggs present. However, the presence of freshly laid or I-day-old eggs significantly shortened the time to onset of oviposition. The cues that elicit oviposition are unknown but it is speculated that they may involve a pheromone.

     

Amelioration of age-dependent increase in oxidative stress markers in male mice by extract of Potentilla fulgens

Objective: To investigate the effect of Potentilla fulgens extract on lipid peroxidation and antioxidant status in male mice as a function of age.

Methods: Eighteen-month-old Swiss albino male mice were administered the dichloromethane-methanol extract of P. fulgens (250?mg/kg b.w.) on alternate days via intraperitoneal route for a period of 14 days. Lipid peroxidation and activities of catalase (CAT) and glutathione peroxidase (GPx1) in liver and kidney were measured and serum oxygen radical absorbance capacity (ORAC) assay was estimated. Phytochemical analysis of P. fulgens extract using high performance thin layer chromatography (HPTLC) was carried out with gallic acid, quercetin, catechin, and epicatechin as markers.

Results: Significant increase in level of thiobarbituric acid-reactive substances (TBARS), decreased GPx1, and CAT activities as well as reduction in ORAC were observed in 18-month-old mice as compared to that of 2-month-old mice. Treatment with P. fulgens extract significantly lowered TBARS level, ameliorated CAT, and GPx1 activities in liver and kidney and improved serum ORAC in aging mice. HPTLC studies revealed well resolved bands of P. fulgens extract containing epicatechin and catechin.

Discussion: This study showed that P. fulgens is a potent antioxidative agent, which can emerge as a promising candidate in alleviating the age-associated oxidative stress and related diseases.     

Phenolic Compounds and Antioxidant Activity of Different Organs of Potentilla fruticosa L. from Two Main Production Areas of China

This report compared the phenolic compounds and antioxidant activity of the leaves, flowers, and stems of Potentilla fruticosa L. collected from two main production areas of P. R. China (Taibai Mountains and the Qinghai Huzhu Northern Mountains). The results indicated that there were significant differences in the phenol contents and antioxidant activities among the different organs and between the two productions. High‐performance liquid‐chromatography analysis indicated that hyperoside, (+)‐catechin, ellagic acid, and rutin were the primary compounds in leaves and flowers; for stems, the content of six phenolic compounds, from two productions, were the lowest. The 1,1‐diphenyl‐2‐picryl hydrazyl (DPPH), 2,2‐azino‐bis(3‐ethylbenzothiazoline‐6‐sulfonic acid) di‐ammonium salt (ABTS), ferric reducing power (FRAP), lipid peroxidation assays, and microbial test system (MTS) were used to evaluate the antioxidant activity. The results demonstrated that the leaves from two productions exhibited powerful antioxidant activity than other organs, which did not significantly differ from that of the positive control (rutin), followed by the flowers and stems. The correlation between the content of phytochemicals and the antioxidant activities of different organs showed that the total phenol, tannin, hyperoside, and (+)‐catechin contents may influence the antioxidant activity, and these compounds can be used as markers for the quality control of P. fruticosa.     

Costs of plasticity in foraging characteristics of the clonal plant Ranunculus reptans

In clonal plants, evolution of plastic foraging by increased lengths of leaves and internodes under unfavourable conditions may be constrained by costs and limits of plasticity. We studied costs and limits of plasticity in foraging characteristics in 102 genotypes of the stoloniferous herb Ranunculus reptans. We grew three replicates of each genotype with and three without competition by the naturally co-occuring grass Agrostis stolonifera. We used regression and correlation analyses to investigate potential costs of plasticity in lengths of leaves and stolon internodes, developmental instability costs of these traits, and a developmental range limit of these traits. We used randomization procedures to control for spurious correlations between parameters calculated from the same data. Under competition the number of rosettes, rooted rosettes, and flowers was 58%, 40%, and 61% lower, respectively, than in the absence of competition. Under competition lengths of leaves and stolon internodes were 14% and 6% smaller, respectively, than in the absence of competition. We detected significant costs of plasticity in stolon internode length in the presence of competition when fitness was measured in terms of the number of rosettes and the number of flowers (selection gradients against plasticity were 0.250 and 0.214, respectively). Within-environment variation (SD) in both foraging traits was not positively correlated with the corresponding plasticity, which indicates that there were no developmental instability costs. More plastic genotypes did not have less extreme trait values than less plastic genotypes for both foraging traits, which indicates that there was no developmental range limit. We conclude that in R. reptans costs of plasticity more strongly constrain evolution of foraging in the horizontal plane (i.e., stolon internode length) than in the vertical plane (i.e., leaf length).     

Seedling establishment,underground kinetics,and clonal reiteration: How do Potentilla inclinata and Inula ensifolia get their multifunctional subterranean systems?

