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991.
The display of female traits by males is widespread in the animal kingdom. In several species, this phenomenon has been shown to function adaptively as a male mating strategy to deceive sexual rivals (female mimicry). Freshly emerged males of the parasitic wasp Lariophagus distinguendus (Hymenoptera: Pteromalidae) are perceived by other males as if they were females because of a very similar composition of cuticular hydrocarbons which function as a sex pheromone in this species inducing courtship behaviour in males. Within 32 h, however, males deactivate the pheromone and are no longer courted by other males. In this paper, behavioural experiments were performed to test hypotheses on potential costs and benefits associated with the female odour in young males. We did not find any benefits, but demonstrated that young males were significantly more often outrivaled in male-male contests when competing with two older males for a female. Also, young males were significantly more often mounted in homosexual courtship events during these contests. Thus, display of female traits by males is not necessarily beneficial, and in fact, can be disadvantageous. We suggest that these costs have favoured the evolution of the pheromone deactivation mechanism in L. distinguendus males. The function of cuticular hydrocarbons as a female courtship pheromone in L. distinguendus might have evolved secondarily from a primary function relevant for both genders, and the deactivation of the signal in males might have caused a shift of specificity of the chemical signal from the species level to the sex level. 相似文献
992.
A new assemblage of basal dichobunoid artiodactyls from the middle-Eocene Shanghuang fissure fillings includes the diacodexeid
Jiangsudon shanghuangensis gen. and sp. nov., a new species of the lantianine dichobunoid Elaschitotherium, Elaschitotherium crepaturus sp. nov., and an indeterminate suoid which is presently the earliest record of this clade. Diacodexeids are also represented
by two forms provisionally referred to cf. Diacodexis sp. and to an indeterminate Diacodexeidae, respectively. The occurrence of diacodexeids in Shanghuang contrasts with the
early and earliest middle-Eocene chronological range of the family in Europe and North America and suggests that the stratigraphic
range of the family in Asia extends up to the middle Eocene. This may reflect particular habitats in coastal China that may
have been relatively stable during the early and middle Eocene, thus preserving forest-dwelling artiodactyls that became extinct
in the other Holarctic regions. Compared to other supposedly coeval North American, European, and Asian faunas, the Shanghuang
mammalian assemblage is most similar to early Uintan faunas of North America but is also remarkable in recording forms close
to taxa that are characteristic of the Wasatchian and Bridgerian North American Land Mammal Ages. The Irdinmanhan age of the
Shanghuang fauna is supported by the mammalian assemblage recovered from the fissure D, but an Arshantan age cannot be completely
ruled out at this point. Although the Shanghuang assemblage is biased towards preservation of small components of the mammalian
fauna, the Shanghuang fauna provide an important and unique window into the Eocene diversity and early evolution of cetartiodactyls
in eastern Asia. 相似文献
993.
The bumblebee Bombus terrestris is not only an effective pollinator, but also a potential invasive alien species outside its native range. Recently, nearly
30% of queens of the Japanese native species Bombus hypocrita sapporoensis and B. hypocrita hypocrita were estimated to copulate with B. terrestris males in the field, suggesting that indigenous bumblebees could be genetically deteriorated through hybrid production with
the introduced species. In this study, we evaluated hybrid production between the introduced B. terrestris and the indigenous B. hypocrita sapporoensis under laboratory conditions. The hatching rate of eggs derived from interspecific matings was 0% and 8.6% depending on the
direction of the cross, which was significantly lower than that from intraspecific matings of B. terrestris (76.9%) and B. hypocrita sapporoensis (78.9%). Genetic studies using microsatellite markers revealed that both haploid and diploid individuals were present in
the egg stage, whereas all hatched larvae were haploid. In addition, histological studies revealed that eggs derived from
interspecific matings terminated development 2 days after oviposition. These results strongly suggested that eggs derived
from interspecific matings are inviable due to post-mating isolation mechanisms. Mass release of exotic pollinators could
cause serious population declines of native bumblebee species. 相似文献
994.
The Mantophasmatodea is the most recently discovered insect order. The fossil records of all other ‘polyneopteran’ orders
extend far in the past, but the current absence of pre-Cenozoic fossils of the Mantophasmatodea contradicts a long evolutionary
history, which has to be assumed from the morphological distinctness of the group. In this paper, we report the first Mesozoic
evidence of a mantophasmatodean from the Middle Jurassic of Daohugou, Inner Mongolia, China. Furthermore, the new fossil shares
apomorphic characters with Cenozoic and recent Mantophasmatodea, suggesting a longer evolutionary history of this order. 相似文献
995.
