Contribution of anadromous fish to the diet of European catfish in a large river system

Many anadromous fish species, when migrating from the sea to spawn in fresh waters, can potentially be a valuable prey for larger predatory fish, thereby efficiently linking these two ecosystems. Here, we assess the contribution of anadromous fish to the diet of European catfish (Silurus glanis) in a large river system (Garonne, southwestern France) using stable isotope analysis and allis shad (Alosa alosa) as an example of anadromous fish. Allis shad caught in the Garonne had a very distinct marine δ¹³C value, over 8‰ higher after lipid extraction compared to the mean δ¹³C value of all other potential freshwater prey fish. The δ¹³C values of European catfish varied considerably between these two extremes and some individuals were clearly specializing on freshwater prey, whereas others specialized on anadromous fish. The mean contribution of anadromous fish to the entire European catfish population was estimated to be between 53% and 65%, depending on the fractionation factor used for δ¹³C.     

Parasitoid-induced mortality of Araneus omnicolor (Araneae, Araneidae) by Hymenoepimecis sp. (Hymenoptera, Ichneumonidae) in southeastern Brazil

All species included in the Polysphincta genus-group develop as ectophagous parasitoids of active spiders, killing their hosts prior to pupation. However, little information regarding natural history and ovipositing behavior of most species are available. In this study we inspected 85 webs of Araneus omnicolor to evaluate the frequency of parasitism and host size preferences of the wasp Hymenoepimecis sp. We also described the web characteristics of normal and parasitized spiders and the wasp ovipositing behavior. About 41% of the adult females of A. omnicolor inspected were parasitized. The highest incidence of parasitism was observed among relatively small females while no egg or larva was found in large individuals. Araneus omnicolor builds a strong web composed of an orb and barrier threads, where the spider rests within a curled leaf. The parasitoid larva builds its cocoon within this refuge, and modified cocoon webs were not observed. The ovipositing behavior of Hymenoepimecis sp. was very similar to that of Hymenoepimecis argyraphaga parasitizing Leucauge argyra, including the position of the sting, the killing of a previously attached larva, and the expelling of the egg from the base of the ovipositor.     

Density and nutritional condition of carabid beetles in wildflower areas of different age

Density and nutritional condition of the five carabid beetle species Agonum mülleri, Anchomenus dorsalis, Anisodactylus binotatus, Pterostichus vernalis and Poecilus cupreus was studied. Carabids were caught in sixteen 1–4-year-old wildflower areas, identified and counted, their nutritional condition was calculated and calculations were related to habitat parameters (i.e. wildflower area age, vegetation cover, soil water content, habitat size, surrounding landscape composition) and sex.Whereas the number of Anisodactylus binotatus caught responded positively to succession in wildflower areas, A. mülleri numbers tended to decrease and the other three species were unaffected. In a stepwise multiple regression species affiliation, sex and age of wildflower area explained together 98.5% of the variance in the pooled nutritional condition of Anchomenus dorsalis, Anisodactylus binotatus, A. mülleri and P. vernalis. Age of wildflower area alone explained 61.7% of the variance and age increased the nutritional condition of carabids. Correspondingly, nutritional condition of Poecilus cupreus was positively correlated with the age of wildflower area. Overall, the nutritional condition of the carabid assemblage studied increased from the first to the second year and then remained stable. To keep the proportion of 1-year-old wildflower areas low, wildflower areas should therefore be maintained for several years to improve the life conditions of carabid beetles and to enhance their beneficial effects in agroecosystems.     

