Exotic Host Plants Research Articles

Dose-dependent dynamics of densovirus infection in two nymphalid butterfly species utilizing native or exotic host plants

Insects are attacked by a diverse range of microbial pathogens in the wild. In herbivorous species, larval host plants frequently play a critical role in mediating susceptibility to infection. Characterizing such plant-mediated effects on herbivore-pathogen interactions can provide insight into patterns of infection across wild populations. In this study, we investigated the effects of host plant use by two North American butterflies, Euphydryas phaeton (Nymphalidae) and Anartia jatrophae (Nymphalidae), on entomopathogen infection across a range of three doses. Both of these herbivores recently incorporated the same exotic plant, Plantago lanceolata (Plantaginaceae), into their host range and are naturally infected by the same entomopathogen, Junonia coenia densovirus (Parvoviridae), in wild populations. We performed two factorial experiments in which E. phaeton and A. jatrophae were reared on either P. lanceolata or a native host plant [Chelone glabra (Plantaginaceae) for E. phaeton; Bacopa monnieri (Plantaginaceae) for A. jatrophae] and inoculated with either a low, medium, or high dose of the virus. In E. phaeton, the outcomes of infection were highly dose-dependent, with inoculation with higher viral doses resulting in faster time to death and greater mortality. However, neither survival nor postmortem viral burdens varied depending upon the host plant that was consumed. In contrast, host plant use had a strong effect on viral burdens in A. jatrophae, with consumption of the exotic plant appearing to enhance host resistance to infection. Together, these results illustrate the variable influences of host plant use on herbivore resistance to infection, highlighting the importance of investigating plant-herbivore relationships within a tritrophic framework.

Pierid Butterflies, Legume Hostplants, and Parasitoids in Urban Areas of Southern Florida.

Are parasitoids less likely to find their Lepidoptera hosts on non-native hostplants than native hostplants? We predicted that with longer periods of coevolution between herbivores and the plants they consume, the parasitoids that provide top-down control would be more attuned to finding their hosts on native plants. To test this hypothesis, we collected immature stages of sulfur butterflies (the cloudless sulfur (Phoebis sennae) and the orange-barred sulfur (Phoebis agarithe) over a three-year period (2008-2011) from native and ornamental hostplants in the genus Senna in three different parts of the urban landscape of Miami, Florida, USA. We reared the immature specimens to pupation and either eclosion of adults or emergence of parasitoids and compared the levels of parasitization among the three areas, and among native vs. exotic hostplants. We found, contrary to our prediction, that caterpillars feeding on non-native leguminous hostplant species were more likely to be parasitized than those feeding on native hostplants. We discuss this surprising finding in the light of recent findings in other plant/herbivore/parasitoid systems.

Endemic island plant–herbivore interactions: Kamehameha butterfly (Nymphalidae) and Hawaiian Urticaceae

AbstractInsect–plant interactions are less well studied than other types of herbivory on islands, precluding a comprehensive understanding of the evolutionary ecology of these interactions. Declines in native island plants and insects call for urgent attention to characterize these species' interactions for their conservation and to better understand evolution in these unique, insular ecosystems. In Hawai‘i, the Kamehameha butterfly (Vanessa tameamea) is one of only two native butterflies, and larvae are specialists on native urticaceous plants. Using a no‐choice bioassay, we investigated performance of V. tameamea reared from egg hatching through eclosion on four native urticaceous host plants, Boehmeria grandis, Pipturus albidus, Touchardia latifolia, and Touchardia oahuensis, and one exotic urticaceous species, Cecropia obtusifolia. Performance varied significantly among the plant diets, with V. tameamea performing best on P. albidus and T. oahuensis among the performance metrics of survival, pupal and adult body mass, and development time. Larval responses to the exotic host plant C. obtusifolia varied among populations, with O‘ahu caterpillars successfully completing development on it, but Hawai‘i Island caterpillars rejecting it completely, suggesting a geographic mosaic for this novel species interaction. Characterization of a suite of nutritive and defensive plant traits revealed significant variability among plant species, but patterns did not align well with V. tameamea performance rankings, making it difficult to identify key drivers of host plant quality. Future work examining additional plant traits under natural conditions would provide new insights, contributing critical ecological information to conserve this charismatic island species.

