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Lepidoptera
Terms modified by Lepidoptera Selected AbstractsTHE PHYLOGENETIC PATTERN OF SPECIATION AND WING PATTERN CHANGE IN NEOTROPICAL ITHOMIA BUTTERFLIES (LEPIDOPTERA: NYMPHALIDAE)EVOLUTION, Issue 7 2006Chris D. Jiggins Abstract Species level phylogenetic hypotheses can be used to explore patterns of divergence and speciation. In the tropics, speciation is commonly attributed to either vicariance, perhaps within climate-induced forest refugia, or ecological speciation caused by niche adaptation. Mimetic butterflies have been used to identify forest refugia as well as in studies of ecological speciation, so they are ideal for discriminating between these two models. The genus Ithomia contains 24 species of warningly colored mimetic butterflies found in South and Central America, and here we use a phylogenetic hypothesis based on seven genes for 23 species to investigate speciation in this group. The history of wing color pattern evolution in the genus was reconstructed using both parsimony and likelihood. The ancestral pattern for the group was almost certainly a transparent butterfly, and there is strong evidence for convergent evolution due to mimicry. A punctuationist model of pattern evolution was a significantly better fit to the data than a gradualist model, demonstrating that pattern changes above the species level were associated with cladogenesis and supporting a model of ecological speciation driven by mimicry adaptation. However, there was only one case of sister species unambiguously differing in pattern, suggesting that some recent speciation events have occurred without pattern shifts. The pattern of geographic overlap between clades over time shows that closely related species are mostly sympatric or, in one case, parapatric. This is consistent with modes of speciation with ongoing gene flow, although rapid range changes following allopatric speciation could give a similar pattern. Patterns of lineage accumulation through time differed significantly from that expected at random, and show that most of the extant species were present by the beginning of the Pleistocene at the latest. Hence Pleistocene refugia are unlikely to have played a major role in Ithomia diversification. [source] THE HISTORICAL BIOGEOGRAPHY OF TWO CARIBBEAN BUTTERFLIES (LEPIDOPTERA: HELICONIIDAE) AS INFERRED FROM GENETIC VARIATION AT MULTIPLE LOCIEVOLUTION, Issue 3 2002Neil Davies Abstract Mitochondrial DNA and allozyme variation was examined in populations of two Neotropical butterflies, Heliconius charithonia and Dryas iulia. On the mainland, both species showed evidence of considerable gene flow over huge distances. The island populations, however, revealed significant genetic divergence across some, but not all, ocean passages. Despite the phylogenetic relatedness and broadly similar ecologies of these two butterflies, their intraspecific biogeography clearly differed. Phylogenetic analyses of mitochondrial DNA sequences revealed that populations of D. iulia north of St. Vincent are monophyletic and were probably derived from South America. By contrast, the Jamaican subspecies of H. charithonia rendered West Indian H. charithonia polyphyletic with respect to the mainland populations; thus, H. charithonia seems to have colonized the Greater Antilles on at least two separate occasions from Central America. Colonization velocity does not correlate with subsequent levels of gene flow in either species. Even where range expansion seems to have been instantaneous on a geological timescale, significant allele frequency differences at allozyme loci demonstrate that gene flow is severely curtailed across narrow ocean passages. Stochastic extinction, rapid (re)colonization, but low gene flow probably explain why, in the same species, some islands support genetically distinct and nonexpanding populations, while nearby a single lineage is distributed across several islands. Despite the differences, some common biogeographic patterns were evident between these butterflies and other West Indian taxa; such congruence suggests that intraspecific evolution in the West Indies has been somewhat constrained by earth history events, such as changes in sea level. [source] HORMONAL CONTROL OF THE VITELLOGENESIS IN THE JAPANESE OAK SILKWORM, ANTHERAEA YAMAMAZ (LEPIDOPTERA: SATURNIIDAE)INSECT SCIENCE, Issue 1 2002YE Gong-yin Abstract Effects of ecdysteroid and juvenile hormone (JH) on vitellogenesis of the Japanese oak silkworm, Antheraea yamami are reported in this article. After topical treatment with 20-hydroxyecdysone alone or JH analog (i.e. methoprene) alone and combined treatment with these two chemicals, vitellogenin (Vg) titers in the fat body and haemolymph at the pupal stage were mostly higher than those of the control, indicating that both ecdysteroid and JH exerted a promoting effect on the synthesis of Vg. In contrast, the Vg uptake was markedly inhibited by JH while stimulating effect of the ecdysteroid could be shown that vitellin (Vt) titer in the ovary was lower after methoprene treatments, but higher after 20-hydroxyecdyson treatments. Meanwhile, effects of these two hormones on Vg synthesis in the fat body were also tested with the incubation in vitro with Grace medium containing H-leucine and the hormones. The results demonstrated that Vg synthesis was stimulated after treating with methoprene alone or 20-hydroxyecdysone alone and combined treating with these two chemicals, and particularly ecdysteroid had more marked positive effect. To comprehensively concluded our results, it could be regarded that ecdysteroid play the main role in the regulation of vitellogenesis for the Japanese oak silkworm. [source] Beta diversity of geometrid moths (Lepidoptera: Geometridae) in an Andean montane rainforestDIVERSITY AND DISTRIBUTIONS, Issue 5 2003Gunnar Brehm Abstract. Turnover in species composition of the extremely species-rich family Geometridae (Lepidoptera) was investigated along an elevational gradient ranging from 1040 m to 2677 m above sea level. Moths were sampled using weak light traps (30 W) in three field periods in 1999 and 2000 in an Andean montane rainforest in the province of Zamora-Chinchipe in southern Ecuador. A total of 13 938 specimens representing 1010 species were analysed. Similarities of ensembles of all geometrid moths and of the subfamilies Ennominae and Larentiinae were calculated using the NESS index (with mmax). Ordinations performed using nonmetric multidimensional scaling (NMDS) and correspondence analysis depicted a gradual change of the ensembles along the altitudinal gradient. Extracted ordination scores significantly correlate with altitude (,0.97 , r , ,0.95, P < 0.001) and with ambient air temperature (0.93 , r , 0.97, P < 0.001). Temperature is therefore assumed to be the most important abiotic determinant responsible for the