Unimodal Batesian polymorphism in the Neotropical swallowtail butterfly Eurytides lysithous (Hbn.)

The Brazilian swallowtail Eurytides lysithous is evidently a Batesian mimic of several Parides species. It is polymorphic for mimetic patterns in both sexes. Various populations contain from one to three major forms, and these seem to depend on two unlinked loci or supergenes. Samples from natural populations, and one reared brood, suggest that one locus controls two white-marked forms, with incomplete dominance producing a third heterozygous form. The heterozygotes are everywhere deficient from Hardy-Weinberg expectations. The second putative locus has an allele epistatic to the first locus which converts the white-marked forms to black, but epistasis is apparently incomplete in heterozygotes. The incomplete dominance and epistasis result in extraordinarily variable polymorphic populations and would allow a genetic analysis for comparison with those already done in the classic Batesian polymorphic swallowtails of the Old World.     

The joint evolution of defence and inducibility against natural enemies

The aminoacyl-tRNA synthetases (aaRSs) ensure the fidelity of the translation of the genetic code, covalently attaching appropriate amino acids to the corresponding nucleic acid adaptor molecules-tRNA. The fundamental role of aminoacylation reaction catalysed by aaRSs implies that representatives of the family are thought to be among the earliest proteins to appear. Based on sequence analysis and catalytic domain structure, aaRSs have been partitioned into two classes of 10 enzymes each. However, based on the structural and sequence data only, it will not be easily understood that the present partitioning is not governed by chance. Our findings suggest that organization of amino acid biosynthetic pathways and clustering of aaRSs into different classes are intimately related to one another. A plausible explanation for such a relationship is dictated by early link between aaRSs and amino acids biosynthetic proteins. The aaRSs catalytic cores are highly relevant to the ancient metabolic reactions, namely, amino acids and cofactors biosynthesis. In particular we show that class II aaRSs mostly associated with the primordial amino acids, while class I aaRSs are usually related to amino acids evolved lately. Reasoning from this we propose a possible chronology of genetic code evolution.     

The effect of inbreeding on defence against multiple enemies in Datura stramonium

The ability of plants to respond to natural enemies might depend on the availability of genetic variation for the optimal phenotypic expression of defence. Selfing can affect the distribution of genetic variability of plant fitness, resistance and tolerance to herbivores and pathogens. The hypothesis of inbreeding depression influencing plant defence predicts that inbreeding would reduce resistance and tolerance to damage by natural enemies relative to outcrossing. In a field experiment entailing experimentally produced inbred and outcrossed progenies, we assessed the effects of one generation of selfing on Datura stramonium resistance and tolerance to three types of natural enemies, herbivores, weevils and a virus. We also examined the effect of damage on relative growth rate (RGR), flower, fruit, and seed production in inbred and outcrossed plants. Inbreeding significantly reduced plant defence to natural enemies with an increase of 4% in herbivore damage and 8% in viral infection. These results indicate inbreeding depression in total resistance. Herbivory increased 10% inbreeding depression in seed number, but viral damage caused inbred and outcrossed plants to have similar seed production. Inbreeding and outcrossing effects on fitness components were highly variable among families, implying that different types or numbers of recessive deleterious alleles segregate following inbreeding in D. stramonium. Although inbreeding did not equally alter all the interactions, our findings indicate that inbreeding reduced plant defence to herbivores and pathogens in D. stramonium.     