Feeding on an exotic host plant enhances plasma levels of phenoloxidase by modulating feeding efficiency in a specialist insect herbivore.

Background: Exotic plant species represent a novel resource for invertebrates and many herbivorous insects have incorporated exotic plants into their diet. Using a new host plant can have physiological repercussions for these herbivores that may be beneficial or detrimental. In this study, we compared how using an exotic versus native host plant affected the immune system response and feeding efficiency of a specialist lepidopteran, the common buckeye (Junonia coenia: Nymphalidae, Hübner 1822). Materials and Methods: In a lab experiment, larvae were reared on either the exotic host plant, Plantago lanceolata (Plantaginaceae), or the native host plant, Mimulus guttatus (Phrymaceae). Beginning at second instar feeding efficiency data were collected every 2days until fifth instar when immune assays were performed. Immune assays consisted of standing phenoloxidase activity, total phenoloxidase activity, and melanization. Results: Interestingly, we found that all three immune system parameters were higher on the exotic host plant compared to the native host plant. The exotic host plant also supported higher pupal weights, faster development time, greater consumption, and more efficient approximate digestibility. In contrast, the native host plant supported higher efficiency of conversion of ingested and digested food. The relationship between immunity and feeding efficiency was more complex but showed a large positive effect of greater host plant consumption on all immune parameters, particularly for the exotic host plant. While not as strong, the efficiency of conversion of digested food tended to show a negative effect on the three immune parameters. Conclusion: Overall, the exotic host plant proved to be beneficial for this specialist insect with regard to immunity and many of the feeding efficiency parameters and continued use of this host plant is predicted for populations already using it.

Insects allocate eggs adaptively according to plant age, stress, disease or damage.

Most herbivorous insects can only survive on a small subset of the plant species in its environment. Consequently, adult females have evolved sophisticated sensory recognition systems enabling them to find and lay eggs on plants supporting offspring development. This leads to the preference–performance or ‘mother knows best’ hypothesis that insects should be attracted to host plants that confer higher offspring survival. Previous work shows insects generally select plant species that are best for larval survival, although this is less likely for crops or exotic host plants. Even within a species, however, individual plants can vary greatly in potential suitability depending on age, access to water or nutrients or attack by pathogens or other herbivores. Here, I systematically review 71 studies on 62 insect species testing the preference–performance hypothesis with sets of plants varying in age, stress, fungal/microbial infection or herbivore damage. Altogether, 77% of insects tested with a native host (N = 43) allocated their eggs to plants best for offspring development, as did 64% (N = 22) of insects tested with an exotic host. Results were similar across plant age, stress, disease and damage categories. These findings show adaptive maternal behaviour in insects occurs for both host species and variation among individual plants.

Augmentative Releases of Two Diachasmimorpha longicaudata (Hymenoptera: Braconidae) Population Lines Under Field-Cage Conditions to Control Ceratitis capitata (Diptera: Tephritidae).

Ceratitis capitata (Wiedemann) (Diptera: Tephritidae), known as Medfly, is a severe agricultural invasive pest in Argentinian fruit-producing regions. The native habitat disturbance and introduction and spread of exotic host plants strongly favored Medfly proliferation. This scenario is common throughout the northern subtropical citrus-growing region. Environmentally friendly strategies to suppress Medfly populations by the National Fruit Fly Control and Eradication Program have currently been taken. One of these actions involves augmentative biological control through releases of the exotic parasitoid Diachasmimorpha longicaudata (Ashmead) (Hymenoptera: Braconidae). Consequently, the hypothesis that the effectiveness of D. longicaudata females, from two different population lines, in controlling Medfly larvae progressively increases as the density of released females increases was tested. One parasitoid line derives from larvae of a biparental Medfly strain. The other hails from irradiated larvae of the genetic sexing Temperature Sensitive Lethal Vienna-8 medfly strain reared at the "BioPlanta San Juan" biofactory. Parasitoids foraged for 24h on peaches artificially inoculated with naked lab-reared biparental Medfly larvae. Peaches were placed near the roof or on the ground in field cages. Five treatments (20, 40, 80, 160, and 320 females released) and a control (no parasitoids) for each population line were carried out throughout summer and autumn 2016. Host density (200 larvae) remained constant. At 320 released parasitoid females, both D. longicaudata population lines highly increased the Medfly mortality in both testing seasons, and foraged skillfully on peaches at both fruit height levels. These data encourage the application of augmentative biological control against Medfly.

