The effects of crop microclimate and associated physiological constraints on the seasonal and diurnal distribution patterns of raspberry beetle (Byturus tomentosus) on the host plant Rubus idaeus

Abstract.

• 1 The occurrence of raspberry beetles (Byturus tomentosus) on the host plant Rubus idaeus is extremely variable between seasons, between days and within days, with occupancy of the available raspberry flowers (the feeding and oviposition sites) varying from 0 to 60%.
• 2 This variation could not be explained by plant chemistry or food quality (leaf nitrogen, carbon or water levels, or floral nectar reward); however, beetle distributions were in part attributable to microclimatic constraints acting via the insects’physiological constraints.
• 3 Initial ascent into raspberry canes from soil emergence sites was limited by the three-fold higher water loss rates from recently eclosed young adult beetles as compared with mature beetles. Young adults reduced their hygric stress by remaining in the humid microclimate of tightly furled primocane leaftips.
• 4 Mature beetles spread upwards over the plant, but showed a preference for insolated sites (tops of canes, east or west facing according to time of day). In such sites their body temperatures could rise above the threshold for flight (requiring a T_b of 15°C in laboratory studies). Flight activity was therefore common only in the early afternoon of warm days. Later in the day, beetles moved down and sometimes off the plants, starting to return at around dawn.
• 5 Thus physiological constraints, even on adult beetles (relatively well-protected insect stadia), can be important components in predicting insect movements and locations on a host plant; they are likely to be even more crucial to less highly sclerotized plant-feeding adult insects and many larval herbivorous pests.

     

The intrinsic rates of increase of insects of different sizes

ABSTRACT.

• 1 A negative relationship between intrinsic rate of increase, r, and body size has only clearly been shown using data for species drawn from a number of phyla and covering several orders of magnitude in size. Analyses for more closely related species are equivocal.
• 2 Data for ninety-one species of insects, from nine orders, were used to examine the correlation between intrinsic rate of increase and size.
• 3 Intrinsic rate of increase was negatively correlated with both length and weight across orders, but no relationship could be shown within orders.
• 4 Generation times were positively related to body size, but there was no relationship between net reproductive rate (R_Q) and size.
• 5 These results support the hypothesis that documented relationships between species size and colonization success in insects could be a consequence of the scaling of intrinsic rate of increase with size.

     

Effects of predation risk and plant resistance on Manduca sexta caterpillar feeding behaviour and physiology

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Morphological,structural and physiological differences in heteromorphic leaves of Euphrates poplar during development stages and at crown scales

• Euphrates poplar (Populus euphratica Oliv.) has heteromorphic leaves including strip, lanceolate, ovate, and broad‐ovate leaves from base to top in the mature canopy.
• To clarify how diameter at breast height (DBH) and tree height affect the functional characteristics of all kinds of heteromorphic leaves, we measured the morphological anatomical structure and physiological indices of five crown heteromorphic leaves of P. euphratica at 2, 4, 6, 8, 10, and 12 m from the same site. We also analysed the relationships between morphological structures and physiological characteristics of heteromorphic leaves and DBH and the height of heteromorphic leaves.
• The results showed that the number of abnormalities regarding blade width, leaf area, leaf thickness, leaf mass per area, cuticle layer thickness, palisade tissue thickness, and palisade tissue/sponge tissue ratio increased with size order and sampling height gradient. Net photosynthetic rate, transpiration rate, stomatal conductance, instantaneous water use efficiency, stable delta carbon isotope ratio, proline and malondialdehyde (MDA) content increased with DBH and sampling height. By contrast, blade length, leaf shape index, and intercellular CO2 concentration decreased with the increase in path order and sampling height gradient. Although MDA content and leaf sponge thickness were not correlated with DBH or sampling height, other morphological structure and physiological parameters were significantly correlated with these variables. In addition, correlations were found among leaf morphology, anatomical structure, and physiological index parameters indicating that they changed with path order and tree height gradient.
• The differences in the morphology, anatomic structure and physiological characteristics of the heteromorphic leaves ofP. euphratica are related to ontogenesis stage and coronal position.

