Geographical variation in host–ant specificity of the parasitic butterfly Maculinea alcon in Denmark

Abstract  1. Maculinea alcon uses three different species of Myrmica host ants along a north–south gradient in Europe. Based on this geographical variation in host ant use, Elmes et al . (1994) suggested that M. alcon might consist of three or more cryptic species or host races, each using a single and different host-ant species.
2. Population-specific differences in allozyme genotypes of M. alcon in Denmark ( Gadeberg & Boomsma, 1997 ) have suggested that genetically differentiated forms may occur in a gradient across Denmark, possibly in relation to the use of different host ants.
3. It was found that two host-ant species are indeed used as hosts in Denmark, but not in a clear-cut north–south gradient. Furthermore, specificity was not complete for many M. alcon populations. Of five populations investigated in detail, one used primarily M. rubra as a host, another exclusively used M. ruginodis , while the other three populations used both ant species. No population in Denmark used M. scabrinodis as a host, although this species was present in the habitat and is known to be a host in central and southern Europe.
4. In terms of number of parasites per nest and number of nests parasitised, M. rubra seems to be a more suitable host in populations where two host species are used simultaneously. Host-ant species has an influence on caterpillar size but this varies geographically. Analyses of pupae did not, however, show size differences between M. alcon raised in M. rubra and M. ruginodis nests.
5. The geographical mosaic of host specificity and demography of M. alcon in Denmark probably reflects the co-evolution of M. alcon with two alternative host species. This system therefore provides an interesting opportunity for studying details of the evolution of parasite specificity and the dynamics of host-race formation.     

Contrasting movement patterns in two species of chequerspot butterflies, Euphydryas aurinia and Melitaea phoebe, in the same patch network

Abstract.  1. Mark–release–recapture studies were conducted on two species of chequerspot butterfly, Euphydryas aurinia and Melitaea phoebe , in the same habitat patch network in Yanjiaping, a small basin in the Taihang Mountains, north-west of Beijing, China, in 2000.
2. Euphydryas aurinia tended to stay in the habitat patches and to move to neighbouring patches, whereas M. phoebe moved widely among patches in the entire network.
3. The parameters of the virtual migration model showed higher daily emigration propensity in M. phoebe and in E. aurinia males than in E. aurinia females, and significantly greater average daily movement distance in M. phoebe than in E. aurinia .
4. The results are consistent with the previous findings showing genetic structuring among local populations of E. aurinia but not among local populations of M. phoebe .
5. Based on the genetic and ecological results, it was concluded that E. aurinia has a classic metapopulation in the study area, whereas M. phoebe appears to have a source–sink metapopulation.
6. In 2000, when there was an overall increase in the abundance of the two species, the limited mobility of E. aurinia resulted in an increase in the average local population size, whereas the increase in the number of local populations in M. phoebe was due to its high mobility .     

Effects of meadow suitability on female behaviour in the alpine butterfly Parnassius smintheus

Abstract  1. Many butterfly populations persist in networks of naturally fragmented habitat patches. Movement and reproductive decisions made by adult females are critical to the persistence of these populations because colonisation of extinct habitat patches in the network requires emigration of fecund adult females from their natal meadow and their subsequent establishment in the extinct patch.
2. Movement and oviposition behaviours of mated Parnassius smintheus females released in suitable meadows (a good- and a poor-quality meadow) and an unsuitable meadow were compared, to determine whether adult females consider meadow suitability for their offspring despite frequent oviposition events off the larval host plant.
3. Bootstrap and correlated random walk analyses of female step lengths and turn angles demonstrated that females flew more randomly in the unsuitable meadow than in the suitable meadows. Although females tended to turn the sharpest angle between landing sites in the good-quality meadow, and fly the smallest distance between landing sites and displace the smallest distance from the release site in the suitable meadows, no significant differences were detected in turn angle, step length, and dispersal rates between suitable and unsuitable meadows.
4. Results from female flight observations and a caged oviposition study suggest that females lay significantly more eggs in suitable habitat than in unsuitable habitat despite not ovipositing on the host plant, and support the above findings.
5. Movement and oviposition behaviours of adult female P. smintheus promote their retention within meadows that can support their offspring.     

