Restoration of an endangered plant,Hygrophila pogonocalyx,leads to an adaptive host shift of the chocolate pansy (Junonia iphita iphita)

Anthropogenic introduction of a plant species may cause novel encounters between the plant and local herbivores, and initiate evolutionary changes in host plant usage by herbivores. Until recently the endemic aquatic plant Hygrophila pogonocalyx was endangered and had a restricted distribution in Taiwan. Massive restoration efforts since 1997 have led to an expansion of the plant's distribution and a novel encounter between it and an Asian butterfly, the chocolate pansy, Junonia iphita (Nymphalidae). This butterfly appears to have colonized H. pogonocalyx, switching from its original host, Strobilanthes penstemonoides var. formosana. In the present study, we aimed to investigate whether the utilization of H. pogonocalyx as a host plant has initiated a differentiation between butterflies using the novel and the original hosts. To this purpose we collected butterflies from patches of the two host plants which grow sympatrically. We tested oviposition preference for the two hosts and larval performance on them. Female adults exhibited distinct oviposition preference toward the host plant their mothers preferred. Offspring showed greater survivorship and pupal weight when fed on the host plant their mothers preferred. Male adults displayed territorial behaviors on the host plant that their mothers had preferred. Finally, the survival rate of offspring produced from cross-mating between individuals with different host plant preference was lower than that of non-hybrids. Taken together, we suggest that genetic differentiation has occurred between individuals preferring H. pogonocalyx versus S. penstemonoides as host plants via host shifting. This process was likely induced by the mass restoration of the formerly rare and endangered plant species.     

Restoration action and species response: oviposition habits of Plebejus icarioides fenderi (Lepidoptera: Lycaenidae) across a restoration chronosequence in the Willamette Valley, Oregon, USA

Habitat restoration is critical to the conservation of rare species. However, restoration efforts often proceed without knowledge of their effects on these species. We investigated the reproductive response of federally endangered Fender’s blue butterfly (Plebejus icarioides fenderi) to prairie restoration in Willamette Valley, Oregon, USA. In 2009 and 2010, we quantified availability of larval host plant, Kincaid’s lupine (Lupinus oreganus), and butterfly oviposition in three restored areas (1–10 years old) and adjacent intact habitat. Oviposition measures in restored areas reached or exceeded intact habitat (0.1 eggs/leaf of host plant and 12 % of time ovipositing) within five years post-restoration. However, none of the restorations provided an equivalent host plant density to intact areas (55 leaves/m²). The different response time of host plants and butterflies to restoration highlights the importance of monitoring both vegetation and oviposition over an ecologically relevant timescale (at least 10 years). For imperiled species, quantifying reproductive response to restoration is critical for adaptive management and successful conservation of the species which restoration efforts are intended to benefit.     

Spatial and temporal patterns of caterpillar performance and the suitability of two host plant species

Abstract. 1. The butterfly Melitaea cinxia uses two host plant species in the Åland Islands of south-west Finland. Survey data show that host plant use is spatially variable and that the two species are not used (fed on by M . cinxia larvae) in proportion to their abundances. The pattern of host plant use by M . cinxia has been attributed in part to plant distribution and spatial variation of butterfly oviposition preference.
2. The additional roles that may be played by spatial variation in host plant quality and larval physiology (performance ability) were investigated. Seven years of field survey data and a series of laboratory experiments were used to demonstrate that neither of these variables contributed measurably to the observed pattern of host plant use.
3. Specifically, while there was great variation among individuals in both the performance ability of caterpillars and host plant suitability, the two plant species appeared equally suitable, there was no within-species geographic variation in plant suitability, and there was no evidence for adaptation of caterpillars to the locally used host plants.     