species turnover among the moths. Matrix correlation tests were performed in order to compare faunal matrices with matrices derived from available environmental factors. Both tree diversity and vegetation structure significantly correlate with faunal data, but tree diversity explains considerably more of the data variability (range: Mantel r = 0.81,0.83, P < 0.001) than vegetation structure (range: Mantel r = 0.35, P < 0.005 to r = 0.43, P < 0.001). Tree diversity also changes gradually and scores of the first NMDS dimension are highly significantly correlated with altitude (r = 0.98, P < 0.001). A common underlying factor such as ambient temperature might also be responsible for such vegetation changes. Additionally, simulated model data was developed that assumed a constant turnover of moth species and equal elevational ranges of all species involved. Despite the simplicity of the models, they fit empirical data very well (Mantel r > 0.80 and P < 0.001 in all models). [source] The wing vestiture of the non-ditrysian Lepidoptera (Insecta).ACTA ZOOLOGICA, Issue 4 2001Comparative morphology, phylogenetic implications Abstract The ultrastructure of the dorsal forewing vestiture in exemplars of all family group taxa of non-ditrysian Lepidoptera is examined, and the evolutionary implications at family level and above are discussed. Wing-scale terminology is reviewed. Three different types of bilayer wing-scale covering are recognized; only a few groups have a single-layer wing-scale covering. The general scale arrangement is random, but a few taxa have clustered scale arrangements and scattered heteroneurans have scales arranged in transverse rows. Cross ribs are present in all taxa, but only as vestiges in eriocraniid cover scales. Ridge dimorphism is widespread in Neolepidoptera. Surprisingly, ridges and cross ribs on the adwing scale surface are of general occurrence in Neopseustidae and Hepialidae, and are even found on parts of the ground scales of many other Neolepidoptera. Morphological evidence strongly indicates that the fused wing-scale types found in non-Coelolepidan Lepidoptera and Neolepidoptera are independently evolved, as evidenced from the presence of vestigial perforations. Absence of perforations is not infallible evidence that a scale is solid. Microtrichia are independently reduced in a number of taxa and probably re-evolved in at least higher nepticulids. Wing vestiture and scale characters indicate that Tischerioidea may be the sister group of Ditrysia. [source] Diversity and abundance patterns of phytophagous insect communities on alien and native host plants in the BrassicaceaeECOGRAPHY, Issue 6 2003Mark Frenzel The herbivore load (abundance and species richness of herbivores) on alien plants is supposed to be one of the keys to understand the invasiveness of species. We investigate the phytophagous insect communities on cabbage plants (Brassicaceae) in Europe. We compare the communities of endophagous and ectophagous insects as well as of Coleoptera and Lepidoptera on native and alien cabbage plant species. Contrary to many other reports, we found no differences in the herbivore load between native and alien hosts. The majority of insect species attacked alien as well as native hosts. Across insect species, there was no difference in the patterns of host range on native and on alien hosts. Likewise the similarity of insect communities across pairs of host species was not different between natives and aliens. We conclude that the general similarity in the community patterns between native and alien cabbage plant species are due to the chemical characteristics of this plant family. All cabbage plants share glucosinolates. This may facilitate host switches from natives to aliens. Hence the presence of native congeners may influence invasiveness of alien plants. [source] Herbivory patterns in mature sugar maple: variation with vertical canopy strata and tree ontogenyECOLOGICAL ENTOMOLOGY, Issue 1 2010SEAN C. THOMAS 1. Although leaf morphology and chemistry show profound changes as trees age, the consequences of such changes to herbivory have received little attention, particularly late in the ontogeny of canopy trees. 2. Using a mobile aerial lift for canopy access, patterns of leaf damage were evaluated in canopy-dominant mature sugar maple (Acer saccharum Marsh) trees ranging from ,20 to 70 cm in diameter, corresponding to an age range of ,40,180 years. 3. Herbivore damage patterns varied in relation to both vertical canopy position (among upper-, mid-, and lower-canopy positions) and with tree size. Damage types attributable to herbivores active on leaf surfaces, including leaf skeletonizers and leaf cutters (both principally Lepidoptera), and leaf stippling inducers (Hemiptera) showed decreases with tree size, and with increasing height in the canopy. In contrast, leaf damage from the most abundant gall-forming arthropod in the system, the eriophyid mite Vasates aceriscrumena, increased markedly with tree size. 4. The results indicate that herbivory patterns vary with both canopy stratum and with tree size in sugar maple, and that the relative strength of vertical stratification and tree ontogeny effects are similar in magnitude. The predominant patterns are of a decrease in herbivory with increasing height in the canopy and with tree size, but certain galling arthropods exhibit the reverse trends. [source] The roles and interactions of reproductive isolation mechanisms in fall armyworm (Lepidoptera: Noctuidae) host strainsECOLOGICAL ENTOMOLOGY, Issue 2010ASTRID T. GROOT 1. The moth Spodoptera frugiperda presents an interesting opportunity to study the evolution of reproductive isolation, because it consists of two host races that may be in the process of speciation. 2. The two races exhibit habitat isolation through host-plant preference, and two types of behavioural isolation, i.e. differences in sex pheromone composition and timing of mating activity at night. 3. In this paper, we review the selection pressures acting upon these three barriers as well as their genetic bases, to address the question of how divergence of the two strains may have evolved. 4. We also address possible interactions between the three barriers, whether and how they may have evolved in concert, and we view the evolution of these three prezygotic isolation barriers in the light of postzygotic isolation. [source] Amino acid sources in the adult diet do not affect life span and fecundity in the fruit-feeding butterfly Bicyclus anynanaECOLOGICAL ENTOMOLOGY, Issue 4 2008FREERK MOLLEMAN Abstract 1.,In tropical forests, the adults of many butterfly species feed on fruits rather than nectar from flowers and have long life spans. Rotting fruit and nectar differ from each other in many respects, including sources of amino acids and microbial life. If amino acids in the adult diet can be used for reproduction, this may have facilitated the evolution of extended life spans in this guild. 