Connectivity compensates for low habitat quality and small patch size in the butterfly <Emphasis Type="Italic">Cupido minimus</Emphasis>

Habitat size, habitat isolation and habitat quality are regarded as the main determinants of butterfly occurrence in fragmented landscapes. To analyze the relationship between the occurrence of the butterfly Cupido minimus and these factors, patch occupancy of the immature stages in patches of its host plant Anthyllis vulneraria was studied in the nature reserve Hohe Wann in Bavaria (Germany). In 2001 and 2002, 82 A. vulneraria patches were surveyed for the presence of C. minimus larvae. The occurrence was largely affected by the size of the food plant patches. In a habitat model that uses multiple logistic regression, the type of management and habitat connectivity are further determinants of species distribution. Internal and temporal validation demonstrate the stability and robustness of the developed habitat models. Additionally, it was proved that the colonization rate of C. minimus was significantly influenced by the distance to the next occupied Anthyllis patch. Concerning long-term survival of (meta-) populations in fragmented landscapes, the results show that lower habitat quality may be compensated by higher connectivity between host plant patches. Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users.     

Habitat-based statistical models for predicting the spatial distribution of butterflies and day-flying moths in a fragmented landscape

1.  Most species' surveys and biodiversity inventories are limited by time and money. Therefore, it would be extremely useful to develop predictive models of animal distributions based on habitat, and to use these models to estimate species' densities and range sizes in poorly sampled regions.
2.  In this study, two sets of data were collected. The first set consisted of over 2000 butterfly transect counts, which were used to determine the relative density of each species in 16 major habitat types in a 35-km² area of fragmented landscape in north-west Wales. For the second set of data, the area was divided into 140 cells using a 500-m grid, and the extent of each habitat and the presence or absence of each butterfly and moth species was determined for each cell.
3.  Logistic regression was used to model the relationship between species' distribution and predicted density, based on habitat extent, in each grid square. The resultant models were used to predict butterfly distributions and occupancy at a range of spatial scales.
4.  Using a jack-knife procedure, our models successfully reclassified the presence or absence of species in a high percentage of grid squares (mean 83% agreement). There were highly significant relationships between the modelled probability of species occurring at regional and local scales and the number of grid squares occupied at those scales.
5.  We conclude that basic habitat data can be used to predict insect distributions and relative densities reasonably well within a fragmented landscape. It remains to be seen how accurate these predictions will be over a wider area.     

Parasitism by the mite Trombidium breei on four U.K. butterfly species

Abstract 1.  The incidence of parasitism by larvae of the mite species Trombidium breei was reported in one population of the lycaenid butterfly Polyommatus icarus , four populations of the satyrine butterfly Maniola jurtina , one population of the satyrine butterfly Aphantopus hyperanthus , and two populations of the satyrine butterfly Pyronia tithonus , as well as on one specimen of the dipteran Alophorus hemiptera . A considerable proportion of butterflies (11-50%) was infested in all study populations.
2. The pattern of infestation was examined in detail in M. jurtina . Males had a significantly higher incidence of infestation than females, and middle-aged butterflies had a higher incidence of infestation than old or young butterflies. The incidence of infestation peaked in the middle of the flight season, and this seasonal effect was independent of the effect of butterfly age.
3. Using a model based on capture-recapture data, it was estimated that a hypothetical ideal male M. jurtina that lives exactly the mean expected lifespan of 9-10 days has an approximately 75% chance of becoming infested with mites at least once during its lifetime, a mean time to first infestation of 3-4 days, and an average infestation persistence time of 2-3 days.
4. Capture-recapture data failed to show any effect of mite infestation on the lifespan or within-habitat movement rate of M. jurtina .
5. In experiments in which individual butterflies were taken out of their normal habitat and released, M. jurtina and P. tithonus that were infested with mite larvae did not differ from uninfested individuals in the efficiency with which they returned to suitable habitat. Thus, parasitism by T. breei larvae had no detectable effects on flight performance or orientation ability.
6. The results suggest that trombidiid mite larvae have limited potential in the biological control of insect pests.     

