Latitudinal patterns in the phenological responses of leaf colouring and leaf fall to climate change in Japan

Aim  To estimate the potential effect of global climate change on the phenological responses of plants it is necessary to estimate spatial variations at larger scales. However, previous studies have not estimated latitudinal patterns in the phenological response directly. We hypothesized that the phenological response of plants varies with latitude, and estimated the phenological response to long-term climate change using autumn phenological events that have been delayed by recent climate change.
Location  Japan.
Methods  We used a 53-year data set to document the latitudinal patterns in the climate responses of the timing of autumn leaf colouring and fall for two tree species over a wide range of latitudes in Japan (31 to 44° N). We calculated single regression slopes for leaf phenological timing and air temperature across Japan and tested their latitudinal patterns using regression models. The effects of latitude, time and their interaction on the responses of the phenological timings were also estimated using generalized linear mixed models.
Results  Our results showed that single regression slopes of leaf phenological timing and air temperature in autumn were positive at most stations. Higher temperatures can delay the timing of leaf phenology. Negative relationships were found between the phenological response of leaves to temperature and latitude. Single regression slopes of the phenological responses at lower latitudes were larger than those at higher latitudes.
Main conclusions  We found negative relationships between leaf phenological responsiveness and latitude. These findings will be important for predicting phenological timing with global climate change.     

Responses of leaf miners to atypical leaf production patterns

Abstract. 1. Larvae of two bivoltine species of leaf-mining Lepidop-tera, Acrocercops sp. and Neurobathra strigifinitella (Clem.), restrict feeding to young, second-flush leaves of their host trees in north Florida.
2. During 1980 and 1981, densities of both species varied greatly among thirty small water oaks ( Quercus nigra ), as did timing and extent of secondary leaf production.
3. In both years leaf-miner density at the end of the first generation (mid-August) was positively correlated with secondary leaf production.
4. Five trees abscised their leaves and reflushed new ones at atypical times of the growing season. When refoliation coincided with emergence of ovipositing adults, Acrocercops sp. and N.strigifinitella densities increased dramatically, indicating that both species are at times limited by availability of young leaves.
5. By staggering termination of diapause these leaf miners can exploit a temporally variable resource.     

Foliar form, colour and surface characteristics influence oviposition behaviour of the carrot fly

Various leaf models made of paper were presented to carrot flies, Psila rosae (F.) (Diptera: Psilidae) in choice assays to investigate the effect of non-chemical plant traits on oviposition behaviour. The surrogate leaves differed in colour, shape, surface coating, size and stem length. In the presence of host-plant extracts, physical factors strongly influenced oviposition. Green, yellow and orange three-dimensional models similar in shape to host-plant leaves (pinnately or ternately compound or dissected) and with a thin cover of paraffin wax were most acceptable to the females. Egg-laying was not affected by leaf size, but was negatively correlated with stem length. The results obtained by testing models with simple leaf silhouettes were confirmed in an experiment using more lifelike imitations of real host and non-host leaves. The findings are discussed by an extensive review of similar studies in three other phytophagous fly species (cabbage root fly, onion fly, Hessian fly).     

Patterns of Assimilate Production and Translocation in Muskmelon (Cucumis melo L.) : I. Diurnal Patterns

Continuous monitoring of steady-state carbon dioxide exchange rates in mature muskmelon (Cucumis melo L.) leaves showed diurnal patterns of photosynthesis and respiration that were translated into distinct patterns of accumulation and phloem export of soluble sugars and amino acids. Leaf soluble sugar patterns in general followed the pattern of photosynthetic activity observed in the leaf, whereas starch accumulated steadily throughout the light period. Sugar and starch levels declined through the dark phase. Phloem exudate analysis revealed that diurnal levels of the major transport sugars (stachyose and sucrose) in the phloem did not appear to correlate directly with the photosynthetic activity of the leaf but instead were inversely correlated with leaf starch accumulation and degradation. The amino acid pool in leaf tissues remained constant throughout the diurnal period; however, the relative contribution of individual amino acids to the total pool varied with the diurnal photosynthetic and respiratory activity of the leaf. In contrast, the phloem sap amino acid pool size was substantially larger in the light than in the dark, a result primarily due to enhanced export of glutamine, glutamate, and citrulline during the light period. The results indicate that the sugar and amino acid composition of cucurbit phloem sap is not constant but varies throughout the diurnal cycle in response to the metabolic activities of the source leaf.     

