Nigel A. D. Bourn

Insect translocations following historic extirpations and assisted colonisation into regions without historical records require assessment prior to species being released. We present a nine‐step framework to assess translocations and use this to evaluate the opportunity to reestablish the black‐veined white butterfly, Aporia crataegi, in Britain, a century after its extinction. The framework first establishes the rationale for translocation (step 1) and assesses whether a species will colonise naturally (step 2). It then assesses why a (reintroduced) species became extinct historically (step 3), whether the climate at proposed release sites is suitable (step 4) and if its habitat requirements are met (step 5). A risk assessment (step 6) is also required. For implementation, source populations are identified (step 7), followed by releases and monitoring (step 8) and ongoing reporting of outcomes and lessons learned (step 9). Aporia crataegi seemingly meets all of the criteria. Unsuitable climate is likely to have led to extirpation but, despite 21st century climate and habitats now appearing to be suitable, natural and human‐created barriers have prevented colonisation. The target area in England contains potential A. crataegi host plants and habitat that would accommodate dispersal across >100 km² of connected landscape. The risks are assessed as low, and potential source populations in western Europe have been identified using climate‐matching analyses. Steps 6–9 are under continuing development. The nine‐step approach provides a convenient framework to assess translocations and has potential to become a model to guide future translocation projects and inform future ‘best practice’ releases.

Citizen-science data are increasingly used to contribute to our understanding of biodiversity change, but analysing such data requires suitable statistical methods, often to deal with forms of bias. We develop a new approach for modelling data from a snapshot, mass-participation citizen-science scheme for UK butterflies, the Big Butterfly Count (BBC). Butterfly abundance varies throughout the year as one or more generations of each species emerge and die off, and the timing (phenology) of emergences varies annually due to weather and climate. Thus, counts from the short 3-week BBC sampling period are susceptible to bias due to this inter-annual variation in phenology. We adapt the Generalised Abundance Index, drawing upon phenology estimates from standardised monitoring scheme data, to account for phenological bias in the estimation of species’ abundance trends from BBC data. The method is demonstrated via application to empirical and simulated data, revealing that not accounting for phenology leads to biased trend estimates, particularly for summer-flying single-generation species. Drawing upon phenology information, the new approach allows for the reporting of abundance trends from a snapshot citizen-science scheme, creating the potential to maximise available data sources to increase our understanding of changes in butterfly populations, particularly in urban environments.

Around the world, the number of species establishing outside of their native range has and continues to increase rapidly. Some of these non‐native species are invasive and can cause negative environmental, economic, and social impacts, including declines in native biodiversity. Species can become established either through natural dispersal or with intentional or inadvertent human assistance, but the relative importance of these two modes over time has been little studied. We compiled data on 116 moth species that became established in Great Britain (GB) between 1900 and 2019. We classed each species as either an immigrant, which had colonised naturally, or an adventive, which had colonised through human assistance, and categorised species as feeding on either native or non‐native larval host plants. We found that the rate of moth species establishment has accelerated steadily, at 21% increase per decade, showing no signs of saturation. Immigrant species showed a steady rate of establishment between 1900 and 1935, followed by a significant acceleration of 11% per decade thereafter, which most closely matches the rate of immigrants that feed on native host plants. Immigrants that feed on non‐native host plants show a slower increase across the whole time period compared to all species, of 13% per decade. Adventive species show a similar rate of increase in establishment to all moth species, at a rate of 26% per decade. Adventives on non‐native host plants show a similar trend, but we find evidence for a post‐1980s increase in the rate of establishment for adventives that feed on native host plants. Our results indicate that the global case for enhanced biosecurity, around both the monitoring of natural colonisations and for the horticultural trade, remains very strong as non‐native colonisations are showing no signs of saturation with ongoing environmental and economic change.

