Survival of the endangered butterfly Lycaena helle in a fragmented environment: Genetic analyses over 15 years

Temporal changes in allele frequencies are often assumed in studies addressing the history of populations affected by different anthropogenic and natural impacts at different time scales. Yet, few studies directly compare the genetic composition of populations over time spans of more than 10 years. Therefore, to test the genetic effects of 15 years of population isolation in the butterfly Lycaena helle, we analysed 472 individuals from 27 samples, of which nine were collected in 1991 and 18 in 2006. Sampling was performed in five mountain regions (Pyrenees, Massif Central, Jura, Vosges and Ardennes). Genetic analyses were performed using five polymorphic microsatellites. Old and new samples of identical or neighbouring populations revealed similar genetic differentiations among these five mountain regions. A comparatively strong genetic differentiation among populations combined with a high amount of private alleles for each mountain area was detected, but mountain‐specific alleles were in most cases identical in 1991 and 2006. Nevertheless, the obtained data also indicate moderate changes between 1991 and 2006 in the species’ genetic structure – genetic differentiation among local populations increased marginally and allele frequencies showed corresponding modifications. A significant decline in genetic diversity was not detectable, and nine private alleles exclusive to a single mountain region were only detected in samples from the year 1991, whereas eleven were only observed in the individuals collected in 2006. These observations might indicate the results of genetic drift within isolated populations.     

Patch occupancy in the endangered butterfly Lycaena helle in a fragmented landscape: effects of habitat quality, patch size and isolation

While there is agreement that both habitat quality and habitat network characteristics (such as patch size and isolation) contribute to the occupancy of patches by any given species, the relative importance of these factors is under debate. This issue is of fundamental ecological importance, and moreover of special concern for conservation biologists aiming at preserving endangered species. Against this background we investigated patch occupancy in the violet copper Lycaena helle, one of the rarest butterfly species in Central Europe, in the Westerwald area (Rhineland-Palatinate, Western Germany). Occupied (n = 102) differed from vacant (n = 128) patches in altitude, size, connectivity, availability of wind shelter, in the abundance of the larval host-plant, in the abundance of a grass species indicating favorable habitat conditions and in the abundance of nitrophilous plants. Overall, patch occupancy was primarily determined by patch size, connectivity and the abundance of the larval host plant, while all other parameters of habitat quality were of subordinate importance. Therefore, our findings suggest that even for extremely sedentary species such as L. helle habitat networks are decisive and—next to the preservation of habitat quality—need to be an integral part of any conservation management for this species.     

Habitat quality matters for the distribution of an endangered leaf beetle and its egg parasitoid in a fragmented landscape

Fragmentation, deterioration, and loss of habitat patches threaten the survival of many insect species. Depending on their trophic level, species may be differently affected by these factors. However, studies investigating more than one trophic level on a landscape scale are still rare. In the present study we analyzed the effects of habitat size, isolation, and quality for the occurrence and population density of the endangered leaf beetle Cassida canaliculata Laich. (Coleoptera: Chrysomelidae) and its egg parasitoid, the hymenopteran wasp Foersterella reptans Nees (Hymenoptera: Tetracampidae). C. canaliculata is strictly monophagous on meadow sage (Salvia pratensis), while F. reptans can also parasitize other hosts. Both size and isolation of habitat patches strongly determined the occurrence of the beetle. However, population density increased to a much greater extent with increasing host plant density ( = habitat quality) than with habitat size. The occurrence probability of the egg parasitoid increased with increasing population density of C. canaliculata. In conclusion, although maintaining large, well-connected patches with high host plant density is surely the major conservation goal for the specialized herbivore C. canaliculata, also small patches with high host plant densities can support viable populations and should thus be conserved. The less specialized parasitoid F. reptans is more likely to be found on patches with high beetle density, while patch size and isolation seem to be less important.     