Potential metapopulation structure and the effects of habitat quality on population size of the endangered False Ringlet butterfly

The False Ringlet (Coenonympha oedippus) is a European butterfly species, endangered due to the severe loss and fragmentation of its habitat. In Hungary, two remaining populations of the butterfly occur in lowland Purple Moorgrass meadows. We studied a metapopulation occupying twelve habitat patches in Central Hungary. Our aim was to reveal what measures of habitat quality affect population size and density of this metapopulation, estimate dispersal parameters and describe phenology of subpopulations. Local population sizes and dispersal parameters were estimated from an extensive mark–release–recapture dataset, while habitat quality was characterized by groundwater level, cover of grass tussocks, bush cover, height of vegetation and grass litter at each habitat patch. The estimated size of the metapopulation was more than 3,000 individuals. We estimated a low dispersal capacity, especially for females, indicating a very low probability of (re)colonization. Butterfly abundance and density in local populations increased with higher grass litter, lower groundwater level and larger area covered by tussocks. We suppose that these environmental factors affect butterfly abundance by determining the microclimatic conditions for both larvae and adult butterflies. Our results suggest that the long-term preservation of the studied metapopulation needs the maintenance of high quality habitat patches by appropriate mowing regime and water regulation. Management also should facilitate dispersal to strengthen metapopulation structure with creating stepping-stones or gradually increase habitat quality in present matrix.     

Higher productivity at the cost of increased host-specificity when Maculinea butterfly larvae exploit ant colonies through trophallaxis rather than by predation

Abstract .1. Field studies were made of the benefits and costs of two feeding strategies in the genus Maculinea, whose final-instar larvae parasitise Myrmica ant colonies. Maculinea arion is an obligate predator of ant brood, whereas M. rebeli and M. alcon mimic ant larvae and are fed (like cuckoos) directly by the workers.
2. Samples of > 1500 Myrmica nests confirmed laboratory-based predictions that, by feeding at a lower trophic level, many (4.7-fold) more individuals of M. rebeli and M. alcon are supported per ant colony than M. arion.
3. Because of their efficient feeding, cuckoo species often occupied sites where their phytophagous early larval populations coincided to only a small extent (> 10%) with host Myrmica colonies, whereas all sites supporting M. arion had 50–100% of the phytophagous stages within foraging range of the host Myrmica species.
4. Greater host-specificity was identified as another consequence of cuckoo-feeding. The ecological cost of this is discussed .
5. The feeding of other Maculinea species had not been fully described: the data suggest that M. nausithous is a predator of ant brood and confirm that M. teleius is predacious .     

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.     

Dynamic populations in a dynamic landscape: the metapopulation structure of the marsh fritillary butterfly

The marsh fritillary butterfly Euphydryas aurinia is an endangered species in most of northern Europe. We describe the metapopulation structure of E. aurinia in Finland, where the species has declined drastically in the past decades. We found two types of habitat patches suitable for the species: semi-permanent meadows and transient clearcuts in the forest. Patch area was the most significant variable predicting the occurrence of E. aurinia in a habitat patch. The species tended to be found in young rather than old clearcuts, apparently because the vegetation became too high in the latter. We used the incidence function model to simulate the metapopulation dynamics of E. aurinia in its dynamic landscape and discovered that the continued presence of the semi-permanent meadows is essential for the survival of the species in the study area in southeast Finland.     

A new species of Ocimum (Lamiaceae) from Swaziland

A new species of Ocimum , O. motjaneanum McCallum & K. Balkwill, endemic to serpentine soils in the north-west of Swaziland, is described and compared with O. obovatum, the species it most closely resembles. It has a very localized distribution with an area of occupancy under threat of encroachment by exotic trees and development, which makes it critically endangered (CR B1a + b(iii)) using the IUCN guidelines. We recommend habitat protection and incorporation of one site into an existing nature reserve to assure the continuation of this species.  © 2004 The Linnean Society of London, Botanical Journal of the Linnean Society , 2004, 145 , 379–383.     