Community fire use,resource change,and livelihood impacts: The downward spiral in the wetlands of southern Sumatra

Fire is an important community wetland management tool in Indonesia, but its increasing use in the wetlands of southern Sumatra is degrading the landscape and diminishing household incomes and livelihood options. We studied evolving community land and fire use, resource and livelihood impacts on two sites of roughly 250 km² each using satellite image analysis and biological and socio-economic surveys. Uncontrolled fire use expanded over time in relation to sonor or swamp rice cultivation, logging, fishing, grazing, and annual cropping on drained wetlands. As a result, most of the landscape has been subject to repeated fires of varying intensities, more extensive in El Niño years. Direct burning by companies played a smaller transitory role in fire ignition over the two decades. But company activities and other large-scale developments contributed to expanding community fire-based land use by bringing in more people, improving access to remote wetlands or making them more flammable. Widespread, repeated fires have transformed the landscape from mature high swamp forests to uniform stands of fire-resistant Gelam (Melaleuca cajuputi) forests and thickets, open savannas and grasslands. These new types of land cover are also degrading. Local communities have rapidly adapted to the changing resources and new opportunities. Logging and fishing declined in importance, and sonor and harvesting of Gelam expanded. But resource depletion has led to falling incomes and fewer livelihood options. The impacts extend beyond local areas as workers migrate into neighbouring forests to extract resources. Large-scale developments, community fire-based management practices and landscape transformation are spreading from accessible to formerly more remote wetlands.     

Intrageneric differences in the four stereoisomers of stenusine in the rove beetle genus, Stenus (Coleoptera, Staphylinidae)

Most species of the rove beetle genus Stenus employ the spreading alkaloid stenusine as an escape mechanism on water surfaces. In the case of danger, they emit stenusine from their pygidial glands, and it propels them over the water very quickly. Stenusine is a chiral molecule with four stereoisomers: (2′R,3R)-, (2′S,3R)-, (2′S,3S)-, and (2′R,3S)-stenusine. The percentile ratio of these four isomers is only known for the most common species of the genus: Stenus comma. With the intention of determining the stereoisomer ratios of five additional species from the two subgenera, Stenus and Hypostenus, we used GC/mass spectrometry measurements with a chiral phase. The results showed that the ratio differs among the genus. These findings can be a basis for chemotaxonomy. It is also possible that the biological function of stenusine, e.g., as antibiotic or fungicide, varies with changing stereoisomer composition.

Conditions controlling the onset of breeding migration of the Japanese mountain stream frog, <Emphasis Type="Italic">Rana sakuraii</Emphasis>

I studied the conditions controlling the timing of breeding migration of the Japanese mountain stream frog Rana sakuraii, an explosive breeder, over 9 years (1992, 1993 and 1999–2005). I analysed two factors: the daily cumulative temperature (DCT) during hibernation and the triggering temperature on the day of migration onset. Frogs hibernated in shallow running water in streams in December. A total of 53,155 breeding migrating adults were captured by traps. Every year, breeding migration was induced by a rise in daily maximum water temperature to about 5°C. However, its date was limited to 1 February at the earliest, and the onset needed a DCT (from 20 January, using 3°C as the threshold for daily effective temperature) of at least about 15°C. Earlier (e.g. in mid- or late January), even if the maximum temperature rose to 5–8°C, migration did not begin. Moreover, even in early February, if the maximum temperature rose to 5°C, if it had been too cold in January and the DCT was low, migration would not begin until mid- or late February. Thus, the earliest date of readiness for migration varied from 1 February to mid-February, depending on the winter DCT. Logistic regression analyses showed that both factors, the DCT and the daily temperature, were significant. I propose that in temperate-zone amphibian explosive breeders, both the passing of an essential number of days and an essential DCT during hibernation are prerequisites for the onset of breeding migration before the daily temperature rises to the threshold.     