The Relationship Between Habitat Selection and Preference for Adult and Larval Food Resources in the Polyphagous Butterfly <Emphasis Type="Italic">Vanessa cardui</Emphasis> (Lepidoptera: Nymphalidae)

Search strategies can have profound fitness-effects for plant-feeding insects. Here I focus on the potential conflict between searching for nectar plants and for larval food plants. I test if the butterfly Vanessa cardui, which can use some of its larval food plants as nectar sources, is able to rationalize this search problem by combining the two search tasks. Lab-experiments revealed a higher oviposition preference for Cirsium arvense over Urtica dioica and a corresponding difference in larval performance. Contrary to predictions, there was no effect of inflorescences on oviposition. However, experiments in large outdoor cages showed a higher occupancy and a higher level of oviposition in patches with access to nectar sources, even on U. dioica. Hence, while there was no preference for individual plants with flowers, the results suggests that V. cardui is simplifying its search task to primarily search for hosts in nectar-rich patches. This strategy allows females to increase oviposition rate, but it is likely that it comes at the expense of not always using optimal host plants in terms of offspring performance.     

The larval ecology of the butterfly Euphydryas desfontainii (Lepidoptera: Nymphalidae) in SW-Portugal: food plant quantity and quality as main predictors of habitat quality

Corresponding to theory, the persistence of metapopulations in fragmented landscapes depends on the area of suitable habitat patches and their degree of isolation, mediating the individual exchange between habitats. More recently, habitat quality has been highlighted as being equally important. We therefore assess the role of habitat area, isolation and quality for the occupancy of larval stages of the regionally threatened butterfly Euphydryas desfontainii occurring in grassland habitats comprising the host plant Dipsascus comosus. We put a special focus on habitat quality which was determined on two spatial scales: the landscape (among patches) and the within-patch level. On the landscape level, occupancy of caterpillars was determined by a presence-absence analysis at 28 host plant patches. On the within-patch level, oviposition site selection was studied by comparing 159 host plants with egg clutches to a random sample of 253 unoccupied host plants within six habitat patches. The occupancy of caterpillars and presence of egg clutches on host plants was then related to several predictors such as patch size and isolation on the landscape level and host plant characteristics and immediate surroundings on the within patch level. On the landscape level, only host plant abundance was related to the presence of caterpillars, while size and isolation did not differ between occupied and unoccupied patches. However, the weak discrimination of larval stages among patches changed on the within-patch level: here, several microclimatic predictors such as sunshine hours and topography, host plant morphology and phenology as well as further potential host plants in the immediate surroundings of the plant chosen for oviposition strongly determined the presence of egg clutches. We strongly suggest promoting the presence of the host plant in topographically and structurally rich habitat patches to offer potential for microclimatic compensation for a species considered threatened by climate change.     

A multiple-scale analysis of host plant selection in Lepidoptera

Lepidoptera play an important role in terrestrial ecosystems as pollinators, as components of the food chain and as indicators for healthy ecosystems due to their sensitivity to change. Heterogeneous landscapes with variability of topographical features, vegetation structure combined with food sources for all life stages are the basis for successful lepidopteran oviposition. A multiple-scale analysis is proposed to understand the hierarchical relationships between selected site to plant characteristics and oviposition preferences for the dingy skipper (Erynnis tages). To achieve this goal, factors driving oviposition at the plant and patch scale were identified and scale dependencies at the site scale were assessed. At the plant scale, tallest host plants were used for oviposition; however relative egg height upon each plant was similar in both host plant species [bird’s-foot trefoil (Lotus corniculatus) and horseshoe vetch (Hippocrepis comosa)]. The main factors preferred by E. tages in L. corniculatus patches were sward height and percent of bare ground, and in H. comosa host plant density patches. Selected patches had slopes of greater gradients (mostly facing south) than patches with no selected host plants. At the site scale, oviposition patches were clustered at small scales and oviposition sites were dispersed at larger scales. Our study suggests that oviposition selection in E. tages is a hierarchical process varying from the site to the plant scale. Our study provides empirical evidence useful to inform landscape management strategies. These can be expanded to assess larger scale vegetation and habitat suitability beyond individual sites for systematic conservation planning.     