2.,This issue was addressed by investigating effects of banana, yeast, and amino acids in the adult diet of the fruit-feeding butterfly Bicyclus anynana (Lepidoptera) on longevity and female reproductive output in two experiments. 3.,Results showed that in the fruit-feeding butterfly B. anynana: (i) banana juice, but not sliced banana or added amino acids extend life span compared with a sugar solution of similar composition; (ii) compared with this sugar solution, other cohorts (banana juice-amino acid enriched) did not have significantly higher reproductive outputs; (iii) yeast does not represent a valuable source of nutrients; (iv) caloric restriction may cause decreased life span and rate of reproduction; and (v) increased rates of reproduction have a life span cost. [source] Host plant variation in plant-mediated indirect effects: moth boring-induced susceptibility of willows to a specialist leaf beetleECOLOGICAL ENTOMOLOGY, Issue 2 2008SHUNSUKE UTSUMI Abstract 1.,We examined the plant-mediated indirect effects of the stem-boring moth Endoclita excrescens (Lepidoptera: Hepialidae) on the leaf beetle Plagiodera versicolora (Coleoptera: Chrysomelidae) in three willow species, Salix gilgiana, S. eriocarpa, and S. serissaefolia. 2.,When the stem-boring moth larvae damaged stems in the previous year, willows were stimulated to produce vigorously growing lateral shoots on these stems. These new lateral shoots were significantly longer and the upper leaves had significantly higher nitrogen and water content than current-year shoots on unbored stems, although the carbon content and leaf dry mass were not different between lateral and current-year shoots. 3.,In the field, leaf beetle larvae and adults had significantly greater densities on lateral shoots of bored stems than on current-year shoots of unbored stems. A laboratory experiment showed that female beetles had significantly greater mass and fecundity when fed on leaves of newly-emerged lateral shoots. Thus, the stem-boring moth had a positive effect on the temporally and spatially separated leaf beetle by increasing resource availability by inducing compensatory regrowth. 4.,The strength of the indirect effects on the density and performance of the leaf beetle differed among willow species, because there was interspecific variation in host quality and herbivore-induced changes in plant traits. In particular, we suggest that the differences in magnitude of the changes among willow species in shoot length and leaf nitrogen content greatly affected the strength of the plant-regrowth mediated indirect effect, coupled with host-plant preference of the leaf beetle. [source] Costs of cannibalism in the presence of an iridovirus pathogen of Spodoptera frugiperdaECOLOGICAL ENTOMOLOGY, Issue 2 2006Trevor Williams Abstract., 1.,The costs of cannibalism were examined in larvae of Spodoptera frugiperda (J. E. Smith) (Lepidoptera: Noctuidae) in the presence of conspecifics infected by a lethal invertebrate iridescent virus (IIV). The hypothesis of a positive correlation between insect density and the likelihood of disease transmission by cannibalism was examined in laboratory microcosms and a field experiment. 2.,Transmission was negligible following peroral infection of early instars with purified virus suspensions or following coprophagy of virus-contaminated faeces excreted by infected insects. In contrast, 92% of the insects that predated infected conspecifics acquired the infection and died prior to adult emergence in the laboratory. Diseased larvae were more likely to be victims of cannibalism than healthy larvae. 3.,The prevalence of cannibalism was density dependent in laboratory microcosms with a low density (10 healthy insects + one infected insect) or high density (30 healthy insects + one infected insect) of insects, and field experiments performed on maize plants infested with one or four healthy insects + one infected insect. 4.,Cannibalism in the presence of virus-infected conspecifics was highly costly to S. frugiperda; in all cases, insect survival was reduced by between ,,50% (laboratory) and ,,30% (field) in the presence of the pathogen. Contrary to expectations, the prevalence of disease was not sensitive to density because cannibalism resulted in self-thinning. As infected individuals are consumed and disappear from the population, the prevalence of disease will be determined by the timescale over which transmission can be achieved, and the rate at which individuals that have acquired an infection become themselves infectious to conspecific predators. [source] Melanism in a larval Lepidoptera: repeatability and heritability of a dynamic traitECOLOGICAL ENTOMOLOGY, Issue 2 2006Kwang Pum Lee Abstract., 1.,Although it is well established that the deposition of melanin pigment in the cuticle of larval Lepidoptera is influenced by both environmental and genetic factors, few studies have examined intra-individual regional variation in the degree of melanism or the ontogenetic dynamics of this trait. Here, heritable and density-dependent effects on within-individual and stage-specific variation in melanism were examined in caterpillars of the Egyptian cotton leafworm, Spodoptera littoralis (Boisduval). 2.,Using quantitative spectrometric methods, it is shown that cuticular melanism changes dramatically within larval stadia, showing the highest and lowest levels of melanism early (first day) and late (final day) in each larval stadium respectively. However, solitary-reared caterpillars were significantly paler than those reared gregariously at all stages of development and maintained greater levels of variation in melanism. This variation in melanism was repeatable and exhibited a significant heritable component (narrow sense heritability based on offspring,parent regressions: h2 = 0.18,0.30). 3.,The degree of melanism was correlated negatively with larval body weight in solitary caterpillars, but not gregarious ones. Melanism also varied spatially, with the lateral longitudinal band being consistently darker than the dorsal or dorso-lateral bands. Crowd-rearing increased melanism in all regions of larval cuticle, but the extent of crowding-induced melanism was more pronounced in the dorsal and dorso-lateral bands than in the lateral one. 4.,These results indicate that although cuticular melanism is a highly dynamic trait, ontogenetic changes in relative cuticular melanism are both predictable and repeatable within individuals and genotypes. This has implications for our understanding of the evolution of melanism and for applying artificial selection on the basis of colour. [source] Selection for discontinuous life-history traits along a continuous thermal gradient in the butterfly Aricia agestisECOLOGICAL ENTOMOLOGY, Issue 6 2005Steve Burke Abstract., 1.,Voltinism may be conceptualised as the product of development rate and the timing of diapause , two components that together translate gradual environmental variation, through periods of growth and development, into ,generational units'. This may result in very different selection pressures on diapause induction and development time in populations with different numbers of generations per year. 2.,Developmental data from univoltine and bivoltine populations of the butterfly Aricia agestis (Lepidoptera: Lycaenidae) in North Wales were used to examine larval development time and the timing of diapause, and their contribution towards voltinism in populations that occur at the same latitude and in geographic proximity to one another along a thermal gradient. 