云南元江芒果园桔小实蝇成虫日活动规律及空间分布格局

利用甲基丁香酚引诱剂和黄板对桔小实蝇Bactrocera dorsalis成虫日活动规律及飞行高度进行了研究,同时根据多种聚集度指标对桔小实蝇成虫的空间分布格局进行了分析。结果表明:元江县挂果期芒果园内桔小实蝇日活动量高峰出现在10:00、16:00左右,活动量低谷出现在8:00、14:00和19:00左右,日间温湿度与其日活动量之间无线性相关关系;成虫飞行高度随时间变化,受降雨影响,雌雄成虫飞行高度存在差异。上午、中午成虫多近地飞行,午后多在1.5 m以上高度飞行,降雨导致成虫飞行活动量大幅减退,多分布于1.5 m以上枝叶附近。株高8 m的3a芒果树4 m高度处黄板捕获虫量最大,其次是2 m高处,6m以上虫量较少。雄性成虫在芒果园中呈聚集分布,原因之一是其自身的聚集行为;雌虫空间分布不均,主要呈聚集分布,少数部分为均匀分布,其聚集由环境因素造成。     

Effects of leaf toughness on mandibular wear of the leaf beetle, Plagiodera versicolora

Abstract. 1. The effects of leaf toughness on mandibular wear of the leaf beetle Plagiodera versicolora Laich. (Coleoptera: Chrysomelidae) were evaluated by feeding adult beetles young (tender) and old (tough) leaves of Salix babylonica and S. alba 'Tristis'.
2. Tough leaves erode the cutting surface of beetle jaws more so than tender leaves.
3. Beetles with worn jaws consumed leaves at a slower rate than ones with less mandibular wear.
4. Because rates of leaf consumption and egg production are positively correlated, increased mandibular wear may reduce beetle fecundity.
5. These results support the belief that leaf toughness may act as a potent defence affecting morphology, feeding behaviour, and ultimately spatial and temporal patterns of herbivores.     

Diurnal effectiveness of pollination by bees and flies in agricultural Brassica rapa: Implications for ecosystem resilience

Bees are known to provide pollination services to a wide range of crops, yet flies are rarely included in estimates of function. As bees and flies differ markedly in their life history characteristics and resource needs, they may be active and hence provide pollination services at different times of the day. Here, we explore the differences in bee and fly diurnal activity patterns and how this may impact upon pollination services provided to Brassica rapa, a mass-flowering crop. We observed pollinators at two-hourly intervals from 6:00 to 20:00 h in twelve fields in New Zealand in 2004–2005. Overall, bees were most active in the middle of the day and were more effective pollinators than flies, driven primarily by the high pollinator efficiency of Apis mellifera and Bombus terrestris. Some fly taxa however, visited flowers early and late in the day when there were few bees. The results of this study demonstrate that fine-scale temporal dynamics and the spatial distribution of crop pollinators may directly affect the quantity of pollination services. The maintenance of biodiversity in agro-ecosystems may therefore be critical to ensure pollinator taxa are available under a range of environmental conditions.     

Influence of weather conditions on fly abundance and its implications for transmission of rabbit haemorrhagic disease virus in the North Island of New Zealand

Blowflies (Diptera: Calliphoridae) and flesh flies (Diptera: Sarcophagidae) are potential vectors of rabbit haemorrhagic disease virus (RHDV) in New Zealand. The associations between habitat and weather factors on the abundance of these flies were investigated. Between October 1999 and June 2001, flies were trapped on open pasture and in dense vegetation patches on farmland in the Himatangi area of the North Island. Five calliphorid species were trapped commonly at scrub edges and the most abundant sarcophagid, Oxysarcodexia varia Walker, was trapped mainly on open pasture. An abundance peak of O. varia was probably associated with the occurrence of a rabbit haemorrhagic disease (RHD) outbreak in the study area. Overall abundance of flies varied according to habitat and species, and species numbers differed between seasons and years. The all-day minimum temperature 3 weeks before trapping was a significant variable in all models of fly abundance, whereas average rainfall did not affect fly abundance. The all-day temperature range was significant only for O. varia. The influence of other climatic factors varied between fly species. Climate dependent variations in fly abundance may contribute to the risk of transmission of RHD, which occurred intermittently on the site during the study period.     