The development of a seedling into an adult plant comprises various underground processes. Time-lapse photography (TLP) makes them visible. This is documented for Potentilla inclinata (Rosaceae) and Inula ensifolia (Asteraceae).After germination, P. inclinata develops a taproot system. Contraction phenomena pull the basal part of the shoot at least 10 mm into the soil. Later, several adventitious roots are generated, and thus the root system changes to a fibrous one. This is followed by cloning without separation of the ramets.Seedlings of I. ensifolia develop a weak primary root. At an early stage, adventitious roots are formed at the leaf rosette. This fibrous root system exerts a strong pulling effect on the shoot. After one vegetation period the basis of the rosette is approx. 30 mm under the soil surface. Cloning includes the formation of many new horizontal shoots, which conquer new sites.These two examples show three functional steps common in the developmental progress of subterranean systems: (I) establishment of the seedling, (II) innovation and survival of the young plant, and (III) reiteration (cloning and dispersal). However, to accomplish these basic development steps the diversity of subterranean systems is enhanced by different organographical components.Furthermore, the development of subterranean systems is a dynamic process consisting of two kinetic processes: the vertical movement during seedling establishment, which brings the innovation buds to a safe soil position, and the horizontal movement during dispersal, which conquers new sites.     

Multitrophic influences on egg distribution in a specialized leaf beetle at multiple spatial scales

Egg distribution in herbivorous beetles can be affected by bottom-up (host plant), and by top-down factors (parasitoids and predators), as well as by other habitat parameters. The importance of bottom-up and top-down effects may change with spatial scale.

In this study, we investigated the influence of host plant factors and habitat structure on egg distribution in the leaf beetle Cassida canaliculata Laich. (Coleoptera: Chrysomelidae), a monophagous herbivore on Salvia pratensis L. (Lamiales: Lamiaceae), on four spatial scales: individual host plant, microhabitat, macrohabitat, and landscape. At the individual host plant scale we studied the correlation between egg clutch incidence and plant size and quality. On all other scales we analyzed the relationship between the egg clutch incidence of C. canaliculata and host plant percentage cover, host plant density, and the surrounding vegetation structure. Vegetation structure was examined as herbivores might escape egg parasitism by depositing their eggs on sites with vegetation factors unfavorable for host searching parasitoids.

The probability that egg clutches of C. canaliculata were present increased with an increasing size, percentage cover, and density of the host plant on three of the four spatial scales: individual host plant, microhabitat, and macrohabitat. There was no correlation between vegetation structure and egg clutch occurrence or parasitism on any spatial scale. A high percentage of egg clutches (38–56%) was parasitized by Foersterella reptans Nees (Hymenoptera: Tetracampidae), the only egg parasitoid, but there was no relationship between egg parasitism and the spatial distribution of egg clutches of C. canaliculata on any of the spatial scales investigated. However, we also discuss results from a further study, which revealed top-down effects on the larval stage.     

Long-term functional plasticity in plant hydraulic architecture in response to supplemental moisture

Background and Aims

Plasticity in structural and functional traits related to water balance may determine plant performance and survival in ecosystems characterized by water limitation or high levels of rainfall variability, particularly in perennial herbaceous species with long generation cycles. This paper addresses whether and the extent to which several such seasonal to long-term traits respond to changes in moisture availability.

Methods

Using a novel approach that integrates ecology, physiology and anatomy, a comparison was made of lifetime functional traits in the root xylem of a long-lived perennial herb (Potentilla diversifolia, Rosaceae) growing in dry habitats with those of nearby individuals growing where soil moisture had been supplemented for 14 years. Traditional parameters such as specific leaf area (SLA) and above-ground growth were also assessed.

Key Results

Individuals from the site receiving supplemental moisture consistently showed significant responses in all considered traits related to water balance: SLA was greater by 24 %; roots developed 19 % less starch storing tissue, an indicator for drought-stress tolerance; and vessel size distributions shifted towards wider elements that collectively conducted water 54 % more efficiently – but only during the years for which moisture was supplemented. In contrast, above-ground growth parameters showed insignificant or inconsistent responses.

Conclusions

The phenotypic changes documented represent consistent, dynamic responses to increased moisture availability that should increase plant competitive ability. The functional plasticity of xylem anatomy quantified in this study constitutes a mechanistic basis for anticipating the differential success of plant species in response to climate variability and change, particularly where water limitation occurs.     

两种生境下鹅绒委陵菜无性系形态的比较

以调查统计的方法研究了矮嵩草草甸和金露梅灌丛两种生境下鹅绒委陵菜无性系的形态特性,研究结果表明：矮嵩草草甸内的鹅绒委陵菜无性系绝大多数特征参数大于金露梅灌丛内,形态可塑性较显著,这与不同生境下的资源异质性特征密切相关。研究为生境适应假说提供又一例证。