The impact of habitat fragmentation on trophic interactions of the monophagous butterfly <Emphasis Type="Italic">Polyommatus coridon</Emphasis>

Theory predicts that habitat fragmentation, including reduced area and connectivity of suitable habitat, changes multitrophic interactions. Species at the bottom of trophic cascades (host plants) are expected to be less negatively affected than higher trophic levels, such as herbivores and their parasitoids or predators. Here we test this hypothesis regarding the effects of habitat area and connectivity in a trophic system with three levels: first with the population size of the larval food plant Hippocrepis comosa, next with the population density of the monophagous butterfly species Polyommatus coridon and finally with its larval parasitism rate. Our results show no evidence for negative effects of habitat fragmentation on the food plant or on parasitism rates, but population density of adult P. coridon was reduced with decreasing connectivity. We conclude that the highly specialized butterfly species is more affected by habitat fragmentation than its larval food plant because of its higher trophic position. However, the butterfly host species was also more affected than its parasitoids, presumably because of lower resource specialization of local parasitoids which also frequently occur in alternative hosts. Therefore, conservation efforts should focus first on the most specialized species of interaction networks and second on higher trophic levels.     

Habitat preference and dispersal of the Duke of Burgundy butterfly (Hamearis lucina) on an abandoned chalk quarry in Bedfordshire, UK

The Duke of Burgundy butterfly (Hamearis lucina) has declined severely since the 1970s and is a UK Biodiversity Action Plan Priority species. Its populations are mostly confined to scrubby calcareous grassland, where management for short-turf species can be detrimental to the butterfly. We briefly review the literature on the Duke of Burgundy and investigate their habitat preferences, survival and dispersal at a chalk grassland reserve in Bedfordshire, UK. We found that adults generally preferred more sheltered locations but that their habitat preferences were less restrictive than choice of food-plants. Females chose larger plants with longer leaves in denser patches on which to lay eggs. Adults showed reasonable dispersal ability with turnover recorded between areas isolated by scrub. Our results indicate that the species is able to use isolated areas of favourable habitat at a reserve scale and that conservation could therefore involve cyclic management to provide suitable habitat year-to-year.     

Habitat associations of the Small Red Damselfly (<Emphasis Type="Italic">Ceriagrion tenellum)</Emphasis> (De Villiers) in heathland in southern England (Zygoptera: Coenagrionidae)

The Small Red Damselfly (Ceriagrion tenellum) (De Villiers) (Odonata: Coenagrionidae: Ceriagrion) is classed as vulnerable (Shirt, British Red Data Book, Nature Conservancy Council, Peterborough, UK, 1987) throughout the UK, and is included in certain Local Biodiversity Action Plans (LBAPs) in the south. A large proportion of any Biodiversity Action Plan is concerned with the requirement of conservation and management programmes. In order to guide them, information about the habitat preferences of the species concerned is vital. Detailed habitat information was collected to include a variety of physical parameters particularly vegetation, both in-channel and bankside. The species was found to be primarily associated with in-channel emergent broad-leaved plants, bankside grasses and rushes, and shallow, narrow channels with dark organic substrate. The consequences of these findings are discussed in relation to the conservation and management of C. tenellum.

The United Kingdom Biodiversity Action Plan moths – selection, status and progress on conservation

As a result of the Earth Summit in 1992, 53 species of moth are covered by the UK Governments Biodiversity Action Plan. The background to the UK Biodiversity Action Plan and the selection of species is discussed. Butterfly Conservations Action for Threatened Moths Project is covered along with its role and approach in overseeing the implementation of the moth Action Plans. A case study on the Straw Belle Aspitates gilvaria (Denis and Schiffermüller) is presented as an example of how an individual Action Plan is being implemented. A subjective consideration of the biological progress with the moth Action Plans is given along with a brief discussion of possible future developments for the UK BAP approach for moths.     