Genetic variations and phylogeography of the swallowtail butterfly Papilio machaon on the Japanese Islands

The swallowtail butterfly Papilio machaon Linnaeus, 1758 is widely distributed in the Holarctic region, including all of the main islands of Japan, as well as Sakhalin, and on other smaller islands south to Yakushima Island. The Japanese population is situated at the margin of the Eurasian distribution range of this species. It is morphologically different from other populations and has been classified as the subspecies hippocrates C. & R. Felder, 1864. The population of the Japanese Islands is considered to be genetically distinct from the continental populations in relation to the geographical history of the Japanese Islands. Therefore, we examined a part of the ND5 gene sequence of the mitochondrial DNA for P. machaon individuals of various localities in Japan and some nearby countries, and found 68 haplotypes in 400 individuals from the Japanese Islands and Sakhalin. A DNA polymorphism analysis revealed that the genetic structure of the Hokkaido population was significantly different from that of the southern populations on the main Japanese islands. These results imply that P. machaon expanded its range from the Amur region of Russia southward through Sakhalin to the Japanese Islands, and that the Tsugaru Strait between Hokkaido and Honshu may have subsequently limited their gene flow as a geographical barrier.     

The effect of host plant on larval survivorship of the Alaskan swallowtail butterfly (Papilio machaon aliaska)

The Alaskan swallowtail butterfly, Papilio machaon aliaska (Lepidoptera: Papilionidae), uses three plant species as host plants. Cnidium cnidiifolium (Turcz.) Schischk. belongs to the family Apiaceae, the ancestral host‐plant family of the P. machaon group. Artemisia arctica Less. and Petasites frigidus (L.) Franch, in contrast, belong to the distantly related Asteraceae family and were colonized relatively recently by this group of butterflies. Previous work has shown that larval survival is highest on the novel host plants when natural enemies are present in the field. Here I examine whether P. m. aliaska fitness varied when individuals were reared on the three host plants in a common environment, free of environmental and ecological complications such as predation. I collected 12 P. m. aliaska females and measured their reproductive success when their progeny were reared on each of the three host plants. I assessed larval fitness on each of the hosts by recording the percentage pupation and percentage emergence as well as by measuring pupal mass. I found that larvae reared on the ancestral host plant, C. cnidiifolium, had higher fitness than did larvae reared on either of the novel host plants, A. arctica or P. frigidus. Larvae reared on C. cnidiifolium were more likely to pupate, achieved a greater pupal mass, and had higher emergence rates than larvae reared on the novel hosts. I interpret these results to mean that, in the absence of predation, the ancestral host plant is a better host for P. m. aliaska larvae than either novel host and I contend that this result does not appear to support the hypothesis that P. m. aliaska populations in central Alaska are divided into host races.     

Carnivore mollusks as natural enemies of invasive land flatworms

There are several records of the carnivorous behaviour of land flatworms, considered to be top‐predators in their micro‐habitats, by preying upon various species of invertebrates. However, there is little knowledge of predators on land‐flatworms. The possible impact of invasive land flatworms on prey populations has caused widespread concern, when considering their predatory behaviour, combined with recent human influence on the distribution of certain species. This work is the first record of predation on land flatworms by a carnivorous snail. Various‐sized land flatworms of 10 native species of the subfamily Geoplaninae, as well as the exotic species Bipalium kewense (subfamily Bipaliinae), were offered to Rectartemon depressus (Gastropoda, Streptaxidae), which accepted all. The predator also fed on the snail Bradybaena similaris. The snails were maintained in laboratory for an average period of 12 months based on a mixed diet of flatworms and B. similaris, suggesting that the snail is a polyphagous predator. Because certain land‐flatworm species have been described as invasive species which may have a potential impact on prey populations in native and man‐made ecosystems, it is proposed that carnivorous snails of other native species, as potential predators of flatworms, should be tested for possible use in biological control programmes of these invasive planarians.     

Cyst ornamentation in aquatic invertebrates: a defence against egg-predation

Hydrobiologia - Eggs, including encysted embryos (cysts) of aquatic invertebrates may not only be thick-walled, but also provided with various external ornamentations such as spines and...     

