Microclimate affects landscape level persistence in the British Lepidoptera

Microclimate has been known to drive variation in the distribution and abundance of insects for some time. Until recently however, quantification of microclimatic effects has been limited by computing constraints and the availability of fine-scale biological data. Here, we tested fine-scale patterns of persistence/extinction in butterflies and moths against two computed indices of microclimate derived from Digital Elevation Models: a summer solar index, representing fine-scale variation in temperature, and a topographic wetness index, representing fine-scale variation in moisture availability. We found evidence of microclimate effects on persistence in each of four 20 × 20 km British landscapes selected for study (the Brecks, the Broads, Dartmoor, and Exmoor). Broadly, local extinctions occurred more frequently in areas with higher minimum or maximum solar radiation input, while responses to wetness varied with landscape context. This negative response to solar radiation is consistent with a response to climatic warming, wherein grid squares with particularly high minimum or maximum insolation values provided an increasingly adverse microclimate as the climate warmed. The variable response to wetness in different landscapes may have reflected spatially variable trends in precipitation. We suggest that locations in the landscape featuring cooler minimum and/or maximum temperatures could act as refugia from climatic warming, and may therefore have a valuable role in adapting conservation to climatic change

A reply to ‘A meta-database of Holocene sediment cores for England: missing data’ (Tooley 2015)

We welcome the response of Tooley (2015) to our article describing a new meta-database of Holocene sediment cores for England. In our article we describe the online publication of this meta-database, arising from systematic meta-search. We define its scope and the meta-data it contains, before providing the data themselves (in the Electronic Supplementary Material online). We note that Prof. Tooley describes the idea of such a database as important and valuable, and we welcome the constructive approach he adopts throughout his article

Subsistence use of papyrus is compatible with wetland bird conservation

Conservationists have historically advocated measures that limit human disturbance. Nevertheless, natural disturbances are important components of many ecosystems and their associated species are often adapted to such regimes. In consequence, conservation managers frequently simulate natural disturbance, particularly in temperate forest systems. This practice is less widespread and seldom studied in tropical regions, where biodiversity conservation and human activities are often thought to conflict. However, many tropical systems have been subject to natural and anthropogenic disturbance over evolutionary timescales, and disturbance may therefore benefit the species they host. Determining whether this is true is especially important in tropical wetlands, where human activities are essential for sustaining local livelihoods. Here we investigate the impacts of disturbance from human resource use on habitat–specialist bird species endemic to papyrus swamps in East and Central Africa. Bird densities were estimated using point counts and related to levels of human activity using physical characteristics of wetland vegetation as a proxy for disturbance. All species were tolerant to some degree of disturbance, with particular species occurring at highest density in intensely disturbed habitat. Species were generally more tolerant to disturbance in larger swamps. Our results suggest that low-intensity use of papyrus wetlands by people is compatible with the conservation of specialist bird species, and highlight the potential benefits of traditional human activities to conserve biodiversity in the tropics

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 and 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.RJ was funded through a UK Natural Environment Research Council studentship (grant reference: NE/N00857X/1).Peer reviewe

Designing effective protected area networks for multiple species

Protected area networks seek to ensure the persistence of multiple species, but their area and extent are limited by available land and conservation resources. Prioritising sites based on their quality, quantity, size, or connectivity is often proposed; potentially using the occupancy and metapopulation dynamics of individual threatened species as surrogates for network effectiveness. However, the extent to which the dynamics of species with overlapping habitat requirements differ, and the implications of this for the optimal network designs for multiple species, are rarely tested. We parameterise metapopulation models for 5 papyrus-specialist birds occupying a network of papyrus swamp in Uganda, each of which possess subtly different ecological characteristics and habitat preferences. We estimate how each responds to different strategies based on prioritising patch size, number, quality and connectivity. The optimal approach differed depending on the metapopulation structure and characteristics of each species. The rank order of strategies also varied with the overall wetland area available and the desired persistence threshold. For individual species, prioritising habitat quality achieved the highest levels of persistence and population size for an equivalent amount of land area conserved. However, connected patches showed greatest overlap across species, thus the most effective strategy to conserve multiple species in the same network prioritised habitat connectivity. This emphasises the importance of individual species' characteristics using the same habitat networks in conservation planning, and demonstrates the utility of prioritising protected sites based on the spatial connectivity of habitat patches, when aiming to conserve multiple species with differing or uncertain habitat requirements.This research was supported by a Natural Environment Research Council (NERC) CASE studentship, in partnership with the Royal Society for the Protection of Birds (RSPB; grant number NE/L501669/1). Additional financial support for fieldwork was provided by The Explorers Club, British Ornithologists' Union, Royal Geographic Society, John Muir Trust, and Gilchrist Educational Trust.Peer reviewe