Flight morphology corresponds to both surrounding landscape structure and local patch conditions in a highly specialized peatland butterfly (Lycaena epixanthe)

1. Movement mediates the response of populations and communities to landscape and habitat spatial structure, yet movement capability may itself be modified by selection pressures accompanying landscape change. Insect flight morphology can be affected by both the landscape surrounding habitat patches and the distribution of resources within habitat patches. 2. This study investigated the relative influence of local habitat patch conditions and surrounding landscape structure on variation in morphological traits associated with flight in the bog copper (Lycaena epixanthe), a butterfly endemic to temperate Nearctic peatlands. 3. Eight habitat patches were sampled to assess the influence of the surrounding landscape (connectivity of potential habitat and matrix composition) and patch size (an integrated proxy of resource density and spatial distribution) on investment into flight, measured by thorax and abdomen mass, and wing area. 4. The results revealed an effect of both local habitat conditions and landscape structure on flight‐related morphological traits. Increasing forest cover in the surrounding landscape, indicative of increased habitat patch isolation, corresponded with less mobile phenotypes in both sexes. Surrounding landscapes with more water were also generally associated with less mobile phenotypes. Investment into flight was greater in smaller peatlands in which host plant density is higher and more homogeneously distributed. 5. The present study highlights that morphological traits associated with mobility may be responding to both local habitat patch characteristics and surrounding landscape structure. It also supports the hypothesis that local habitat conditions contribute to morphological variation in butterflies.     

The predictive accuracy of population viability analysis: a test using data from two small mammal species in a fragmented landscape

This study examines the predictive accuracy of the population viability analysis package, ALEX (Analysis of the Likelihood of EXtinction). ALEX was used to predict the probability of patch occupancy for two species of small native Australian mammals (Antechinus agilis and Rattus fuscipes) among 13 patches of suitable habitat in a matrix of plantation pines (Pinus radiata). The study was retrospective, running each simulation from 1900 until 1997, and the model parameterised without knowledge of the 1997 observed field data of patch occupancy. Predictions were made over eight scenarios for each species, allowing for variation in the amount of dispersal between patches, level of environmental stochasticity, and size of habitat patches. Predicted occupancies were compared to the 1997 field data of patch occupancy using logistic regression, testing H _random, that there was no relationship between observed and predicted occupancy, and H _perfect, that there was a perfect, 1:1 relationship between observed and predicted occupancies. Rejection of H _random and failure to reject H _perfect was taken as a good match between observed and predicted occupancies. Such a match was found for one scenario with R. fuscipes, and no scenarios with A. agilis. In general, patch occupancy was underestimated, with field surveys finding that 9 of the 13 patches were occupied by R. fuscipes and 10 by A. agilis. Nonetheless, PVA predictions were in the right direction, whereby patches predicted to have a high probability of occupancy were generally occupied, and vice versa. A post hoc search over additional scenarios found few scenarios with a better match than the original eight. The results of this study support the notion that PVA is best thought of as a relative, rather than absolute predictor of the consequences of management actions in threatened populations.     

Recruitment limitations in Primula vulgaris in a fragmented landscape

Plant recruitment is limited by dispersal, if seeds cannot arrive at potential recruitment sites, and by establishment, due to a low availability of safe sites for recruitment. Seed-sowing experiments, scarcely applied along gradients of landscape alteration, are very useful to assess these limitations. Habitat loss and fragmentation may foster recruitment limitations by affecting all the processes from seed dispersal to seedling establishment. In this study, we perform a seed-sowing experiment to disentangle the importance of dispersal and establishment limitations in different stages of recruitment of the perennial herb Primula vulgaris in fragmented forests of the Cantabrian Range (Northwestern Spain). We evaluated the influence of ecological gradients resulting from habitat loss and fragmentation (modifications of habitat amount at the landscape and microhabitat scales, changes in the species’ population size, changes in seed predation and seedling herbivory) on seedling emergence, survival and early growth. We found strong evidence of dispersal limitation, as seedling emergence was very low in experimental replicates where no seeds were added. This limitation was independent of landscape alterations, as we found no relation with any of the ecological gradients studied. Establishment limitations at the germination phase were also unrelated to ecological gradients, probably because these limitations are more related to fine-scale environmental gradients. However, further monitoring revealed that seedling survival after summer and winter periods and seedling growth were conditioned by landscape alteration, as we found effects of habitat amount at the landscape and microhabitat scales, of presence of populations of P. vulgaris and of seedling herbivory. These effects were complex and sometimes opposite to what can be expected for adult plants, revealing the presence of different requirements between life stages.     