Convergent evolution in the antennae of a cerambycid beetle, <Emphasis Type="Italic">Onychocerus albitarsis,</Emphasis> and the sting of a scorpion

Venom-injecting structures have arisen independently in unrelated arthropods including scorpions, spiders, centipedes, larval owlflies and antlions, and Hymenoptera (wasps, ants, and bees). Most arthropods use venom primarily as an offensive weapon to subdue prey, and only secondarily in defense against enemies. Venom is injected by biting with fangs or stinging with a specialized hypodermic structure used exclusively for the delivery of venom (usually modified terminal abdominal segments). A true sting apparatus, previously known only in scorpions and aculeate wasps, is now known in a third group. We here report the first known case of a cerambycid beetle using its antennae to inject a secretion that causes cutaneous and subcutaneous inflammation in humans. Scanning electron microscopy revealed that the terminal antennal segment of Onychocerus albitarsis (Pascoe) has two pores opening into channels leading to the tip through which the secretion is delivered. This is a novel case of convergent evolution: The delivery system is almost identical to that found in the stinger of a deadly buthid scorpion.     

Shade tree management affects fruit abortion, insect pests and pathogens of cacao

The mortality of cacao fruits caused by early fruit abortion or insect and pathogen attacks was investigated in differently managed agroforestry systems in Central Sulawesi, Indonesia. Nine agroforestry systems shaded by three different types of tree stands were selected, which represented a decrease in structural heterogeneity: forest remnants, diverse planted trees and one or two species of planted leguminose trees. After standardized manual cross-pollination, the development of 600 fruits on 54 trees (6 trees per agroforest) was followed during 18 weeks of fruit development. In total, 432 of all fruits were lost before maturity, which seriously undermined yields. The proportion of harvested fruits per tree (overall average: 27 ± 4%) was not affected by canopy type. Although shade cover did not have a significant effect, losses due to fruit abortion were most likely under forest shade, where nitrogen-fixing leguminose shade trees were absent. Fruit losses due to pathogenic infections and insect attacks increased with the homogenization of the agroforests, supporting the hypothesis that agricultural homogenization increases risks of pest outbreaks. In conclusion, shade management may be improved to increase yields from cacao using highly diversified natural shade agroforestry systems.     

N and P dynamics in the litter layer and soil of Mexican semi-arid forests, state of Morelos

In central Mexico, it is common for farmers to retain useful trees in abandoned lands after maize cultivation, creating a park-like landscape of scattered trees for extensive livestock grazing, among other land uses (mature forests, secondary forests, and livestock grazing in secondary forests). Among these trees Acacia cochliancantha and Ipomoea arborescens are the most common species associated with this land use in the region. The objective of this study was to assess the effects of both tree species on soil N and P recycling. To this end, we measured N and P concentrations in leaves of both species; and the seasonal N and P (total and dissolved) content in the litter, and total N and P, inorganic N, and bicarbonate-extractable-P concentrations, and the N transformations in the soil, in samples collected under crown of Acacia and Ipomoea and in open areas. Trees of different species varied in their capacity to cycle N. The leaves of Acacia were richer in N than those of Ipomoea (29.7 and 25.0 mg N g⁻¹, respectively), and nutrient resorption was higher in leguminous trees than in Ipomoea (by 20% in the case of N, and 35% in the case of P). Acacia trees had higher effects on soils than Ipomoea trees, like consistent increases of N concentrations (by 30% in the case of total N, and by 50% in the case of inorganic N) and transformations (N mineralization and nitrification in rainy season increases by a factor of 20 and 36, respectively). On the other hand, Ipomoea produced senescent leaves and accumulated forest litter with less P concentration (0.8 and 0.7 mg P g⁻¹, respectively) in relation to Acacia (senescent leaves: 1.3 mg P g⁻¹; litter: 1.1 mg P g⁻¹), reflecting the lower availability of the nutrient in the soil. The total litter N and P pools decreased in the rainy season under crown of both species, as the dissolved P pool did. The total soil N and P concentrations did not change with sampling season. However, potential N transformations and bicarbonate P under both species were higher in dry season than in rainy season samples. Comparison with other land uses in the region suggests that the Acacia–Ipomoea system cycles low quantity of nutrients, but there are no notable differences in the availability of P in the soils. These results demonstrate that scattered trees improve the N and P cycling following the discontinuation of agricultural practices, and the effects will vary depending on the tree species.     

