The effects of habitat fragmentation on niche requirements of the marsh fritillary, Euphydryas aurinia, (Rottemburg, 1775) on calcareous grasslands in southern UK

The marsh fritillary, Euphydryas aurinia, has declined greatly in distribution across its range within Europe, resulting in its designation as a protected species under Annex II of the 1979 Bern Convention and the EC Habitats and Species Directive. The decline has been linked to a marked reduction in the extent of suitable calcareous and wet grassland habitats, habitats which have been lost through conversion of land to agriculture or urban areas, or reduced in quality due to inappropriate management. The UK is now one of the major strongholds for this butterfly in Europe, although much of the remaining habitat is small, isolated and highly fragmented. E. aurinia populations fluctuate greatly due to the combined effects of biotic (e.g. parasitoids) and abiotic (e.g. climate change) factors. We quantified the habitat associations of larval webs of E. aurinia on fragmented versus extensive (unfragmented) calcareous grassland habitat in southern England to test the hypothesis that habitat requirements of E. aurinia are more constrained within fragmented landscapes. Within both fragmented and unfragmented landscapes the quality and quantity of its main host plant in the UK, Succisa pratensis, was positively related to numbers of E. aurinia larval webs found. The sward height was also important at predicting the distribution of larval webs in both landscapes, although the heights were greater within sites in the unfragmented (≈20 cm) compared to fragmented (≈15 cm) landscape. We also found significant effects of elevation and the cover of bare ground on numbers of larval webs. Elevation was strongly correlated with the availability of host plant, whilst bare ground was only significant on sites within the fragmented landscape, showing a negative relationship with number of larval webs. Our results further emphasise the importance of not only maintaining the habitat quality of extant calcareous grassland sites for E. aurinia in the UK, but also increasing the size and connectivity of these sites to increase the chances and rate of (re)colonisation of unoccupied but suitable habitat. In addition, we show that the habitat requirements of E. aurinia on sites in a large unfragmented landscape may be less specific and thus require less extensive management than that required to create optimal conditions necessary at smaller, more isolated sites in fragmented landscapes.     

Host plants and pollination regions for the long‐distance migratory noctuid moth,Hadula trifolii Hufnagel in China

Nocturnal moths are important pollinators of plants. The clover cutworm, Hadula trifolii, is a long‐distance migratory nocturnal moth. Although the larvae of H. trifolii are polyphagous pests of many cultivated crops in Asia and Europe, the plant species pollinated by the adult are unclear. Pollen species that were attached to individual migrating moths of H. trifolii were identified based on pollen morphology and DNA to determine their host plants, geographic origin, and pollination areas. The moths were collected on their seasonal migration pathway at a small island, namely Beihuang, in the center of the Bohai Sea of China during 2014 to 2018. Pollen was detected on 28.60% of the female moths and 29.02% of the male, mainly on the proboscis, rarely on compound eyes and antennae. At least 92 species of pollen from 42 plant families, mainly from Asteraceae, Amaranthaceae, and Pinaceae, distributed throughout China were found on the test moths. Migratory H. trifolii moths visited herbaceous plants more than woody plants. Pollen of Macadamina integrifolia or M. tetraphylla was found on moths early in the migratory season. These two species are distributed in Guangdong, Yunnan, and Taiwan provinces in China, indicating that migratory moths probably traveled about 2000 km from southern China to the Beihuang Island in northern China. Here, by identifying plant species using pollen, we gained a better understanding of the interactions between H. trifolii moths and a wide range of host plants in China. This work provides valuable and unique information on the geographical origin and pollination regions for H. trifolii moths.     