Rare charophytes in Scotland's coastal saline lagoons

Summary

Recently collected data comparing the distribution and performance of the rare lagoonal charophyte Lamprothamnium papulosum across a number of UK coastal lagoon sites, including nine sites in the Western Isles, is presented. The surveys revealed that the species occurred over a wide range of salinities but was absent from sites with high phosphorus concentrations. The sites in the Western Isles held the most extensive populations and were least threatened by nutrient pollution. The discovery of two other endangered and vulnerable charophytes of brackish water, Tolypella nidifica and Chara baltica, at two of the Western Isles sites further highlights the importance of Scotland's saline lagoon resource. The use of the autoecological data on salinity and nutrient conditions for supporting Biodiversity Action Plan implementation for Lamprothamnium papulosum and for saline lagoon conservation in general is considered. Status summaries for all the charophyte species of brackish water recorded in Scotland are also provided.     

Genetic diversity and differentiation of fragmented reedbeds (<Emphasis Type="Italic">Phragmites australis</Emphasis>) in the United Kingdom

Reedbeds, which are dominated by the common reed Phragmites australis, provide one of the most important aquatic habitats in the United Kingdom, and have been identified as a priority habitat under the UK Biodiversity Action Plan. Ongoing conservation and management of reedbeds is necessary because past eradication and fragmentation have been extensive. However, there has been little consideration of the potential long-term effects that may arise if processes such as founder effects during restoration projects, or genetic bottlenecks following harvesting, are leading to reductions in genetic diversity. In this study, we used microsatellite data to compare the genetic diversity of 19 P. australis stands in the UK, and found that neither size, management, nor habitat disturbance were affecting genetic diversity. Mixed reproduction (clonal and sexual), possibly combined with gene flow across relatively small spatial scales, appears to be maintaining genetic diversity within most stands. However, most stands were highly genetically differentiated from one another, which implies low gene flow. Long-term genetic diversity in managed stands may therefore require periodic bolstering from other populations, combined with the simultaneous cultivation of multiple generations. In addition, low gene flow suggests that managers should actively introduce plants into all areas in which reedbeds are desired. In conclusion, our study shows that reedbed restoration and maintenance do not seem to be adversely affecting the population genetics of P. australis, but the importance of genetic diversity should be factored into long-term projects.     

Reconstruction of the colonization route from glacial refugium to the northern distribution range of the European butterfly Polyommatus coridon (Lepidoptera: Lycaenidae)

Genetic analyses are useful tools for reconstructing glacial distribution patterns and postglacial expansion corridors. However, little information is available about the latter. We reconstruct the expansion corridors of the butterfly Polyommatus coridon from its glacial refugium to the northern edge of its current distribution by comparing populations from southern Lower Saxony (central Germany) to other existing genetic data sets. The populations from Lower Saxony clearly belonged to a western lineage that expanded postglacially from the Adriatic‐Mediterranean region. They form part of a southern German group passing through the Burgundian Gap. In the southern German group, populations belong to a western subgroup. Therefore, expansion followed the Rhine valley and through Hesse, finally reaching southern Lower Saxony and western Thuringia in central Germany. Thus, we present a complete colonization route from the glacial refugium to the northern distribution range of P. coridon. Such data are useful for understanding the biogeographic structure and migration corridors for other mobile Mediterranean species.     

The influence of ecological and life history factors on ectothermic temperature–size responses: Analysis of three Lycaenidae butterflies (Lepidoptera)

Body size has been shown to decrease with increasing temperature in many species, prompting the suggestion that it is a universal ecological response. However, species with complex life cycles, such as holometabolous insects, may have correspondingly complicated temperature–size responses. Recent research suggests that life history and ecological traits may be important for determining the direction and strength of temperature–size responses. Yet, these factors are rarely included in analyses. Here, we aim to determine whether the size of the bivoltine butterfly, Polyommatus bellargus, and the univoltine butterflies, Plebejus argus and Polyommatus coridon, change in response to temperature and whether these responses differ between the sexes, and for P. bellargus, between generations. Forewing length was measured using digital specimens from the Natural History Museum, London (NHM), from one locality in the UK per species. The data were initially compared to annual and seasonal temperature values, without consideration of life history factors. Sex and generation of the individuals and mean monthly temperatures, which cover the growing period for each species, were then included in analyses. When compared to annual or seasonal temperatures only, size was not related to temperature for P. bellargus and P. argus, but there was a negative relationship between size and temperature for P. coridon. When sex, generation, and monthly temperatures were included, male adult size decreased as temperature increased in the early larval stages, and increased as temperature increased during the late larval stages. Results were similar but less consistent for females, while second generation P. bellargus showed no temperature–size response. In P. coridon, size decreased as temperature increased during the pupal stage. These results highlight the importance of including life history factors, sex, and monthly temperature data when studying temperature–size responses for species with complex life cycles.     