Climate-driven variation in the quality and phenology of novel hosts presents a variable window of opportunity for a range-expanding herbivore

Comunicación de Congreso-Conferencia invitadaClimate-driven geographic range shifts have been associated with transitions between dietary specialism and generalism at range margins. The mechanisms underpinning these often transient niche breadth modifications are poorly known, but utilisation of novel resources likely depends on phenological synchrony between the consumer and resource. We use a climate-driven range and host shift by the butterfly Aricia agestis to test how climate-driven changes in host phenology and condition affect phenological synchrony, and consider implications for host use. Our data suggest that the perennial plant which was the primary host before range expansion is a more reliable resource than the annual Geraniaceae upon which the butterfly has become specialised in newly colonised parts of its range. In particular, climate-driven phenological variation in the novel host Geranium dissectum generates a narrow and variable ‘window of opportunity’ for larval productivity in summer. Therefore, although climatic change may allow species to shift hosts and colonise novel environments, specialisation on phenologically-limited hosts may not persist at ecological margins as climate change continues. We highlight the potential role for phenological (a)synchrony in determining lability of consumer-resource associations at range margins, and the importance of considering causes of synchrony in biotic interactions when predicting range shifts

Climate-driven variation in biotic interactions provides a narrow and variable window of opportunity for an insect herbivore at its ecological margin

Climate-driven geographic range shifts have been associated with transitions between dietary specialism and generalism at range margins. The mechanisms underpinning these often transient niche breadth modifications are poorly known, but utilization of novel resources likely depends on phenological synchrony between the consumer and resource. We use a climate-driven range and host shift by the butterfly Aricia agestis to test how climate-driven changes in host phenology and condition affect phenological synchrony, and consider implications for host use. Our data suggest that the perennial plant that was the primary host before range expansion is a more reliable resource than the annual Geraniaceae upon which the butterfly has become specialized in newly colonized parts of its range. In particular, climate-driven phenological variation in the novel host Geranium dissectum generates a narrow and variable ‘window of opportunity’ for larval productivity in summer. Therefore, although climatic change may allow species to shift hosts and colonise novel environments, specialization on phenologically limited hosts may not persist at ecological margins as climate change continues. We highlight the potential role for phenological (a)synchrony in determining lability of consumer–resource associations at range margins and the importance of considering causes of synchrony in biotic interactions when predicting range shifts.Research was funded by the Natural Environment Research Council (PhD studentship grant NE/L002434/1 to J.E.S.) and by the Botanical Society of Britain and Ireland (BSBI Science and Research Council grant to J.E.S.).Peer reviewe

Microclimate and resource quality determine resource use in a range-expanding herbivore

The consequences of climate change for biogeographic range dynamics depend on the spatial scales at which climate influences focal species directly and indirectly via biotic interactions. An overlooked question concerns the extent to which microclimates modify specialist biotic interactions, with emergent properties for communities and range dynamics. Here, we use an in-field experiment to assess egg-laying behaviour of a range-expanding herbivore across a range of natural microclimatic conditions. We show that variation in microclimate, resource condition and individual fecundity can generate differences in egg-laying rates of almost two orders of magnitude in an exemplar species, the brown argus butterfly (Aricia agestis). This within-site variation in fecundity dwarfs variation resulting from differences in average ambient temperatures among populations. Although higher temperatures did not reduce female selection for host plants in good condition, the thermal sensitivities of egg-laying behaviours have the potential to accelerate climate-driven range expansion by increasing egg-laying encounters with novel hosts in increasingly suitable microclimates. Understanding the sensitivity of specialist biotic interactions to microclimatic variation is, therefore, critical to predict the outcomes of climate change across species’geographical ranges, and the resilience of ecological communities.Research was funded by the Natural Environment Research Council (PhD studentship grant no. NE/L002434/1 to J.E.S.).Peer reviewe

Microclimate, climate change and wildlife conservation

Climate is a major control on the geographical distributions of species. Estimates of climate change for the 2080s project an increase of 2-4°C in the mean temperature of British summers, and an increase of 1-6°C in the mean temperature of British winters (Murphy et al. 2009)