Within-patch mobility and flight morphology reflect resource use and dispersal potential in the dryad butterfly Minois dryas

Knowledge of mobility is essential for understanding animal habitat use and dispersal potential, especially in the case of species occurring in fragmented habitats. We compared within-patch movement distances, turning angles, resting times, and flight-related morphological traits in the locally endangered butterfly, the dryad (Minois dryas), between its old populations occupying xerothermic grasslands and newly established ones in wet meadows. We expected that the latter group should be more mobile. Individuals living in both habitat types did not differ in their body mass and size, but those from xerothermic grasslands had wider thoraxes and longer wings, thus lower wing loading index (defined as body mass to wing length ratio). The majority of movements were short and did not exceed 10 m. Movement distances were significantly larger in males. However, there was no direct effect of habitat type on movement distances. Our results suggest that the dryads from xerothermic grasslands have better flight capabilities, whereas those from wet meadows are likely to invest more in reproduction. This implies that mobility is shaped by resource availability rather than by recent evolutionary history. Lower female mobility may have negative implications for the metapopulation persistence because only mated females are able to (re)colonise vacant habitat patches efficiently. Conservation efforts should thus be focused on maintaining large habitat patches that prevent stochastic local extinctions. Furthermore, the recommendation of promoting the exchange of individuals among patches through improving matrix permeability, as well as assisted reintroductions of the species into suitable vacant habitats should also improve its conservation.     

Local extinction event despite high levels of gene flow and genetic diversity in the federally-endangered Miami blue butterfly

A certain level of genetic diversity and connectivity between populations is necessary to allow small populations to persist over time. In this study, we investigate the last two populations of the highly endangered Miami blue butterfly, one of which was extirpated in 2010. We investigate whether an erosion of genetic diversity was the cause for the extirpation of the Bahia Honda State Park (BHSP) population. As the level of existing molecular diversity within and gene flow between the last two populations of the endangered Miami blue butterfly was unknown, we present data from twelve polymorphic microsatellite loci as an assessment. We show that greater genetic diversity (allelic richness and observed heterozygosity) than originally predicted existed in the BHSP population prior to its extirpation and values were even greater in the Key West National Wildlife Refuge population. Allelic frequencies show short-range gene flow between neighboring habitat patches and underline the importance of habitat connectivity. It does not appear that loss of genetic diversity was the cause for the loss of the BHSP population. Greater consideration of habitat connectivity should be considered for short and long-term conservation and management of this taxon.     

Root vole movement patterns: do ditches function as habitat corridors?

1. Ditches are often connected to root vole habitat patches (i.e. moist reed patches) in the Netherlands. Due to the linear structure of ditches and because ditch habitat is qualitatively similar to root vole habitat patches, we hypothesized that ditches could function as habitat corridors facilitating dispersal movement of root voles. In order to test this hypothesis, we radiotracked root voles released in a landscape novel to them, consisting of ditches and agricultural meadows.
2. Agricultural meadows often surround the marsh patches inhabited by root voles. As the meadows are mowed regularly, we included the length of the meadow vegetation as an experimental factor in the study.
3. Assuming that ditches function as habitat corridors, we expected root voles in the ditches to move faster and more unidirectionally than root voles in the meadows, and to prefer the ditches to meadows.
4. We found that the ditches did not facilitate faster movements than the meadows. Although the root voles moved back and forth within the ditches, they showed a more directional movement pattern than the root voles in the meadows. Furthermore, the root voles preferred the ditch habitat irrespective of the vegetative cover in the meadow.
5. We conclude that ditches could function as habitat corridors for root voles, as they preferred to move in ditches when in unfamiliar areas.     