Use of an exotic host plant shifts immunity, chemical defense, and viral burden in wild populations of a specialist insect herbivore.

Defense against natural enemies constitutes an important driver of herbivore host range evolution in the wild. Populations of the Baltimore checkerspot butterfly, Euphydryas phaeton (Nymphalidae), have recently incorporated an exotic plant, Plantago lanceolata (Plantaginaceae), into their dietary range. To understand the tritrophic consequences of utilizing this exotic host plant, we examined immune performance, chemical defense, and interactions with a natural entomopathogen (Junonia coenia densovirus, Parvoviridae) across wild populations of this specialist herbivore. We measured three immune parameters, sequestration of defensive iridoid glycosides (IGs), and viral infection load in field‐collected caterpillars using either P. lanceolata or a native plant, Chelone glabra (Plantaginaceae). We found that larvae using the exotic plant exhibited reduced immunocompetence, compositional differences in IG sequestration, and higher in situ viral burdens compared to those using the native plant. On both host plants, high IG sequestration was associated with reduced hemocyte concentration in the larval hemolymph, providing the first evidence of incompatibility between sequestered chemical defenses and the immune response (i.e., the “vulnerable host” hypothesis) from a field‐based study. However, despite this negative relationship between IG sequestration and cellular immunity, caterpillars with greater sequestration harbored lower viral loads. While survival of virus‐infected individuals decreased with increasing viral burden, it ultimately did not differ between the exotic and native plants. These results provide evidence that: (1) phytochemical sequestration may contribute to defense against pathogens even when immunity is compromised and (2) herbivore persistence on exotic plant species may be facilitated by sequestration and its role in defense against natural enemies.

Eriophyoid mites (Acari: Prostigmata) from Brazil: an annotated checklist

The superfamily Eriophyoidea constitute a group of phytophagous mites of particular economic and evolutionary interest due to their intimate association with host plants and their agricultural importance as harmful or beneficial organisms. Studies on the Eriophyoidea fauna in Brazil started in the early 1900s with botanical works on cecidias and were continued with researchers looking for and reporting on eriophyid mites causing damage to agricultural crops. Therefore, in this annotated checklist, we compile information from just over a century on eriophyid mites reported or described from Brazil. Its purpose is to facilitate plant protection strategies and guide future work on this important group of phytophagous mites. In addition to taxonomy, we present information on host plants and general aspects of cecidia attributed to eriophyoid mites but without genus/species identification. Compilation was based on: i) literature, including papers, books, theses and congress/symposium publications; ii) specimens deposited in mite collections in Brazil. On each species we present: i) suprageneric/generic classification, synonyms and previous genus/era assignments, including references on original and/or additional descriptions; ii) type host plant and other host(s) plant(s) found in the country; iii) host relationships and remarks on symptoms; iv) localities of occurrences at States/Federal District and municipal levels; and v) host plant status in Brazil as well as biomes where they occur or are cultivated. A total of 234 valid eriophyoid mite species are recorded: 196 Eriophyidae, 20 Diptilomiopidae and 18 Phytoptidae, distributed in 92 genera. Host plants comprised 233 species, belonging to 141 genera and 56 plant families. Four new reports of eriophyoid mites in Brazil are presented based on specimens deposited in reference collections. A new combination is presented for Propeaciota secundum (Flechtmann, Amrine Stasny) in the genus Khanthongella. In addition, data on observations and descriptions of 67 cecidias attributed to eriophyoid mites in five states and on 21 plant families are presented. Geographically, the distribution of species reports of eriophyoids around Brazil is highly uneven, with more than 64% of species (151 spp.) in the Southeast region, which surely reflects a lack of research elsewhere. Regarding host plant specificity, 77.7% are reported on only one host species, 88.9% on one host genus and 98.3% on one host family. Regarding host status 64.1% of species are exclusively associated with native host plants, 27% with naturalized or exotic cultivated host plants, and 6.4% from both native and naturalized or exotic host plants.