     

Sexes in gynodioecious Geranium sylvaticum do not differ in their isotopic signature or photosynthetic capacity

• In gynodioecious plants, females are expected to produce more or better seeds than hermaphrodites in order to be maintained within the same population. Even though rarely measured, higher seed production can be achieved through differences in physiology.
• In this work, we measured sexual dimorphism in several physiological traits in the gynodioecious plant Geranium sylvaticum. Photosynthetic rate, stomatal conductance, transpiration rate, WUE and isotopic signatures were measured in plants growing in two habitats differing in light availability.
• Females have been reported to produce more seeds than hermaphrodites. However, we did not observe any significant difference in seed output between the sexes in these experimental populations. Similarly, the sexes did not differ in any physiological trait measured. Seed production was strongly limited by light availability. Likewise, differences between plants growing in full light versus low light were detected in most physiological parameters measured.
• Our results show that the sexes in G. sylvaticum do not show any evidence of sexual dimorphism in physiology, which concurred with a lack of sexual differences in seed output.

     

Life on the edge: survival and behavioural responses of freshwater gill‐breathing snails to declining water level and substratum drying

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Sexual size dimorphism and the integration of phenotypically plastic traits

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Chironomid biomass determination from larval shape

SUMMARY.

• 1 Ash-free dry weights and dry weights of each larval instar were determined for nine chironomid taxa using unpreserved material. Larval weight (wμg) was related to body length measurements (l mm) by the equation In w= In a+b In l.
• 2 For a given taxon. the constants In a and b were dependent on larval size and shape, respectively: b was found to increase with larval length, while taxa with characteristically stout larvae yielded higher values for In a.
• 3 Comparison of measurements of freshly-killed chironomid larvae with measurements taken after preservation in 70% ethanol showed no change in body shape due to preservation. Length measurements from larvae preserved in this way are therefore suitable for use in the calculation of larval biomass when the relationship to the unpreserved weight is known.
• 4 Maximum larval lengths and mean body proportions (length: width ratios) are reported for thirty-two chironomid taxa.

     

Metabolic rates of a hypogean and an epigean species of copepod in an alluvial aquifer

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Associative bacteria influence maize (Zea mays L.) growth,physiology and root anatomy under different nitrogen levels

• Despite the great diversity of plant growth‐promoting bacteria (PGPB ) with potential to partially replace the use of N fertilisers in agriculture, few PGPB have been explored for the production of commercial inoculants, reinforcing the importance of identifying positive plant–bacteria interactions. Aiming to better understand the influence of PGPB inoculation in plant development, two PGPB species with distant phylogenetic relationship were inoculated in maize.
• Maize seeds were inoculated with Bacillus sp. or Azospirillum brasilense . After germination, the plants were subjected to two N treatments: full (N+) and limiting (N?) N supply. Then, anatomical, biometric and physiological analyses were performed.
• Both PGPB species modified the anatomical pattern of roots, as verified by the higher metaxylem vessel element (MVE ) number. Bacillus sp. also increased the MVE area in maize roots. Under N+ conditions, both PGPB decreased leaf protein content and led to development of shorter roots; however, Bacillus sp. increased root and shoot dry weight, whereas A. brasilense increased photosynthesis rate and leaf nitrate content. In plants subjected to N limitation (N?), photosynthesis rate and photosystem II efficiency increased in maize inoculated with Bacillus sp., whilst A. brasilense contained higher ammonium, amino acids and total soluble sugars in leaves, compared to the control.
• Plant developmental and metabolical patterns were switched by the inoculation, regardless of the inoculant bacterium used, producing similar as well as distinct modifications to the parameters studied. These results indicate that even non‐diazotrophic inoculant strains can improve the plant N status as result of the morpho‐anatomical and physiological modifications produced by the PGPB .

     

Postembryonal growth and its variability of the three marine fishes with special reference to the mechanism of growth variation in fishes

1. To study the relation of growth variation to the behaviour pattern, newly hatched Hemiramphus sajori, Chrysophrys major and Zebrias zebra were reared in 30 litter aquaria during one month, and body length was measured four times.
2. In Hemiramphus sajori coefficient of variation of body length (CV) first increased but showed a tendency to decrease with development of schooling behaviour.
3. In Chrysophrys major CV markedly increased and mode of the distribution curve of body length inclined towards the left side, associated with appearance of aggression and cannibalism.
4. In Zebrias zebra, when behaviour pattern changed from planktonic to demersal some of the small individuals nearly ceased growing. At that time CV of body length remarkably increased and the mode of the distribution curve of body length shifted towards the right side.
5. In all the species a positive correlation was seem between specific growth rate and initial body length soon after intensive feeding began. An negative correlation was observed in most of individuals of Hemiramphus sajori after the appearance of schooling behaviour. When a conspicuous increase in CV and skewness in distribution curve took place, a separate type of correlation was seen in large and small group in the population.
6. Based on above mentioned and other materials a general mechanism of growth variation in fishes was discussed.

