Evolutionary conservatism of oviposition preference in a widespread polyphagous insect herbivore, Papilio zelicaon

We analyzed geographic differentiation in oviposition preference in the anise swallowtail butterfly, Papilio zelicaon Lucas, which is one of the most widely distributed and polyphagous butterflies in western North America. Among 13 populations that span 1200 km of the range of P. zelicaon in the Pacific Northwest of North America, the overall oviposition preference hierarchy has not diverged significantly, even though these populations differ in the plant species they use in the field. The results indicate that differences in host availability and use have not favored major reorganizations in the preference hierarchy of ovipositing females. Instead, this butterfly has a conserved preference hierarchy that varies within a narrow range among populations. All populations ranked the four test plant species in the same overall relative order, even though these populations differ in the plant species they use in the field. Received: 9 February 1996 / Accepted: 24 February 1997     

Hostplant utilization by African and Australian butterflies

A review of the larval hostplant associations of African and Australian butterflies highlights their overall conservatism in host choice—the most widely exploited families are cosmopolitan or pan- tropical in range. Thus there is no apparent relationship between butterfly diversity and endemic plant novelty at the family level. Such conservatism in hostplant preferences suggests that butterflies encounter few opportunities to make gross hostplant shifts, with the likelihood of the limited available options being repeatedly explored through time. Attempts to detect any simple parallel cladogenesis between butterflies and their larval hosts must allow for the probability of homoplasy. Similarities in the host ranges of the Papilionoidea, Hesperioidea and Hedyloidea might suggest that the Malvales constitute the ancestral host group of the butterflies.     

Body size, egg size, and their interspecific relationships with ecological and life history traits in butterflies (Lepidoptera: Papilionoidea, Hesperioidea)

The interspecific relationships between egg size and body size in butterflies (Papilionoidea and Hesperiidae), and between size and egg and larval development time, larval trophic specificity, foodplant structure, climate, and phenology were investigated based on a sample of more than 1180 species. The independent contrasts mediod was used to avoid taxonomy-dependent results. Egg size is allometrically related to adult wing length by a slope of 0.43. Based on a subset of species, fecundity is correlated to adult body size, and there is evidence for a compromise between egg number and egg size (relative to adult size) across species. Butterfly size increases in correlation to the mean annual temperature of me species geographic range, but decreases in relation to increased aridity (or die length of the dry season). Larger butterflies tend to have longer larval development times, use large or structurally complex host plants, and are more likely to lay their eggs in batches, irrespective of climate. Larger eggs tend to develop more slowly, and give rise to larvae with longer developmental periods that will result in larger adults. No evidence was found to support a relationship between butterfly body size and polyphagy. A complex pattern of interrelationships links body size (and egg size) to other traits, although correlations other than mat between egg size and body size are generally low. The results suggest the necessity of separating climate and seasonality into components that are relevant to insect life histories in comparative studies.     

Valeur trophique des plantes nourricières et préférence de ponte chez Parnassius apollo L. (Lepidoptera,Papilionidae)

A mountain butterfly species, Parnassius apollo is protected by the CITES convention of Washington and is threatened or extinct in many European massifs. The definition of the ecological factors which can affect its survival, in particular its relations with its larval foodplants, are important to design conservation policies. The larva of P. apollo is oligophagous and feeds on various species of Crassulaceae. The results of observations and experiments on the female laying preferences and on the efficiency of some of these plants for larval development are exposed here. The two species most cited as foodplants in literature, Sedum album and S. maximum, appeared to be the most efficient. Other species, although frequently mentioned, were rejected and another one performed poorly. A comparison with other cases of foodplant specificity in butterflies is presented and the implications of these results for conservation are discussed.     