The potential contribution of conifer plantations to the UK Biodiversity Action Plan

Summary

The detrimental effects of conifer plantations on open ground habitats have been well catalogued and discussed, but the potential contribution of planted forests to the conservation of woodland biodiversity has not been quantified to the same extent. This quantification is needed urgently to help forest managers fulfil commitments to biodiversity enhancement as outlined in the UK Biodiversity Action Plan, the UK Forestry Standard and the UK Woodland Assurance Scheme (UKWAS). Results are presented from a five-year programme of research aimed at obtaining baseline information on biodiversity in planted forests and evaluating the contribution of planted forests to the conservation of native flora and fauna. Fifty-two plots were surveyed in total, covering a range of different tree crops (Scots pine Pinus sylvestris L., Sitka spruce Picea sitchensis (Bong.) Carr., Norway spruce Picea abies L. and Corsican pine Pinus nigra var maritima (Aitón) Melville) and stand ages (pre-thicket, mid-rotation, mature and over-mature) in three contrasting bioclimatic zones (upland, foothills and lowlands) throughout Britain. Additional plots were established in semi-natural woodland to allow comparisons between the biodiversity of plantations and native stands. Over 2000 species were recorded in total, including 45 Red Data Book species. Planted stands had similar or richer fungal and invertebrate communities to those of the native stands but poorer lichen and vascular plant communities. The latter were strongly affected by shading, dense, mid-rotation Sitka spruce stands having the lowest species counts. In contrast, these stands had a high diversity of mycorrhizal fungi, including a number of rare and threatened species normally associated with native pine wood. Bryophyte species-richness was related more to climate than woodland type, with the wetter upland spruce and native oak stands having the most diverse communities. Compared to the younger planted stands, over-mature planted stands had a higher proportion of species characteristic of semi-natural woodland stands. This related to greater structural diversity and higher deadwood volumes in the over-mature stands. It is concluded that conifer plantations make a positive contribution to biodiversity conservation in the UK and hence to the UK Biodiversity Action Plan. No single stand or crop type provides ‘optimal’ conditions for biodiversity, but the habitat value of plantations could be enhanced by increasing the area managed under alternative systems to clear-felling, such as ‘continuous cover’ and/or non-intervention natural reserves.     

Grey Partridge Perdix perdix in the UK: recovery status,set‐aside and shooting

The Grey Partridge Perdix perdix is a European Species of Conservation Concern and a priority species under the UK Biodiversity Action Plan. The Game & Wildlife Conservation Trust (GWCT) launched a major programme to help partridge recovery in the UK, built on the GWCT’s Partridge Count Scheme (PCS) and including a demonstration site from 2002. We contrast the national picture of no population change since 1999 from BTO monitoring with a doubling of spring pair density on PCS sites. At the demonstration site, where set‐aside was used for habitat creation, Grey Partridge breeding density increased six‐fold, to 18 pairs/km², then fell back. The drop coincided with bad weather but also with the disappearance of rotational set‐aside when the set‐aside rate fell to zero, which halved the amount of brood‐rearing habitat. Non‐rotational set‐aside remained unchanged, as did the amount of nesting habitat that it provided. Grey Partridge density was significantly linked to rotational set‐aside, especially wild bird cover, but not to non‐rotational set‐aside. The demonstration project also showed that, with appropriate precautions, it was possible to shoot over 60% of Red‐legged Partridges Alectoris rufa while maintaining Grey Partridge losses below 5%. On PCS sites, the annual change in spring density in recent years differed in relation to neither shooting pressure nor intensity of Red‐legged Partridge releasing. Provision of brood‐rearing habitats and game cover increased with the latter, and probably counteracts the shooting losses of Grey Partridges on Red‐legged Partridge shoots when, as on PCS sites, active measures keep those losses below 20%. Targeted personal advice channelled through the PCS has been fundamental to these successes and must be expanded.     