Habitat loss and fragmentation have caused declines in the abundance and distribution of butterflies, particularly habitat specialists. The Chequered Skipper, Carterocephalus palaemon, has been extinct in England since 1976 after declining from the 1940s predominantly due to changes in woodland management including afforestation and the decline in traditional coppice management. To enable C. palaemon to flourish again, this species was reintroduced from Belgium to England in 2018 with the aim of establishing a resident breeding population. Here, we report on the recent reintroduction, outlining the reintroduction method used, the establishment status of the species in England, the clinical health of reintroduced individuals, and post-release monitoring results. Furthermore, we assess the habitat suitability of sites around the original release site to determine which were similar to the current re-location site and could be used for future reintroductions, and to aid the targeting of further management to increase habitat suitability. Since 2018, 128 Chequered Skipper butterflies have been reintroduced from Belgium to Rockingham Forest in England. Health examinations demonstrated that individuals were healthy, and this in part resulted in the population establishing at the first release site and the area of occupancy increasing each year to 2022. However, the reintroduced population has yet to naturally colonise other areas within Rockingham Forest and therefore is not yet a functioning metapopulation. Despite the project still being in its infancy, we are able to report on a successful five years. Implications for insect conservation: Rigorous scientific research has provided the evidence to support reintroductions, and will continue to be used to ensure the ecology and population dynamics of this species is sufficiently understood so that Chequered Skipper populations can thrive again in England.

Despite large numbers of reintroduction projects taking place and the high cost involved, there is a generally low success rate. Insects in particular are understudied within reintroduction ecology, with guidelines focusing on more iconic vertebrate taxa. Species distribution models (SDMs) examine the associations between species observations and environmental variables to find the conditions in which populations could survive. This study utilises two frequently used SDM approaches, a regression model (general linear model (GLM)) and a machine learning method (MaxEnt) to model habitat suitability for Chequered Skipper, Carterocephalus palaemon, butterflies, which are being reintroduced to Northamptonshire following extinction in England. We look at how SDMs using widespread remotely sensed variables could be used to inform the reintroduction process by finding areas of suitable habitat that were previously overlooked. These remotely sensed variables have the potential to inform reintroductions without extensive on the ground research as they cover huge areas and are widely available. We found that both models are successful in discriminating between presences and absences, using only a limited number of explanatory variables. We conclude that these wide-scale SDMs are useful as a first step in the decision-making process in determining appropriate sites for reintroductions, but that they are less accurate when establishing precisely where species should be placed.

Context: Efforts to adapt conservation to climate change often focus on facilitating range shifts to higher latitudes, by enhancing landscape capacity for poleward expansion. The need to protect populations at trailing edges of species distributions, and how and where to do so, has received less attention. Objectives: We assess how population declines caused by variation over space and time in exposure to climate change can necessitate conservation adaptation to climate change throughout species’ geographic ranges. We propose approaches for conservation in landscapes where species are vulnerable. Methods: We synthesize primary literature relating to recent landscape-scale changes to species distributions to identify evidence for patchy patterns of climate-driven decline. We use this evidence to propose a framework to adapt terrestrial species conservation. Results: Patchy retractions occur throughout species ranges as environmental heterogeneity results in spatial variation in climate and rates of climate change, whereas equatorward range margins are often not the first place to exceed climatic limits. Furthermore, climate effects on fitness, survival and reproduction interact with habitat quality, creating both localized extinction hotspots and climatically resilient microrefugial landscapes across species ranges. Conservation can benefit from the identification of vulnerable versus microrefugial landscapes, and implementation of targeted interventions. Conclusions: A focus on expansions and retractions at broad latitudinal range margins risks overlooking declines throughout species’ distributions. Understanding fine-resolution ecological responses to the climate can help to identify resilient microrefugial landscapes, and targeted management to promote cooler or more stable conditions can complement facilitation of broader-scale range shifts.

We present a genome assembly from an individual male Carterocephalus palaemon (the Arctic Skipper; Arthropoda; Insecta; Lepidoptera; Hesperiidae). The genome sequence is 394.5 megabases in span. The whole assembly is scaffolded into 31 chromosomal pseudomolecules, including the Z sex chromosome. The mitochondrial genome has also been assembled and is 15.78 kilobases in length. Gene annotation of this assembly on Ensembl identified 17,032 protein coding genes.