Interaction of glucosinolate content of Arabidopsis thaliana mutant lines and feeding and oviposition by generalist and specialist lepidopterans

The diamondback moth, Plutella xylostella L. (Lepidoptera: Plutellidae), is an insect specialized on glucosinolate-containing Brassicaceae that uses glucosinolates in host-plant recognition. We used wild-type and mutants of Arabidopsis thaliana (L.) Heynh. (Brassicaceae) to investigate the interaction between plant glucosinolate and myrosinase content and herbivory by larvae of the generalist Helicoverpa armigera Hübner (Lepidoptera: Noctuidae) and the specialist P. xylostella. We also measured glucosinolate changes as a result of herbivory by these larvae to investigate whether herbivory and glucosinolate induction had an effect on oviposition preference by P. xylostella. Feeding by H. armigera and P. xylostella larvae was 2.1 and 2.5 times less, respectively, on apk1 apk2 plants (with almost no aliphatic glucosinolates) than on wild-type plants. However, there were no differences in feeding by H. armigera and P. xylostella larvae on wild-type, gsm1 (different concentrations of aliphatic glucosinolates compared to wild-type plants), and tgg1 tgg2 plants (lacking major myrosinases). Glucosinolate induction (up to twofold) as a result of herbivory occurred in some cases, depending on both the plant line and the herbivore. For H. armigera, induction, when observed, was noted mostly for indolic glucosinolates, while for P. xylostella, induction was observed in both aliphatic and indolic glucosinolates, but not in all plant lines. For H. armigera, glucosinolate induction, when observed, resulted in an increase of glucosinolate content, while for P. xylostella, induction resulted in both a decrease and an increase in glucosinolate content. Two-choice tests with wild-type and mutant plants were conducted with larvae and ovipositing moths. There were no significant differences in preference of larvae and ovipositing moths between wild-type and gsm1 mutants and between wild-type and tgg1 tgg2 mutants. However, both larvae and ovipositing moths preferred wild-type over apk1 apk2 mutants. Two-choice oviposition tests were also conducted with P. xylostella moths comparing undamaged plants to plants being attacked by larvae of either P. xylostella or H. armigera. Oviposition preference by P. xylostella was unaffected as a result of larval plant damage, even in the cases where herbivory resulted in glucosinolate induction.     

Fate of cocaine in the lymantriid Eloria noyesi, a predator of Erythroxylum coca

Larvae of the lymantriid moth Eloria noyesi, which are obligate feeders on Erythroxylum coca, excrete most of the ingested cocaine as unchanged base. Cocaine, analysed by mass fragmentography, is readily, detectable in the blood of larvae and is presumably sequestered during larval feeding, since it is present in the bodies of adult moths that do not feed on E. coca. Cocaine is an effective feeding deterrent for the ant Monomorium pharaonis when present at a concentration below that found in the leaves of E. coca.     

Flowers for better pest control? Effects of apple orchard groundcover management on mites (Acari), leafminers (Lepidoptera,Scitellidae), and fruit pests

Flowering companion plants provide nectar, pollen, alternative prey, shelter, and overwintering habitat for arthropod natural enemies and thus might increase their abundance and efficacy in pest control in agricultural fields. We report the results of a 6-year study on the effects of annual and perennial flowering herbs sown in alleys of an apple orchard on phytophagous and predacious mites, leafminer moths and their parasitoids and on pests causing fruit injury. Plots with weed-free bare ground and with regularly mowed grass served as controls. The abundance and diversity of predatory phytoseiid mites increased in the presence of flowering ground cover plants. However, this positive effect on phytoseiids was confined only to spring and autumn and intraguild predation (Typhlodromus pyri gradually displaced Amblyseius andersoni in the presence of flowers) also constrained their enhancement. Spider mites’ (Tetranychidae) abundance was low in all years and did not increase with the alley herb coverage. Incidence of the leafminer Leucoptera malifoliella was similar among the treatments despite the higher parasitism rate and parasitoid diversity in the plot with flowering herbs. We demonstrated that in the presence of flowering ground cover plants, the sex ratio of eulophid parasitoids' (mainly Chrysocharis pentheus) reared from L. malifoliella larvae and pupae shifted towards a male bias. Ground cover management had no effect on fruit injury caused by codling moth (Cydia pomonella) and summer fruit tortrix moth (Adoxophyes orana) and on the percentage of apples without insect damage.     