Pathogen invasion triggers an evolutionary trap for an endangered checkerspot butterfly dependent on an exotic host plant

Exotic pathogen invasions can change host eco-evolutionary interactions and possibly create an evolutionary trap when the pathogen generates mismatches between developmental phenology and reproductive cues. Taylor’s checkerspot butterfly (Euphydryas editha taylori), is an endangered species of western North America with 80 % of the extant populations dependent on an exotic host, Plantago lanceolata. Survey of occupied, recently extinct, and unsuccessful butterfly reintroduction sites spanning 4° of latitude revealed widespread disease on P. lanceolata caused by Pyrenopeziza plantaginis. This fungal pathogen, new to North America, reduces the standing crop of P. lanceolata foliage throughout the winter post-diapause larval feeding period. However, disease is absent when adult butterflies and pre-diapause larvae are active. Diseased plants were frequent in Taylor’s checkerspot populations with a history of persistence, but >90 % of the host plants in these populations had initiated new leaves within the first few weeks of post-diapause larval feeding. Conversely, host plants in recently extinct and unsuccessfully reintroduced populations were severely diseased, >66 % mean foliage necrosis/plant, and <23 % had initiated new leaves. Feeding choice trials with 25 larvae indicated that new leaves were strongly and consistently preferred by post-diapause larvae over all other available leaf types, both diseased and non-diseased. Because the influence of disease on post-diapause larval food resources is developmentally disassociated from oviposition, P. plantaginis invasion appears to have triggered an evolutionary trap for Plantago-dependent populations of Taylor’s checkerspot.     

The role of a mound-building ecosystem engineer for a grassland butterfly

Both land use intensification and abandonment within grasslands lead to a homogenisation of vegetation structure. Therefore, specially structured microsites such as vegetation gaps with bare ground play an important role for species conservation within grasslands. Vegetation gaps are crucial for the establishment of low-competitive plant species and offer special microclimatic conditions essential for the development of the immature stages of many invertebrate species. The influence of small-scale soil disturbance in the form of mounds created by ecosystem engineers such as ants or moles on biodiversity is therefore of special scientific concern. The effects of mound-building species on plant species diversity have been extensively studied. However, knowledge on the significance of these species for the conservation of other animals is rare. In this study we analyse the importance of mounds created by the European mole (Talpa europaea) as an oviposition habitat for the small copper (Lycaena phlaeas) within Central European mesotrophic grasslands. Our study showed that host plants occurring at molehills were preferred for oviposition. Oviposition sites were characterised by an open vegetation structure with a high proportion of bare ground (with a mean coverage of about 50 %), a low cover of herbs and low-growing vegetation (mean height: 4.5 cm). Our study clearly illustrates the importance of small-scale soil disturbance for immature stages of L. phlaeas and the conservation of this species within mesotrophic grasslands. Mound-building ecosystem engineers, such as T. europaea, act as important substitutes for missing dynamics within mesotrophic grasslands by diversifying vegetation structure and creating small patches of bare soil.     

Fitness costs of butterfly oviposition on a lethal non-native plant in a mixed native and non-native plant community

Non-native plants may be unpalatable or toxic, but have oviposition cues similar to native plants used by insects. The herbivore will then oviposit on the plant, but the offspring will be unable to develop. While such instances have been described previously, the fitness costs at the population level in the wild due to the presence of the lethal host have not been quantified, for this or other related systems. We quantified the fitness cost in the field for the native butterfly Pieris macdunnoughii in the presence of the non-native crucifer Thlaspi arvense, based on the spatial distributions of host plants, female butterflies and eggs in the habitat and the survival of the larvae in the wild. We found that 2.9 % of eggs were laid on T. arvense on average, with a survival probability of 0, yielding a calculated fitness cost of 3.0 % (95 % confidence interval 1.7–3.6 %) due to the presence of the non-native in the plant community. Survival probability to the pre-pupal stage for eggs laid on two native crucifers averaged 1.6 % over 2 years. The magnitude of the fitness cost will vary temporally and spatially as a function of the relative abundance of the non-native plant. We propose that the fine-scale spatial structure of the plant community relative to the butterflies’ dispersal ability, combined with the females’ broad habitat use, contributes to the fitness costs associated with the non-native plant and the resulting evolutionary trap.     