Role of morphological variables of the visitor butterfly species in relation to their foraging behaviour on Lantana camara: Implication for conservation

The study of foraging behaviour of butterflies has been an important focus among the lepidopterists for years. Although established as invasive weed plant, the role Lantana camara as an important host plant as well as a food plant for the butterfly species is now well-known. The present study aims to interpret the role of morphological variables of the visitor butterflies in relation to their foraging behaviour on Lantana camara. Butterflies with longer proboscis were more efficient in foraging on flowers of Lantana camara than the butterflies with shorter ones, when the species containing proboscis same as or longer than their body length were excluded. Longer relative proboscis length (RPL) have selective advantage for foraging over Lantana camara up to a certain point (RPL = 0.881) and after that larger relative proboscis length often obstructs foraging behaviour as the handling time increases and these butterflies face more resistance against incoming nectar than the others.The residuals (body weight-wing span) also act as important factor.The handling time of the butterflies on Lantana camara shows a negative relationship with the residuals. The findings suggests that in case of Lantana camara as a nectaring plant butterfly species with longer proboscis have selective advantage for exploitation of the resource than the species with shorter ones and plantation of Lantana camara may be useful for conserving the long tongued butterfly species.     

Vertical stratification of ithomiine butterfly (Nymphalidae: Ithomiinae) mimicry complexes: the relationship between adult flight height and larval host-plant height

Data are presented which confirm previous findings that sympatric mimicry complexes dominated by unpalatable Neotropical ithomiine butterflies (Nymphalidae: Ithomiinae) are vertically stratified by height of flight. Flight height of ithomiine species is positively correlated with the height of their larval host-plants. Thus members of a mimicry complex utilize host-plants of similar heights. Non-mimetic British woodland butterflies also show a positive relationship between flight height and host-plant height, which suggests that the relationship is independent of mimicry. I propose that female butterflies fly at heights which maximize the probability of encountering their larval host-plants, and that males fly at similar heights to females in order to maximize the probability of encountering potential mates. Female butterflies probably encounter plants of similar heights to their larval hosts more frequently than they encounter plants of other heights. I suggest that butterfly species may therefore be more likely to make host shifts to plant species of a similar height to their current host-plants. Finally, I discuss how the relationship between flight height and height of larval host-plants, coupled with microhabitat-dependent selection on colour pattern, could lead to the evolution in sympatry of vertically stratified mimicry complexes.     

Habitat associations of thermophilous butterflies are reduced despite climatic warming

Climate warming threatens the survival of species at their warm, trailing‐edge range boundaries but also provides opportunities for the ecological release of populations at the cool, leading edges of their distributions. Thus, as the climate warms, leading‐edge populations are expected to utilize an increased range of habitat types, leading to larger population sizes and range expansion. Here, we test the hypothesis that the habitat associations of British butterflies have expanded over three decades of climate warming. We characterize the habitat breadth of 27 southerly distributed species from 77 monitoring transects between 1977 and 2007 by considering changes in densities of butterflies across 11 habitat types. Contrary to expectation, we find that 20 of 27 (74%) butterfly species showed long‐term contractions in their habitat associations, despite some short‐term expansions in habitat breadth in warmer‐than‐usual years. Thus, we conclude that climatic warming has ameliorated habitat contractions caused by other environmental drivers to some extent, but that habitat degradation continues to be a major driver of reductions in habitat breadth and population density of butterflies.     

Basal hatching by Maculinea butterfly eggs: a consequence of advanced myrmecophily?

Larvae of Maculinea alcon and M. rebeli are unique among Holarctic Lycaenidae in hatching through the base of the eggshell and emerging on the opposite side of the leaf to the egg. This occurs because the exposed upper surfaces of their eggs have exceptionally thick shells. Other species of Maculinea have normal or unusually thin-shelled eggs. It is suggested that both types of Maculinea eggshell have evolved to reduce mortalities from parasitoids and predators. Maculinea alcon and M. rebeli are forced to lay in exposed places due to the structure of their foodplants, and protect their eggs with thick shells. The other three species hide their eggs deep within the inflorescences of their foodplants; M. nausithous and M. teleius require thin flexible shells to achieve this. These adaptations are necessary because Maculinea eggs often occur at much higher densities on their initial foodplants and are hence more vulnerable—than is the case with other Lycaenidae. This is a consequence of myrmecophily. Maculinea population size is regulated more by the status of the ant host than by that of the initial foodplant. Large Maculinea populations, and high densities of eggs, occur on the many sites where the ant is abundant but the foodplant is scarce. Maculinea alcon and M. rebeli eggs occur at the highest densities, and need the greatest protection, due to the advanced form of myrmecophily found in these species. Whereas M. anon, M. teleius and M. nausithous larvae are predators of ant brood, M. alcon and M. rebeli feed mainly at a lower trophic level on ant regurgitations. This leads to roughly seven times more M. alcon and M. rebeli adults emerging per ant nest, and to a similar increase in egg densities per foodplant.     