Genetic erosion in a stenotopic heathland ground beetle (Coleoptera: Carabidae): a matter of habitat size?

Two centuries ago large areas of north-west Europe were covered by coherent heathlands which hosted numerous specialized species. Changes in land use made heathlands fragmented and rare, consequently, they are in the focus of nature conservation efforts today. But how large should remaining heathland patches be in order to secure the survival of populations of specialized species? We investigated the genetic diversity at five allozyme loci of Poecilus lepidus, a flightless and stenotopic heathland ground beetle. 29 populations from differently sized heathland patches in north-west Germany were analyzed. Results show a weak but significant genetic differentiation and no evidence for isolation by distance or other patterns of spatial autocorrelation. Linear regression analysis revealed significant relationships between patch size, allelic richness, number of alleles and expected heterozygosity. These findings are explained by severe habitat fragmentation together with strong fluctuations in population size which have been reported for this species in the past. To conserve the vast majority of the species’ genetic diversity for a period of 100 years we suggest to maintain heathland patches of at least 50 ha in size.     

Management of modern agricultural landscapes increases nest predation rates in Black‐tailed Godwits Limosa limosa

Effective conservation of endangered species requires a solid understanding of the demographic causes of population change. Bird populations breeding on agricultural grasslands have declined because their preferred habitat of herb‐rich meadows has been replaced by grassland monocultures. The timing of agricultural activities in these monocultural grasslands is critical, as they often coincide with the nesting phase of breeding birds. Here, we aim to identify the effect of habitat management and targeted nest protection on nest survival of Black‐tailed Godwits Limosa limosa in the Netherlands, a population that has shown a 70% reduction in breeding population size since the 1970s. To protect nests in monocultures from destruction, farmers are paid to either delay mowing or leave a patch of unmown grass around the nest, a patch which in practice varied in size. In herb‐rich meadows, which are typically managed for bird conservation purposes, mowing occurs after hatching. Nest survival declined as the season advanced, more steeply on monocultures than on meadows. Targeted nest protection was only partially successful, as nest predation was considerably higher on mown grassland monocultures with small unmown patches around the nest than in mown monocultures with large unmown patches and in unmown fields. Increased predator densities over the years have been suggested as an important cause of the trend towards lower nest survival, but here we show that nest survival was higher on herb‐rich meadows than on monocultures, and similar to the 1980s. It thus seems that increased predator densities are an increased threat during the egg stage only if habitat quality is low. High‐quality habitat in the form of herb‐rich meadows therefore provides a degree of protection against predators.     

Habitat use and population biology of the Danube Clouded Yellow butterfly Colias myrmidone (Lepidoptera: Pieridae) in Romania

The Danube Clouded Yellow (Colias myrmidone) is one of the most endangered butterflies in Europe. Its distribution range shrank dramatically in the last few decades due to the extinction of populations in Western and Central Europe. Ecological studies were commenced when populations were already at the verge of extinction, thus our knowledge on the population ecology and habitat use of this butterfly is very limited. Here we report the results of a study on habitat preferences, egg distribution and demography of C. myrmidone in Romania, perhaps the last remaining stronghold of the species in Central Europe. We found that Danube Clouded Yellow adults occurred mainly in mesophilous grasslands created by forest clearing and then maintained by low intensity grazing allowing bushes and forest-edge vegetation to develop and host Chamaecytisus species to grow. Butterflies highly preferred lightly grazed pastures over hay meadows and abandoned grasslands, their density was positively related to host plant density. Egg-laying females preferred habitat patches with relatively high cover of the host plant and tall vegetation. Both apparent survival rate and encounter probability were lower for females than males, and parameter estimations also had much higher errors for females. These indicate that much higher sampling effort is needed to estimate and monitor population parameters for females than for males. Our results provide guidelines for the habitat management and population monitoring of Colias myrmidone, thus may significantly contribute to its successful conservation.     