Synchronisation of adult activity of the archaic moth, <Emphasis Type="Italic">Micropterix calthella</Emphasis> L. (Lepidoptera,Micropterigidae), with anthesis of sedges (<Emphasis Type="Italic">Carex</Emphasis> spp., Cyperaceae) in an ancient wood

Micropterix calthella L. (Micropterigidae) is a small, day-flying moth from the basal-most extant lineage of the Lepidoptera. The species name reflects its conspicuous presence on Caltha palustris L. (Ranunculaceae). However, adults also favour sedges (Carex spp., Cyperaceae), on which they gather gregariously to feed on pollen and find mates. In a UK ancient wood, the phenology of eight sedge species together with individual moth and mating pair densities were monitored from 15th April to 8th June 2009. 4841 moth sightings were recorded. Moths on Carex spikes at various developmental stages were compared with null models to test for preference patterns. Approximately 99% of individuals selected Carex spikes where dehiscing anthers were present. The sedge phenology data suggest three distinct periods of pollen production. Overlaying this with the moth data reveals moth phenology strongly linked to a suite of early and mid-season woodland sedges. Of the twenty-eight other angiosperm species (seventeen families) in flower, only Ranunculus ficaria L. (Ranunculaceae) and R. repens L. attracted moths. Adult moths kept in captivity on potted Carex flacca Schreb. for 10 days laid eggs at the plant-soil interface. When C. flacca pollen production ceased, surviving adults were moved onto freshly dehiscing anthers of potted C. pallescens L., where they survived a further 14 days. Soil-dwelling first instar larvae were observed to consume C. sylvatica Huds leaves. In a choice experiment, larvae were significantly more likely to consume C. sylvatica than Stellaria media (L.) Vill. (Caryophyllaceae) leaf material (previously noted to be favoured by larvae). Synchrony between adult moths and Carex spp., and the use of Carex by both adults and larvae, suggests sedges may be host plants for M. calthella in lowland ancient woodlands.     

Geographic variation in oviposition preference for male and female host plants in a geometrid moth: implications for evolution of host choice

Several dioecious plant species exhibit sexual dimorphisms in defensive traits. However, the effects of sexual dimorphism on defense against herbivores remain poorly understood. Eurya japonica (Thunb.) (Theaceae) is a dioecious shrub that shows sexual dimorphism in the chemical defense of flower buds. Female calyces contain higher concentrations of total phenolics and condensed tannins than do male calyces. Male flower buds are edible for a florivore moth, Chloroclystis excisa (Butler) (Lepidoptera: Geometridae), whereas the female flower buds are lethal to the moth larvae. The moths prefer to oviposit on male over female E. japonica flower buds. As the moths also occur in areas lacking E. japonica, we tested whether the oviposition preference for E. japonica flower sex differed between moths sympatric and allopatric with E. japonica. The moths sympatric with E. japonica showed a stronger preference for male E. japonica than the moths allopatric with E. japonica. Our phylogeographic study using mitochondrial cytochrome oxidase subunit I gene sequences revealed little genetic differentiation between moth populations sympatric and allopatric with E. japonica. These results suggest that the adaptive oviposition preference for flower sex of E. japonica has evolved rapidly in C. excisa.     

Characterizing the interaction between the bogus yucca moth and yuccas: do bogus yucca moths impact yucca reproductive success?

Yucca moths are most well known for their obligate pollination mutualism with yuccas, where pollinator moths provide yuccas with pollen and, in exchange, the moth larvae feed on a subset of the developing yucca seeds. The pollinators, however, comprise only two of the three genera of yucca moths. Members of the third genus, Prodoxus, are the bogus yucca moths and are sister to the pollinator moths. Adult Prodoxus lack the specialized mouthparts used for pollination and the larvae feed on plant tissues other than seeds. Prodoxus larvae feed within the same plants as pollinator larvae and have the potential to influence yucca reproductive success directly by drawing resources away from flowers and fruit, or indirectly by modifying the costs of the mutualism with pollinators. We examined the interaction between the scape-feeding bogus yucca moth, Prodoxus decipiens, and one of its yucca hosts, Yucca filamentosa, by comparing female reproductive success of plants with and without moth larvae. We determined reproductive success by measuring a set of common reproductive traits such as flowering characteristics, seed set, and seed germination. In addition, we also quantified the percent total nitrogen in the seeds to determine whether the presence of larvae could potentially reduce seed quality. Flowering characteristics, seed set, and seed germination were not significantly different between plants with and without bogus yucca moth larvae. In contrast, the percent total nitrogen content of seeds was significantly lower in plants with P. decipiens larvae, and nitrogen content was negatively correlated with the number of larvae feeding within the inflorescence scape. Surveys of percent total nitrogen at three time periods during the flowering and fruiting of Y. filamentosa also showed that larval feeding decreased the amount of nitrogen in fruit tissue. Taken together, the results suggest that although P. decipiens influences nitrogen distribution in Y. filamentosa, this physiological effect does not appear to impact the female components of reproductive success.     