Diet breadth and host plant diversity of tropical- vs. temperate-zone herbivores: South-East Asian and West Palaearctic butterflies as a case study

1. Data on host plant associations of butterflies (Papilionoidea, excluding Hesperiidae) from two biogeographical regions were used to investigate (1) whether tropical herbivores are more narrowly specialized with regard to host plant choice than those of northern temperate zones, and (2) whether tropical butterflies show a greater diversity of host plant affiliations. 2. There was no evidence for a more restricted diet breadth of tropical butterflies, with diet breadth being measured as number of host plant families used per species. In the families Papilionidae, Pieridae, and Nymphalidae, host plant ranges of West Palaearctic and South-East Asian species are similar, whereas in one speciose group within the Lycaenidae, the Polyommatini, tropical species are significantly more polyphagous. 3. Diet breadth also differs among higher butterfly taxa. While Papilionidae, Pieridae, the nymphalid subfamilies Satyrinae, Morphinae, Libytheinae and Apaturinae, as well as the temperate-zone Polyommatini in the Lycaenidae are composed predominantly of host specialists, the degree of polyphagy is higher among the remaining nymphalid subfamilies and in many lycaenids. These results challenge strongly the view that tropical herbivores are generally more specialized in this regard than herbivores of higher latitudes. Rather, chemical constraints and phylogenetic conservatism shape host plant associations in many taxa in such a way that differences between temperate and tropical representatives are slight. 4. Host plant diversity, measured as the number of plant families used per butterfly family and by application of the log-series model, is much higher in South-East Asian Nymphalidae and Lycaenidae (the two largest families) than in their Western Palaearctic relatives. No such differences are observed in the Papilionidae and Pieridae (the two smaller families). Besides effects of sample size, the strong association of papilionid and pierid butterflies with plants characterized by a small set of classes of secondary plant compounds might generally restrict their capability to utilize a broader taxonomic range of host plants. 5. The results indicate that high floral diversity can be reflected by higher diversity of host plant affiliations of herbivores, but taxonomic idiosyncrasies render it difficult to draw generalized conclusions.     

Does herbivore diversity depend on plant diversity? The case of California butterflies

It is widely believed that the diversity of plants influences the diversity of animals, and this should be particularly true of herbivores. We examine this supposition at a moderate spatial extent by comparing the richness patterns of the 217 butterfly species resident in California to those of plants, including all 5,902 vascular plant species and the 552 species known to be fed on by caterpillars. We also examine the relationships between plant/butterfly richness and 20 environmental variables. We found that although plant and butterfly diversities are positively correlated, multiple regression, path models, and spatial analysis indicate that once primary productivity (estimated by a water-energy variable, actual evapotranspiration) and topographical variability are incorporated into models, neither measure of plant richness has any relationship with butterfly richness. To examine whether butterflies with the most specialized diets follow the pattern found across all butterflies, we repeated the analyses for 37 species of strict monophages and their food plants and found that plant and butterfly richness were similarly weakly associated after incorporating the environmental variables. We condude that plant diversity does not directly influence butterfly diversity but that both are probably responding to similar environmental factors.     