Sex-specific indicators of landscape use by servals: Consequences of living in fragmented landscapes

The conversion of wetlands and its associated habitat for farming, residential development and commercial purposes has led to many small disconnected patches of native vegetation surrounded by generally inhospitable human altered land uses. Such human interventions pose a serious threat to the survival of wetland dependent indicator species such as the serval (Leptailurus serval) in the Drakensberg Midlands of KwaZulu-Natal, South Africa. To address the effects of habitat fragmentation on serval space use we used GPS fixes of collared individuals for 100 days between May 2013 and January 2014. We tracked five females and eleven male servals with GPS-UHF collars. Fragmentation indices at the class level (wetland, forest with bushland, grassland and cropland) were measured within the collared serval's minimum convex polygon area (MCP) of home range. Serval use points and fragmentation indices were extracted to each sub-landscape unit of 2 km² falling within the MCP home range. The response of serval population to fragmentation indices was analyzed using generalized linear models at three levels: male, female and the overall population. We found that core area of wetland positively explained landscape use by servals. Effects of forest core area, forest proximity and patch richness were important for landscape use by male servals. Male and female serval use declined with increase in complex shapes of forest and grassland, wetland clumpiness for females and overall, and cropland patches for servals overall. Our results showed that wetland is a key determinant for the survival of male and female servals in fragmented landscapes therefore effective conservation of serval population demands adequate viable native habitat.     

Persistence of species in a fragmented urban landscape: the importance of dispersal ability and habitat availability for grassland butterflies

Some species cope with, and survive in, urban areas better than others.From a conservation viewpoint it is important to understand why some species arerare or are excluded in the urban landscape, in order that we might take actionto conserve and restore species. Two ecological factors that might explain thedistribution and abundance of butterfly species in the urban landscape aredispersal ability and the availability of suitable habitat. The influence ofthese factors was assessed by examining the distribution and genetic structureof four grassland butterfly species in the West Midlands conurbation, UK. Thefour species differ in their distribution and abundance, mobility and habitatspecificity. No significant fit to the isolation-by-distance model was found forany of the study species at this spatial scale. MeanF _ST values revealed a non-significant level ofpopulation structuring for two species, Pieris napi (L.)and Maniola jurtina (L.), but moderate and significantpopulation differentiation for Pyronia tithonus (L.) andCoenonympha pamphilus (L.). Results suggest that thesespecies are limited more by the availability of suitable habitat than by theirability to move among habitat patches. Conservation strategies for thesegrassland species should initially focus on the creation and appropriatemanagement of suitable habitat. More sedentary species that have already beenexcluded from the conurbation may require a more complex strategy for theirsuccessful restoration.     

Influence of habitat,litter type,and soil invertebrates on leaf-litter decomposition in a fragmented Amazonian landscape

Amazonian forest fragments and second-growth forests often differ substantially from undisturbed forests in their microclimate, plant-species composition, and soil fauna. To determine if these changes could affect litter decomposition, we quantified the mass loss of two contrasting leaf-litter mixtures, in the presence or absence of soil macroinvertebrates, and in three forest habitats. Leaf-litter decomposition rates in second-growth forests (>10 years old) and in fragment edges (<100 m from the edge) did not differ from that in the forest interior (>250 m from the edges of primary forests). In all three habitats, experimental exclusion of soil invertebrates resulted in slower decomposition rates. Faunal-exclosure effects were stronger for litter of the primary forest, composed mostly of leaves of old-growth trees, than for litter of second-growth forests, which was dominated by leaves of successional species. The latter had a significantly lower initial concentration of N, higher C:N and lignin:N ratios, and decomposed at a slower rate than did litter from forest interiors. Our results indicate that land-cover changes in Amazonia affect decomposition mainly through changes in plant species composition, which in turn affect litter quality. Similar effects may occur on fragment edges, particularly on very disturbed edges, where successional trees become dominant. The drier microclimatic conditions in fragment edges and second-growth forests (>10 years old) did not appear to inhibit decomposition. Finally, although soil invertebrates play a key role in leaf-litter decomposition, we found no evidence that differences in the abundance, species richness, or species composition of invertebrates between disturbed and undisturbed forests significantly altered decomposition rates.     