Sperm number is often a good predictor of success in sperm competition; however, it has become increasingly clear that, for
some species, variation in probability of paternity cannot be explained by sperm number alone. Intraspecific variation in
ejaculate characteristics, such as the number of viable sperm and sperm longevity, may play an equally important role in determining
fertilization success. Here, we assess variation among ejaculates in three factors that may contribute to fertilization success
(number of sperm per ejaculate, viability, and longevity), in a population of Peron’s tree frog (Litoria peronii). We detected large variation among males in the number of sperm per ejaculate and the proportion of viable sperm within
ejaculates, which could not be explained by variation in either male size or body condition. However, the proportion of viable
sperm released by males increased over the season. Finally, we assessed sperm longevity (proportion viable sperm determined
using a dual-fluorochrome vital dye) at two different temperatures. At 23°C, on average, 75% of sperm remained viable after
2 h, but there were significant differences amongst males with the percentage of viable sperm ranging from 43% to 95%. For
sperm incubated at 4°C, ejaculates varied fivefold in sperm longevity with some males having 50% viable sperm after 5 days.
Our data suggest that ejaculate characteristics (sperm number, viability, and longevity) vary widely in Peron’s tree frog
and may therefore play an important role in determining siring success both in the presence and absence of sperm competition.
We discuss the results in relation to selection on ejaculate traits via natural and sexual selection in this and other amphibians. 相似文献
996.
Flower colour is an important signal used by flowering plants to attract pollinators. Many anthophilous insects have an innate colour preference that is displayed during their first foraging bouts and which could help them locate their first nectar reward. Nevertheless, learning capabilities allow insects to switch their colour preferences with experience and thus, to track variation in floral nectar availability. Manduca sexta, a crepuscular hawkmoth widely studied as a model system for sensory physiology and behaviour, visits mostly white, night-blooming flowers lacking UV reflectance throughout its range in the Americas. Nevertheless, the spectral sensitivity of the feeding behaviour of naïve moths shows a narrow peak around 450 nm wavelengths, suggesting an innate preference for the colour blue. Under more natural conditions (i.e. broader wavelength reflectance) than in previous studies, we used dual choice experiments with blue- and white-coloured feeders to investigate the innate preference of naïve moths and trained different groups to each colour to evaluate their learning capabilities. We confirmed the innate preference of M. sexta for blue and found that these moths were able to switch colour preferences after training experience. These results unequivocally demonstrate that M. sexta moths innately prefer blue when presented against white flower models and offer novel experimental evidence supporting the hypothesis that learning capabilities could be involved in their foraging preferences, including their widely observed attraction to white flowers in nature. 相似文献
997.
Ventral polarization vision in tabanids: horseflies and deerflies (Diptera: Tabanidae) are attracted to horizontally polarized light 总被引:1,自引:0,他引:1
Adult tabanid flies (horseflies and deerflies) are terrestrial and lay their eggs onto marsh plants near bodies of fresh water
because the larvae develop in water or mud. To know how tabanids locate their host animals, terrestrial rendezvous sites and
egg-laying places would be very useful for control measures against them, because the hematophagous females are primary/secondary
vectors of some severe animal/human diseases/parasites. Thus, in choice experiments performed in the field we studied the
behavior of tabanids governed by linearly polarized light. We present here evidence for positive polarotaxis, i.e., attraction
to horizontally polarized light stimulating the ventral eye region, in both males and females of 27 tabanid species. The novelty
of our findings is that positive polarotaxis has been described earlier only in connection with the water detection of some
aquatic insects ovipositing directly into water. A further particularity of our discovery is that in the order Diptera and
among blood-sucking insects the studied tabanids are the first known species possessing ventral polarization vision and definite
polarization-sensitive behavior with known functions. The polarotaxis in tabanid flies makes it possible to develop new optically
luring traps being more efficient than the existing ones based on the attraction of tabanids by the intensity and/or color
of reflected light. 相似文献
998.
The plant surface is the substrate upon which herbivorous insects and natural enemies meet and thus represents the stage for
interactions between the three trophic levels. Plant surfaces are covered by an epicuticular wax layer which is highly variable
depending on species, cultivar or plant part. Differences in wax chemistry may modulate ecological interactions. We explored
whether caterpillars of Spodoptera frugiperda, when walking over a plant surface, leave a chemical trail (kairomones) that can be detected by the parasitoid Cotesia marginiventris. Chemistry and micromorphology of cuticular waxes of two barley eceriferum wax mutants (cer-za.126, cer-yp.949) and wild-type cv. Bonus (wt) were assessed. The plants were then used to investigate potential surface effects on
the detectability of caterpillar kairomones. Here we provide evidence that C. marginiventris responds to chemical footprints of its host. Parasitoids were able to detect the kairomone on wild-type plants and on both
cer mutants but the response to cer-yp.949 (reduced wax, high aldehyde fraction) was less pronounced. Experiments with caterpillar-treated wt and mutant leaves
offered simultaneously, confirmed this observation: no difference in wasp response was found when wt was tested against cer-za.126 (reduced wax, wt-like chemical composition) but wt was significantly more attractive than cer-yp.949. This demonstrates for the first time that the wax layer can modulate the detectability of host kairomones. 相似文献
999.