Butterfly community structure in fragmented habitats

We analysed effects of habitat fragmentation on the diversity, abundance, and life history traits of butterflies on 33 calcareous grasslands. Diversity of butterflies was positively correlated with habitat area (as was plant diversity), but not with habitat isolation. In contrast to expectations, butterfly densities of polyphagous and oligophagous species declined with habitat area whereas densities of monophagous species increased. The z -values, i.e. the slope of species–area relationships, increased with food plant specialization, from 0.07 in polyphagous, 0.11 in oligophagous, 0.16 in strongly oligophagous to 0.22 in monophagous species, and were 0.14 in plant species. Significant z -values were not only found for total species richness, based on a sample size adjusted to fragment area ( z  = 0.12), but also for the local density of butterfly species richness, based on equal sample size across all habitat fragments ( z  = 0.06). To our knowledge, this is the first study to show differential responses of monophagous, oligophagous and polyphagous species to area with respect to species richness and population density.     

Host plant availability potentially limits butterfly distributions under cold environmental conditions

Species ranges are shaped by both climatic factors and interactions with other species. The stress gradient hypothesis predicts that under physiologically stressful environmental conditions abiotic factors shape range edges while in less stressful environments negative biotic interactions are more important. Butterflies provide a suitable system to test this hypothesis since larvae of most species depend on biotic interactions with a specific set of host plants, which in turn can shape patterns of occurrence and distribution. Here we modelled the distribution of 92 butterfly and 136 host plant species with three different modelling algorithms, using distribution data from the Swiss biodiversity monitoring scheme at a 1 × 1 km spatial resolution. By comparing the ensemble prediction for each butterfly species and the corresponding host plant(s), we assessed potential constraints imposed by host plant availability on distribution of butterflies at their distributional limits along the main environmental gradient, which closely parallels an elevational gradient. Our results indicate that host limitation does not play a role at the lower limit. At the upper limit 50% of butterfly species have a higher elevational limit than their primary host plant, and 33% have upper elevational limits that exceed the limits of both primary and secondary hosts. We conclude that host plant limitation was not relevant to butterfly distributional limits in less stressful environments and that distributions are more likely limited by climate, land use or antagonistic biotic interactions. Obligatory dependency of butterflies on their host plants, however, seems to represent an important limiting factor for the distribution of some species towards the cold, upper end of the environmental gradient, suggesting that biotic factors can shape ranges in stressful environments. Thus, predictions by the stress gradient hypothesis were not always applicable.     

Latitudinal gradients in butterfly body sizes: is there a general pattern?

We tested for the existence of latitudinal gradients in the body sizes of butterflies in North America, Europe, Australia and the Afrotropics. We initially compared body sizes (measured as male forewing length) of all butterflies found in 5° latitudinal bands in each region, and then evaluated the relationship between body size and latitude statistically using the latitudinal midpoint of each species' distribution. Trends were examined for species in all butterfly families together and for each family separately. We found that gradients in body sizes were inconsistent in different geographical regions and butterfly families; in some cases species were larger towards the tropics, in some they were smaller, and in other cases there were no relationships. Most of the gradients, when they existed, reflected between-family effects arising from changes in the relative numbers of species in each family across regions. We conclude that general ecological explanations for geographical trends in butterfly body sizes are inappropriate, and gradients largely reflect historical patterns of speciation within and between taxa in each biogeographical realm. Thus, the robustness of body size gradients found in other insect groups should be confirmed in future studies by including more than one geographical region whenever possible.     

The relationship between diet breadth and geographic range size in the butterfly subfamily Nymphalinae--a study of global scale

The "oscillation hypothesis" has been proposed as a general explanation for the exceptional diversification of herbivorous insect species. The hypothesis states that speciation rates are elevated through repeated correlated changes--oscillations--in degree of host plant specificity and geographic range. The aim of this study is to test one of the predictions from the oscillation hypothesis: a positive correlation between diet breadth (number of host plants used) and geographic range size, using the globally distributed butterfly subfamily Nymphalinae. Data on diet breadth and global geographic range were collected for 182 Nymphalinae butterflies species and the size of the geographic range was measured using a GIS. We tested both diet breadth and geographic range size for phylogenetic signal to see if species are independent of each other with respect to these characters. As this test gave inconclusive results, data was analysed both using cross-species comparisons and taking phylogeny into account using generalised estimating equations as applied in the APE package in R. Irrespective of which method was used, we found a significant positive correlation between diet breadth and geographic range size. These results are consistent for two different measures of diet breadth and removal of outliers. We conclude that the global range sizes of Nymphalinae butterflies are correlated to diet breadth. That is, butterflies that feed on a large number of host plants tend to have larger geographic ranges than do butterflies that feed on fewer plants. These results lend support for an important step in the oscillation hypothesis of plant-driven diversification, in that it can provide the necessary fuel for future population fragmentation and speciation.     