Performance of Danaini larvae is affected by both exotic host plants and abiotic conditions.

The consequences of the introduction of invasive plants for the diet of herbivorous insects have been little explored in nature where, potentially, abiotic and biotic factors operate. In this study, we examined the larval performance of two Neotropical Danaini butterflies when using either a native or an exotic Apocynaceae species as host plant in both field and laboratory experiments. Hosts greatly differ in their amount of latex exudation and other physicochemical traits, as well as in the amount of evolutionary time they have interacted with herbivores. First, herbivore performance on the hosts was investigated under laboratory conditions. Larvae of both Danaini species took more time to develop on the exotic host; larval survivorship did not vary between hosts. Second, first instar survivorship on both hosts was evaluated in two field sites, one site per host. To do so, in both sites half of the larvae were bagged (protected against both abiotic and biotic factors) while the remainder were nonbagged (exposed). The interaction between larval exposure with the use of the exotic host reduced larval survival. We concluded that the combined effects of host plant traits and abiotic factors reduced survival of herbivores in field conditions. Therefore, the performance of herbivores when using hosts of different origins should be considered together with the multiple ecological factors found in natural environments, as these factors can modify the result of plant–herbivore interactions.

Fijian swallowtail butterfly Papilio schmeltzi (Papilionidae: Lepidoptera) shows clear preference–performance relationships on both native and exotic host plants

AbstractThe swallowtail butterfly Papilio schmeltzi is endemic to the Fiji Islands. To date, P. schmeltzi larvae and eggs have been found exclusively on a native Fijian shrub, Micromelum minutum, even though numerous other seemingly suitable native and exotic species of Rutaceae now occur in its Fijian forest habitat. This study used outdoor cages and laboratory studies to examine oviposition preferences and larval development of P. schmeltzi on four species of Rutaceae: the native species Micromelum minutum and Euodia hortensis and the introduced species Murraya koenigii and Citrus reticulata. The female oviposition preference sequence was the same as that for larval feeding preference, which ran, from most preferred, as Micromelum minutum > C. reticulata > Murraya koenigii > E. hortensis. The survival of the first and fifth instar larvae was highest (≥80%) when maintained on leaves of M. minutum and C. reticulata and lowest when reared on Murraya koenigii (≤20%) and E. hortensis (≤4%). Of the two preferred host plants, P. schmeltzi larvae gained weight more quickly, consumed a larger area of leaf and pupated earlier when reared on the natural host Micromelum minutum compared with the exotic C. reticulata. In quantitative nutritional studies, the consumption rate of leaf material, and the relative growth rate of the P. schmeltzi larvae, was highest when reared on Micromelum minutum compared with C. reticulata, although the efficiency of converting leaf biomass into larval biomass was highest when reared on C. reticulata, especially in the later instars. Overall, the results of our study indicate the plants on which P. schmeltzi females choose to lay eggs are not restricted to native Fijian plant species but are appropriate when viewed in terms of subsequent larval preferences, survival and growth rate.

Host Range Expansion of an Endemic Insect Herbivore is Associated With High Nitrogen and Low Fibre Content in Exotic Pasture Plants.

Endemic moth species of the genus Wiseana spp. (Hepialidae) have become serious pests of introduced pasture plants in New Zealand. The original native host plants of these moths have not been confirmed. This study investigated the performance (survival, development time, weight gain) of three Wiseana species on seven putative host plants: five native and two exotic species. The aim was to identify native hosts for the three Wiseana species and to compare their performance on native plants and exotic pasture plants. The chemical composition of the seven putative host plants was investigated to compare native and exotic plant chemistries, and to test for associations between plant characteristics and performance of selected Wiseana species. Carbon, nitrogen, silica and fibre contents were measured for each plant species; primary metabolite composition was determined by gas chromatography-mass spectrometry. For the three moth species, increased survival and weight gain were significantly associated with high nitrogen and low fibre contents in one exotic host plant, white clover (Trifolium repens), although one species, W. umbraculata, did not complete development to adult on any of the plants tested, including clover. Two exotic plants (T. repens, Lolium perenne × Lolium multiflorum), and two native plants (Aciphylla squarrosa and Festuca actae) supported W. copularis development to the adult stage, but only one exotic (T. repens) and one native (F. actae) species supported complete development of W. cervinata. Exotic and native plant species had distinct metabolite profiles, but there was no significant association between metabolite composition and Wiseana performance. We conclude that W. copularis and W. cervinata, but not W. umbraculata, have expanded their host range, because of their ability to use both native and new hosts. No evidence was found for a host shift, i.e., a loss of performance on the ancestral host compared with the new host.