Biogeography meets conservation: the genetic structure of the endangered lycaenid butterfly Lycaena helle (Denis & Schiffermüller, 1775)

Cold‐adapted species are thought to have had their largest distribution ranges in central Europe during the glacial periods. Postglacial warming caused severe range shifts of such taxa into higher latitudes and altitudes. We selected the boreomontane butterfly Lycaena helle (Denis & Schiffermüller, 1775) as an example to demonstrate the genetic effects of range changes, and to document the recent status of highly fragmented remnant populations. We analysed five polymorphic microsatellite loci in 1059 individuals sampled at 50 different localities scattered over the European distribution area of the species. Genetic differentiation was strong among the mountain ranges of western Europe, but we did not detect similarly distinct genetic groups following a geographical pattern in the more eastern areas. The Fennoscandian populations form a separate genetic group, and provide evidence for a colonization from southern Finland via northern Scandinavia to south‐central Sweden. Species distribution modelling suggests a large extension of the spatial distribution during the last glacial maximum, but highlights strong retractions to a few mountain areas under current conditions. These findings, combined with our genetic data, suggest a more or less continuous distribution of L. helle throughout central Europe at the end of the last ice age. As a consequence of postglacial warming, the species retreated northwards to Fennoscandia and escaped increasing temperatures through altitudinal shifts. Therefore, the species is today restricted to population remnants located at the mountain tops of western Europe, genetically isolated from each other, and evolved into genetically unique entities. Rising temperatures and advancing habitat destruction threaten this wealth of biodiversity. © 2010 The Linnean Society of London, Biological Journal of the Linnean Society, 2010, 101 , 155–168.     

Relative contributions of local and regional factors to species richness and total density of butterflies and moths in semi-natural grasslands

Metapopulation theory predicts that species richness and total population density of habitat specialists increase with increasing area and regional connectivity of the habitat. To test these predictions, we examined the relative contributions of habitat patch area, connectivity of the regional habitat network and local habitat quality to species richness and total density of butterflies and day-active moths inhabiting semi-natural grasslands. We studied butterflies and moths in 48 replicate landscapes situated in southwest Finland, including a focal patch and the surrounding network of other semi-natural grasslands within a radius of 1.5 km from the focal patch. By applying the method of hierarchical partitioning, which can distinguish between independent and joint contributions of individual explanatory variables, we observed that variables of the local habitat quality (e.g. mean vegetation height and nectar plant abundance) generally showed the highest independent effect on species richness and total density of butterflies and moths. Habitat area did not show a significant independent contribution to species richness and total density of butterflies and moths. The effect of habitat connectivity was observed only for total density of the declining butterflies and moths. These observations indicate that the local habitat quality is of foremost importance in explaining variation in species richness and total density of butterflies and moths. In addition, declining butterflies and moths have larger populations in well-connected networks of semi-natural grasslands. Our results suggest that, while it is crucial to maintain high-quality habitats by management, with limited resources it would be appropriate to concentrate grassland management and restoration to areas with well-connected grassland networks in which the declining species currently have their strongest populations. Electronic supplementary material  The online version of this article (doi:) contains supplementary material, which is available to authorized users.     

Habitat use by Oncifelis guigna and Pseudalopex culpaeus in a fragmented forest landscape in central Chile

Native forests in Chile have been replaced by exotic plantations, generating a mosaic of forest fragments immersed in a matrix of plantations and farms. This landscape change could affect habitat availability for native carnivores such as Oncifelis guigna (Felidae) and Pseudalopex culpaeus (Canidae). We determine the potential impact of native forest fragmentation on these species, assessinghabitat use by these carnivores. The study was carried out in continuous forest (150 ha), native forest fragments (<10 ha) and surrounding pine plantations in central Chile (35°59 S, 72°41 W). We placed scent-stations (SSs) in three types of habitat from January to August 2000, setting a total of 620 SSs to determine habitat selection. We characterized structure and composition of 100 m² of vegetation aroundevery SS, and measured its distance to nearest native forest patch, road and bottom creek. O. guigna preferred habitats with dense bush cover, far from roads and close to large patches of native forest, being almost exclusively restricted to this type of habitat. On the other hand, P. culpaeus preferred openhabitats, close to roads, relying extensively on pine plantations but scarcely using forest and forest fragments. Our results suggest that native forest fragmentation, considering habitat use only, would have a negative effect on O. guigna populations. Thus, forest size reduction and isolation may reduce O.guigna survival in a pine dominated landscape. In contrast, P. culpaeus, a generalist species that would use habitat depending on its abundance, may adapt to changes in this landscape.     