3.,The critical photoperiod for diapause induction in univoltines and bivoltines from the same latitude differed by more than 1.5 h. 4.,Development time also differed significantly between these populations, in line with predictions that bivoltines would need to exhibit shorter development times in order to achieve two complete generations per year. Shorter development times for bivoltines result in lower pupal weights, suggesting a trade-off exists between generation number and body size that may dictate the position of the transition zone between the two life-history strategies. Analysis of development times in a third population, from southern England, with greater thermal availability than those from North Wales, further supports this hypothesised trade-off. 5.,To achieve the conversion of a continuous thermal gradient into the binary biological response from univoltism to bivoltism, bivoltines speed up development, reduce adult body size and shift their diapause induction response. [source] Egg maturation strategy and its associated trade-offs: a synthesis focusing on LepidopteraECOLOGICAL ENTOMOLOGY, Issue 4 2005Mark A. Jervis Abstract., 1.,Insects vary considerably between and within orders, and even within the same genus, in the degree to which the female's lifetime potential egg complement is mature when she emerges as an adult. 2.,The ,ovigeny index' (OI) , the number of eggs females have ready to lay divided by the lifetime potential fecundity , quantifies variation in the degree of early life concentration of egg production, and also variation in initial reproductive effort. 3.,Here, an integrated set of hypotheses is presented, based on a conceptual model of resource allocation and acquisition, concerning trade-offs at the interspecific level between initial investment in egg production (as measured by OI) and other life-history traits in holometabolous insects. 4.,The evidence supporting each of these hypotheses is reviewed, and particular attention is paid to the Lepidoptera, as relevant life-history data are rapidly accumulating for this ecologically and economically important group. 5.,There is evidence at the interspecific level supporting: (i) a link between OI and a trade-off between soma and non-soma in Trichoptera and Hymenoptera (the proportionate allocation to soma decreases with increasing OI); (ii) a negative correlation between OI and dependency on external nutrient inputs (via adult feeding) in Hymenoptera and in Lepidoptera; (iii) a negative correlation between OI and the degree of polyandry (and nuptial gift, i.e. spermatophore, use) in Lepidoptera; (iv) negative correlations between OI and resource re-allocation capabilities (egg and thoracic musculature resorption) in Hymenoptera and in Lepidoptera; (v) a negative correlation between lifespan and OI in Trichoptera, Hymenoptera, and Lepidoptera, indicating a cost of reproduction; (vi) a link between winglessness and an OI of one in Lepidoptera; (vii) a negative correlation between OI and the degree of female mobility in winged Lepidoptera; and (viii) a negative correlation between OI and larval diet breadth (as mediated by oviposition strategy) in Lepidoptera. [source] Community structure of arboreal caterpillars within and among four tree species of the eastern deciduous forestECOLOGICAL ENTOMOLOGY, Issue 6 2003Keith S. Summerville Abstract., 1.,A seasonally replicated experimental design was used to address the question of how differences within and among host tree species affect arboreal caterpillar communities. 2.,Seasonal variation influenced caterpillar community composition most significantly, and the similarity among caterpillar assemblages did not necessarily follow the pattern of phylogenetic relatedness among host trees. 3.,Species richness and abundance of caterpillars were higher on oaks and maples than on American beech. Diversity partitioning models revealed that , diversity was only occasionally greater or less than expected by chance alone. 4.,When , diversity was significant, values tended to be greater than expected by chance among replicate trees within each species and lower than expected by chance among the four tree species. 5.,Differences among trees appeared important for determining patterns of species presence/absence for rare species and influencing patterns of species dominance within caterpillar assemblages. Differences among tree species had a significant effect on overall lepidopteran community composition and mean species diversity (i.e. , diversity). 6.,Because , diversity of caterpillars among host trees was lower than expected by chance, host specificity within the Lepidoptera may be less prevalent than thought previously. [source] Impact of avian and arthropod predation on lepidopteran caterpillar densities and plant productivity in an ephemeral agroecosystemECOLOGICAL ENTOMOLOGY, Issue 5 2003Cerruti R. R. Hooks Abstract., 1.,Most studies evaluating the combined impact of spiders and other predators on herbivore densities in agroecosystems have focused primarily on their trophic connections with invertebrate predators (e.g. carabids, chrysopids); however linkages among spiders and vertebrate predators may also help structure the population dynamics of insect herbivores. A field experiment was conducted to examine the impact of avian and spider predation on lepidopteran caterpillar densities and plant productivity within a Brassica agroecosystem. 2.,Arthropod abundance, leaf-chewing damage, and final plant productivity associated with broccoli, Brassica oleracea L. (var. italica), were recorded for four treatments: (1) bird present but spiders removed; (2) both birds and spiders present; (3) birds excluded, spiders present; and (4) birds and spiders both excluded. 3.,Densities of Artogeia rapae L. (Lepidoptera: Pieridae) and Trichoplusia ni Hübner (Lepidoptera: Noctuidae) large caterpillars and post feeding stages were reduced significantly by bird predation. The abundance of large caterpillars was also reduced on spider-inhabited plants during early plant growth; however the assemblage of birds and spiders did not suppress caterpillar densities more significantly than either predator alone. 