Fen meadows on the move for the conservation of <Emphasis Type="Italic">Maculinea (Phengaris) teleius</Emphasis> butterflies

In the Netherlands, a single population of the obligate myrmecophilic butterfly Maculinea (Phengaris) teleius has survived on only 3 ha of habitat for more than 25 years, whereas at least 40 ha of habitat are thought to be required for a sustainable metapopulation. Therefore, 170 ha of farmland is being restored to wet meadows within a LIFE?+?project by large-scale soil excavation and hay inoculation. For successful restoration, the habitat requirements of the butterfly, with Sanguisorba officinalis as host plant and its particular life cycle as parasite of the ant species Myrmica scabrinodis, have to be taken into account. We tested whether colonization of nests of this ant species in the restoration areas is facilitated by translocation of sods collected from fen meadows. We divided 54 sods, each sized 1 m², randomly over six patches and measured vegetation development and ant presence in the sods and surrounding control plots for 2 years. In the first summer, significantly more Myrmica ants were found in the transplanted sods in comparison to the surrounding area. Herb cover had a significant positive effect on Myrmica ant presence while it did not affect the presence of the pioneer ant species Lasius niger. In the second year, Myrmica ants were found in the surrounding control plots as well. This study contributes to the knowledge-base required for the design of restoration projects aimed at expanding the habitat of the critically endangered butterfly Maculinea (Phengaris) teleius.     

Early succession of butterfly and plant communities on set-aside fields

 Hypotheses on secondary succession of butterfly and plant communities were tested using naturally developed 1- to 4-year-old set-aside fields (n = 16), sown fields (n = 8) and old meadows (n = 4) in 1992 in South Germany. Pioneer successional fields (1st and 2nd year of succession, dominated by annuals) and early successional fields (3rd and 4th year of succession where perennials, especially grasses became dominant) had fewer plant species than mid-successional fields (old meadows). In contrast to established hypotheses, mean number of plant species decreased from 1- to 4-year-old set-aside fields. Species richness of butterfly communities did not change during the first four years of succession, but species composition changed greatly. Pioneer successional fields were characterized by (1) specialized butterflies depending on annual pioneer foodplants (e.g. Issoria lathonia), and (2) species preferring the pioneer successions despite their host plants being more abundant on early and mid-successional fields (e.g. Papilio machaon). The variability in butterfly species richness was best explained by flower abundance which was closely correlated with plant species richness. Species whose abundance was correlated with habitat connectivity were significantly smaller than species which correlated with flower abundance. Numbers of caterpillar species were correlated with numbers of adult butterfly species. Life-history features of butterflies changed significantly from pioneer to early and mid-successional fields. We found decreasing body size and migrational ability, decreasing numbers of species hibernating as imago, decreasing numbers of generations and increasing larval stage duration with age of succession, but, contrary to expectation, host plant specialization, numbers of egg-cluster laying species and egg diameter did not change with successional age. Received 18 September 1995 / Accepted: 17 July 1996     

Population level correlation between pre-alighting and post-alighting host plant preference in the Glanville fritillary butterfly

1. In many populations of the Glanville fritillary butterfly Melitaea cinxia, ovipositing females exhibit a post‐alighting preference for one of the potential host plant species available. The work reported here aimed to establish whether females with different post‐alighting preferences can discriminate between their host plant species prior to alighting, and whether pre‐alighting and post‐alighting preferences are correlated at the population level. 2. Alighting and oviposition events were recorded for groups of females from six populations in greenhouse and field experiments. 3. Landing frequencies did not change with experience, indicating that M. cinxia females did not learn from previous encounters with host plants. 4. Females from populations exhibiting post‐alighting preference searched efficiently for their host plants in the sense that they landed mainly on the species on which they oviposited predominantly. Pre‐alighting and post‐alighting preferences were correlated at the population level. 5. The correlation between pre‐alighting and post‐alighting preferences helps to explain why in nature, where the host plants often occur in distinct patches, females are more likely to colonise habitat patches in which their preferred host plant is abundant.     