Tyramine from the leaves of wild parsnip: a stimulant and synergist for oviposition by the black swallowtail butterfly

Abstract .Oviposition stimulants from the foliage of wild parsnip, Pastinaca sativa (Apiaceae), were isolated by column chromatography and HPLC and tested in bioassay experiments with hand-held female black swallowtail butterflies, Papilio polyxenes (Lepidoptera: Papilionidae). Two of the stimulants were identified as tyramine and trans -chlorogenic acid. A combination of tyramine, trans -chlorogenic acid and an active neutral fraction was needed to elicit a significant oviposition response. These results are discussed in the context of previous research on the oviposition stimulants of swallowtail butterflies and on the significance of tyramine as a neuromodulator of physiological processes in invertebrates.     

The status of the swallowtail butterfly in Britain

• 1 Since the early 1950s, when the British swallowtail butterfly (Papilio machaon britannicus) became extinct at Wicken Fen, this subspecies has been confined to marshes around the Norfolk Broads. Here too, however, its abundance appears to be declining.
• 2 The ecology of the butterfly has been studied in Norfolk and at Wicken (by small-scale introductions) and the main factors determining its abundance are described.
• 3 A morphometric study of museum specimens has shown that populations of the butterfly in Norfolk and at Wicken differed in a number of size and shape characters. These differences were most marked between 1890 and 1920, but subsequently were almost lost.
• 4 Studies of the status and performance of the butterfly's food plant, Peucedanum palustre have shown that it is smaller, produces less seed, and is shorter-lived at Wicken than in Norfolk.
• 5 In the light of these findings, the possibility of successfully re-establishing the butterfly at Wicken, and the possible causes of the decline of the species in Norfolk are discussed.

     

Divergence in larval responses to food plants between temperate and tropical populations of the black swallowtail butterfly

ABSTRACT.

• 1 Larvae of the black swallowtail butterfly, Papilio polyxenes Fabr., from New York and Costa Rica were reared under the same environmental conditions on Daucus carota L. and Spananthe paniculata Jacq. (Umbelliferae), which are the host plants most commonly used by the two populations, respectively. Feeding rates, growth rates and feeding efficiencies of the fifth instar larvae were measured by standard techniques.
• 2 Larvae from each population grew faster on the host-plant species from their region of origin than did larvae from the other population, though differences on S.paniculata were not significant. On D.carota the faster growth by New York larvae was attributable to greater efficiency. On S.paniculata, by contrast, the somewhat faster growth by Costa Rican larvae seemed to have resulted chiefly from faster feeding. The two populations have thus come to differ in metabolic and, probably, behavioural responses to host plants.
• 3 S.paniculata was a superior host plant for larvae of both populations, even though the total energy, nitrogen and water content of its foliage was similar to that of D.carota.
• 4 These results are consistent with the hypothesis that insects in the two populations have diverged in adaptation to their host plants following curtailment of gene flow between them as the species colonized Central America from the north.

     

两种杀虫剂对稻田捕食性天敌集团捕食功能的影响

将稻田各类捕食性天敌作为一集团,运用功能法评价了甲胺磷和杀虫双对该集团捕食功能的影响,由于各类捕食性天敌对杀虫剂敏感性的不同,甲胺磷和杀虫双造成的各类天敌的死亡率和残存天敌个体的捕食功能减退率均不同。实验表明,隐翅虫类和狼蛛类对甲胺磷较为敏感,而对杀虫双,肖蛸类最为敏感。杀虫双对隐翅虫类的致死作用及捕食功能影响较小。就集团的捕食功能而言,甲胺磷影响明显大于杀虫双,但在总的功能减退率组分中,甲胺磷致     

Chemical defence of Battus philenor larvae against attack by the parasitoid Trogus pennator

