John W. Dover

The influences of landscape structure on butterfly distribution and movement: a review

We review the literature on the influence of landscape structure on butterfly distribution and movement. We start by examining the definition of landscape commonly used in spatial ecology. Landscape-level processes are reviewed before focusing on the impact of the geometry and spatial arrangement of habitat patches on butterflies e.g. the nature of the matrix, patch size and shape, minimum area requirements, immigration and emigration, and temporal habitat dynamics. The role of landscape elements is reviewed in terms of corridors (and stepping-stones), barriers, nodes, environmental buffers, and prominent landmark features.

The importance of shelter for butterflies in open landscapes

In Britain, much emphasis has been placed on conserving butterfly species in specialized habitats, since this is where most of it‘s threatened butterflies exist, whilst the wider countryside has been largely overlooked. However, there is increasing awareness that small improvements to the dominant landscape could potentially reap huge benefits to the populations of many of Britain‘s butterfly species. Recent studies have also stressed the importance of the landscape scale in the conservation of butterflies in small fragmented habitats. In this paper, we examine data from a variety of sources and conclude that the importance of shelter in open landscapes may be underestimated since recording is often restricted to the optimum conditions suggested by the Butterfly Monitoring Scheme. In less favourable conditions, butterflies may place greater reliance on those components of the landscape offering shelter. In light of the current policy of agricultural de-intensification we discuss how modifications to our current landscapes could benefit a wide range of species.

Factors affecting the distribution of satyrid butterflies on arable farmland

1. The effects of biotic and abiotic factors on the distribution of three species of satyrid butterfly (Aphantopus hyperantus, Pyronia tithonus and Maniola jurtina) in arable field margins were studied in a block of arable farmland on a North Hampshire farm. 2. Non-floral factors affecting distribution included the degree of shelter, insolation, width of hedgebank or grass verge, and uncultivated habitat. Farm tracks adjacent to the field boundaries exerted a negative effect on abundance. 3. Floral variables affecting distribution included the abundance of flowers of bramble (Rubus fruticosus), thistle-like Compositae, marjoram (Origanum vulgare) and mayweeds (Matricaria spp.) in conservation headlands. Negative variables included abundance of cow parsley (Anthriscus sylvestris) and old mans beard (Clematis vitalba); although the latter was negative for A. hyperantus and M. jurtina, it was a positive variable for P. tithonus. 4. The distribution of butterflies in arable field margins is discussed in relation to landscape structure, microclimate and resources.

Movement of two grassland butterflies in the same habitat network: the role of adult resources and size of the study area

Abstract. 1.  Movement patterns of two butterfly species (meadow brown Maniola jurtina L. and scarce copper Lycaenae virgaureae L.) were studied in a 172 ha area within a landscape with a high percentage of suitable habitats for mark–release–recapture experiments.

Linear features and butterflies: the importance of green lanes

Abstract Green lanes are unmetalled tracks between fields of variable width, which may be sunk below or raised above field level, and bounded on both sides by ‘grass’ banks, hedgerows or dry-stone walls. In the UK they have no unique planning status and have been overlooked as discrete landscape elements. Green lanes were surveyed for butterflies in 1997 on lowland arable farmland on the Trafford/north Cheshire border (Warburton) and on upland grassland in the Yorkshire Dales (Ribble Valley). At the lowland site the green lanes were bounded by vegetation and were compared with grass banks and single hedgerow field boundaries; at the upland farm, the green lanes were bounded by dry-stone walls and were compared with grass banks and single dry-stone walls. Data from earlier work on a largely arable farm (Manydown) in Hampshire in 1987 and 1988 were re-analysed to make comparisons between a green lane, the rides and glades of two coppiced woodlands, and the grass banks and single hedgerows surrounding arable fields. Green lanes, whether bounded by vegetation or stone were superior to other common farmland biotopes with the exception of woodland, in terms of both butterfly abundance and species richness. Multiple regression of the Warburton data indicated the importance of green lanes, adjacent habitat type, and nectar sources for species richness and butterfly abundance. The interior of green lanes had lower windspeeds, and more bramble nectar sources than hedgerows or grass banks. By their nature they occupy a larger area of uncropped land, and are subject to a reduced disturbance regime and reduced inputs of agrochemicals and fertilisers. Their value as biodiversity reservoirs in intensively managed land is likely to be high.

