Habitat associations of day-flying Lepidoptera and their foodplants within nature reserves in Bedfordshire, UK

Species often associate with specific habitat characteristics, resulting in patchy distributions, whereby they only occupy a proportion of available habitat. Understanding which characteristics species require is a valuable tool for informing conservation management. We investigated the associations of eleven species of day-flying Lepidoptera larvae and their foodplants with habitat characteristics within calcareous grassland reserves in Bedfordshire, UK, across two scales relevant to land managers and target species: the reserve (cardinal aspect, vegetation type) and foodplant patch scale (foodplant height and density). We investigated whether ecological traits (habitat specialism, as defined at a national-scale, and overwintering life stage) influenced the strength of associations. At the reserve scale, we found variation in associations with habitat characteristics across species, with species that overwinter at non-adult life stages having more restricted associations, indicating that they may be more vulnerable to environmental change. Associations were generally stronger with vegetation type than aspect, which can be manipulated more easily by land managers. Seven species had similar associations with habitat characteristics to their foodplants, implying that management to benefit foodplants will also benefit larvae. However, the remaining four species had different associations to their foodplants, and may require alternative management approaches. At the foodplant patch scale, four species were associated with foodplant characteristics, which could be used to inform effective fine-scale management. Implications for insect conservation: Diverse habitat associations imply that topographic and vegetation variation are valuable for supporting diverse assemblages of butterflies and their foodplants

Consistent oviposition preferences of the Duke of Burgundy butterfly over 14 years on a chalk grassland reserve in Bedfordshire, UK

Funder: Christ's College, University of Cambridge (GB)Funder: Isaac Newton Trust; doi: http://dx.doi.org/10.13039/501100004815Funder: Museums Association and Esmée Fairbairn Collections Fund (GB)Abstract: The Duke of Burgundy butterfly (Hamearis lucina) is known to have specific habitat requirements for its larval foodplants. However, no studies have yet investigated whether these preferences vary over time or in relation to climate, and there is a paucity of data on whether management on reserves can replicate preferred conditions. Here, we build upon existing research to confirm which characteristics Duke of Burgundy prefer for their larval foodplants, whether preferences remain consistent across years, and whether conservation management on reserves can replicate these conditions. Fieldwork was carried out at Totternhoe Quarry Reserve, a chalk grassland site in Bedfordshire, UK. Confirming previous research, we found that large Primula plants in dense patches were chosen for oviposition, but that once chosen there was no preference to lay eggs on a plant’s largest leaf. Chosen foodplants were also more sheltered and in closer proximity to scrub than their controls. However, at a finer scale, we found little evidence for any preference based on differences in microclimate, or vegetation height immediately surrounding the plants. This suggests features that alter microclimatic conditions at a larger scale are relatively more important for determining the suitability of oviposition sites. Nearly all preferences remained consistent over time and did not vary between years. Management of scrub on the reserve was able to reproduce some preferred habitat features (high plant density), but not others (large plant size). Implications for insect conservation: The consistency of findings across years, despite inter-annual variation in temperature, rainfall and number of adults, indicates that the Duke of Burgundy is conservative in its foodplant choice, highlighting its need for specific habitat management. Targeted management for foodplants could form part of a tractable set of tools to support Duke of Burgundy numbers on reserves, but a careful balance is needed to avoid scrub clearance leaving plants in sub-optimal conditions

Oviposition behaviour and emergence through time of the small blue butterfly (Cupido minimus) in a nature reserve in Bedfordshire, UK.

ABSTRACT: Climate change affects butterflies in many ways, influencing the timing of emergence and reproduction, habitat preferences, and behaviour. The small blue (Cupido minimus Fuessley, 1775) is highly specialised in its host plant requirements, feeding on the seeds of a single species, kidney vetch (Anthyllis vulneraria), on which the larvae occur singly to avoid cannibalism. The butterfly is likely to be vulnerable to temperature-related changes in oviposition, adult emergence, and host plant flowering times, and is, therefore, a good model species for investigating climate change-related impacts. Using 26 years of data from the national UK Butterfly Monitoring Scheme (1993-2019) from one nature reserve, and 4 years of targeted egg searches (2006, 2007, 2008, 2020) from three reserves in Bedfordshire, UK, we investigated the effects of local temperature on small blue emergence date and total abundance, whether flowerhead or local environmental characteristics predicted small blue oviposition behaviour, and whether this changed between years. Small blue adults emerged on earlier dates over time, and earlier in years with higher maximum February temperatures. Total adult abundance was not predicted by monthly temperatures or total abundance in the previous year. Oviposition behaviour was broadly consistent across years, with egg presence more likely and egg abundance higher on kidney vetch flowerheads that were taller than the surrounding vegetation, and surrounded by taller vegetation and fewer mature flowerheads. The effect of solar radiation differed between years, with a negative effect on the probability of egg presence in 2007 and 2008, but a positive effect in 2020. Egg abundance per flowerhead was highly variable between years, with 2006 having four times more eggs per flowerhead than other years. This was likely driven by high adult abundance in 2006, which could have increased competition for flowerheads. IMPLICATIONS FOR INSECT CONSERVATION: Our results indicate that management for greater availability of taller kidney vetch amongst taller vegetation would encourage small blue oviposition on a greater number of flowerheads, providing a possible means of reducing competition and increasing larval survival, and that this would be effective despite variation in adult abundance between years. The high level of competition we observed in the year with the highest adult abundance indicates that higher numbers of host plants should be encouraged to reduce competition and larval cannibalism in peak years, increasing the likelihood of long-term population persistence and growth. SUPPLEMENTARY INFORMATION: The online version contains supplementary material available at 10.1007/s10841-021-00360-5.SITA Trust Landfill Community, Bedfordshire and Northamptonshire Butterfly Conservation, Balfour Browne fund, Natural England, Isaac Newton Trust/Wellcome TrustISSF/University of Cambridge Joint Research Grants Scheme (RG89529

