Two gynandromorphs of Sympetrum striolatum (Charpentier, 1840) (Odonata: Libellulidae)

Two gynandromorphs of the dragonfly Sympetrum striolatum , with different features, are described here, with special emphasis on the genitalic structures.     

Wing morphology and migration status,but not body size,habitat or Rapoport's rule predict range size in North‐American dragonflies (Odonata: Libellulidae)

Understanding why species range sizes vary is important for predicting the impact of environmental change on biodiversity. Here we use a multi‐variable approach in a phylogenetic comparative context to understand how four morphological, two ecological, and two eco‐geographical variables are associated with range size, latitudinal range and longitudinal range in 81 species of North‐American libellulid dragonflies. Our results show that: 1) migratory species and species with a more expanded basal hindwing lobe have a larger range size; 2) opposite to Rapoport's rule, latitudinal range is negatively correlated with mid‐range latitude; 3) longitudinal range is predicted by wing morphology and migration; 4) body size and larval habitat are not correlated with range size, latitudinal range or longitudinal range. These results suggest that dispersal‐related traits, such as wing shape and migratory status, are important factors in predicting the range size of libellulid dragonflies. In addition, the reverse Rapoport's rule suggests that more northern‐centred species might be more specialized than more southern‐centred species. We suggest that the variables predicting range size are likely imposed by taxon‐specific morphological, ecological, physiological and behavioural traits. Taxon‐specific knowledge is thus necessary to understand the dynamics of range sizes and is important to implement successful restoration and conservation plans of threatened species.     

Temporal priority and intra-guild predation in temporary waters: an experimental study using Namibian desert dragonflies

Abstract. 1. Intra-guild predation between early larval instars of two co-existing dragonflies, Sympetrum fonscolombii and Trithemis kirbyi , was investigated with respect to temporal advantage and growth. Three situations were simulated experimentally: (1) Sympetrum fonscolombii began development 11 days before T. kirbyi . (2) Trithemis kirbyi began development 11 days before S. fonscolombii . (3) Both species began on the same day.
2. With a temporal advantage of 11 days to the second species, the resulting larval density of the respective first species was significantly higher than that of the second species.
3. Without a temporal advantage, the survival of S. fonscolombii was higher than that of T. kirbyi , and S. fonscolombii had a larger size due to faster growth than T. kirbyi . Hence, it is assumed that survival depended on early oviposition as well as on larval growth.
4. To test the relevance of the laboratory results, observations at artificial ponds in the Namibian semi-desert were conducted. Trithemis kirbyi was the first species colonising these ponds while S. fonscolombii arrived 15 days later. In field samples, many more Trithemis larvae than Sympetrum larvae were found, a pattern similar to the laboratory experiments in which T. kirbyi enjoyed a temporal advantage.     

Body size and social dominance influence breeding dispersal in male Pachydiplax longipennis (Odonata)

1. Dispersal behaviour can be affected by an individual's phenotype, by the environmental or social context they experience, and by interactions between these factors. Differential dispersal propensities between individuals may also be an important modifier of functional connectivity between populations. To assess how a key trait, body size, affected both social interactions and dispersal behaviour, this study examined the relationship between body size, antagonistic interactions, and breeding dispersal in male dragonflies (Pachydiplax longipennis) across a seasonal decline in adult body size. 2. During a seasonal peak in male body size in this study, dispersers were smaller than non‐dispersers. Later in the season, the body size of dispersers and non‐dispersers did not differ. 3. Focal observations found that body size was related to competitive dominance, large males engaged in aggressive chases more often and smaller males were more frequently pursued. 4. These results indicate that when large males were present, small males were more likely to disperse suggesting that dispersal is a tactic adopted by social subordinates in this context. If breeding dispersal is typically undertaken by subordinate males, functional connectivity between populations may be less than estimated from absolute dispersal rates.     

