Landscape-scale dynamics of a threatened species respond to local-scale conservation management

Landscape-scale approaches are increasingly advocated for species conservation but ensuring landscape level persistence by enlarging the size of patches or increasing their physical connectivity is often impractical. Here, we test how such barriers can be overcome by management of habitat at the local (site-based) level, using a rare butterfly as an exemplar. We used four surveys of the entire UK distribution of the Lulworth Skipper (Thymelicus acteon) over 40 years to test how local habitat influences population density and colonization / extinction dynamics, and parameterized, validated and applied a metapopulation model to simulate effects of varying local habitat quality on regional persistence. We found the total number of populations in four distribution snapshots between 1978 and 2017 varied between 59-84, and from 1997 to 2017 34% of local populations showed turnover (colonization or extinction). Population density was closely linked to vegetation characteristics indicative of management, namely height and food plant frequency, both of which changed through time. Simulating effects of habitat quality on metapopulation dynamics 40 years into the future suggests coordinated changes to two key components of quality (vegetation height and food plant frequency) would increase patch occupancy above the range observed in the past 40 years (50-80%). In contrast, deterioration of either component below threshold levels leads to metapopulation retraction to core sub-networks of patches, or eventual extirpation. Our results indicate that changes to habitat quality can overcome constraints imposed by habitat patch area and spatial location on relative rates of colonization and local extinction, demonstrating the sensitivity of regional dynamics to targeted in situ management. Local habitat management therefore plays a key role in landscape-scale conservation. Monitoring of population density, and the monitoring and management of local (site-level) habitat quality, therefore represent effective and important components of conservation strategies in fragmented landscapes.Natural Environment Research Council (NERC)Butterfly Conservatio

Changes in habitat associations during range expansion: disentangling the effects of climate and residence time

The distributions of many species are not at equilibrium with their environment. This includes spreading non-native species and species undergoing range shifts in response to climate change. The habitat associations of these species may change during range expansion as less favourable climatic conditions at expanding range margins may constrain species to use only the most favourable habitats, violating the species distribution model assumption of stationarity. Alternatively, changes in habitat associations could result from density-dependent habitat selection; at range margins, population densities are initially low so species can exhibit density-independent selection of the most favourable habitats, while in the range core, where population densities are higher, species spread into less favourable habitat. We investigate if the habitat preferences of the non-native common waxbill Estrilda astrild changed as they spread in three directions (north, east and south-east) in the Iberian Peninsula. There are different degrees of climatic suitability and colonization speed across range expansion axes, allowing us to separate the effects of climate from residence time. In contrast to previous studies we find a stronger effect of residence time than climate in influencing the prevalence of common waxbills. As well as a strong additive effect of residence time, there were some changes in habitat associations, which were consistent with density-dependent habitat selection. The combination of broader habitat associations and higher prevalence in areas that have been colonised for longer means that species distribution models constructed early in the invasion process are likely to underestimate species’ potential distribution

Optimizing the biodiversity gain from agri-environment schemes

How best to optimize the biodiversity gain from agri-environment schemes (AES) has recently been identified as a key policy-relevant question. Here, the effects of two features of lowland agricultural landscapes on the abundance and diversity of larger moths are contrasted. Although both features bring about positive effects, hedgerow trees have a larger impact than 6 m wide grassy field margins. Whilst AES payments are given to create and maintain grass margins, no financial reward is currently offered for the retention of hedgerow trees. Furthermore, it was only in areas where the amount of land under AES was experimentally increased, by targeting farmers, that the presence of hedgerow trees resulted in a substantially higher abundance (+60%) and diversity (+38%) of moths. Thus, by using larger moths as bio-indicators of landscape-scale quality, it is demonstrated that improvements to the cost-effectiveness of AES could be achieved, firstly, by providing more appropriate financial rewards to farmers for different landscape features, and secondly, through landscape-scale targeting of farmers to encourage participation in AES. © 2009 Elsevier B.V. All rights reserved

Accounting for habitat when considering climate: has the niche of the Adonis blue butterfly changed in the UK?

The dramatic recovery of three species of grassland specialist butterfly threatened with extinction at their high latitude range limits in the 1980s has been attributed to two factors: increased grazing on calcareous grassland sites and warmer air temperatures. Both result in the warming of soil surface temperatures, favourable to the larvae of these species. We address the influence of both of these factors on the habitat usage of the butterfly Polyommatus bellargus, undergoing recovery at its northern range edge. We test the hypothesis that the larval niche of P. bellargus has become less constrained in the past three decades, whilst controlling for changes in habitat structure. Once habitat change has been accounted for we find no evidence for a broadening of the larval niche of P. bellargus. Further, we show that coincident with the recovery of P. bellargus there have been drastic reductions in average turf height across UK chalk grasslands, but changes in air temperature have been highly variable. We conclude that changes to soil surface temperatures caused by reducing turf heights will have been a more consistent influence than air temperature increases, and so habitat improvements through increased grazing will have been the major driver of recovery in P. bellargus. We consider the need to account for changes in habitat when exploring the impacts of recent climate change on local habitats in thermophilous species, and emphasise the continued importance of habitat management to support such species under variable local climates

Molecular evidence for a recent founder event in the UK populations of the Adonis blue butterfly (Polyommatus bellargus)

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. © Springer Science+Business Media B.V. 2007

Funding and delivering the routine testing of management interventions to improve conservation effectiveness

Evidence-based approaches are key for underpinning effective conservation practice, but major gaps in the evidence of the effectiveness of interventions limit their use. Conservation practitioners could make major contributions to filling these gaps but often lack the time, funding, or capacity to do so properly. Many funders target the delivery of conservation and can be reluctant to fund primary research. We analysed the literature testing the effectiveness of interventions. Of a sample of 1,265 publications published in 2019 that tested conservation interventions, 96% included academics. Only 21% included conservation practitioners, of which just under half were first or last author. A community of conservation funders and practitioners undertook a series of workshops to explore means of improving the quality and quantity of intervention testing. A survey of the suggested proportion of conservation grants that should be allocated to testing intervention effectiveness showed practitioners tended to prefer larger percentages (median 3-6%) than funders (median 1-3%), but the overlap was considerable. Funders can facilitate the testing of interventions through a range of measures, including welcoming applications that incorporate testing, allocating funds to testing, and providing training and support to deliver testing. The funders represented by the authors of this paper have committed to these actions. Practitioners can contribute by committing to routine testing, benefiting from funding allocated specifically to testing, and establishing processes for testing interventions. The organisations of the practitioner authors have committed to test at least one intervention per year and share findings, regardless of outcome. Currently, practitioners rarely lead the testing of conservation actions. We suggest processes by which both funders and practitioners can make this routine. This will not only improve the effectiveness and cost-efficiency of practice, but also make conservation more attractive to funders.This paper arose from a series of workshops attended by funders and practitioners, focused on how to integrate evidence in conservation. We thank all participants. The first workshop was hosted by Lord Mountevans at the House of Lords, UK, with funding from Arcadia. Subsequent workshops were held online. We thank Kate Willott for providing the 2019 references from the Conservation Evidence database. We are also grateful to two anonymous reviewers whose feedback provided helpful suggestions for improving this manuscript