Plant community composition and attributes reveal conservation implications for newly created grassland on capped landfill sites

Biodiversity conservation through restoring degraded habitats or creating new habitats is advocated in the UK Biodiversity Action Plan. Restored grasslands on capped landfill sites are semi-natural habitats that could potentially support a wide range of plant communities. However, it is unknown whether these re-created habitats represent a significant resource in terms of biodiversity conservation. The UK National Vegetation Classification (NVC) was used to study these communities on nine restored capped landfill sites together with paired reference sites in the East Midlands region of the UK during 2007. Plant species data were collected by random quadrats along two 100 m transects from each site. The effects of restoration were investigated by examining plant attributes and Ellenberg indicators on restored landfill sites in comparison to paired reference sites. A total of 170 plant species were found from both sets of sites. There were no significant differences for most of the plant attributes between restored landfill sites and reference sites, though reference sites had significantly higher mean frequencies of native plants, nationally decreasing species and perennial species. In total 26 broad NVC community types were identified of which more than 70% fell within mesotrophic grassland (MG). The diversity of NVC communities confirms that underlying environmental factors such as soil fertility are important, dictating the type of plant communities that exist. It is recommended that management of these capped landfill sites should be targeted towards specific NVC community types to meet conservation targets.     

The UK Machair Habitat Action Plan: Progress and problems

Summary

Machair is a complex dune grassland habitat confined to Scotland and Ireland. With two-thirds of the world area of machair in Scotland, the UK has a special responsibility for this resource, and the UK Machair Habitat Action Plan identifies a range of realistic management targets and actions aimed at protecting and enhancing the habitat.

Machair's conservation importance is substantially reliant on active, traditional management, but quantitative and location-based information on management is rarely available, and this will have an impact on any numerical targets in the Plan. Though progress has been made on many of the actions, further measurable progress will very much depend, not only on improvements in the information base, but also in the understanding of relationships between land use and biodiversity.

Progress to date on actions and targets is evaluated, and problems are identified.     

Upland habitat conservation in Scotland: a review of progress and some proposals for action

Summary

The uplands cover around 70% of Scotland's land surface. Many of the extensive and well-developed habitats are internationally distinctive in their floristics. Almost 250 Sites of Special Scientific Interest are designated primarily for upland habitat interests, and there are 23 upland National Nature Reserves. The EC Habitats Directive lists 23 ‘natural habitat’ types found in the Scottish uplands. More than 70 potential Special Areas of Conservation, proposed for designation under the Directive, have been identified by Scottish Natural Heritage. The UK Biodiversity Action Plan has statements for five principal upland habitats, and costed action plans are being developed for each of these. The impact of man, since the 1940s, points to heavy grazing pressure, poor burning practices and acidic deposition as the major influences on habitat change. Actions are discussed for the conservation of key upland habitats in five biogeographical zones. A distinction is made between the need to restore habitats to areas from which they have been lost and the enhancement or rehabilitation of existing areas of the habitat. Examples are given of suggested criteria for ‘favourable condition’ under the EC Habitats Directive. More generally, examples are given of some desired changes in habitat composition for improved conservation.     

The Chalk-hill Blue Polyommatus coridon (Lycaenidae, Lepidoptera) in a highly fragmented landscape: How sedentary is a sedentary butterfly?

The habitats of many species are fragmented. Therefore, the survival in a metapopulation depends on the stability of the single populations and the amount of movements between patches. We chose the calcareous grassland specialist butterfly species Polyommatus coridon as a model. As study area, we selected a mosaic-like landscape in Rhineland-Palatinate (western Germany) with several well preserved calcareous grassland fragments. We marked a total of 2,211 individuals during July and August 2003. The overall recapture ratio was 7.1%. The estimated mean butterfly densities over the whole flight season ranged from 52 to 487 individuals per hectare. The within-patch movements were relatively low (13.3%) compared with the between-patch movements (3.2%). Therefore, the metapopulation structure appears to be intact in our study area.     