4.,Plants protected by birds, spiders, and birds plus spiders sustained less folivory attributable to leaf chewing caterpillars than check plants. Plant productivity was also greater for predator-protected plants than check plants. 5.,Although spiders and parasitoids were responsible for some of the mortality inflicted upon lepidopteran caterpillars, it was concluded that in this study system, birds are the most important natural enemies of folivores. [source] Host shifting by Operophtera brumata into novel environments leads to population differentiation in life-history traitsECOLOGICAL ENTOMOLOGY, Issue 5 2003Adam J. Vanbergen Abstract., 1. Operophtera brumata L. (Lepidoptera: Geometridae), a polyphagous herbivore usually associated with deciduous trees such as oak Quercus robur L., has expanded its host range to include the evergreen species heather Calluna vulgaris (L.) Hull and, most recently, Sitka spruce Picea sitchensis (Bong.) Carrière. 2. Phenology, morphology, and survival of O. brumata were measured at several life-history stages in populations from the three different host plant communities sampled from a range of geographical locations. The data were used to test for population differences, reflecting the marked differences in host-plant secondary chemistry, growth form, and site factors such as climate. The hypothesis that spruce-feeding populations originated from populations feeding on moorland, commonly sites of coniferous afforestation, was also tested. 3. Altitude, not host plant species, was the major influence on the timing of adult emergence. An effect of insect population independent of altitude was found, implying that additional unidentified factors contribute to this phenological variation. Larval survival and adult size varied between populations reared on different host plant species. Survival of larvae was affected negatively when reared on the novel host plant, Sitka spruce, versus the natal plant (oak or heather) but oak and heather-sourced insects did not differ in survivorship on Sitka spruce. 4. Host range extension into novel environments has resulted in population differentiation to the local climate, demonstrating that host shifts pose challenges to the herbivore population greater than those offered by the host plant alone. The hypothesis that Sitka spruce feeding populations have arisen predominantly from moorland feeding populations was not supported. [source] Parasitism and ant protection alter the survival of the lycaenid Hemiargus isolaECOLOGICAL ENTOMOLOGY, Issue 2 2003Jennifer A. Weeks Abstract. 1. Although the majority of lycaenid,ant associations is facultative, few studies have documented the protection benefits provided by ants to lycaenids that are tended facultatively (Pierce & Easteal, 1986; Peterson, 1993). 2. Larvae of Hemiargus isola (Lepidoptera: Lycaenidae) feeding on Dalea albiflora are tended facultatively by several species of ant. In 1999 and 2000, the levels of parasitism and the identities of attendant ants were determined for larvae of H. isola. In addition, the presence of ants was manipulated experimentally to determine the efficacy of protection provided by attendant ants to H. isola. 3. Lycaenids were parasitised by a braconid wasp, Cotesia cyaniridis (Riley), and a tachinid fly, Aplomya theclarum (Scudder). In 1999 and 2000, 62 and 65% of larvae were parasitised; the percentage of the population parasitised did not differ significantly between years. In both 1999 and 2000, parasitism by the braconid wasp C. cyaniridis accounted for >,99% of all parasitism events. 4. Four species of ant, Crematogaster sp., Dorymyrmex sp., Forelius sp., and Formica sp., were associated with 88,99% of the tended lycaenids collected in both 1999 and 2000. For both years, there was a single, numerically dominant species associated with >80% of the tended larvae collected, but the identity of this numerically dominant ant differed between years. 5. Experimental exclusion of ants from D. albiflora plants resulted in 78% larval mortality as a result of parasitism, nearly twice that of larvae that were tended by ants on unmanipulated plants. [source] Autumnal moth , why autumnal?ECOLOGICAL ENTOMOLOGY, Issue 6 2001Toomas Tammaru Summary 1. As for some other spring-feeding moths, adult flight of Epirrita autumnata (Lepidoptera: Geometridae) occurs in late autumn. Late-season flight is a result of a prolonged pupal period. Potential evolutionary explanations for this phenological pattern are evaluated. 2. In a laboratory rearing, there was a weak correlation between pupation date and the time of adult emergence. A substantial genetic difference in pupal period was found between two geographic populations. Adaptive evolution of eclosion time can thus be expected. 3. Metabolic costs of a prolonged pupal period were found to be moderate but still of some ecological significance. Pupal mortality is likely to form the main cost of the prolonged pupal period. 4. Mortality rates of adults, exposed in the field, showed a declining temporal trend from late summer to normal eclosion time in autumn. Lower predation pressure on adults may constitute the decisive selective advantage of late-season flight. It is suggested that ants, not birds, were the main predators responsible for the temporal trend. 5. Egg mortality was estimated to be low; it is thus unlikely that the late adult period is selected for to reduce the time during which eggs are exposed to predators. 6. In a laboratory experiment, oviposition success was maximal at the time of actual flight peak of E. autumnata, however penalties resulting from sub-optimal timing of oviposition remained limited. [source] Associations between host migration and the prevalence of a protozoan parasite in natural populations of adult monarch butterfliesECOLOGICAL ENTOMOLOGY, Issue 2 2000Sonia M. Altizer Summary 1. Monarch butterflies Danaus plexippus (L.) (Lepidoptera: Nymphalidae) are susceptible to infection by the obligate protozoan parasite Ophryocystis elektroscirrha (McLaughlin and Myers) (Apicomplexa: Neogregarinida). Because monarchs form resident and migratory populations in different parts of the world, this host,parasite system provides the opportunity to examine how variation in parasite prevalence relates to host movement patterns. 2. Parasite prevalence was evaluated using 14 790 adult monarchs captured between 1968 and 1997. Comparison of three populations in North America indicated that parasite prevalence is associated negatively with host dispersal distances. A continuously breeding, nonmigratory population in southern Florida showed high prevalence (over 70% heavily infected). The western population migrates moderate distances to overwintering sites on the Pacific Coast and has intermediate prevalence (30% heavily infected). The eastern migratory population, which travels the longest distance to Mexican overwintering sites, has exhibited less than 8% infection throughout the past 30 years. 