贵州草海越冬斑头雁日间行为模式及环境因素对行为的影响

2011年12月至2012年2月,在贵州省威宁县草海国家级自然保护区,采用瞬时扫描取样法对越冬斑头雁(Anser indicus)种群进行了日间行为时间分配和活动节律的研究.结果表明,斑头雁越冬期间的主要行为是取食和静息,分别占50.48％和43.79％,并呈现出早上和傍晚的双取食高峰,中午的静息高峰.各时间段的取食、静息和饮水行为存在显著差异.对不同生境中斑头雁行为的统计结果表明,在陆地生境中的主要行为是取食,在浅水沼泽生境中的主要行为是静息,推测食物丰富度和干扰水平是影响不同栖息地行为模式的主要因素.利用偏相关分析环境温度和湿度对斑头雁行为的影响表明,气温是影响斑头雁日间行为模式的主要因素.气温升高时,斑头雁增加静息行为减少取食行为;气温降低时则减少静息行为增加取食行为.     

Host preferences in a phonotactic parasitoid of field crickets: the relative importance of host song characters

Abstract.  1. Predators, including insect parasitoids, often eavesdrop on prey signals, and as a result, predation can have important effects on the evolution of prey signalling behaviour.
2. The phonotactic parasitoid fly, Ormia ochracea , uses the calling songs of male field crickets to locate their field crickets hosts. In the western USA, this fly parasitises the variable field cricket, Gryllus lineaticeps . Previous work with one fly population suggested that female flies, like female field crickets, preferentially orient to male songs with higher chirp rates and longer chirp durations, although a limited range of male song types was used in this previous study. The current study, with a different fly population, used field-based, two-speaker choice tests to examine: (1) the effect of male chirp rate and chirp duration on fly attraction, using a natural range of song types; and (2) the relative importance of these song types in host selection by the flies.
3. Three lines of evidence suggested that chirp rate is more important than chirp duration in host selection. (a) The flies consistently preferred higher chirp rates but only sometimes preferred longer chirp durations. (b) The flies consistently preferred higher chirp rate/shorter chirp duration songs to lower chirp rate/longer chirp duration songs. (c) Preferences for longer chirp durations could be eliminated by increasing the amplitude of the less attractive song type, while preferences for higher chirp rates could only sometimes be eliminated by increasing the amplitude of the less attractive song type.
4. Fly predation may favour lower chirp rates and shorter chirp durations in G. lineaticeps , and may have resulted in stronger selection on chirp rate than on chirp duration.     

Spatial and temporal partitioning of behaviour by adult dacines: direct evidence for methyl eugenol as a mate rendezvous cue for Bactrocera cacuminata

Abstract. Resource use in adult Dacinae (Diptera: Tephritidae) is believed to be restricted to the host plant (i.e. the plant that provides fruit for oviposition and larval development). However, studies on Bactrocera cacuminata did not support this hypothesis. Thus, it was hypothesized that adult flies partition their diurnal activities between spatially separated resources (host plant, sugar, protein and methyl eugenol) as a function of the physiological status of the fly (immature, mature–unmated, mature–mated). In accordance with a priori predictions, the results of a field‐cage study show that there are significant diurnal patterns in abundance and behaviour, and that flies of different physiological status use resources differently. Immature flies spend most of their time foraging for sugar and protein to facilitate development. Sexually mature flies forage for sugars during the day, and at dusk, responded strongly to methyl eugenol and mate. The fact that polygynous males wait at methyl eugenol at dusk whereas the mated, monandrous females spend their time ovipositing in fruit and are nonresponsive to methyl eugenol, supports Metcalf's hypothesis that such phenylpropanoids serve as mate rendezvous cues.     

An experimental study of the breakdown of submerged leaves by hyphomycetes and invertebrates in Morocco