Molecular evidence for a recent founder event in the UK populations of the Adonis blue butterfly (<Emphasis Type="Italic">Polyommatus bellargus</Emphasis>)

Contrary to accepted theories of post-glacial colonisation of the UK approximately 10,000 year BP (yBP), historical population data for Polyommatus bellargus suggests the butterfly was either extremely rare or not present before 1775. We examined the phylogeography of the species by sequencing the ‘hypervariable’ mitochondrial control region of UK and French butterflies. Overall, 22 polymorphic nucleotide sites were identified within the control region. French specimens were highly variable, with 17 polymorphic sites, whereas most UK specimens were monomorphic. Average nucleotide diversity was 0.026 (SD 0.016, n = 8) in France, whilst the UK values ranged from 0.00 (n = 6) (for every UK population outside Dorset, n = 43) to 0.01 (SD 0.008, n = 7) (Dorset). The mean number of pairwise differences among the French samples was 7.42, whilst the UK values ranged from 0.00 (all populations except Dorset) to 0.295 (Dorset). One French haplotype differed from the predominant UK version by just a single nucleotide substitution. It seems implausible that the species can have been resident in the UK for 10,000 years without accumulating variation at this mitochondrial region. Thus, the results suggest that either a severe genetic bottleneck or founder event has occurred recently in the UK.     

Microsatellite markers to assess the influence of population size, isolation and demographic change on the genetic structure of the UK butterfly Polyommatus bellargus

Five microsatellite DNA markers were isolated and used to quantify population genetic structure among a subset of UK populations of the Adonis blue (Polyommatus bellargus Rottemburg). Specifically, whether population size, degree of isolation or history of bottlenecking in 1976-1978 can explain current patterns of genetic variation. The butterfly is at its northern range limit in the UK, where it exists as a highly fragmented metapopulation on isolated pockets of calcareous grassland. Most populations were affected by a severe bottleneck in the late 1970s, when a drought caused the host plant (Hippocrepis comosa) to wilt. Mantel tests and spatial autocorrelation analysis indicated a significant effect of isolation by distance among the UK populations, a relationship that broke down at greater geographical scales (> 23.85 km), probably because of large areas of unsuitable habitat presenting barriers to gene flow. Similarly, amova revealed that variation among geographical regions was almost double that observed within regions. Larger populations were found to support significantly higher levels of genetic diversity, suggesting that small populations may lose genetic diversity through drift. If, as in other butterfly species, low genetic diversity increases the probability of population extinction, then these populations are likely to be under threat. Neither isolation nor a history of bottlenecks appeared to influence genetic diversity. The results indicate that adequate population size a crucial factor in the conservation of genetic diversity in P. bellargus in the UK.     

Conserving freshwater biodiversity: The value,status and management of high quality ditch systems

Freshwater biodiversity is globally threatened and while most conservation efforts are focussed on natural and larger freshwater systems such as rivers and lakes, in many lowland agricultural landscapes artificial water bodies including ditches may be equally important as habitats for freshwater species. Ditches occur across the agricultural landscape but in particular, those associated with coastal and floodplain grazing marsh, have high conservation value. The importance of this habitat for rare and threatened species afforded priority status under the UK Biodiversity Action Plan is explored. The characteristics of ditches that have high conservation value are described and a set of targets against which such ditches can be assessed are presented. An analysis of the current condition of Sites of Special Scientific Interest (SSSI) for the wider coastal and floodplain grazing marsh habitat demonstrates the range of pressures affecting these sites and highlights that alongside generic freshwater issues such as eutrophication and non-native species, these sites have a unique set of pressures associated with their ongoing management and the vulnerable location of many sites at the coast. Wider conservation strategies for freshwater biodiversity in lowland landscapes across Europe need to factor in the different management requirements of artificial habitats such as ditches alongside more ambitious restoration projects for natural waterbodies. In low lying coastal areas the threat of coastal squeeze for many important grazing marshes will require a strategic approach to allow upstream migration of important biodiversity.     