3. Variation in parasite loads within North American migratory populations was investigated to determine whether the prevalence of heavy infection and average parasite loads declined during migration or overwintering. Average parasite loads of summer-breeding adults in western North America decreased with increasing distance from overwintering sites. This suggests that heavily infected monarchs are less likely to remigrate long distances in spring. No differences in the frequency of heavily infected adults were found among eastern or western North American monarchs throughout the overwintering period, however, suggesting that this parasite does not affect overwintering mortality. 4. Changes in the prevalence of monarchs with low parasite loads demonstrate that spore transfer occurs during migration and overwintering, possibly when adult butterflies contact each other as a result of their clustering behaviour. 5. This study of geographical and temporal variation in O. elektroscirrha among populations of D. plexippus demonstrates the potential role of seasonal migration in mediating interactions between hosts and parasites, and suggests several mechanisms through which migratory behaviour may influence parasite prevalence. [source] Health food versus fast food: the effects of prey quality and mobility on prey selection by a generalist predator and indirect interactions among prey speciesECOLOGICAL ENTOMOLOGY, Issue 2 2000Micky D. Eubanks Summary 1. In order to understand the relative importance of prey quality and mobility in indirect interactions among alternative prey that are mediated by a shared natural enemy, the nutritional quality of two common prey for a generalist insect predator along with the predator's relative preference for these prey was determined. 2. Eggs of the corn earworm Helicoverpa zea (Lepidoptera: Noctuidae) were nutritionally superior to pea aphids Acyrthosiphum pisum (Homoptera: Aphididae) as prey for big-eyed bugs Geocoris punctipes (Heteroptera: Geocoridae). Big-eyed bugs survived four times as long when fed corn earworm eggs than when fed pea aphids. Furthermore, only big-eyed bugs fed corn earworm eggs completed development and reached adulthood. 3. In two separate choice experiments, however, big-eyed bugs consistently attacked the nutritionally inferior prey, pea aphids, more frequently than the nutritionally superior prey, corn earworm eggs. 4. Prey mobility, not prey nutritional quality, seems to be the most important criterion used by big-eyed bugs to select prey. Big-eyed bugs attacked mobile aphids preferentially when given a choice between mobile and immobilised aphids. 5. Prey behaviour also mediated indirect interactions between these two prey species. The presence of mobile pea aphids as alternative prey benefited corn earworms indirectly by reducing the consumption of corn earworm eggs by big-eyed bugs. The presence of immobilised pea aphids, however, did not benefit corn earworms indirectly because the consumption of corn earworm eggs by big-eyed bugs was not reduced when they were present. 6. These results suggest that the prey preferences of generalist insect predators mediate indirect interactions among prey species and ultimately affect the population dynamics of the predator and prey species. Understanding the prey preferences of generalist insect predators is essential to predict accurately the efficacy of these insects as biological control agents. [source] The evolution of floral scent and insect chemical communicationECOLOGY LETTERS, Issue 5 2010Florian P. Schiestl Ecology Letters (2010) 13: 643,656 Abstract Plants have evolved a range of strategies to manipulate the behaviour of their insect partners. One powerful strategy is to produce signals that already have a role in the animals' own communication systems. To investigate to what extent the evolution of floral scents is correlated with chemical communication in insects, I analyse the occurrence, commonness, and evolutionary patterns of the 71 most common ,floral' volatile organic compounds (VOCs) in 96 plant families and 87 insect families. I found an overlap of 87% in VOCs produced by plants and insects. ,Floral' monoterpenes showed strong positive correlation in commonness between plants (both gymnosperms and angiosperms) and herbivores, whereas the commonness of ,floral' aromatics was positively correlated between angiosperms and both pollinators and herbivores. According to a multivariate regression analysis the commonness of ,floral' aromatics was best explained by their commonness in pollinators, whereas monoterpenes were best explained by herbivores. Among pollinator orders, aromatics were significantly more common in Lepidoptera than in Hymenoptera, whereas monoterpenes showed no difference among the two orders. Collectively, these patterns suggest that plants and insects converge in overall patterns of volatile production, both for attraction and defence. Monoterpenes seem to have evolved primarily for defence under selection by herbivores, whereas aromatics evolved signalling functions in angiosperms, primarily for pollinator attraction. [source] Synergistic sex pheromone components of the grey-spotted tussock moth, Orgyia ericaeENTOMOLOGIA EXPERIMENTALIS ET APPLICATA, Issue 3 2010Guo-Fa Chen Abstract The grey-spotted tussock moth, Orgyia ericae Germar (Lepidoptera: Lymantriidae), is an important pest of deciduous trees and woody scrublands in northern China. In a field trapping experiment conducted during the flight of the first generation of 2009, synthetic (Z)-6-heneicosen-11-one, a common Orgyia spp. sex pheromone component, attracted O. ericae males. Gas chromatography-mass spectrometry analyses (full scan or selected ion-monitoring mode) of pheromone gland extracts from females revealed the presence of a major, a minor, and a trace component, i.e., (6Z,9Z)-heneicosa-6,9-diene, (6Z,9Z)-tricosa-6,9-diene, and (Z)-6-heneicosen-11-one, respectively. Field experiments during the flight of the second generation showed that (6Z,9Z)-tricosa-6,9-diene, the minor component, was inactive alone or in any combination with the other two components, whereas (6Z,9Z)-heneicosa-6,9-diene and (Z)-6-heneicosen-11-one were weakly attractive when tested individually. However, traps baited with a binary blend of (6Z,9Z)-heneicosa-6,9-diene and (Z)-6-heneicosen-11-one caught seven-fold more moths than any other treatment (except the ternary blend), indicating a strong synergistic interaction between the two components. The analytical and field trapping data suggested that (6Z,9Z)-heneicosa-6,9-diene and (Z)-6-heneicosen-11-one are likely the key sex pheromone components of female O. ericae. This synergistic blend will be useful as an efficient monitoring tool, and possible