     

Responses of periphyton to changes in current velocity, suspended sediment and phosphorus concentration

SUMMARY.

• 1 Research was performed in laboratory streams to evaluate periphytic biomass accrual, export, and community composition over a range of limiting nutrient (phosphorus) concentrations with variable velocity, and suspended sediment addition, in comparison to constant velocity and no suspended sediment. In fixed-velocity treatments, velocity increase to 60 cm s^?1 significantly enhanced biomass accrual, but further increase resulted in substantial biomass reduction. Average biomass loss rates did not change significantly over a velocity range of 10–80 cm s^?1. Diatoms were favoured at relatively high velocities and low phosphorus concentrations, whereas the blue-green Phormidium tended to dominate at higher SRP concentrations and the green Mougeotia seemed to prefer lower velocities.
• 2 Sudden increases in velocity raised instantaneous loss rates by an order of magnitude or more, but these high rates persisted only briefly. As a result, marked biomass reductions were not apparent a day after the velocity change. Dominance change from filamentous green or blue-green to diatoms immediately after the increase was reversed within 2 days. Loss rate increases due to solids addition were much smaller than those accompanying velocity increase, but simultaneous velocity elevation and solids addition produced instantaneous loss rates approximately double those with velocity increase alone.
• 3 The experiments demonstrated that an elevation in velocity, above that to which algae were accustomed, led to increased loss rates and temporarily reduced biomass. However, recolonization and growth after biomass reduction were apparently rapid. Substantial export of periphyton following solids addition required erosion of the protective boundary layer accompanied by a velocity increase. These results arc applicable to understanding the response of lotic periphytic algae to elevated, turbid storm discharges and similar runoff or high-flow events.
• 4 Areal uptake rates of P by algae growing in the laboratory streams increased with soluble reactive phosphorus (SRP) concentration, up to approximately 15 μg I^?1 in overlying water. They also increased above 35 cm s ^?1. Overall, uptake rate seemed to vary inversely with biomass. The ralio of areal uptake rate/biomass was significantly less where mean biomass was 411±6 mg chl a m^?2 compared to 223±17 mg chl a m^?2.
• 5 The results suggested that although nutrient uptake is primarily a surface phenomenon, diffusion to interior cells can also determine the responses of attached communities. Both diffusion and uptake rate were stimulated by increasing nutrient concentration and velocity up to certain levels, but became limited by biofilm thickness and scouring.

     

In-field cover crop strips support carabid communities and shape the ecological trait repartition in maize fields

1. The enhancement of pest regulation service in crops depends for a large part on the capacity of agroecological practices to increase the presence of key species or functional traits in arthropod communities within fields.
2. We investigated the effects of undestroyed strips of winter cover crops in maize fields on carabid community composition, and on the distribution of three ecological traits: diet, wing status and body size.
3. We found that the community composition and the distribution of ecological traits in the in-field cover crop strips had commonalities with both adjacent cropped areas and field margins. Some species were recorded mostly or only in the strips indicating that strips could support carabid species and help increase local diversity from the first year of establishment.
4. The activity-density of Poecilus cupreus and Pterostichus melanarius was higher in the cropped proximity of the strip, and the body size was influenced by the distance from the strip.
5. Our results suggest that carabid communities are shaped by the habitat type, but the influence of such agroecological infrastructures on communities of adjacent crops is minor beyond a distance of 10 m. However, overall species abundance was increased and thus potentially provided enhanced pest regulation.

     

Reproductive strategies of female butterflies: variation in and constraints on fecundity

ABSTRACT.

• 1 This study first examines the reproductive strategy of female Speyeria mormonia Edwards (Lepidoptera: Nymphalidae):
• 2 Egg weight and number laid per day decrease with age.
• 3 Survival and daily egg number may be affected by temperature; mean daily egg weight is not affected by temperature.
• 4 Daily egg number is not correlated with body size. In the central range of body size, egg weight is also not correlated with body size. However, exceptionally large or small females lay respectively heavier or lighter eggs than average.
• 5 A simple trade-off between offspring size and number does not occur within females on a daily basis, or among females averaged over their lifespans.
• 6 Fat body resources are depleted at a rate independent of body size.
• 7 Females are essentially monogamous.
• 8 Age-specific fecundity data reported here for S.mormonia are next compared with data for other Lepidoptera with different adult feeding habits and egg maturation patterns, and hence different possibilities for adult feeding to play a role in egg production. Based on these comparisons, I propose that the shape of the age-specific fecundity curve for each species under optimal conditions is constrained by the potential importance of adult nutrients in egg production.