Microhabitat selection as an antipredator strategy in the aquatic insect Pachydiplax longipennis Burmeister (Odonata: Libellulidae)

Summary An investigation of the larval dragonfly fauna associated with the plant, Sagittaria platyphylla, was conducted in a small pond. Despite the presence of several larval anisopteran species in the pond, only Pachydiplax longipennis larvae were found on Sagittaria plants. A study of the microspatial distribution of P. longipennis larvae on S. platyphylla indicated that larvae use the various regions of a plant in a highly non-random fashion. Larvae show a strong preference for the leaf axil area. A generalized predator, the bluegill sunfish (Lepomis macrochirus), was allowed to selectively eat either of two larvae placed in various plant regions. This experiment indicated that larvae in a leaf axil area were significantly less susceptible to bluegill predation than larvae positioned in other plant regions. The microspatial distribution of starved larvae revealed that larvae with high hunger levels occupied the leaf axil area significantly less than well fed larvae, suggesting 1) larvae do not use these regions as feeding sites, and 2) high hunger levels may induce a behavioral shift in habitat use, with starved larvae forced into areas of high predation risk by the need to fulfill nutritional requirements.     

实验增温对藏北高寒草甸植物繁殖物候的影响

全球气候变暖对高寒和极地地区的植物物候产生强烈的影响。该研究主要关注增温条件下藏北高寒草甸不同功能型植物繁殖时间(生殖物候)的改变。实验采用开顶箱式增温方法, 对3个主要功能群浅根-早花、浅根-中花和深根-晚花植物的现蕾、开花、结实时间进行观测。研究结果表明: (1)增温导致了土壤水分胁迫, 显著推迟了浅根-早花植物高山嵩草(Kobresia pygmaea)的繁殖时间; (2)增温显著提前了浅根-中花植物钉柱委陵菜(Potentilla saundersiana)和深根晚花植物紫花针茅(Stipa purpurea)和矮羊茅(Festuca coelestis)的繁殖时间; (3)增温没有显著影响浅根-中花植物楔叶委陵菜(Potentilla cuneata)和深根-晚花植物无茎黄鹌菜(Youngia simulatrix)的繁殖时间; (4)增温缩短了3种类型植物的开花持续时间。这些结果显示增温改变了藏北高寒草甸群落中多数物种的繁殖时间, 这预示着在未来更热更干的生长季, 青藏高原高寒草甸系统的植物物候格局可能会被重塑。     

DNA Taxonomy and the identification of immature insect stages: the true larva of Tauriphila argo (Hagen 1869) (Odonata: Anisoptera: Libellulidae)

For many insect taxa, larval morphology plays a decisive role in various fields like taxonomy, phylogeny or ecology. However, species identification is usually based on imaginal characters and the identification of larvae depends upon an established link to unequivocally identified imagines. This taxonomic correspondence of larvae and imagines is far from being established in many odonate species. We have employed a molecular approach to link larval and adult specimens in Tauriphila argo (Hagen, 1869). The sequenced mt SSU gene fragments of the reared female, supposedly a T. argo female, and a clearly identified male specimen of the species were identical. However, the larva of the reared female clearly differed from the described T. argo larva, previously matched to the species. From this observation, we conclude that the previously described larva of T. argo does not belong to this species because of too many phenotypic differences that far exceed the generally observed intraspecific variation.

It can be foreseen that the molecular approach will prove to be effective in identifying unknown larvae in many insect species. Additionally, the discrimination of sibling species or the linkage of allotypes and holotypes will become feasible with this approach.     

Larval morphology and range of three West Asiatic species of the genus Onychogomphus Selys, 1854. (Insecta: Odonata)

The previously unknown larvae of O. assimilis (Schneider, 1845) and O. lefebvrei (Rambur, 1842) are described, while that of O. flexuosus (Schneider, 1845) is redescribed, all from material from SW. Turkmenistan and Tajikistan. Their distributions extend from the eastern mediterranean to central-west Asia and are mapped. A differential diagnosis and key to the identification of the larvae of four central Asiatic species of the genus Onychogomphus is given.     

Energy expenditure and food intake of territorial male Pachydiplax longipennis (Odonata: Libellulidae)

ABSTRACT.