Top-down and bottom-up controls on an herbivore on a native and introduced plant in a tropical agricultural landscape.

The recent introduction in a tropical agricultural environment of a weedy open-habitat plant (Solanum myriacanthum) and subsequent host range expansion of a common forest-edge butterfly (Mechanitis menapis) onto that plant provides an opportunity to examine reconfiguration of tritrophic networks in human-impacted landscapes. The objectives of this study were (1) determine if the caterpillars on the exotic host are more or less limited by plant defenses (bottom-up forces) and if they experience enemy release (decrease of top-down pressure) and (2) define how anthropic open pasture habitat influences the herbivore’s tritrophic niche. Field and laboratory monitoring of larval survival and performance on a native (Solanum acerifolium) host plant and the exotic (S. myriacanthum) host plant were conducted in the Mindo Valley, Ecuador. Plant physical defenses were also measured. Results showed that larval mortality was mostly top-down on S. acerifolium, linked to parasitism, but mostly bottom-up on S. myriacanthum, possibly linked to observed increased plant defenses. Thus, in the absence of co-evolved relationships, herbivores on the exotic host experienced little top-down regulation, but stronger bottom-up pressures from plant defenses. These findings provide a rare empirical example of enemy-free space as a mechanism underlying host-range expansion. S. myriacanthum was less colonized in open pastures than in semi-shaded habitats (forest edges, thickets): fewer eggs were found, suggesting limited dispersal of adult butterflies into the harsh open environments, and the survival rate of first instar larvae was lower than on semi-shaded plants, likely linked to the stronger defenses of sun-grown leaves. These findings show how environmental conditions modulate the rewiring of trophic networks in heavily impacted landscapes, and limit a biocontrol by a native herbivore on an invasive plant in open habitats.

Effect of patch size of the exotic host plant Calotropis procera (Apocynaceae) on herbivory

Abstract Calotropis procera is a xerophytic perennial milkweed shrub native to Asia and Africa, which currently is also widely distributed throughout the Brazilian Caatinga. C. procera is well defended against herbivores, especially with latex and toxic steroidal cardenolides. The goal of this study was to evaluate how patch size of this exotic host plant affect insect herbivory. Eight patches were selected containing a varied number of C. procera individuals (5, 8, 29, 31, 55, 79, 116, and 172 individuals/patch) in the Caatinga. Patches were divided into four categories according to the number of C. procera individuals: very small (5 and 8), small (29 and 31), intermediate (55 and 79), and large (116 and 172). The percentage of herbivory was greater in patch categories with more individuals. Among the herbivorous insects associated with C. procera, larvae of Danaus spp. (Lepidoptera: Nymphalidae) were commonly observed feeding on all patches. These herbivores present specialized behaviors to circumvent the presence of latex on the host leaves. Adult Danaus spp. females probably had higher probability to find large patches of C. procera, leaving a greater abundance of eggs and, consequently, increasing the herbivory by their larvae in these patches. In contrast to immigration tendency, emigration from large patches may be lower, because there is a higher probability of finding resources (e. g. suitable C. procera leaves) inside large patches compared with small patches. We conclude that patch size of the host plant C. procera is a major factor affecting herbivory.