Changes in carabid beetle diversity within a fragmented agricultural landscape

The distribution of carabid and cicindelid (Coleoptera: Carabidae) beetles in five distinct habitats (riparian, mature orchard, pine windbreak, young orchard, natural veld), within Tambuti Citrus Estate (Swaziland) was examined by pitfall trapping over 18 months. Habitats with high vegetation and litter cover had the highest species diversity and larger specimens, e.g. riparian border and pine windbreak, while the lowest diversity was observed in intensively managed mature citrus orchards. While species such as Tefflus delagorguei Guérin occurred in all the habitats sampled, certain species illustrated habitat specificity; e.g. Dromica ambitiosa Péringuey was observed only in the pine windbreaks while Haplotrachelus sp. Chaudoir occurred mainly in the vegetated riparian and natural veld habitats. Four unidentified carabid beetles were exclusive to the riparian border habitat. This habitat was the only one with a distinct assemblage of species in the agricultural mosaic studied. Multivariate analyses were used to assess the role of soil and environmental variables in relation to the ground beetle diversity within the agricultural mosaic studied.     

Host-parasitoid extinction and colonization in a fragmented prairie landscape

Few field studies of natural populations have examined the factors influencing local extinctions and colonization of empty habitat patches for a prey species and its predator. In this study, I carried out a census of planthopper (Prokelisia crocea; Hemiptera: Delphacidae) and egg parasitoid (Anagrus columbi; Hymenoptera: Mymaridae) incidence and densities in 147 host-plant patches (Spartina pectinata; Poaceae) over seven planthopper generations in a tall-grass prairie landscape. For both species, the likelihood of going extinct in a patch was related to a number of patch-specific variables: density, temporal variability in density, proportion of hosts parasitized (planthopper only), host-plant density, patch size, patch isolation, and composition of the surrounding matrix. Colonization likelihood was related only to the physical attributes of the patch. There was high patch turnover in this prairie landscape. On average, planthoppers went extinct in 23% of the patches and A. columbi went extinct in 51% of the patches in each generation. For the planthopper, extinction likelihood increased with a decrease in patch size and the proportion of the matrix composed of mudflat. Parasitism of eggs had no effect on the extinction likelihood of local P. crocea populations, suggesting that A. columbi may not play a major role in the patch dynamics of its host. The likelihood of extinction for A. columbi was dependent on factors that spanned three trophic levels. An increase in plant density, decrease in host density and decrease in parasitoid density all increased the likelihood of A. columbi extinction within a patch. The dependency on multiple trophic levels may explain the higher extinction risk for the parasitoid than its host. A. columbi extinction was also affected by the matrix habitat surrounding the patch—the effect was the opposite of that for P. crocea. Finally, vacant patches were colonized at rates of 53% and 34% per generation for the planthopper and parasitoid, respectively. For both species, colonization probabilities decreased with an increase in patch isolation. High host densities in a patch also favored high rates of colonization by A. columbi. I discuss how anthropogenic changes to the prairie landscape can affect the metapopulation dynamics and persistence time of this host-parasitoid interaction.     