     

The competition amongDrosophila larvae in different growth stages

1. The experiment was conducted in order to examine the influence of the difference in the growth stage of the competitors on the intraspecific competition. Drosophila melanogaster, “wild” and its mutant “ebony” were used as materials.
2. The earlier developed or older larvae have considerable advantage, such as the increase of the body weight of flies, and of the total weight of flies from one vial, and high constant emerging percentage, while the younger competitors received the opposite influence in addition to the increase of the larval-pupal duration.
3. The grand total yields (the yield of “wild” plus that of “ebony”) from one vial were almost constant even the difference in the growth stage between competitors is changed.

     

Homing in the Digger Wasp Bembix rostrata (Hymenoptera,Sphecidae) in Relation to Sex and Stage1

In the digger wasp Bembix rostrata in males and females of different stages the homing rates and times after release from different distances were investigated.

• 1 The homing rate decreased with increase of distance (up to 3000 m).
• 2 In females the homing rate increased with progressing stage, from emerging over digging to provisioning.
• 3 Numbers for homing times followed the same order: highest in emerging, medium in digging and lowest in provisioning females.
• 4 Males showed similar homing rates as digging females. No significant differences between age groups could be found.
• 5 The results indicate an effect of sex and stage on the homing capacity. Differences may be traced back to motivation (provisioning females) and lack of experience (emerging females). Landmark orientation, which may include particular search strategies, is a probable orientation mechanism.

     

Reproductive biology and pollinators in two enantiostylous Qualea species (Vochysiaceae) in the Brazilian Cerrado

• Enantiostyly is a floral polymorphism in which two floral forms in the same species differ in deflection of the stigma to right or left position. In monomorphic enantiostylous plants, flowers of the two morphs occur within the same individual, usually in the same proportion. In self‐compatible species the function of monomorphic enantiostyly is proposed to increase outcrossing rates and offer a reproductive advantage under pollination limitation. Enantiostylous species are usually self‐compatible and show heteranthery, with poricide anthers and pollen as pollinator reward; however, there are families, such as Vochysiaceae, that have different characteristics.
• We analysed the reproductive system and pollination biology of Qualea parviflora and Q. multiflora, two enantiostylous species from the Brazilian Cerrado that have specific morphological and physiological traits. For this, we characterized flower traits, performed hand pollinations and studied floral visitors.
• We found no differences between morphs in the proportion of flowers, nectar produced or its concentration, pollen quantity and fruit set. Both species were self‐incompatible and quite generalist regarding floral visitors.
• Enantiostyly in self‐incompatible plants seems to confer a reproductive advantage by reducing self‐interference resulting from stigma clogging. This novel result helps to expand our knowledge on this complex floral polymorphism and opens new avenues for future research on this topic.

     

Photoperiod and variation in life history traits in core and peripheral populations in the damselfly Lestes sponsa

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Statistical characteristics of the density-independent population fluctuation and the evaluation of density-dependence and regulation in animal populations

In this study it was proved that the “density-independent population” shows the following characteristics if the analysis is made using time-series samples:

1. The slope b in the density-on-density regression between successive developmental stages has a general tendency to become smaller than 1, though the bias approaches zero if one or more of the following three conditions are satisfied: (a) the data cover a large number of generations, (b) the variance of the rate of population change for the period concerned is small relative to that for the residual period in a whole generation, and (c) the population has a distinct trend to either increase or decrease over generations.
2. The variance for the generation-to-generation population fluctuation increases continually as the number of generations is increased, even if the population has no inherent trend to increase or decrease. For a fixed number of generations, however, the variance remains constant among different developmental stages.

On the basis of these theoretical results, a modified method for detecting density-dependence from time-series samples was presented, together with a new, tentative technique of variance analysis to evaluate the regulation of numbers directly. The results of applying these methods to some sets of data from both hypothetical and actual populations illustrated their validity for use in population studies.     

Terrestrial organic matter quantity or decomposition state does not compensate for its poor nutritional quality for Daphnia

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