SUMMARY. 1. Mechanisms of the breakdown of submerged leaves under the warm and dry Moroccan climate, including the interaction between hyphomycetes and invertebrates, were investigated.
2. Laboratory experiments were performed on dried leaves of Salix sp. and Nerium oleander .
3. During the first month under the experimental conditions, Melanopsis praemorsa, Physa acula (Gastropoda) and Hydropsyche maroccana (Trichoptera), respectively, were responsible for a loss of weight of 38, 21 and 13% in willow leaves, and 40, 15 and 8% in oleander leaves.
4. The weight lost by willow leaves inoculated with the fungi Alatospora acuminata, Anguillospora longissima, Lemonniera aquatica and Tetracladium marchalianum increased with time, but varied according to the fungal species. Loss of weight and increase in nitrate and phosphate content of the leaves were greatest with Lemonniera and smallest with Tetracladium .
5. When the leaves thus colonized by each of the four fungal species were exposed to each of the three invertebrates, the amount of material consumed increased with the time of fungal conditioning and varied according to the fungus and to the invertebrate. Greatest consumption was by Melanopsis feeding on leaves conditioned by Lemonniera , in which case assimilation percentage by the gastropod was as high as 75%.
6. Owing to their numbers in the field, and to the quantity of leaf material they ingest, gastropods appear as the main shredders in the streams considered, thus replacing the Crustacea that often play this part under temperate climates. Breakdown seems faster in Morocco than in France, mainly because of a shorter initial time lag in weight loss.     

Avoidance of occupied hosts by the Hessian fly: oviposition behaviour and consequences for larval survival

Abstract 1. Unoccupied wheat plants and wheat plants occupied by conspecific eggs or larvae were presented to ovipositing female Hessian flies in choice tests.
2. The presence of conspecific eggs on the leaf surfaces of wheat plants did not appear to have any effect on the responses of ovipositing Hessian fly females.
3. The presence of conspecific larvae at the base and nodes of wheat plants for 1, 6, or 11 days had significant effects on Hessian fly oviposition. Eggs oviposited on plants were inversely proportional to larval densities and days of larval occupation.
4. Feeding by Hessian fly larvae is associated with several changes in wheat plants. One of these changes, the growth arrestment of the plant, was measured by recording the heights of plants used in oviposition tests. Plant heights were inversely proportional to both larval densities and days of occupation. Plant heights were directly proportional to eggs oviposited on plants.
5. The consequences of adult female avoidance of plants occupied by conspecific larvae were investigated by allowing females to oviposit on unoccupied plants and 1-day, 6-day, and 11-day larval occupied plants, then scoring at the end of the first larval instar the survival of the offspring that resulted from this oviposition.
6. Survival during the first larval instar was 88% for the offspring of females that oviposited on unoccupied plants, decreasing to 82, 31, and 4% on the 1-day, 6-day, and 11-day occupied plant treatments. On these four plant treatments, a positive correlation was found between larval performance (i.e. survival) and the preferences of ovipositing females.
7. On the four plant treatments, relationships between first-instar larval density and first-instar larval survival varied significantly. On unoccupied plants, survival was inversely proportional to density. On plants oviposited on at 6 days of larval occupation, survival was directly proportional to density.     

Pheromone deposition on leaf territories by male Caribbean fruit flies,Anastrepha suspensa (loew) (Diptera: Tephritidae)

Male Caribbean fruit flies apply everted anal membranes associated with pheromone glands to the substrate while on leaf territories. There is a peak in abdominal dipping at the onset of the photoperiod, followed by a decline and then a more extensive period of activity in the second half of the photoperiod. During peak signaling periods, most males had a distinct set of lateral abdominal phermone glands protruded for most of the time. However, the frequency of anal pheromone gland dipping varied considerably over time. Episodes of wing fanning (which may disperse pheromones) and abdomen dipping coincide during a male's tenure on a host leaf. Host-plant leaves were contained for 48 h with signaling males or immature females or kept without insects. Several, though not all, of the constituents of the pheromone were found on leaves within 1 h of removing signaling males. None of these compounds occurred on either type of control leaf. Mature virgin female flies were more likely to be found in contact with host leaves that had been previously exposed for 48 h to the activities of sexually mature males than with unexposed control leaves. There was no difference in the reaction of mature virgin female flies to unexposed control leaves or leaves previously exposed to the activities of other sexually immature female or male flies for 48 h. Presumably, the deposition of pheromones by mature males accounts for the difference in reactions.     