Reduced pesticide inputs on cereal field margins: the effects on butterfly abundance

Abstract. 1. On a study farm in Hampshire where large blocks of cereal fields had the pesticide inputs on their headlands experimentally and selectively reduced (the practice known as ‘conservation headlands’), numbers of butterflies were monitored over 4 years by using transect counts.

Conservation headlands: effects on butterfly distribution and behaviour

Abstract The gamebird management system known as Conservation Headlands, whereby the outermost 6 m of cereal fields are selectively sprayed, is known to affect the distribution and abundance of many non-game species including butterflies. Previous work on butterflies in the arable environment showed that more butterflies were found associated with field margins which had received reduced pesticide inputs, but only speculated on the mechanism which produced the enhanced numbers. This study examines the differences in butterfly behaviour between field margins with conservation headlands and those sprayed according to normal farm practice. The results show distinct within-season differences in behaviour patterns. Spring emerging butterflies in field margins sprayed according to normal farm practice are principally associated with the field boundary habitat (the hedgerow), whilst those in fields with conservation headlands are principally associated with the headland. The proportion of time spent in flight, feeding, resting and mate location behaviours also changed with headland regime. In normally sprayed field margins the principal activity was flight, in field margins with conservation headlands this dominance was broken with striking increases in foraging activity on headland flora. Butterflies that emerged in the summer were less strongly associated with the headland than those that emerged in the spring. The discussion relates these differences to the changing nature of the flora of the field boundary and headlands over the season and the population structure of the species studied. The role of resource provisioning for non-target species in the arable environment, and the effect of resources on landscape permeability to dispersing individuals are also discussed.

Experimental simulation of some visual and physical components of a hedge and the effects on butterfly behaviour in an agricultural landscape

Experiments on the corridor function of linear features in real landscapes are difficult and expensive to carry out using the classic replicated and controlled experimental regimes usually required as formal proof of a concept. We describe two experiments using model structures to simulate different attributes of hedges for their potential role in initiating corridor movement.

Corridors and barriers in biodiversity conservation: a novel resource-based habitat perspective for butterflies

Habitat loss and fragmentation, exacerbated by projected climate change, present the greatest threats to preservation of global biodiversity. As increasing habitat fragmentation and isolation of residual fragments exceeds the dispersal capacity of species, there is the growing need to address connectivity to maintain diversity. Traditionally, habitat corridors have been proposed as a solution. But, the concept of corridors (barriers) is poorly understood; typically they are defined as linear habitats linking up habitat patchwork, and are advocated without a detailed understanding of the elements making up species’ habitats and the cost-effectiveness of alternative solutions. Yet, landscapes comprise an enormous range of ‘linear’ structures that can function in different ways to promote species’ persistence and diversity. In this review, a functional definition of corridor (barrier) is developed to give prominence to connectivity as opposed to ad hoc structures purported to advance connectivity. In developing the concept, urgency to accommodate environmental changes compels a growing emphasis on organism diversity rather than a preoccupation with single species conservation. The review, in focusing on butterflies to address the issue of corridors for patchwork connectivity, draws attention to fundamental divisions among organisms in any taxon: generalists and specialists. Both groups benefit from large patches as these necessarily house species with specialist resources as well as generalists with very different resource types. But, generalists and specialists require very different solutions for connectivity, from short-range habitat corridors and gateways for specialists to habitat and resource stepping stones (nodes, surfaces) for generalists. Connectivity over extensive areas is most critical for moderate generalists and their conservation requires emphasis being placed on space–time resource heterogeneity; landscape features, of whatever dimensionality and structure, provide a vital framework for developing the variety of suitable conditions and resources for enhancing their diversity.

Grassland butterflies and low intensity farming in Europe

In this paper we describe the impact of the abandonment of traditional farming practices on butterflies and their habitats in traditional, often montane, pastoral systems. We link these declines to socioeconomic factors: illustrating how the failure of the CAP to support traditional farming leads to structural changes in farming enterprises—features which may be obscured by crude statistics on stock. We then call for the scheduled CAP reforms in 2013 to be radically realigned to support rather than destroy biodiversity so that any new EU agri-biodiversity commitments have an effective funding stream to support them.