Epicuticular wax of large and small white butterflies,<Emphasis Type="Italic"> Pieris brassicae</Emphasis> and<Emphasis Type="Italic"> P. rapae crucivora</Emphasis>: qualitative and quantitative comparison between diapause and non-diapause pupae

We compared the quantity and quality of the epicuticular wax of diapause and non-diapause pupae in two closely related Pieris species, P. brassicae and P. rapae crucivora. Main components of their epicuticular wax were identified as hydrocarbons. In P. brassicae, more than 95% of hydrocarbons were saturated regardless of whether the pupae were in diapause or not. In P. rapae crucivora, 93% of hydrocarbons were saturated in non-diapause pupae whereas in diapause pupae 41% were saturated and 59% unsaturated. From measurements of body surface area by nuclear magnetic resonance microimaging, we calculated the average thickness of the wax layer. The thickness in diapause and non-diapause pupae of P. brassicae was 800 and 160 nm, respectively. In P. rapae crucivora, the thickness was 195 nm in diapause and 11 nm in non-diapause. This is the first report to clarify the compositional difference in epicuticular wax between diapause and non-diapause pupae.     

Bee-hawking by the wasp, <Emphasis Type="BoldItalic">Vespa velutina</Emphasis>, on the honeybees <Emphasis Type="BoldItalic">Apis cerana</Emphasis> and <Emphasis Type="BoldItalic">A</Emphasis>. <Emphasis Type="BoldItalic">mellifera</Emphasis>

The vespine wasps, Vespa velutina, specialise in hawking honeybee foragers returning to their nests. We studied their behaviour in China using native Apis cerana and introduced A. mellifera colonies. When the wasps are hawking, A. cerana recruits threefold more guard bees to stave off predation than A. mellifera. The former also utilises wing shimmering as a visual pattern disruption mechanism, which is not shown by A. mellifera. A. cerana foragers halve the time of normal flight needed to dart into the nest entrance, while A. mellifera actually slows down in sashaying flight manoeuvres. V. velutina preferentially hawks A. mellifera foragers when both A. mellifera and A. cerana occur in the same apiary. The pace of wasp-hawking was highest in mid-summer but the frequency of hawking wasps was three times higher at A. mellifera colonies than at the A. cerana colonies. The wasps were taking A. mellifera foragers at a frequency eightfold greater than A. cerana foragers. The final hawking success rates of the wasps were about three times higher for A. mellifera foragers than for A. cerana. The relative success of native A. cerana over European A. mellifera in thwarting predation by the wasp V. velutina is interpreted as the result of co-evolution between the Asian wasp and honeybee, respectively.     

Germination of Deyeuxia angustifolia as affected by soil type, burial depth, water depth and oxygen level

Deyeuxia angustifolia is a dominant species in the Sanjiang Plain, the largest freshwater marsh wetland in China. However, this species has declined because of great environment changes. In the effects of sea-level rise and greenhouse gas, magnitude and frequency of flood and rate of deposit in wetland increased greatly. Thus, in this paper, effects of soil environment (soil type, burial depth, water depth and oxygen concentration) on seed germination of D. angustifolia were investigated. Both soil type and burial depth affected seedling emergence. Seedlings emerged through 1-, 2-, 4-mm sand, and at 1-and 2-mm mud. Regardless of soil, seedling emergence time increased and emergence percentage decreased with increasing burial depth. For example, seedlings started to emerge on the 4th day and the final emergence percentage was 30% when covered with1-mm mud, whereas the initial emergence time was on the 6th day and the final emergence percentage was only 8% when covered with 2-mm mud. At the same burial depth, emergence percentage was higher in sand than in mud. Increasing water depth inhibited seed germination. Germination percentage in 2-cm water level (20%) was 1.2 times higher than that in 12-cm water level (9%). Oxygen concentration also affected germination. In the 21% oxygen concentration, germination was started on the 2nd day and the germination percentage was 36%, while seed started to germinate on the 4th day and the germination percentage was only 3% at the 7% oxygen concentration. These data indicate that seed germination of D. angustifolia was highly sensitive to soil type, burial depth, water depth, oxygen concentration, and these responses may be an explicit indication of maladjustment to environment changes, and an important reason accounting for the decline of this species in the Sanjiang Plain.     