Host-plant patch qualities and presence of a likely competitor species affect the distribution and abundance of a rare British moth, <Emphasis Type="Italic">Cucullia lychnitis</Emphasis>

Understanding the environmental factors that affect the distribution and abundance of rare and threatened species can help identify priority sites for conservation action such as habitat management. The moth Cucullia lychnitis is identified in UK legislation as a priority species for conservation. Its conspicuous larvae feed on a patchily distributed host plant Verbascum nigrum, but are entirely absent from some host plant patches within the species’ range. Environmental variability among patches was investigated to understand factors affecting (i) patch occupancy by C. lychnitis and (ii) abundance of C. lychnitis, where present. Occupancy of individual V. nigrum plants within occupied patches was also investigated. The likelihood of patch occupancy increased with patch size, and decreased with patch isolation. Abundance of C. lychnitis was negatively correlated with patch isolation and with abundance of the weevil Cionus nigritarsis, which exploits the same host plant and may be a competitor. Within occupied patches, larvae of C. lychnitis were significantly more likely to be found on taller plants with more flower spikes; such plants are typical of established rather than newly-created patches. These results may help to guide efforts to conserve C. lychnitis, highlighting the importance of habitat connectivity and indicating potential management actions to promote features positively associated with larval incidence and abundance.     

Convergent evolution of anti-bat sounds

Bats and their insect prey rely on acoustic sensing in predator prey encounters—echolocation in bats, tympanic hearing in moths. Some insects also emit sounds for bat defense. Here, we describe a previously unknown sound-producing organ in Geometrid moths—a prothoracic tymbal in the orange beggar moth (Eubaphe unicolor) that generates bursts of ultrasonic clicks in response to tactile stimulation and playback of a bat echolocation attack sequence. Using scanning electron microscopy and high-speed videography, we demonstrate that E. unicolor and phylogenetically distant tiger moths have evolved serially homologous thoracic tymbal organs with fundamentally similar functional morphology, a striking example of convergent evolution. We compared E. unicolor clicks to that of five sympatric tiger moths and found that 9 of 13 E. unicolor clicking parameters were within the range of sympatric tiger moths. Remaining differences may result from the small size of the E. unicolor tymbal. Four of the five sympatric clicking tiger moth species were unpalatable to bats (0–20 % eaten), whereas E. unicolor was palatable to bats (86 % eaten). Based on these results, we hypothesize that E. unicolor evolved tymbal organs that mimic the sounds produced by toxic tiger moths when attacked by echolocating bats.     

Stable isotopes of Lithosiini and lichens in Hong Kong show the biodindicator potential of lichenivorous moths

Urban landscapes provide unique environments for a wide variety of plants and animals, but their suitability may be limited by anthropogenic impacts such as pollution. We examined the potential utility of lichen and lichen-feeding moths as biodindicators of air pollution in Hong Kong by comparing carbon (C) and nitrogen (N) stable isotope values in lichens, lichenivorous and non-lichenivorous moths (Lepidoptera: Erebidae) and a moth outgroup (Lepidoptera: Geometridae). Our results show that stable isotope values for C and N were similar for lichens and lichen feeding moths, while non-lichen feeding moths formed a distinct group. In addition, we found consistent δ¹³C and δ¹⁵N values across moth body parts, indicating that any portion of the specimen is suitable for isotopic fingerprinting. Our results highlight that lichen feeding moths may be useful for integrating signals of atmospheric nitrogen pollution and could therefore have utility in monitoring and quantifying air quality over time and space.     