control tool, to combat this economically and ecologically important forest defoliator. [source] Impact of spinosad on ichneumonid-parasitized Choristoneura rosaceana larvae and subsequent parasitoid emergenceENTOMOLOGIA EXPERIMENTALIS ET APPLICATA, Issue 2 2010J.E. Cossentine Abstract The impact of low levels of spinosad on the obliquebanded leafroller, Choristoneura rosaceana Harris (Lepidoptera: Tortricidae), and the koinobiont endoparasitoid, Apophua simplicipes Cresson (Hymenoptera: Ichneumonidae), was assessed when the parasitoid was in the larval stage within second- and fourth-instar hosts. These are developmental stages that would be exposed to spring orchard treatments of the insecticide. Oral spinosad LC50 levels for unparasitized obliquebanded leafroller hosts were <1% of the recommended orchard treatment levels. Apophua simplicipes survival was significantly reduced within parasitized spinosad-treated second- and fourth-instar larval hosts. Both the leafroller host and parasitoid were much more susceptible (ca. 65-fold) to spinosad when larval hosts fed on spinosad-treated leaf material as opposed to being treated topically. When hosts were exposed to extremely low doses of spinosad, a small percentage of parasitoids was able to survive to emerge as adults. These laboratory trials predict that applications of spinosad may reduce biological control of C. rosaceana populations by ichneumonid endoparasitoids developing within treated hosts. [source] Effects of elevated CO2 associated with maize on multiple generations of the cotton bollworm, Helicoverpa armigeraENTOMOLOGIA EXPERIMENTALIS ET APPLICATA, Issue 1 2010Jin Yin Abstract Under elevated environmental carbon dioxide (CO2), leaf chewers tend to compensate for decreased leaf nutritional quality with increased consumption; mortality and development times also increase and cause a reduction in the fitness of leaf chewers. However, the effect of elevated CO2 on multiple successive generations of these and other insects is not well understood. Furthermore, information about the direct effects of increased environmental CO2 on developmental time and consumption of herbivores is lacking. In this paper, we tested the hypothesis that cascade effects of elevated CO2 through plants, rather than the direct effects of elevated CO2, are the main factors decreasing the fitness of cotton bollworm, Helicoverpa armigera Hübner (Lepidoptera: Noctuidae). We used two series of experiments to quantify the growth, development, and consumption of H. armigera fed on an artificial diet or C4 plants (maize) grown under two CO2 levels (ambient vs. double ambient). In the first series of experiments, elevated CO2 had no effect on the population abundance or individual consumption for three successive generations of cotton bollworms fed on an artificial diet. In the second series of experiments, elevated CO2 reduced population abundance of cotton bollworm larvae for two successive generations when they were fed maize milky grains. The specific effects were longer larval duration, lower fecundity, and decreased rm of cotton bollworms. Furthermore, elevated CO2 increased individual consumption when cotton bollworm was fed maize milky grains for two successive generations and decreased the population's total consumption in the first generation but increased it in the second generation. The results from this study indicate that: (1) The effects of elevated CO2 on three successive generations of cotton bollworm fed on artificial diet were weak, or even non-existent, and (2) elevated CO2 increased the consumption when cotton bollworm were fed maize. Our study also suggests that the damage inflicted by cotton bollworm on maize (a C4 plant) will be seriously affected by the increases in atmospheric CO2, which is unlike our previous results for spring wheat (a C3 plant). [source] Synergistic effect of insect herbivory and plant parasitism on the performance of the invasive tree Schinus terebinthifoliusENTOMOLOGIA EXPERIMENTALIS ET APPLICATA, Issue 2 2009Veronica Manrique Abstract Schinus terebinthifolius Raddi (Anacardiaceae) is an introduced tree from South America that has invaded many ecosystems throughout central and south Florida, USA. Exploratory surveys in the plant's native range identified several potential biocontrol agents, including the leaflet rolling moth, Episimus unguiculus Clarke (Lepidoptera: Tortricidae). The larval stages of E. unguiculus tie together the plant leaflets while feeding and can completely defoliate small plants. The native love vine, Cassytha filiformis L. (Lauraceae), has been found parasitizing S. terebinthifolius in Florida. Natural processes such as plant parasitism may be one of the components of an integrated approach for S. terebinthifolius management in Florida. Thus, the objective of this study was to evaluate the combined effects of insect herbivory and plant parasitism on the performance of S. terebinthifolius. A factorial design experiment was conducted in the greenhouse to determine the effect of C. filiformis parasitism and E. unguiculus feeding damage on the growth and biomass of S. terebinthifolius. Results showed that plant parameters, including leaflet biomass, growth rate, and flower production, were negatively affected by plant parasitism and insect herbivory. Moreover, the decrease in S. terebinthifolius performance was greater when these two factors were combined, indicative of a synergistic relationship. In addition, the combined effect of C. filiformis and E. unguiculus suppressed plant performance for at least 2 months after the moths were removed. Therefore, increased control of S. terebinthifolius stands may be achieved in those areas where C. filiformis is present in Florida (e.g., pinelands, hammock forests) if the biocontrol agent E. unguiculus is approved for release. [source] Resistance of apple trees to Cydia pomonella egg-laying due to leaf surface metabolitesENTOMOLOGIA EXPERIMENTALIS ET APPLICATA, Issue 1 2008Nadia Lombarkia Abstract During host plant selection and particularly after alighting on a plant, chemical cues from the plant surface influence an insect's acceptance of the plant and, subsequently, its egg-laying behaviour. Primary metabolites in the phylloplane may be more important than hitherto known. We have shown that soluble carbohydrates, such as glucose, fructose, and sucrose, and sugar alcohols, such as sorbitol, quebrachitol, and myo -inositol, can be detected by insects after contacting the plant and that they positively influence egg-laying of the codling moth, Cydia pomonella (L.) (Lepidoptera: Tortricidae), on apple trees. We addressed the question whether a lack of these substances could also explain apple tree resistance to C. pomonella in terms of reduced egg-laying. Leaf surface washings were collected in an apple orchard by spraying water on the resistant cultivar X65-11 and on