Host intra-clutch variation,cuckoo egg matching and egg rejection by great reed warblers

Prevailing theory predicts that lower levels of intra-clutch variation in host eggs facilitate the detection of brood parasitism. We assessed egg matching using both human vision and UV-VIS spectrophotometry and then followed the nest fate of great reed warblers naturally parasitised by European cuckoos. Rejection was predicted by the following three variables: matching between cuckoo and host eggs on the main chromatic variable defined by principal components analysis of the egg spectra (which has a strong loading in the UV); the number of host eggs in the nest; and human estimates of intra-clutch variation. The first variable is not correlated to human estimates of matching, which do not predict rejection. In line with another recent study, rejection rates were predicted by higher levels of intra-clutch variation in the host eggs, suggesting that higher rather than lower levels of intra-clutch variation can facilitate the discrimination of cuckoo eggs by hosts. We suggest that the importance of intra-clutch variation is context dependent, with intra-clutch variation being important when there is good matching between the host and the cuckoo eggs. Our results also suggest that both spectrometric and human visual assessments of egg matching and intra-clutch variation are prudent: the former provide the best method of estimating reflectance variation, whereas the latter include some assessment of patterns of maculation.     

Improvement of detection method of Cryptosporidium and Giardia in reclaimed water

Cryptosporidium and Giardia are two typical species of pathogenic protozoans that seriously endanger water quality. Previous works indicated that detection of Cryptosporidium and Giardia with modified United States Environmental Protection Agency (USEPA) method-1623 using a membrane filtration-elution for sample concentration attained better recovery and lower cost compared to the USEPA method-1623. Several improvements of membrane filtration-elution step as well as immunomagnetic separation (IMS) steps were investigated and an optimized method for detection of Cryptosporidium and Giardia in wastewater reclamation system was recommended in this paper. The experimental results show that an overnight soak of the membrane after scraping and vortex agitation before elution could enhance and stabilize the recovery. Increasing turbidity to 4 NTU by adding kaolin clay before filtration could effectively improve the recovery of low-turbidity water. Washing the concentrate after centrifugation and twice acid dissociation both reduced the impact of water quality to protozoan recovery. Protozoans in different water samples were determined by this optimized method, and the recovery of Cryptosporidium and Giardia were above 70% and 80% respectively, much higher than the acceptance of method-1623. __________ Translated from Environmental Science, 2006, 27(12): 2547–2552 [译自: 环境科学]     

Interactive effects of ozone and powdery mildew (Sphaerotheca fuliginea) on bottle gourd (Lagenaria siceraria)

Interacting effects of ozone at 0.05, 0.1 and 0.2 ppm and powdery mildew infection were studied with respect to the growth, flowering and fruit-setting of bottle gourd, and ozone injury, fungal colonization, conidia size and germination. Intermittent exposure in closed-top chambers to ozone at 0.1 or 0.2 ppm, and infection by Sphaerotheca fulginea, each caused significant suppressions of plant growth, flowering and fruit-setting. Fungal colonization was increased by exposures to 0.05 ppm ozone, but decreased by 0.2 ppm ozone. Less browning and necrosis (symptoms of ozone phytotoxicity) appeared on the leaves of mildew-inoculated plants exposed to ozone at 0.1 and 0.2 ppm. Conidia collected from plants exposed to 0.1 and 0.2 ppm were smaller, contained fewer fibrosin bodies and showed poor germination in-vitro. Fumigations with ozone at 0.05 ppm increased the germination of conidia collected from the exposed plants or of the conidia directly exposed to ozone on glass slides in microgas exposure cabinets. Distortion and wall rupturing of the conidia were induced by exposure to ozone at 0.2 ppm for 12 h. Ozone at 0.05 ppm and S. fuliginea jointly suppressed the root and shoot growth of bottle gourd significantly more than the sum of individual effects (synergistic interaction). The fungus infection partially protected the plants from injury by ozone at 0.2 ppm, and exposure to ozone at 0.2 ppm inhibited fungal development. Antagonistic reductions of damage to bottle gourd growth by simultaneous mildew infection and ozone at 0.2 ppm were observed. The study revealed that powdery mildew infection may become severe on bottle gourd grown in areas polluted with mild level of ozone (0.05 ppm) whereas, at 0.1 ppm O₃ or more, the disease will be suppressed.     