The effect of multi‐species host density on superparasitism and sex ratio in a gregarious parasitoid

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The roles of foraging environment,host species,and host diet for a generalist pupal parasitoid

Even for parasitoids with a wide host range, not all host species are equally suitable, and host quality often depends on the plant the host feeds on. We compared oviposition choice and offspring performance of a generalist pupal parasitoid, Pteromalus apum (Retzius) (Hymenoptera: Pteromalidae), on two congeneric hosts reared on two plant species under field and laboratory conditions. The plants contain defensive iridoid glycosides that are sequestered by the hosts. Sequestration at the pupal stage differed little between host species and, although the concentrations of iridoid glycosides in the two plant species differ, there was no effect of diet on the sequestration by host pupae. The rate of successful parasitism differed between host species, depending on the conditions they were presented in. In the field, where plant‐associated cues are present, the parasitoid used Melitaea cinxia (L.) over Melitaea athalia (Rottemburg) (Lepidoptera: Nymphalidae), whereas more M. athalia were parasitised in simplified laboratory conditions. In the field, brood size, which is partially determined by rate of superparasitism, depended on both host and plant species. There was little variation in other aspects of offspring performance related to host or plant species, indicating that the two host plants are of equal quality for the hosts, and the hosts are of equal quality for the parasitoids. Corresponding to this, we found no evidence for associative learning by the parasitoid based on their natal host, so with respect to these host species they are truly generalist in their foraging behaviour.     

Habitat and host plant use of the Large Copper Butterfly Lycaena dispar in an urban environment

The Large Copper (Lycaena dispar) has been extensively studied due to its high conservation priority. The species has declined severely in North-West Europe, but is currently expanding in Central and North-East Europe. In this study, we investigated egg deposition patterns at three different spatial scales (site, plant, and leaf level) for L. dispar at 23 sites within the municipality of Vienna (Austria). In one season, a total of 2,457 eggs were counted on six Rumex species, of which two (R. stenophyllus, R. patientia) represent novel host plant records. Rumex crispus harboured 87.6% of all egg counts and was significantly preferred (4.4 eggs per plant) over the second-ranked R. obtusifolius for oviposition (1.1 eggs per plant). At the habitat scale, eggs were observed at all study sites. Egg numbers per site were equal across landscape zones, including stretches of waste land in urban habitats, except for lower egg numbers on meadows at the margin of the Vienna forest. Mowing was negatively related to the number of eggs found on all three studied scales. We conclude that L. dispar eggs are easier to find compared to adult butterflies, the butterfly can utilize more host plant species than what was previously known, and that mowing has a strong negative influence on the local butterfly populations. Urban wastelands provide important habitats, in which the species can sustain substantial population densities which are in comparison to those in the countryside. Conservation action should focus on applying less intensive rotational mowing, preferably involving mowing of suitable sites every 2?years.     

Combining larval habitat quality and metapopulation structure – the key for successful management of pre-alpine Euphydryas aurinia colonies

This study aims to analyse larval habitat preferences and landscape level population structure of the threatened Marsh Fritillary butterfly, Euphydryas aurinia, and discusses implications for the conservation and management of this strongly declining species in central Europe. Whereas current management strategies are mainly based on studies of habitat requirements of adult individuals, we intend to emphasise larval habitat quality and population processes at the landscape level as additional key factors. Microhabitat preference analysis of egg-laying females showed that eggs were predominantly laid on prominent large-sized host plant individuals. Additionally, when Succisa pratensis was used as a host plant (as opposed to Gentiana asclepiadea), host individuals in open vegetation structure were preferred. Optimal oviposition conditions were present in recently abandoned calcareous fen meadows and at the edges of such meadows currently in use. A two-year patch-occupancy study in the northern pre-alpine region of south-west Germany indicated that E. aurinia lives in a metapopulation. In a logistic-regression model, patch size, isolation, and habitat quality explained 82% of the observed patch-occupancy pattern in 2001. Our data suggest that a suitable conservation strategy must incorporate both the conservation of a network of suitable habitat patches, and efforts to maximise local habitat quality by ensuring that host plants can grow to a large size and are surrounded by sparse and low vegetation cover.     