Impact of reassociation with a coevolved herbivore on oviposition deterrence in a hostplant

Although selection by herbivores for increased feeding deterrence in hostplants is well documented, selection for increased oviposition deterrence is rarely examined. We investigated chemical mediation of oviposition by the parsnip webworm (Depressaria pastinacella) on its principal hostplant Pastinaca sativa to determine whether ovipositing adults choose hostplants based on larval suitability and whether hostplants experience selection for increased oviposition deterrence. Webworms consume floral tissues and florivory selects for increased feeding deterrents; moths, however, oviposit on leaves of pre-bolting plants. Exclusive use of different plant parts for oviposition and larval feeding suggests oviposition should select for increased foliar deterrents. Recent webworm colonization of New Zealand (NZ) allowed us to assess phenotypic changes in foliar chemicals in response to webworm oviposition. In a common garden experiment, we compared NZ populations with and without a history of infestation from 2004 to 2006 for changes in leaf chemistry in response to oviposition. Three leaf volatiles, cis- and trans-ocimene, and β-farnesene, elicit strong responses in female moth antennae; these compounds were negatively associated with oviposition and are likely oviposition deterrents. Leaf β-farnesene was positively correlated with floral furanocoumarins that deter florivory; greater oviposition on plants with low floral furanocoumarins indicates that moths preferentially oviposit on parsnips most suitable for larval growth. Unlike florivory, high oviposition on leaves did not lower plant fitness, consistent with the fact that NZ parsnip foliar chemistry was unaffected by 3–6 years of webworm infestation. Thus, in this system, selection by ovipositing moths on foliar chemistry is weaker than selection by larvae on floral chemistry.     

Host location and suitability of the armyworm larvae of Mythimna unipuncta for the tachinid parasitoid Exorista larvarum

This work evaluates the efficiency of Exorista larvarum (L.) (Diptera: Tachinidae) in localizing and parasitizing the larvae of the noctuid moth Mythimna unipuncta (Haworth) (Lepidoptera: Noctuidae) in laboratory conditions, in a wind tunnel and in PVC cages. The most important cue in host localization by E. larvarum females was host-induced plant volatiles. Visual cues, natural maize volatiles and artificially damaged plants were less efficient for host localization. Mortality in M. unipuncta larvae on which E. larvarum females laid eggs was high. This finding indicates that E. larvarum could effectively contribute to lowering the population size of M. unipuncta, even if only few parasitoids successfully complete their development in the host. Further studies with other possible hosts must be done to apply E. larvarum successfully against M. unipuncta larvae in maize fields.     

Phenotypic divergence and inter-specific trait correlation in a plant-pollinator/seed predator mutualism

Plant-pollinator interactions have been suggested as key drivers of morphological divergence and speciation of the involved taxa. These interactions can also promote sexual dimorphism in both the plant and pollinator, particularly if the pollinator is also a seed-eater and/or exerts different selection pressures on male and female plants. Here we tested the hypotheses that plant-pollinator interactions can be reflected in trait variation and sexual dimorphism in both organisms within and across populations. Across nine European populations, we examined intraspecific variation and sexual dimorphism in phenotypic traits potentially involved in the plant–insect interaction of the dioecious white campion Silene latifolia (Caryophyllaceae) and its specialist pollinator Hadena bicruris (Noctuidae). This interaction is expected to entail sex-specific selective pressures, as female moths lay eggs on female plants and the larvae predate on the seeds during their development. We compared divergence in phenotypic traits among populations and between sexes within populations, examined correlations between plant and pollinator traits, and between phenotypic distances and genetic distances among co-occurring populations for both plants and insects. We found key differences in phenotypic traits across populations of both the plant and moth, though only in the moth were these differences correlated with geographic distances. We also found evidence for sexual dimorphism in the plant but not in the pollinator. Evolution of floral sexual dimorphism in S. latifolia most likely results from the joint contribution of different selective forces, including biotic interactions with H. bicruris moths.     