Genetic diversity in adult and seedling populations of <Emphasis Type="Italic">Primula vulgaris</Emphasis> in a fragmented agricultural landscape

Habitat fragmentation is known to generally reduce the size of plant populations and increase their isolation, leading to genetic erosion and increased between-population genetic differentiation. In Flanders (northern Belgium) Primula vulgaris is very rare and declining. Populations have incurred strong fragmentation for the last decades and are now restricted to a few highly fragmented areas in an intensively used agricultural landscape. Previous studies showed that small populations of this long-lived perennial herb still maintained high levels of genetic variation and low genetic differentiation. This pattern can either indicate recent gene flow or represent historical variation. Therefore, we used polymorphic microsatellite loci to investigate genetic variation and structure in adult (which may still reflect historical variation) and seedling (recent generation, thus affected by current processes) life stages. The recent generation (seedlings) showed a significant loss of observed heterozygosity (H _o) together with lower expected heterozygosity (H _e), a trend for higher inbreeding levels (F _IS) and higher differentiation (F _ST) between populations compared to the adult generation. This might result from (1) a reduction in effective population size, (2) higher inbreeding levels in the seedlings, (3) a higher survival of heterozygotes over time due to a higher fitness of heterozygotes (heterosis) and/or a lower fitness of homozygotes (inbreeding depression), (4) overlapping generations in the adult life stage, or (5) a lack of establishment of new (inbred) adults from seedlings due to degraded habitat conditions. Combining restoration of both habitat quality and gene flow between populations may be indispensable to ensure a sustainable conservation of fragmented populations.     

Species richness, composition and abundance of fruit-feeding butterflies in the Brazilian Atlantic Forest: comparison between a fragmented and a continuous landscape

Aim  To evaluate frugivorous butterflies as indicators of forest disturbance in the Brazilian Atlantic Forest.
Location  The study area is located in the municipality of Cotia, São Paulo State, south-eastern Brazil (23°35'−23°50' S, 46°45'−47°15' W).
Methods  Sampling was done at four sites inside a large forest block, the Morro Grande State Reserve, and in five forest fragments in an adjacent fragmented landscape. Butterflies were sampled with portable traps, baited with a fermented mixture of banana and sugar cane juice. Sampling was carried out during the period most favourable for the capture of frugivorous butterflies in south-eastern Brazil.
Results  All richness-related results indicated no effect of forest fragmentation on the frugivorous butterfly guild, concurring with the suggestion of appreciable resistance of Atlantic Forest butterflies to habitat modification. However, species composition discriminated between the two landscapes, indicating that fragmentation may have effects beyond simple species richness. When species were analysed individually, clear patterns of distribution emerged, with some species that were very abundant in the fragmented landscape being practically absent in the continuous landscape, and vice versa. This pattern seems consistent even for some subfamilies.
Main conclusion  Our findings support the usefulness of the frugivorous butterfly guild as a biological indicator of forest disturbance effects in one of the world's most threatened ecosystems.     

State‐space modeling reveals habitat perception of a small terrestrial mammal in a fragmented landscape

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Distribution and colonisation ability of three parasitoids and their herbivorous host in a fragmented landscape

Habitat fragmentation can disrupt communities of interacting species even if only some of the species are directly affected by fragmentation. For instance, if parasitoids disperse less well than their herbivorous hosts, habitat fragmentation may lead to higher herbivory in isolated plant patches due to the absence of the third trophic level. Community-level studies suggest that parasitoids tend to have limited dispersal abilities, on the order of tens of metres, much smaller than that of their hosts, while species-oriented studies document dispersal by parasitoids on the scale of kilometres. In this study the distribution patterns of three parasitoid species with different life histories and their moth host, Hadena bicruris, a specialist herbivore of Silene latifolia, were compared in a large-scale network of natural fragmented plant patches along the rivers Rhine and Waal in the Netherlands. We examined how patch size and isolation affect the presence of each species. Additionally, experimental plots were used to study the colonisation abilities of the species at different distances from source populations.In the natural plant patches the presence of the herbivore and two of the parasitoids, the gregarious specialist Microplitis tristis and the gregarious generalist Bracon variator were not affected by patch isolation at the scale of the study, while the solitary specialist Eurylabus tristis was. In contrast to the herbivore, the presence of all parasitoid species declined with plant patch size. The colonisation experiment confirmed that the herbivore and M. tristis are good dispersers, able to travel at least 2 km within a season. B. variator showed intermediate colonisation ability and E. tristis showed very limited colonisation ability at this spatial scale. Characteristics of parasitoid species that may contribute to differences in their dispersal abilities are discussed.