Improving conservation and management of the imperiled Carson Valley silverpot butterfly <Emphasis Type="Italic">Speyeria nokomis carsonensis</Emphasis> (Lepidoptera: Nymphalidae) based on rapid assessments of distribution,habitat, and threats

The immediacy of conservation decisions for imperiled species often requires rapid assessments of fundamental species-specific data to appropriately guide conservation resources, regulatory actions, and mitigation activities. The goal of this paper was to inform future conservation and management decisions for the imperiled Carson Valley silverspot butterfly (Speyeria nokomis carsonensis), a species that has been subject to conservation attention, yet very little is known about its distribution and habitat. Surveys for S. nokomis carsonensis and its habitat were conducted during 2004–2005. An 88% decline in the number of historic subpopulations was observed, but 30 new subpopulations were discovered. Among the 62 sites that either had populations or were considered potentially suitable habitat, three distinct habitat types were delineated: agricultural seeps, isolated springs, and riparian meadows. Riparian sites comprised 58% of all sites and little variation was observed in the proportion of occupancy across habitat types. Disturbance was substantially greater in unoccupied sites than in sites occupied by S. nokomis carsonensis. Livestock grazing was the primary threat (50% of sites) to habitat, while water diversions were a secondary threat (7 sites). The variability in habitat and threats identifies that even for highly specialized subspecies, all habitats simply cannot be considered equal candidates for inclusion in a conservation strategy for the butterfly. Adopting proactive management policies that conserve suites of sites within each habitat type and reduce grazing intensity within S. nokomis carsonensis habitats should be a priority to reduce threats and circumvent a prospective listing pursuant to the US Endangered Species Act.     

How limited is dispersal in the rare beetle, Cryptocephalus decemmaculatus (Chrysomelidae, Cryptocephalinae)?

As suitable habitat becomes increasingly fragmented the ability of a species to reach new areas may often dictate whether populations persist or perish. An understanding of dispersal ability is a prerequisite for informed management decisions. This is particularly true for species that have become restricted to one or a small number of sites, as is the case for several species of Cryptocephalus beetle in the UK. Using mark–release–recapture, host-plant marking and direct observations we investigated population size, movement through suitable habitat and the flight behaviour of Cryptocephalus decemmaculatus. In the UK this species is known from only two sites and it is listed as a priority species on the UK Biodiversity Action Plan. At the time of the study, the one known English site for this species supported a population of ~500 individuals. The adult beetles move through their habitat using suitable host-plants as ‘stepping stones’. There appears to be no interchange of adults between sub-populations that are separated by small areas of unsuitable habitat (e.g. small tracts of woodland or areas devoid of scrub), a result reinforced by studies of genetic differentiation between sub-populations. The small population size of this beetle and its association with, mid-successional habitats makes it vulnerable to local extinction. Furthermore, its limited dispersal ability means that other habitat patches are unlikely ever to be colonised naturally.     

Impact of game bird release on the Adonis blue butterfly Polyommatus bellargus (Lepidoptera Lycaenidae) on chalk grassland

Polyommatus bellargus is a priority species of butterfly in the UK as a result of its scarcity and the rate of population decline over the last few years. In the UK, the species is associated with chalk grassland on hot, south-facing slopes suitable for the growth of the food plant Hippocrepis comosa. Shooting game birds is a popular pastime in the UK. Over 40 million game birds, principally Phasianus colchicus and Alectoris rufa, are bred and released into the countryside each year for shooting interests. There is a concern that the release of such a large number of non-native birds has an adverse effect on native wildlife. A study was carried out over a period of 3 years out to examine whether there was any evidence that A. rufa released into chalk grassland habitat negatively affects populations of P. bellargus. A comparison was made between sites where large numbers of A. rufa were released versus sites where no, or few, birds were released. The study involved the construction of exclosures in these sites to allow an examination of the number of butterflies emerging from H. comosa when the birds were excluded versus when the birds had free range across the area. Where birds were present the on-site vegetation was shorter than where they were absent indicating that the birds were definitely influencing habitat structure. However, the evidence that A. rufa was negatively influencing the number of adult butterflies emerging was not strong, although there was a largely non-significant tendency for higher butterfly emergence when the birds were excluded or absent.