Temporal variation in different life stages of moths (Lepidoptera) from a southwestern temperate forest of Korea: A preliminary study

Two study sites in a temperate forest in Mt. Seungdal-san, Muan, Jeonnam in southwestern Korea were selected for the collection of caterpillars and adult moths (Lepidoptera). Here, we determined (1) the characteristics of moth fauna based on lepidopteran larvae and adults, and (2) the differences in temporal variation between these two developmental stages. In addition, we investigated the life history of moth species collected at the surveyed sites. Of the 206 caterpillars collected, 17 moth species from 9 families were successfully reared. A total of 342 adult moth species and 2108 individuals from 15 families were collected. Twenty-two plants were identified as host plants of 188 caterpillars. Two tree species, Prunus serrulata var. spontanea and Quercus serrata, were widely distributed in the study sites. Leaf water content (%) of Quercus serrata and Carpinus laxiflorawas the highest in June, whereas the leaf water content of Platycarya strobilacea was the highest in August. We postulated that many of the variables in the temperate forest, such as host plant availability, parasitoids, disease, and weather, affected the lepidopteran caterpillar populations. There were differences in species composition among the sampling methods which suggest the need for diverse methods to uncover total biodiversity. However, it should be noted that a long term and well-planned study with efficient rearing of caterpillars is needed to better understand these correlations.     

Gelechiidae moths are capable of chemically dissolving the pollen of their host plants: first documented sporopollenin breakdown by an animal

Background

Many insects feed on pollen surface lipids and contents accessible through the germination pores. Pollen walls, however, are not broken down because they consist of sporopollenin and are highly resistant to physical and enzymatic damage. Here we report that certain Microlepidoptera chemically dissolve pollen grains with exudates from their mouthparts.

Methodology/Principal Findings

Field observations and experiments in tropical China revealed that two species of Deltophora (Gelechioidea) are the exclusive pollinators of two species of Phyllanthus (Phyllanthaceae) on which their larvae develop and from which the adults take pollen and nectar. DNA sequences placed the moths and plants phylogenetically and confirmed that larvae were those of the pollinating moths; molecular clock dating suggests that the moth clade is younger than the plant clade. Captive moths with pollen on their mouthparts after 2-3 days of starvation no longer carried intact grains, and SEM photographs showed exine fragments on their proboscises. GC-MS revealed cis-β-ocimene as the dominant volatile in leaves and flowers, but GC-MS analyses of proboscis extracts failed to reveal an obvious sporopollenin-dissolving compound. A candidate is ethanolamine, which occurs in insect hemolymphs and is used to dissolve sporopollenin by palynologists.

Conclusions/Significance

This is the first report of any insect and indeed any animal chemically dissolving pollen.     

Host‐plant associated genetic divergence of two Diatraea spp. (Lepidoptera: Crambidae) stemborers on novel crop plants

Diatraea lineolata and Diatraea saccharalis (Lepidoptera: Crambidae) are moths with stemboring larvae that feed and develop on economically important grasses. This study investigated whether these moths have diverged from a native host plant, corn, onto introduced crop plants including sorghum, sugarcane, and rice. Diatraea larvae were collected from these four host plants throughout the year in El Salvador and were reared on artificial diet until moths or parasitoids emerged. Adult moths were subsequently identified to species. Amplified fragment length polymorphisms (AFLPs) and mitochondrial DNA cytochrome oxidase I (COI) were used to examine whether or not there was genetic divergence of D. lineolata or D. saccharalis populations on the four host plants. Percent parasitism was also determined for each moth on its host plants. D. lineolata was collected from corn in the rainy season and sorghum in the dry season. D. saccharalis was most abundant on sugarcane in the rainy season and sorghum in the dry season. The AFLP analysis found two genetically divergent populations of both D. lineolata and D. saccharalis. Both moths had high levels of parasitism on their dominant host plant in the rainy season, yet had low levels of parasitism on sorghum in the dry season. The presence of two genotypes of both Diatraea spp. on sorghum suggest that host‐associated differentiation is occurring on this novel introduced crop plant.     