Occupancy modeling of <Emphasis Type="Italic">Parnassius clodius</Emphasis> butterfly populations in Grand Teton National Park,Wyoming

Estimating occupancy patterns and identifying vegetation characteristics that influence the presence of butterfly species are essential approaches needed for determining how habitat changes may affect butterfly populations in the future. The montane butterfly species, Parnassius clodius, was investigated to identify patterns of occupancy relating to habitat variables in Grand Teton National Park and Bridger-Teton National Forest, Wyoming, United States. A series of presence–absence surveys were conducted in 2013 in 41 mesic to xeric montane meadows that were considered suitable habitat for P. clodius during their flight season (June–July) to estimate occupancy (ψ) and detection probability (p). According to the null constant parameter model, P. clodius had high occupancy of ψ?=?0.78?±?0.07 SE and detection probability of p?=?0.75?±?0.04 SE. In models testing covariates, the most important habitat indicator for the occupancy of P. clodius was a strong negative association with big sagebrush (Artemisia tridentata; β = ??21.39?±?21.10 SE) and lupine (Lupinus spp.; β?=???20.03?±?21.24 SE). While P. clodius was found at a high proportion of meadows surveyed, the presence of A. tridentata may limit their distribution within montane meadows at a landscape scale because A. tridentata dominates a large percentage of the montane meadows in our study area. Future climate scenarios predicted for high elevations globally could cause habitat shifts and put populations of P. clodius and similar non-migratory butterfly populations at risk.     

Dispersal and gene flow in the rare, parasitic Large Blue butterfly Maculinea arion

Dispersal is crucial for gene flow and often determines the long‐term stability of meta‐populations, particularly in rare species with specialized life cycles. Such species are often foci of conservation efforts because they suffer disproportionally from degradation and fragmentation of their habitat. However, detailed knowledge of effective gene flow through dispersal is often missing, so that conservation strategies have to be based on mark–recapture observations that are suspected to be poor predictors of long‐distance dispersal. These constraints have been especially severe in the study of butterfly populations, where microsatellite markers have been difficult to develop. We used eight microsatellite markers to analyse genetic population structure of the Large Blue butterfly Maculinea arion in Sweden. During recent decades, this species has become an icon of insect conservation after massive decline throughout Europe and extinction in Britain followed by reintroduction of a seed population from the Swedish island of Öland. We find that populations are highly structured genetically, but that gene flow occurs over distances 15 times longer than the maximum distance recorded from mark–recapture studies, which can only be explained by maximum dispersal distances at least twice as large as previously accepted. However, we also find evidence that gaps between sites with suitable habitat exceeding ～20 km induce genetic erosion that can be detected from bottleneck analyses. Although further work is needed, our results suggest that M. arion can maintain fully functional metapopulations when they consist of optimal habitat patches that are no further apart than ～10 km.     

Drivers of local densities of endangered Lycaena helle butterflies in a fragmented landscape

Due to their specialised habitat requirements, butterflies are particularly vulnerable to habitat loss and fragmentation. Understanding the drivers of local abundances of species is essential for their effective conservation in fragmented landscapes. We investigated factors affecting population densities of an endangered European butterfly, the Violet Copper (Lycaena helle), occurring in a small metapopulation near the city of Kraków, southern Poland. The environmental parameters tested as predictors of the local densities of the species included both the variables associated with spatial structure of habitats such as patch sizes, their isolation and fragmentation as well as those potentially reflecting habitat quality. Patch area and vegetation height turned out to be the only factors significantly influencing L. helle densities, both having a positive effect. The positive impact of patch area is a bit surprising, since its relationship with population densities is typically negative in butterflies. In our study system it is likely to derive from source-sink dynamics as the smaller habitat patches are apparently too small to sustain viable local populations. In turn, the positive influence of vegetation height implies that the ongoing succession does not deteriorate the quality of the recently abandoned meadows yet, whereas higher turf may provide better sheltering places. The loss of almost half of L. helle habitat patches in the study area in recent years is alarming. However, its inclusion into the Natura 2000 system should help to conserve the species as long as this act is followed by proper management of its habitats.