Extinction-colonization dynamics and host-plant choice in butterfly metapopulations

Species living in highly fragmented landscapes often occur as metapopulations with frequent population turnover. Turnover rate is known to depend on ecological factors, such as population size and connectivity, but it may also be influenced by the phenotypic and genotypic composition of populations. The Glanville fritillary butterfly (Melitaea cinxia) in Finland uses two host-plant species that vary in their relative abundances among distinct habitat patches (dry meadows) in a large network of approximately 1,700 patches. We found no effect of host species use on local extinction. In contrast, population establishment was strongly influenced by the match between the host species composition of an empty habitat patch and the relative host use by larvae in previous years in the habitat patches that were well connected to the target patch. This "colonization effect" could be due to spatially variable plant acceptability or resistance or to spatially variable insect oviposition preference or larval performance. We show that spatial variation in adult oviposition preference occurs at the relevant spatial scale and that the other possible causes of the colonization effect can be discounted. We conclude that the colonization effect is generated by host preference influencing the movement patterns of ovipositing females. Migrant females with dissimilar host preferences have different perceptions of relative patch quality, which influences their likelihood of colonizing patches with particular host composition.     

Food plant density,patch isolation and vegetation height determine occurrence in a Swedish metapopulation of the marsh fritillary <Emphasis Type="Italic">Euphydryas aurinia</Emphasis> (Rottemburg, 1775) (Lepidoptera,Nymphalidae)

The occurrence pattern of the marsh fritillary was studied within a patch network on the Baltic island Öland, Sweden. Presence/absence was established for potentially suitable habitat patches (n = 158) on calcareous moist grassland and analyzed in a multiple logistic regression model where patch area, patch isolation and nine habitat quality variables were included as explanatory variables. Larval food plant density was positively, and patch isolation negatively, correlated to the presence of Euphydryas aurinia. Area did not contribute to the explanation of the occurrence pattern. Significant interactions between larval food plant density times patch isolation, and larval food plant density times vegetation height, show that with low food plant density the butterfly primarily occurs in patches with a vegetation height of 4–10 cm, within a distance of 250 m from nearest occupied patch. In patches with a high food plant density the butterfly occurs in patches where the vegetation height is higher, 4–16 cm, and the distance to nearest occupied patch can be longer, up to 1.4 km. This study supports earlier findings in other regions, suggesting that a network of adjacent patches with a high food plant density and a vegetation height within the preferred threshold, despite their size, is an apparent conservation goal.     

Indirect interaction between butterfly species mediated by a shared pupal parasitoid

Indirect interactions among species can greatly affect their abundances and the structure of the community they live in. Using a field experiment, we tested the hypothesis that congeneric butterfly species interact indirectly through a shared pupal parasitoid. We predicted that symmetrical apparent competition would lead to high parasitism of both species, and the effect would increase with regional butterfly abundance. Instead, parasitism of one host, Melitaea cinxia, was reduced in the presence of the second host, M. athalia. Parasitism of M. athalia did not differ whether or not M. cinxia was present. This pattern did not vary with regional butterfly abundance, though overall rate of parasitism did. Details of the experiment suggest that the apparent commensalism occurred because M. cinxia pupae are protected by silk tents whereas M. athalia are exposed, causing locally foraging parasitoids to favour the more accessible host where the two are present together. The local short-term apparent commensalism favouring M. cinxia opposes the landscape scale trend, in which parasitism increases where butterfly density is high. The outcome of this study illustrates short-term apparent commensalism, that host suitability can depend on relative accessibility, and that indirect interactions occurring at different scales may be in opposition.