• 1 Field observations of males of the dragonfly, Pachydiplax longipennis (Burmeister), were used to determine how individuals of this species allocate energy to different activities during territory occupancy.
• 2 The effects of biological and physical factors on the species’daily activity pattern were examined. The proportion of time spent in flight was independent of temperature but increased asymptotically with increasing population density.
• 3 Measurements of assimilation efficiency and the quantity of faeces produced per day were used to calculate daily intake of food. An independent estimate of food consumption was derived from data on gut contents and clearance rate.
• 4 Food intake appears to exceed only slightly the energy required to maintain a territory, with little available for other activities. The activity pattern may be determined in part by the amount of energy available to individuals.

     

Effect of open-field experimental warming on the leaf phenology of oriental oak (Quercus variabilis) seedlings

Aims An open-field warming experiment enables us to test the effects of projected temperature increase on change in plant phenology with fewer confounding factors and to study phenological response to temperature ranges beyond natural variability. This study aims to (i) examine the effect of temperature increase on leaf unfolding and senescence of oriental oak (Quercus variabilis Blume) under experimental warming and (ii) measure temperature-related parameters used in estimating phenological response to temperature elevation.Methods Using an open-field warming system with infrared heaters, we increased the air temperature by ~3°C in the warmed plots compared with that of the control plots consistently for 2 years. Leaf unfolding and senescence dates of Q. variabilis seedlings were recorded and temperature-related phenological parameters were analysed.Important findings The timing of leaf unfolding was advanced by 3–8 days (1.1–3.0 days/°C) and the date of leaf senescence was delayed by 14–19 days (5.0–7.3 days/°C) under elevated air temperatures. However, the cumulative degree days (CDD) of leaf unfolding were not significantly changed by experimental warming, which suggest the applicability of a constant CDD value to estimate the change in spring leaf phenology under 3°C warming. Consistent ranges of advancement and temperature sensitivity in spring phenology and delayed autumn phenology and proposed temperature parameters from this study might be applied to predict future phenological change.     

Growth of Odontesthes bonariiensis (Atherinidae) larvae feeding on suboptimal zooplankton densities

Synopsis In this study we investigate the effect of food availability (zooplankton biomass) on the growth of Odontesthes bonariensis (Atherinidae) larvae. The larvae were stocked in four 45 m² outdoor tanks at relatively high densities (100 and 200 larvae m^–2). Because of the high stocking densities, the zooplankton biomass was depleted in all tanks. However, the patterns of food limitation, and particularly periods of severe food shortage, differed in tanks stocked at different densities. We could therefore, observe the effect of food limitation in larvae that differed in weight and age. The effects of variables suspected to influence O. bonariensis growth rates (age and weight of larvae, available zooplankton biomass, mean individual weight of available preys, total ingested prey weight, and mean weight of ingested preys) were investigated using standard multiple regression methods, and a model assuming: (1) an allometric relationship between maximum growth rates and weight of larvae, and (2) an inverse relationship between growth depression and the available zooplankton biomass. Both methods were consistent in showing that only the weight of larvae, and the availability of zooplankton prey had significant effects on the growth of O. bonariensis. The model's results additionally suggest that, if the observed growth rates are scaled by the maximum growth rate corresponding to the larva weight, the effect of zooplankton biomass is largely independent of age and weight of larvae.     

Influences on variation in territorial tenures of male white-faced dragonflies (Leucorrhinia intacta) (Odonata: Libellulidae)

Some individuals in species with extended periods of territorial occupancy may change territory locations within a single bout of territorial activity. Length of occupancy of mating territories among males in a local population of white-faced dragonflies (Leucorrhinia intacta) varied from more than 6 h to 15 min or less. Males with short tenures often established territories in several locations on the pond during a day. Several hypotheses have been proposed to explain shifting territorial sites rather than remaining in a single site during one bout of territoriality. We attempted to test the hypothesis that males shift to leave low-quality sites. Site quality may be affected by costs of defense in relation to intruder rate and the mating benefits of holding the territory. To test whether variation in these possible effects of benefits and costs of territoriality influenced tenure, we manipulated local quality of oviposition substrate and perch density. The quality of oviposition substrate, but not perch density, influenced both potential benefits and costs of territoriality. Female density was higher in areas with good substrate, but so were rates of males intruding into the territories, rates of chasing by territorial males, and local density of territorial males. More matings occurred in areas with good substrate, but among males with tenures of 15 min or more, mating success per male and tenure lengths did not differ statistically among treatments. Defense costs were low for all treatments and perhaps were not an important influence on tenure duration. Territorial males in this population probably adjusted local density to expected mating success by initial choice of site rather than by varying tenure length. Variation in tenure length at a site resulted, in part, from stochastic external factors, such as predation attempts.     