The Role of Olfactory Cues for the Search Behavior of a Specialist and Generalist Butterfly

Searching for resources is often a challenging task, especially for small organisms such as insects. Complex stimuli have to be extracted from the environment and translated into a relevant behavioral output. A first step in this process is to investigate the relative roles of the different senses during search for various resources. While the role of olfaction is well documented in nocturnal moths, the olfactory abilities of the closely related diurnal butterflies are poorly explored. Here we investigated how olfactory information is used in the search for host plants and asked if these abilities varied with levels of stimulus complexity. Thus, we tested two nymphalid butterfly species with divergent host plant range in a two-choice olfactometer testing different combinations of host and non-host plants. The experiments show both the monophagous Aglais urticae and the polyphagous Polygonia c-album could navigate towards an odor source, but this ability varied with context. While mated females exhibited a preference for their host plant, unmated females of both species did not show a preference for host plant cues. Furthermore, both species showed inabilities to make fine-tuned decisions between hosts. We conclude that olfactory cues are important for butterflies to navigate towards targets. We argue that there are limitations on how much information can be extracted from host volatiles. These results are discussed in the light of neural processing limitations and degree of host plant specialization, suggesting the necessity of other sensory modalities to sharpen the decision process and facilitate the final oviposition event.     

Butterfly assemblages in a traditional agricultural landscape: importance of secondary forests for conserving diversity,life history specialists and endemics

Satoyama, the traditional agricultural landscape in Japan, has drawn much attention from the viewpoint of biodiversity conservation. It is composed of diverse vegetation types, including secondary forests, paddy fields and cultivated fields in a narrow area (ca. 1 km²). To clarify the characteristics of butterfly assemblage and the relative contribution of each vegetation type to butterfly diversity and endemism in satoyama, we conducted a line-transect survey along a 1.1-km route with five sections (two forest interior, one interior-edge, one edge-openland and one openland). Life history features (voltinism, host plant range and host plant type) and endemism of butterflies were discussed in relation to their abundance and vegetation association. Fifty-one species and 856 individuals were recorded. Species richness was highest in the two sections with edges, 32 and 36 species, respectively. Analysis of vegetation association of each butterfly species showed that 16 species were forest interior species, 24 forest edge species and 11 openland species, indicating that vegetation diversity enhanced butterfly diversity. However, the point is that forest interior and edge species contained many specialists sensitive to human impact (univoltine and/or oligophagous species) and many species within temperate East Asia including all endemic species. In contrast, most openland species were generalists (multivoltine and/or polyphagous species) feeding on herbs/grasses with the widest geographic range. Since secondary forests kept more butterfly diversity and specialists than openlands, and had all endemic species, they must be maintained without over fragmentation in order to avoid loss of specialists and endemics in satoyama.     

Phoresy in the field: natural occurrence of Trichogramma egg parasitoids on butterflies and moths

Phoretic insects utilize other animals to disperse to new environments. We recently discovered how egg parasitoids use an exciting phoretic strategy to reach egg-laying sites of their butterfly hosts. In the laboratory, female Trichogramma wasps detect and mount mated female cabbage white butterflies that emit an anti-aphrodisiac pheromone. Hardly any information exists about the natural occurrence of phoresy in wasps of this genus. Therefore, we monitored the presence of phoretic Trichogramma wasps on lepidopteran hosts in the field. Only female wasps were found at low prevalence on six lepidopteran species. Wasps were mostly found on female hosts and mainly on abundant solitary host species. This is the first report of phoretic Trichogramma wasps on butterflies in nature. We suggest that phoresy is only one of several strategies used by these polyphagous egg parasitoids. The evolution of phoresy is discussed in relation to the nutritional ecology of egg parasitoids.     