Novel prey boosts the expansion of host-plant range in a native predatory bug

Anthocoris nemoralis (Fabricius) is a Palearctic predator associated with psyllids in their native region. We found it preying on the non-native psyllid Glycaspis brimblecombei Moore, on Eucalyptus camaldulensis Dehnh. Here, we demonstrate the predator acceptance of E. camaldulensis leaves as a substrate for oviposition. We further tested the ability of A. nemoralis to complete its life cycle on E. camaldulensis trees, while feeding on G. brimblecombei. For this purpose, we enclosed infested branches in bags with adult predators, during one-month trials. At the end of the trials we found eggs, nymphs and newly born adults of A. nemoralis, confirming that a complete life cycle had occurred. The psyllid population growth rate was lower in the bags with predators than in the control. These results point out: (1) the ability of A. nemoralis to feed and complete a life cycle on exotic novel prey; (2) the acceptance of an exotic host plant; and (3) A. nemoralis as a potential candidate for the biological control against invasive psyllid species.

Host plant-dependent effects of microbes and phytochemistry on the insect immune response.

Herbivorous insects can defend themselves against pathogens via an immune response, which is influenced by the nutritional quality and phytochemistry of the host plant. However, it is unclear how these aspects of diet interact to influence the insect immune response and what role is played by ingested foliar microbes. We examined dietary protein, phytochemistry, and the caterpillar microbiome to understand variation in immune response of the Melissa blue butterfly, Lycaeides melissa. We also asked if these factors have host plant-specific effects by measuring L. melissa immune response when reared on a recently colonized exotic host plant (Medicago sativa) as compared to the immune response on an ancestral, native host (Astragalus canadensis). L. melissa did not experience immunological benefits directly related to consumption of the novel plant M. sativa. However, we did find negative, direct effects of phytochemical diversity and negative, direct effects of diet-derived microbial diversity on constitutive immune response for caterpillars fed M. sativa, as measured by phenoloxidase activity. Foliar protein did not directly influence the immune response, but did do so indirectly by increasing weight gain. Our results highlight the important effects of host diet on caterpillar physiology and raise the possibility that foliar microbiota, despite being rapidly passed through the gut, can affect the caterpillar immune response.

Acizzia errabunda sp. nov. and Ctenarytaina insularis sp. nov.: Descriptions of two new species of psyllids (Hemiptera: Psylloidea) discovered on exotic host plants in New Zealand.

A recent molecular-based assessment of the psyllid fauna of New Zealand reported two genetically distinct, undescribed psyllid taxa on host plants not native to that country. Here, a morphological examination confirmed species-level variation that resulted in the description of two new psyllid species: Acizzia errabunda sp. nov. (Hemiptera: Psyllidae) from Acacia baileyana F. Muell and Ctenarytaina insularis sp. nov. (Hemiptera: Aphalaridae) from Syzygium smithii (Poir.) Nied. Furthermore, the examination of specimens from entomological collections and from observations recorded on an online database enabled a better understanding of the distribution and host plant associations of these psyllid species. The description of A. errabunda is based on material collected in both New Zealand and Australia from the same plant species, A. baileyana, whereas the psyllid C. insularis has been found to be present in Brunei and New Zealand on S. smithii and in New Caledonia on Melaleuca quinquenervia (Cav.) S. T. Blake.

Insects allocate eggs adaptively across their native host plants

Finding plants for their eggs is the only parental care shown by many winged insects. Hatched juveniles often feed on one individual plant until gaining the power of flight as adults. Females are therefore predicted to lay more eggs on plants supporting high offspring survival. Many experiments comparing egg-laying and offspring survival across plant species refute this, leading to alternative concepts including ‘enemy free space’, ‘optimal bad motherhood’ and ‘neural constraints’. Whether tested plants have the same geographic origin as the insect is often overlooked. Using 178 oviposition–performance studies, we found when insects and plants share a native range, 83% of insect species associated their eggs with plants conferring highest offspring survival. This was broadly true across insect taxa and for generalists and specialists. Only 57% did so with non-native plants. That females are attracted to hosts with high offspring survival is a well-supported theory that does not necessarily apply to exotic host plants.