Impacts of Climate Change on the Distribution of Larix Spp. and Pinus Sylvestris and Their Climatypes in Siberia

Inter- and intraspecific effects of climate change were assessed for the dominant conifers of Siberia (60–140^∘E and 48–75^∘N): Larix spp. (L. sibirica, L. dahurica, and L. sukaczewii) and Pinus sylvestris . The approach employed a tri-variate (degree-days above 5 ^∘C, degree-days below 0 ^∘C, and a moisture index) estimate of the climatic envelope within which exists the actual ecological distribution of a species and their constituent climatypes (genotypes physiologically attuned to similar environments). Limits of the actual ecological distribution were approximated by reducing the climatic envelope according to effects of permafrost and interspecific competition. Climatypes were mapped within the climatic envelope according to the climatic interval that must separate populations for reasonable assurance of genetic differentiation. This interval was calculated from response functions that related 13-year growth and survival of a species to the difference in climate between the provenance of a climatype and the climate of numerous test sites distributed across Russia. Mapping species' distributions and their climatypes was done for the contemporary climate and for future climates predicted by the HadCM3GGa1 scenario of Hadley Centre. The results showed that if the forests of the future are to reflect the adaptedness of today, the distribution of species will shift and genotypes within species will be redistributed. Some contemporary climatypes are projected to disappear from Siberia while others common elsewhere would evolve. To mitigate these effects, climatypes should be transferred today to the expected future location of their climatic optima, a distance that is likely to approach 700–1200 km for these species.     

First evidence of regular common cuckoo, <Emphasis Type="Italic">Cuculus canorus</Emphasis>, parasitism on eastern olivaceous warblers, <Emphasis Type="Italic">Hippolais pallida elaeica</Emphasis>

Coevolution is defined as specialized relationships between species that lead to a reciprocal evolutionary change. A particularly suitable model system for studying coevolution is the interactions between obligate avian brood parasites and their hosts. The common cuckoo (Cuculus canorus, hereafter cuckoo) is a well-known brood parasite, which utilizes a range of smaller passerines as hosts. However, warblers of the genus Hippolais have rarely been reported as being victims of cuckoos, and furthermore, few data exist on the occurrence of antiparasite defenses in these hosts. In this study, we examined possible host–parasite coevolution between cuckoos and eastern olivaceous warblers (Hippolais pallida elaeica, hereafter olivaceous warblers) in three closely situated areas in northwestern Bulgaria. The olivaceous warbler has never been reported to be a regular cuckoo host. However, the present study, carried out in 2001–2003 shows that the olivaceous warbler is regularly and heavily parasitized by the cuckoo in this area. Parasitism rate was high (26.6%, 34/128) and consistent among years, with some variation between areas. The cuckoo egg mimicry was moderately good, and olivaceous warbler rejection rate of such eggs was 50%. Cuckoo eggs laid in olivaceous warbler nests had a whitish to whitish-green ground color, and the majority appeared to be distinctly different from cuckoo eggs found in other host species in the area. The olivaceous warbler proved to be a rather good host for cuckoos as 20.6% (7/34) of cuckoo eggs laid produced fledglings, a breeding success comparable to other suitable hosts in Europe. This is the first in-depth study of brood parasitism in a warbler of the genus Hippolais, and cuckoos parasitizing olivaceous warblers probably represent a previously unknown gens.     