Evolutionary responses by butterflies to patchy spatial distributions of resources in tropical environments

The greatest diversity of butterflies and their host plants occurs in tropical regions. Some groups of butterflies in the tropics exhibit monophagous feeding in the larval stage, exploiting only one family of plants; others are polyphagous, feeding on plants in two or more distinct families. The two major types of tropical habitats for butterflies, namely primary and secondary forests, offer very different evolutionary opportunities for the exploitation of plants as larval food. Butterflies are faced with the major logistical problem, as are many other herbivorous insects, of depositing eggs on the correct plant for successful larval feeding. This paper, using the concepts of phenotype set and spatial patchiness of resources, attemps to make some predictions as to the optimal phenotypic systems for monophagous and polyphagous feeding in tropical butterflies, as related to the spatial patchiness of larval host plants in primary and secondary forests. In addition to the secondary compound chemistry of larval host plants as playing a role in the evolution of monophagy and polyphagy, the assumption is made that the spatial patchiness of host plants within and among different families also acts as a major factor in determining optimal ranges of phenotypes for different patterns of larval feeding. Owing to the high spatial patchiness of primary forest species of canopy trees and vines, it is predicted that butterflies exploiting these will be mostly polyphagous, whereas secondary forests having stable formations of fewer plant species and larger patches of these plants, will have mostly monophagous species. Forest understories may have both monophagous and polyphagous species, depending upon the layer of forest and the general type of understory (i.e. palmaceous or dicotyledonous). Field data on some groups of butterflies from tropical America support these predictions. Polyphagous butterflies are predicted to possess a genetic system of mixed morphs with a population being polymorphic as a whole; monophagous butterflies are predicted to have individuals all more or less similar genetically, and with a high amount of genic variation within individuals. Other forms of monophagy may evolve in species that are essentially monomorphic but with various mechanisms (physiological, developmental, behavioral) of phenotypic flexibility at the individual level. Although the environment is essentially coarse-grained for larvae since most are sedentary and polymorphism is an optimal adaptive strategy, the oviposition strategy of the adult must also be considered and some situations (i.e. forest canopy) have resources (host plants) distributed in a fine-grained fashion. Other forms of limited polyphagy may result from monomorphic genetic systems in which there is considerable phenotypic flexibility.     

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     

Species traits explain recent range shifts of Finnish butterflies

This study provides a novel systematic comparative analysis of the species characteristics affecting the range margin shifts in butterflies towards higher latitudes, while taking phylogenetic relatedness among species into account. We related observed changes in the northern range margins of 48 butterfly species in Finland between two time periods (1992–1996 and 2000–2004) to 11 species traits. Species with positive records in at least ten 10 km × 10 km grid squares (in the Finnish National Butterfly Recording Scheme, NAFI) in both periods were included in the study. When corrected for range size change, the 48 butterfly species had shifted their range margins northwards on average by 59.9 km between the study periods, with maximum shifts of over 300 km for three species. This rate of range shifts exceeds all previously reported records worldwide. Our findings may be explained by two factors: the study region is situated in higher latitudes than in most previous studies and it focuses on the period of most prominent warming during the last 10–15 years. Several species traits exhibited a significant univariate relationship with the range margin shift according to generalized estimation equations (GEE) taking into account the phylogenetic relatedness among species. Nonthreatened butterflies had on average expanded their ranges strongly northwards (84.5 km), whereas the distributions of threatened species were stationary (−2.1 km). Hierarchical partitioning (HP) analysis indicated that mobile butterflies living in forest edges and using woody plants as their larval hosts exhibited largest range shifts towards the north. Thus, habitat availability and dispersal capacity of butterfly species are likely to determine whether they will be successful in shifting their ranges in response to the warming climate.