Low quality diet and challenging temperatures affect vital rates, but not thermal tolerance in a tropical insect expanding its diet to an exotic plant

Determining responses of organisms to changing temperatures is a research priority, as global warming threatens populations and ecosystems worldwide. Upper thermal limits are frequently measured as the critical thermal maximum (CTmax), a quick bioassay where organisms are exposed to increasing temperatures until individuals are not able to perform basic motor activities such as walking or flying. A more informative approach to understand organism responses to global warming is to evaluate how vital rates, such as growth or survival, change with temperatures. The main objectives of this study are: (1) to determine if factors affecting insect vital rates such as diet quality, developmental temperatures or acclimation also affect CTmax and (2) to determine if vital rates of different life stages (i.e., insect larvae or adults) display different responses to temperature changes. If different life stages have particular thermal requirements, this may indicate different susceptibility to global warming. This study focuses on Cephaloleia belti (Coleoptera: Chrysomelidae), a tropical insect currently expanding its diet to an exotic host plant. We determined how high and low-quality diets (i.e., native vs novel host), as well as exposure temperatures affect CTmax of adult beetles. We also estimated larval and adult survival when feeding on high and low quality host plants, when exposed to temperatures typical of the elevational distribution of this species, or when exposed to projected temperatures in 100 years. We did not detect an effect of diet quality or acclimation on CTmax. However, larvae and adults had different thermal requirements. CTmax is not affected by previous diet or acclimation as an adult. We propose that to understand processes involved in the adaptation and persistence of ectotherm populations in a warming world, studies must explore responses beyond CTmax, and focus on the response of vital rates to changing temperatures.

Experimental assemblage of novel plant-herbivore interactions: ecological host shifts after 40 million years of isolation.

Geographic isolation is the first step in insect herbivore diet specialization. Such specialization is postulated to increase insect fitness, but may simultaneously reduce insect ability to colonize novel hosts. During the Paleocene-Eocene, plants from the order Zingiberales became isolated either in the Paleotropics or in the Neotropics. During the Cretaceous, rolled-leaf beetles diversified in the Neotropics concurrently with Neotropical Zingiberales. Using a community of Costa Rican rolled-leaf beetles and their Zingiberales host plants as study system, we explored if previous geographic isolation precludes insects to expand their diets to exotic hosts. We recorded interactions between rolled-leaf beetles and native Zingiberales by combining DNA barcodes and field records for 7450 beetles feeding on 3202 host plants. To determine phylogenetic patterns of diet expansions, we set 20 field plots including five exotic Zingiberales, recording beetles feeding on these exotic hosts. In the laboratory, using both native and exotic host plants, we reared a subset of insect species that had expanded their diets to the exotic plants. The original plant-herbivore community comprised 24 beetle species feeding on 35 native hosts, representing 103 plant-herbivore interactions. After exotic host plant introduction, 20% of the beetle species expanded their diets to exotic Zingiberales. Insects only established on exotic hosts that belong to the same plant family as their native hosts. Laboratory experiments show that beetles are able to complete development on these novel hosts. In conclusion, rolled-leaf beetles are pre-adapted to expand their diets to novel host plants even after millions of years of geographic isolation.

Survival, body mass and potential fecundity of the invasive moth Cameraria ohridella (Lepidoptera: Gracillariidae) on its original host plant Aesculus hippocastanum and Aesculus glabra

Performance of the invasive horse-chestnut leaf miner, Cameraria ohridella Deschka & Dimic, 1986 (Lepidoptera: Gracillariidae), was studied on two host plants: the white-flowering horse-chestnut Aesculus hippocastanum L. and the Ohio buckeye Aesculus glabra Willd. C. ohridella developed successfully on both host plants; however, mine density and survival were much higher on A. hippocastanum than on A. glabra. The pupal mass and potential fecundity were strongly affected by the host plant on which the larvae fed. On A. hippocastanum pupae were significantly heavier and females more fecund than those on A. glabra. Furthermore, on both host plants there was a significant positive correlation between the number of oocytes in ovaries and pupal body mass, and as a consequence, heavier females produced more eggs. Our study demonstrates that the mine density, survival, pupal mass and potential fecundity were significantly lower on A. glabra than on A. hippocastanum. The observed lower performance of C. ohridella on the exotic host plant was assumed to be due to its poor food quality (nutritional and chemical composition).