Plant origin of Okinawan propolis: honeybee behavior observation and phytochemical analysis

Propolis is a natural resinous product collected by honeybees from certain plants. It has gained popularity as a food and alternative medicine. Poplar and Baccharis are well known as the source plants of European and Brazilian propolis, respectively. However, the propolis from Okinawa, Japan, contains some prenylflavonoids not seen in other regions such as Europe and Brazil, suggesting that the plant origin of Okinawan propolis is a particular plant that grows in Okinawa. To identify the plant origin of Okinawan propolis, we observed the behavior of honeybees as they collected material from plants and caulked it inside the hive. Honeybees scraped resinous material from the surface of plant fruits of Macaranga tanarius and brought it back to their hive to use it as propolis. We collected samples of the plant and propolis, and compared their constituents by high-performance liquid chromatography with a photo-diode array detector. We also compared their 1,1-diphenyl-2-picryl-hydrazyl radical scavenging activity. The chemical constituents and biological activity of the ethanol extracts of the plant did not differ from those of propolis. This indicates directly that the plant origin of Okinawan propolis is M. tanarius. S. K. and J. N. contributed equally to this work.     

Dental microwear patterns of extant and extinct Muridae (Rodentia, Mammalia): ecological implications

Extant species of Muridae occupy a wide array of habitats and have diverse dietary habits. Consequently, their dental microwear patterns represent a potential clue to better understand the paleoecology of their extinct relatives, which are abundant in many Old World Neogene localities. In this study, dental microwear is investigated for specimens of 17 extant species of murine and deomyine rodents in order to test the reliability of this method and infer dietary preferences on the fossil species Saïdomys afarensis. This extinct form comes from a mid-Pliocene site (AL 327) located at the Hadar Formation (Ethiopia) known to have delivered many hominid specimens of Australopithecus afarensis. A significant correlation between microwear patterns and diet is detected. Thus, grass, fruit, and insect eaters display, respectively, high amounts of fine scratches, wide scratches, and large pits. Moreover, some aspects of the paleoecology of S. afarensis, including feeding habits, could be assessed in regard to its dental microwear pattern. Indeed, it probably had feeding habits similar to that of living grass eaters. These results concur with the presence of open to woodland areas covered by an herbaceous vegetal layer, including monocotyledons, in the vicinity of this mid-Pliocene locality.     

The energetic costs of stereotyped behavior in the paper wasp, Polistes dominulus

Polistes wasps engage in many behavioral interactions. Although there has been debate over the meaning of these interactions, these stereotypical behaviors can be used to determine a colony’s linear dominance hierarchy. Due to the implicit relationship between behavioral and reproductive dominance, behavioral interactions are commonly used to distinguish the reproductively dominant alpha foundress from the beta foundress. It has been suggested that in order to maintain reproductive control, the alpha foundress is forced to remain at a physiologically constrained activity limit. This, in turn, may allow aggressive interactions to be used as determinants influencing reproductive partitioning between cooperating individuals. Energetic costs can place important limitations on behavior, but the energetic cost of the interactions has not previously been measured. To address this, we measured the CO₂ production of 19 non-nestmate pairs displaying interactive and noninteractive behavior. The rate of energy used during interaction behavior was positively associated with published rankings of aggression. However, our results indicate that interactions are not very energetically costly in Polistes, particularly when compared to the likely cost of foraging. These data suggest that maintaining reproductive dominance is not very energetically expensive for the dominant and that the dominant foundress expends energy at a lower rate than the subordinate foundress. Electronic Supplementary Material  The online version of this article (doi:) contains supplementary material, which is available to authorized users.