Effects of crude oil on survival,morphology, and anatomy of two aquatic macrophytes from the Amazon floodplains

Aquatic herbaceous macrophytes grow in profusion in the Amazon fertile varzea floodplains. A large number of species occur but only a few are particularly abundant, supporting food chains, contributing substantially to carbon and nutrient cycles. Their growth and role in the ecosystem depend, among other, on its life cycles and habits, floating or semi-aquatic. Although in the last decades, petroliferous activity intensified in the Central Amazon region and so did oil spills, the effect of petroleum on the native aquatic plants is unknown. The present study was designed to test experimentally the survival and morpho-anatomical modifications of the free floating water hyacinth Eichhornia crassipes and the semi-aquatic grass Echinochloa polystachya to 10 different concentrations of crude oil. Higher concentrations of crude oil caused the mortality in both species; however, lethal dose (LD₅₀) values showed that E. polystachya was more sensitive than E. crassipes. Despite the higher tolerance of E. crassipes, the inhibition of root and leaf growth as well as anatomical modifications in leaves were registered in higher concentrations. Additionally, the oil caused a reduction in leaf numbers in both species. Although mortality of the floating species was lower, it may increases over time, since important alterations in morphology and anatomy occurred. These results show that oil spills in the Amazon varzea can cause severe alterations in the aquatic flora and in the floodplain dynamics.     

The mating system ofBrechmorhoga pertinax (Hagen): The evolution of brief patrolling bouts in a “territorial” dragonfly (Odonata: Libellulidae)

Males of Brechmorhoga pertinax(Hagen) patrolled and competed for narrow strips of stream edge, 2–8 m long, containing a few barely submerged patches of sandy or fine gravel substrate. These scarce patches were used as oviposition sites by females that usually, but not always, mated with a patrolling male just prior to egg-laying. Females visited the oviposition sites evenly throughout the day from 0830 to 1430 but male activity rose until midday and then declined sharply after 1330. Some gravid females refused to mate in the midafternoon despite male efforts to copulate with them. The average patrolling bout by a male lasted less than 15 min, with defenders usually leaving immediately after one or two aggressive interactions with intruders or leaving voluntarily without apparent cause. Many individuals returned for additional bouts of patrolling at the same site, but the total daily period of patrolling for any one individual almost never exceeded 1 h.     

Floral phenology and morphology of black cottonwood,Populus trichocarpa (Salicaceae)

Seasonal changes in the development of reproductive structures are documented for Populus trichocarpa Torr. and Gray. Buds were collected and studied from several trees for a 2-yr period, but to maintain a congruous phenology, representative structures from only one male and one female tree are presented. Collected tissues were fixed, dehydrated, embedded in wax, sectioned, and differentially stained. The development of reproductive meristems begins early in the spring, before leaves emerge. However, the anatomy of male and female flowers is virtually indistinguishable until late spring. The structures of the gynoecium develop in about 2 wk, then continue to enlarge through the summer and autumn until the trees become dormant. The unilocular ovary consists of usually three, but sometimes four carples. Stamen development begins in the center of a disk-shaped meristematic region and proceeds centrifugally. Megasporogenesis and microsporogenesis take place late in the winter, approximately 2 wk before anthesis. Dissection of mature flowers revealed 30–50 seeds per capsule on female trees and 40–60 stamens on male trees. When compared to most other Populus species, P. trichocarpa has a relatively large number of reproductive structures.     