Abstract 1. Parasitoids in the genus Trogus (Hymenoptera: Ichneumonidae) attack the larvae of swallowtail butterflies (Lepidoptera: Papilionidae). Only two of the three major tribes of the subfamily Papilioninae are attacked although species of all three tribes commonly occur together. The tribe Troidini is relatively free of parasitoids of any kind, and it has been proposed that the aristolochic acids sequestered by troidines protect them from parasitism.
2. The responses of T. pennator (Fabricius) to the sympatric troidine Battus philenor (Linnaeus) were examined. Three hypotheses that could explain why this wasp does not parasitise B. philenor were considered. (1) Battus philenor does not produce compounds used by the wasp to locate hosts. (2) The larval integument contains compounds that deter attack. (3) The parasitoid offspring cannot survive in B. philenor .
3. The first hypothesis was not supported as the frass of B. philenor larvae was found to act as a searching arrestant comparable to the frass of a host species.
4. The second hypothesis was supported. The B. philenor larvae were rejected when the wasps examined them using their antennae, and ethanolic washes of B. philenor cuticle deterred attack by T. pennator when applied to otherwise acceptable host larvae. Bioassays of fractions of the ethanolic wash and of pure aristolochic acids established that aristolochic acids were at least partly responsible for the deterrent effect.
5. The third hypothesis was also supported. Larvae of B. philenor attacked by the parasitoids developed into butterflies.
6. These results indicate that both behavioural and physiological barriers, the former attributable at least in part to sequestered compounds and the latter of unknown mechanism, prevent T. pennator from parasitising B. philenor .     

Assessing the impact of arthropod natural enemies on crop pests at the field scale

There are many reasons why it is important that we find ways to conserve, and better utilize natural enemies of invertebrate crop pests. Currently, measures of natural enemy impact are rarely incorporated into studies that purport to examine pest control. Most studies examine pest and natural enemy presence and/or abundance and then qualitatively infer impact. While this provides useful data to address a range of ecological questions, a measure of impact is critical for guiding pest management decision‐making. Often some very simple techniques can be used to obtain an estimate of natural enemy impact. We present examples of field‐based studies that have used cages, barriers to restrict natural enemy or prey movement, direct observation of natural enemy attack, and sentinel prey items to estimate mortality. The measure of natural enemy impact used in each study needs to be tailored to the needs of farmers and the specific pest problems they face. For example, the magnitude of mortality attributed to natural enemies may be less important than the timing and consistency of that mortality between seasons. Tailoring impact assessments will lead to research outcomes that do not simply provide general information about how to conserve natural enemies, but how to use these natural enemies as an integral part of decision‐making.     

Chemical defence against predators in a sub-Arctic fjord

The development of chemical defences in marine organisms is supposed to be driven by intense pressure of predation and competition. While benthic communities in tropical and also Antarctic regions are thought to be mainly structured by intra- and interspecific interactions, these factors are proposed to be less important in northern high latitudes. Consequently, selective pressure for chemical defence should be low in these regions. To investigate the incidence of chemical defence against predation in northern high latitudes, crude extracts of 18 abundant sessile or slow-moving invertebrate species (4 sponges, 3 actinians, 1 soft coral, 4 bryozoans, 3 ascidians and the egg mass of a gastropod) from Kongsfjord (Spitsbergen) were tested for feeding deterrent activity. Laboratory assays were performed by offering artificial food with extracts to two different predators, the amphipod Anonyx nugax which is a common species in Kongsfjord, and the starfish Asterias rubens from the North Sea. Of the 18 extracts tested, 2 (Haliclona viscosa, Hormathia nodosa) exhibited significant feeding deterrent effects in the amphipod assay. Furthermore, 6 extracts had a significantly stimulating effect on the amphipod feeding, and 10 extracts did not affect consumption. In the starfish assay, only the crude extract of H. viscosa was significantly rejected. For H. viscosa, feeding deterrence could be established for two pure compounds, and for H. nodosa for one fraction. The present data show that feeding deterrent compounds are present in sub-Arctic marine invertebrates from Kongsfjord but are less abundant than in temperate, tropical and Antarctic species.     