the susceptible cultivar P5R50A4. The washings were tested on a nylon cloth on isolated females under no-choice conditions. The washings were analysed and synthetic blends, each consisting of the six metabolites in the proportions established in the leaf surface washings of both cultivars, were then tested for their effect on egg-laying of C. pomonella. Dose,response egg-laying tests were carried out on substrates impregnated with the X65-11 leaf surface blend at 1, 100, 1 000, and 10 000 times the natural dose. Egg-laying behaviour in the bioassays with leaf surface washings of both cultivars closely resembled egg-laying in the orchard. Washings of P5R50A4 stimulated egg-laying to a greater extent than those of X65-11 and the water control. Synthetic blends reduced substrate acceptance and egg-laying, compared to the washings of X65-11. Ratios between components within the blend are responsible for this resistance. In conclusion, quantities and ratios of the six primary metabolites found on the leaf surface may influence host preference of C. pomonella as well as their egg-laying behaviour, thus they may play a role in the trees' resistance to the codling moth. [source] Lymantria dispar herbivory induces rapid changes in carbon transport and partitioning in Populus nigraENTOMOLOGIA EXPERIMENTALIS ET APPLICATA, Issue 1 2008Benjamin A. Babst Abstract We tested for rapid changes in photosynthate transport and partitioning in response to Lymantria dispar (L.) (Lepidoptera: Lymantriidae) (gypsy moth) herbivory in Populus nigra L. (Salicaceae). Transport and partitioning of [11C]-photosynthate from young mature leaves were measured in vivo before and 18 h after leaf chewing by gypsy moth larvae, which were caged on three older leaves. Following herbivory, there was an increase in export speed of recently fixed carbon from younger mature leaves. The increased export speed was due to a quicker transit time of 11C through the leaf, rather than a change in transport speed through the phloem. Additionally, basipetal partitioning of [11C]-photosynthate was increased following herbivory. Neither of these changes was observed in control plants. This enhancement of export occurs even though herbivores are well known to induce increases in carbon allocation to secondary metabolites within leaves. Our results demonstrate that the use of non-destructive imaging of 11C tracer is a powerful tool for examining plant responses to herbivory. Although the mechanisms underlying the rapid increase in carbon flux to stems and roots remain to be elucidated, our results raise the possibility of a coordinated whole plant response to herbivory. Thus, even when the herbivore specializes on only one plant tissue type, a whole plant approach may be key to understanding how plants respond to herbivory. [source] Interspecific competition between the ichneumonid Campoletis chlorideae and the braconid Microplitis mediator in their host Helicoverpa armigeraENTOMOLOGIA EXPERIMENTALIS ET APPLICATA, Issue 1 2008Shen-Peng Tian Abstract We investigated interspecific competition between Campoletis chlorideae Uchida (Hymenoptera: Ichneumonidae) and Microplitis mediator (Haliday) (Hymenoptera: Braconidae) in their host, the cotton bollworm, Helicoverpa armigera (Hübner) (Lepidoptera: Noctuidae) under laboratory conditions. Cotton bollworm larvae were allowed to be parasitized by both wasp species simultaneously or sequentially at different time intervals. When host larvae were parasitized simultaneously by both parasitoids, the majority of the cocoons produced were of M. mediator. When host larvae were parasitized initially by M. mediator followed by C. chlorideae at 12 or 24 h, parasitoids emerging from the multiparasitized hosts were mainly M. mediator. In contrast, when host larvae were parasitized initially by C. chlorideae, followed by M. mediator 12 or 24 h later, parasitoids emerging from the multiparasitized hosts were mainly C. chlorideae. Dissections of host larvae at various time intervals after parasitization by the two parasitoids showed that first instars of M. mediator could physically attack the larvae of C. chlorideae, but not the eggs of C. chlorideae. When a host was parasitized by both wasp species sequentially, more host larvae died and the number of wasp offspring was significantly reduced compared to a host parasitized by only one wasp. Conversely, in simultaneous multiparasitism, the host mortality and wasp offspring production were not significantly different from those parasitized by single wasp species. [source] Diadegma mollipla parasitizing Plutella xylostella: host instar preference and suitabilityENTOMOLOGIA EXPERIMENTALIS ET APPLICATA, Issue 1 2008Robert S. Nofemela Abstract Oviposition decisions (i.e., host selection and sex allocation) of female parasitoids are expected to correspond with host quality, as their offspring fitness is dependent on the amount and quality of resources provided by a single host. The host size model assumes that host quality is a linear function of host size, with larger hosts believed to contain a greater quantity of resources, and thus be more profitable than smaller hosts. We tested this assertion in the laboratory on a solitary larval,pupal parasitoid Diadegma mollipla (Holmgren) (Hymenoptera: Ichneumonidae) developing on three instars (second,fourth) of one of its hosts, the diamondback moth, Plutella xylostella (L.) (Lepidoptera: Plutellidae). In a no-choice test, parasitism levels and sex ratio (i.e., proportion of female progeny) were significantly high in hosts attacked in the second instar followed by third then fourth instars. However, the few parasitoids that completed a generation from the fourth instars did so significantly faster than conspecifics that started development in the other two instars. In direct observations, however, the parasitoids (i) randomly attacked the various host instars, (ii) spent a similar period examining the various host instars with their ovipositors, (iii) subdued all three host instars with about the same effort, and (iv) no statistical differences were observed in the attack rates on the three host instars. In a choice test, the females parasitized significantly more third instars followed by second then fourth instars. However, total parasitism in this experiment was 43% lower compared to parasitism of only second instars in the no-choice test. No significant differences were detected in progeny sex ratios. In both choice and no-choice tests, significantly more fourth instars died during the course of the experiments than second instars, while third instars were intermediate. The higher parasitism of third than second instars in the choice test indicates that the females perceived larger hosts as higher quality than smaller hosts, despite their lower suitability for larval development. [source] | |||||||||||||||||||||||||||||||||||||||||||