Effects of temperature on the development and survival of an endangered butterfly, Shijimiaeoides divinus barine (Leech) (Lepidoptera: Lycaenidae)

The effects of temperature on the development and survival of Shijimiaeoides divinus barine were examined in the laboratory in 2008. The eggs and larvae were reared at temperatures of 15, 17.5, 20, 25, 30 and 35°C with a long-day photoperiod of 16 h light : 8 h dark (16L : 8D). The highest hatchability of eggs was 88.0% at 20°C, but hatchability at high temperatures of 30 and 35°C was 30 and 0%, respectively. The lowest and highest survival rates from the first to third instar were 18.8% at 15°C and 76.9% at 20°C. Few deaths were observed after the fourth instar. The shortest developmental periods of the eggs and larvae were 4.0 and 15.8 days at 30°C, and the durations of the egg and larval stages increased significantly as the temperature decreased. The developmental zero and thermal constants were 9.6°C and 82.6 degree–days for the egg stage, and 10.7°C and 306.8 degree–days for the larval stage. The developmental period of the natural population of S. divinus barine in Azumino City, Nagano Prefecture was calculated using the developmental zero, thermal constants and Azumino City temperature data.     

Early warning signals detect critical impacts of experimental warming

Earth's surface temperatures are projected to increase by ~1–4°C over the next century, threatening the future of global biodiversity and ecosystem stability. While this has fueled major progress in the field of physiological trait responses to warming, it is currently unclear whether routine population monitoring data can be used to predict temperature‐induced population collapse. Here, we integrate trait performance theory with that of critical tipping points to test whether early warning signals can be reliably used to anticipate thermally induced extinction events. We find that a model parameterized by experimental growth rates exhibits critical slowing down in the vicinity of an experimentally tested critical threshold, suggesting that dynamical early warning signals may be useful in detecting the potentially precipitous onset of population collapse due to global climate change.     

The effects of parasitic water mite larvae (Arrenurus spp.) on zygopteran imagoes (Odonata)

Arrenurus larvae, ectoparasitic on zygopteran imagoes, attach to the host's cuticle and tear it to obtain the host's tissue fluids. Within the host's epidermis, each larval mite produces a feeding device, the stylostome, a narrow gelatinous resilient blind sac. Heavy mite infestation brings about several wounds in close proximity, accompanied by loss of more or less extensive areas of the epidermis. Despite wound repair by congregating hemocytes, local lack of epidermis seems to enfeeble the host, presumably owing to desiccation. Heavily mite-loaded zygopterans have lost the typical agility and are easily caught. A mite-induced mortality seems to exist in zygopteran populations; the infestation contributes to reduced longevity. The study of formation and decline of the arrenurid stylostome in zygopterans renders it possible to trace cellular defence reactions under natural conditions. Most stylostomes seem to thwart the ability of the host to recognize them as foreign bodies. The host's defence appears as a two-step reaction: (1) initial hemolymph clotting and deposition of melanin associated with aggregating hemocytes at the penetration site, (2) occasional subsequent melanization and cellular encapsulation of the stylostome.     

Effects of environmental factors on survival, growth, and production of American shad larvae

Episodic increases in temperature of 5°C above 20° C, over 48 h or declines in pH of 1·0 unit from pH 7·0 reduced survival of yolk-sac and feeding-stage larvae of American shad Alosa sapidissima . Over 16 days all measures of survival, growth, and production were more favourable at each higher temperature in the 15–25° C range. More favourable responses were also obtained at the higher prey level (500 v . 50 Artemia nauplii l^-1) and at the higher pH (7·5 v . 6·5). Combinations of high temperature and high prey levels, at pH 7·5, led to highest larval production. Little growth or production occurred at 15° C, regardless of pH or prey level. The effect of pH was strong with respect to survival, but weak with respect to growth. In attempts to restore American shad populations by larval stocking, release times and sites can be critical to optimize survival and eventual returns. Releases of larvae potentially will be most effective when made at temperatures >20° C, pH>7·0, and prey levels >50 1^-1. These conditions are most likely to occur in Maryland tributaries of Chesapeake Bay between mid-May and early June.