Histological Comparisons of Fergusobia/Fergusonina-Induced Galls on Different Myrtaceous Hosts

The putative mutualism between different host-specific Fergusobia nematodes and Fergusonina flies is manifested in a variety of gall types involving shoot or inflorescence buds, individual flower buds, stems, or young leaves in the plant family Myrtaceae. Different types of galls in the early-to-middle stages of development, with host-specific species of Fergusobia/Fergusonina, were collected from Australian members of the subfamily Leptospermoideae (six species of Eucalyptus, two species of Corymbia, and seven species of broad-leaved Melaleuca). Galls were sectioned and histologically examined to assess morphological changes induced by nematode/fly mutualism. The different gall forms were characterized into four broad categories: (i) individual flower bud, (ii) terminal and axial bud, (iii) ''basal rosette'' stem, and (iv) flat leaf. Gall morphology in all four types appeared to result from species-specific selection of the oviposition site and timing and number of eggs deposited in a particular plant host. In all cases, early parasitism by Fergusobia/Fergusonina involved several layers of uninucleate, hypertrophied cells lining the lumen of each locule (gall chamber where each fly larva and accompanying nematodes develop). Hypertrophied cells in galls were larger than normal epidermal cells, and each had an enlarged nucleus, nucleolus, and granular cytoplasm that resembled shoot bud gall cells induced by nematodes in the Anguinidae.     

Pattern of defoliation and its effect on photosynthesis and growth of Goldenrod

1. Leaf area was removed from Solidago altissima in either a dispersed pattern (half of every leaf removed) or a concentrated pattern (every other leaf removed) and effects on leaf gas exchange, vegetative growth and flowering were examined relative to undefoliated controls. Gas exchange was measured for leaves remaining after defoliation and for regrowth leaves that developed post-damage (at 7, 16 and 26 days post-defoliation).
2. Area-based photosynthetic rates of leaves remaining after defoliation were not affected by either dispersed or concentrated damage, but damage of both types enhanced area-based photosynthesis of regrowth leaves at 16 days post-defoliation and to a lesser extent at 26 days post-defoliation.
3. Dispersed damage, but not concentrated damage, stimulated mass-based photosynthesis of undamaged leaves remaining after defoliation. Undamaged leaves remaining after defoliation and regrowth leaves on damaged plants had higher specific leaf area (leaf area/leaf mass) than comparable leaves on control plants. Mass-based photosynthesis was more strongly elevated by defoliation than area-based photosynthesis because of this increase in specific leaf area.
4. Plants with dispersed damage recovered more quickly from defoliation; they had higher relative growth rates in the first week post-defoliation than plants with concentrated damage. Both types of defoliation caused similar reductions in flower production.
5. These results add to accumulating evidence that dispersed damage is generally less detrimental to plants than concentrated damage and suggest that physiological changes in leaves may be part of the reason.     

The role of substrate preparation in the symbiosis between the leaf-cutting ant Acromyrmex octospinosus (Reich) and its food fungus

Abstract. 1. In laboratory nests the ants thoroughly licked leaf fragments by a rasping action of their glossa before inoculating the food fungus. The extent of this licking varied with the substrate and was influenced by the thickness of surface leaf waxes and by the chemical attractiveness of the substrate.
2. Microscopy and wettability studies showed that licking removes the wax layer present on leaves. It also removes or inhibits micro-organisms present.
3. Chemically de-waxed and decontaminated leaves and ant-licked leaves proved the best substrates for artificially culturing the ant fungus.
4. The process of substrate preparation circumvents some of the normal defence mechanisms of green plants against fungal attack. The ant fungus thus utilizes nutritionally richer resources of green leaves normally available only to specialized parasitic fungi, rather than the nutritionally inferior shed leaves normally available to saprophytic fungi.     

The decision to reject an oviposition site: sequential analysis of the post-alighting behaviour of Delia floralis

Abstract.The post-alighting behaviour of gravid female turnip root fly, Delia floralis (Fallén) (Diptera: Anthomyiidae), was observed in the laboratory, using four plant genotypes differing in antixenotic resistance, to stimulate a range of oviposition-related behavioural events. Analysis of the behavioural sequences of individual female flies suggested that during the post-alighting behaviour of D. floralis , the decision to reject a highly resistant plant was predominantly based on plant cues received during a stationary period immediately after landing on the leaf (the leaf contact phase). Female flies that rejected a plant immediately after the leaf contact phase did so after spending approximately twice as long in the leaf contact phase as those flies that continued to explore the plant. On a plant genotype of intermediate susceptibility, D. floralis females on the stem of the plants increased proboscis extension. The mechanisms involved in early host plant rejection decisions and the possible ecological advantages of such behaviour patterns to female flies seeking suitable oviposition sites are explored. The potential advantages of using detailed studies of individual behaviour sequences to focus studies seeking to elucidate chemical oviposition stimuli on the plant's surface are also discussed.