Low nutritive quality as a plant defence: Effects of herbivore-mediated interactions

Summary A plant may lower its nutritive quality, for herbivores, by using secondary compounds, morphological characters and/or having a lowered nutrient content. If such traits decrease the amount of resources lost through herbivory, then they act as antiherbivore defences. However, if herbivores compensate for the lowered nutrient availability, by increasing their intake rates or by prolonging their feeding periods, then this may render the defence useless. I analyse the conditions for evolution of this type of plant defences in a game theoretical model. The predictions of the model depend on the amount of compensatory feeding performed by the herbivores and on the herbivores' mobility in relation to the spatial structure of the plant population. When herbivores cannot compensate for a lowered nutritive quality, the defence can evolve irrespective of the type of herbivore. When herbivores can compensate for such defences, the outcome depends on how the herbivores compensate. In situations where herbivores compensate only on defended plants, which could correspond to immobile herbivores, this type of defence can evolve only if the level of compensation is lower than a certain critical value. When herbivores compensate more on defended than on undefended plants, e.g. because of low mobility, the outcome depends on the level of compensation performed on defended plants. If this level of compensation is high, then the model predicts a stable coexistence of defended and undefended plants and, if it is low, then the populations can consist of only defended plants. When herbivores compensate more on undefended plants than on defended ones, e.g. highly mobile herbivores, the result is populations consisting of either only defended plants, or only undefended plants. Consequently, the fact that herbivores may compensate for lowered nutrient quality does not, as such, nullify the notion of low nutrient quality as a plant defence. However, compensatory feeding may restrict the conditions for the evolution of such defences.     

Evaluating the enemies hypothesis in a clover‐cabbage intercrop: effects of generalist and specialist natural enemies on the turnip root fly (Delia floralis)

• 1 The relative importance of the resource concentration hypothesis and the enemies hypothesis was investigated for the turnip root fly Delia floralis in a cabbage–red clover intercropping system compared with a cabbage monoculture.
• 2 Delia floralis egg densities were measured as well as the activity‐densities of generalist predators in a field experiment during two growing seasons. In the second year, a study of egg predation with artificially placed eggs was conducted, in addition to a predator exclusion experiment, to estimate total predation during the season. Parasitization rates were estimated from samples of pupae.
• 3 Delia floralis oviposition was greater in the monoculture during both years. The predator activity‐densities differed between treatments and study years. The known natural enemies of Delia spp., Bembidion spp. and Aleochara bipustulata showed a strong response to a cultivation system with higher activity‐densities in the monoculture. The response, however, appeared to be caused primarily by habitat preferences and not by D. floralis egg densities.
• 4 The reduction in the number of D. floralis pupae in the intercropping may be explained by a disruption in oviposition behaviour caused by the presence of clover because neither predation, nor parasitization rates differed between cultivation systems.

     

Between-clutch interactions affect a benefit of group feeding for pipevine swallowtail larvae

Abstract.  1. In California, early instar larvae of the pipevine swallowtail ( Battus philenor ) develop at an accelerated rate when feeding in large groups compared with small groups due to a plant-mediated response to feeding group size. Larvae benefit from accelerated growth because the time larvae remain in early stages, where mortality is highest, is reduced. Occasionally, multiple clutches are laid on the same plant stem. Clutch size modification by females ovipositing on plant with previously laid clutches and the effect of kinship and group size on larval behaviour was examined. The direct and indirect interactions between clutches were investigated to determine if group size and time between clutch establishment affects the performance of early instar larvae.
2. Larger groups consume the young foliage more quickly and develop at an accelerated rate compared with smaller groups. Older foliage available to later clutches is an inferior food resource compared with younger foliage.
3. There was no evidence that females adjust clutch size in response to the presence of conspecific clutches.
4. Second groups of larvae readily joined previously established feeding groups. There were no observed behavioural differences between sibling and mixed-family groups.
5. The effect of a second group on the growth of the initial group was dependent on the size of both groups and the time interval between the arrival of the two groups.
6. Accelerated growth associated with larger feeding aggregations was absent when these groups were introduced to plants with previously established groups.
7. It is beneficial for ovipositing females to avoid plants with previously laid clutches because direct and indirect interactions with established clutches compromises larval performance.