"From freeze with moths": first discovery of a habitat in Andean salars for noctuid moths

Noctuid moths flutter in the high Andes nights at 4,000 m. s. n. m. Their larvae feed on aerial or underground parts of succulent plants. Many of these species are new to science. Strategies and adaptations of the moths for survival in the high Andes mountains are: a circulatory system that includes an abdominal thoracic countercurrent heat exchanger, and they are insulated from the environment by a coat of dense hair like scales. Recently, during January and July 2004, in the northern desert of Chile, called Salar de Punta Negra, under the salt crust we found a large number of pupae and larvae that correspond to three new species of noctuid moth - this pupation site is located in a 10 m wide area surrounding a water body; the mean observed density is 13 to 15 pupae per 100 cm(2). This is a new extreme habitat conquered by noctuid moths.     

Feeding on Host Plants with Different Concentrations and Structures of Pyrrolizidine Alkaloids Impacts the Chemical-Defense Effectiveness of a Specialist Herbivore

Sequestration of chemical defenses from host plants is a strategy widely used by herbivorous insects to avoid predation. Larvae of the arctiine moth Utetheisa ornatrix feeding on unripe seeds and leaves of many species of Crotalaria (Leguminosae) sequester N-oxides of pyrrolizidine alkaloids (PAs) from these host plants, and transfer them to adults through the pupal stage. PAs confer protection against predation on all life stages of U. ornatrix. As U. ornatrix also uses other Crotalaria species as host plants, we evaluated whether the PA chemical defense against predation is independent of host plant use. We fed larvae from hatching to pupation with either leaves or seeds of one of eight Crotalaria species (C. incana, C. juncea, C. micans, C. ochroleuca, C. pallida, C. paulina, C. spectabilis, and C. vitellina), and tested if adults were preyed upon or released by the orb-weaving spider Nephila clavipes. We found that the protection against the spider was more effective in adults whose larvae fed on seeds, which had a higher PA concentration than leaves. The exceptions were adults from larvae fed on C. paulina, C. spectabilis and C. vitellina leaves, which showed high PA concentrations. With respect to the PA profile, we describe for the first time insect-PAs in U. ornatrix. These PAs, biosynthesized from the necine base retronecine of plant origin, or monocrotaline- and senecionine-type PAs sequestered from host plants, were equally active in moth chemical defense, in a dose-dependent manner. These results are also partially explained by host plant phylogeny, since PAs of the host plants do have a phylogenetic signal (clades with high and low PA concentrations in leaves) which is reflected in the adult defense.     

Limiting the cost of mutualism: the defensive role of elongated gynophore in the leafflower–moth mutualism

Mutualisms are interactions from which both partners benefit but may collapse if mutualists’ costs and benefits are not aligned. Host sanctions are one mechanism whereby hosts selectively allocate resources to the more cooperative partners and thereby reduce the fitness of overexploiters; however, many mutualisms lack apparent means of host sanctions. In mutualisms between plants and pollinating seed parasites, such as those between leafflowers and leafflower moths, pollinators consume subsets of the seeds as larval food in return for their pollination service. Plants may select against overexploiters by selectively aborting flowers with a heavy egg load, but in many leafflower species, seeds are fully eaten in some fruits, suggesting that such a mechanism is not present in all species. Instead, the fruits of Breynia vitis-idaea have stalk-like structures (gynophore) through which early-instar moth larvae must bore to reach seeds. Examination of moth mortality in fruits with different gynophore lengths suggested that fruits with longer gynophore had higher moth mortality and, therefore, less seed damage. Most moth mortality occurred at the egg stage or as early larval instar before moths reached the seeds, consistent with the view that gynophore functions to prevent moth access to seeds. Gynophore length was unaffected by plant size, extent of moth oviposition, or geography; thus, it is most likely genetically controlled. Because gynophores do not elongate in related species whose pollinators oviposit directly into the ovary, the gynophore in B. vitis-idaea may have evolved as a defense to limit the cost of the mutualism.