Ants of the genus Camponotus are able to discriminate recognition cues of colony members (nestmates) from recognition cues of workers of a different colony (non-nestmates) from a distance of 1 cm. Free moving, individual Camponotus floridanus workers encountered differently treated dummies on a T-bar and their behavior was recorded. Aggressive behavior was scored as mandibular threat towards dummies. Dummies were treated with hexane extracts of postpharyngeal glands (PPGs) from nestmates or non-nestmates which contain long-chain hydrocarbons in ratios comparable to what is found on the cuticle. The cuticular hydrocarbon profile bears cues which are essential for nestmate recognition. Although workers were prevented from antennating the dummies, they showed significantly less aggressive behavior towards dummies treated with nestmate PPG extracts than towards dummies treated with non-nestmate PPG extracts. In an additional experiment, we show that cis-9-tricosene, an alkene naturally not found in C. floridanus' cuticular profile, is behaviorally active and can interfere with nestmate recognition when presented together with a nestmate PPG extract. Our study demonstrates for the first time that the complex multi-component recognition cues can be perceived and discriminated by ants at close range. We conclude that contact chemosensilla are not crucial for nestmate recognition since tactile interaction is not necessary. 相似文献
1000.
Vulnerability assessment and adaptation to the impacts of sea level rise on the Kingdom of Bahrain 总被引:2,自引:0,他引:2
S. Al-Jeneid M. Bahnassy S. Nasr M. El Raey 《Mitigation and Adaptation Strategies for Global Change》2008,13(1):87-104
This paper assesses quantitatively the impact of sea level rise (SLR) at the global and regional scale as a result of climate
change (CC) on the coastal areas of the Kingdom of Bahrain’s islands (36 Islands). The standard Intergovernmental Panel on
Climate Change (IPCC) guidelines was modified as appropriate for the situation of the study area. Geographic Information Systems
(GIS) coupled with Remote Sensing (RS) were used as the main techniques of collecting, analyzing, modeling simulating and
disseminating information to build SLR scenarios in a geographically referenced context. Also, these tools were used to assess
vulnerability and risk of the coastal area of the islands with the expectation that coastal planner and government authorities
will profit from integrating these knowledge into a broad based environmental decision making. Three SLR scenarios: low, moderate
and high were developed to examine the impacts from SLR on all islands. The low SLR scenario (Optimistic) assumes a 0.5-m
rise above current sea level, the moderate scenario (Intermediate) assumes a one meter rise, and the high scenario (Pessimistic)
assumes a 1.5 m rise in sea level. Two more SLR scenarios were assumed to perform risk analysis, a 2 and 5 meter rise above
current sea level. The simulation of SLR are quite straightforward, emphasizing on the uses of both of the data that are incorporated
from the satellite images and the created Digital Elevation Model (DEM) to estimate SLR scenarios that are adapted in the
study. These data were used to predict consequences of the possibility of the rise in sea level at different scenarios which
may alter the landuse and patterns of human communities. Results indicate that low-lying coastal areas of Bahrain islands
are at risk from the effects of any SLR resulting from CC. These islands are vulnerable under different SLR Scenarios. More
than 17% of the country total area may be inundated under 1.5 m SLR in 2100. The total area that might be lost under different
sea level scenarios will vary from more than 77 km2 if SLR reaches 0.5 m, to about 100 km2 under 1.0 m SLR and may reach 124 km2 under 1.5 m SLR scenario. The total inundated areas due to risk scenarios will reach 133 km2, if the SLR rises to 2.0 m, and it is estimated to be more than (22%) of the main island total area. Under the second scenario,
if the SLR reaches 5.0 m, the main islands will lose approximately half of its area (47%) equal to 280 km2. Hawar islands group will lose about (30%) of its total area under 2.0 m SLR, which is about 15.5 km2.A SLR adaptation policy framework (APF) and adaptation policy initiatives (APIs) are suggested for planners to build upon
for reducing the likely effects of SLR in the Kingdom of Bahrain. The framework is composed of four steps namely, acquisition
of information, planning and design, implementation and monitoring and evaluation. A general policy framework for a national
response to SLR is suggested. Additionally, a range of policy adaptation options/initiatives to sustain coastal developments
under the likely effects of SLR are recommended. 相似文献