Thermoregulatory ability and mechanism do not differ consistently between neotropical and temperate butterflies

Climate change is a major threat to species worldwide, yet it remains uncertain whether tropical or temperate species are more vulnerable to changing temperatures. To further our understanding of this, we used a standardised field protocol to (1) study the buffering ability (ability to regulate body temperature relative to surrounding air temperature) of neotropical (Panama) and temperate (the United Kingdom, Czech Republic and Austria) butterflies at the assemblage and family level, (2) determine if any differences in buffering ability were driven by morphological characteristics and (3) used ecologically relevant temperature measurements to investigate how butterflies use microclimates and behaviour to thermoregulate. We hypothesised that temperate butterflies would be better at buffering than neotropical butterflies as temperate species naturally experience a wider range of temperatures than their tropical counterparts. Contrary to our hypothesis, at the assemblage level, neotropical species (especially Nymphalidae) were better at buffering than temperate species, driven primarily by neotropical individuals cooling themselves more at higher air temperatures. Morphology was the main driver of differences in buffering ability between neotropical and temperate species as opposed to the thermal environment butterflies experienced. Temperate butterflies used postural thermoregulation to raise their body temperature more than neotropical butterflies, probably as an adaptation to temperate climates, but the selection of microclimates did not differ between regions. Our findings demonstrate that butterfly species have unique thermoregulatory strategies driven by behaviour and morphology, and that neotropical species are not likely to be more inherently vulnerable to warming than temperate species

Day-flying Lepidoptera larvae have a poorer ability to thermoregulate than adults

Changes to ambient temperatures under climate change may detrimentally impact small ectotherms that rely on their environment for thermoregulation, however there is currently a limited understanding of insect larval thermoregulation. As holometabolous insects, Lepidoptera differ in morphology, ecology, and behaviour across the life cycle, and so it is likely that adults and larvae differ in their capacity to thermoregulate. In this study we investigate the thermoregulatory capacity (buffering ability) of 14 species of day-flying Lepidoptera, whether this is influenced by body length or gregariousness, whether it differs between adult and larval life stages. We also investigated what thermoregulation mechanisms are used; microclimate selection (choosing locations with a particular temperature) or behavioural thermoregulation (controlling temperature through other means, such as basking). We found that Lepidoptera larvae differ in their buffering ability between species and body lengths, but gregariousness did not influence buffering ability. Larvae are worse at buffering themselves against changes in air temperature than adults. Therefore Lepidoptera may be more vulnerable to adverse temperature conditions during their larval life stage. Adults and larvae rely on different thermoregulatory mechanisms; adults primarily use behavioural thermoregulation, whereas larvae use microclimate selection. This implies that larvae are highly dependent on the area around their foodplant for effective thermoregulation. These findings have implications for the management of land and species, for example highlighting the importance of creating and preserving microclimates and vegetation complexity surrounding Lepidoptera foodplants for larval thermoregulation under future climate change.EAJ was supported by the Cambridge Conservation Initiative (CCI) Evolution Education Trust (EET) Knowledge-Studentship. AJB was funded by a NERC Highlight topic grant (GLiTRS project NE/V007173/1), and the project was developed from an Isaac Newton Trust/Wellcome Trust ISSF/University of Cambridge Joint Research Grants Scheme grant (RG89529) to AJB and ECT

Day‐flying lepidoptera larvae have a poorer ability to thermoregulate than adults

Funder: Cambridge Conservation Initiative, Evolution Education Trust (EET)AbstractChanges to ambient temperatures under climate change may detrimentally impact small ectotherms that rely on their environment for thermoregulation; however, there is currently a limited understanding of insect larval thermoregulation. As holometabolous insects, Lepidoptera differ in morphology, ecology and behaviour across the life cycle, and so it is likely that adults and larvae differ in their capacity to thermoregulate. In this study, we investigated the thermoregulatory capacity (buffering ability) of 14 species of day‐flying Lepidoptera, whether this is influenced by body length or gregariousness, and whether it differs between adult and larval life stages. We also investigated what thermoregulation mechanisms are used: microclimate selection (choosing locations with a particular temperature) or behavioural thermoregulation (controlling temperature through other means, such as basking). We found that Lepidoptera larvae differ in their buffering ability between species and body lengths, but gregariousness did not influence buffering ability. Larvae are worse at buffering themselves against changes in air temperature than adults. Therefore Lepidoptera may be more vulnerable to adverse temperature conditions during their larval life stage. Adults and larvae rely on different thermoregulatory mechanisms; adults primarily use behavioural thermoregulation, whereas larvae use microclimate selection. This implies that larvae are highly dependent on the area around their foodplant for effective thermoregulation. These findings have implications for the management of land and species, for example, highlighting the importance of creating and preserving microclimates and vegetation complexity surrounding Lepidoptera foodplants for larval thermoregulation under future climate change.</jats:p

Habitat associations of day-flying Lepidoptera and their foodplants within nature reserves in Bedfordshire, UK

Species often associate with specific habitat characteristics, resulting in patchy distributions, whereby they only occupy a proportion of available habitat. Understanding which characteristics species require is a valuable tool for informing conservation management. We investigated the associations of eleven species of day-flying Lepidoptera larvae and their foodplants with habitat characteristics within calcareous grassland reserves in Bedfordshire, UK, across two scales relevant to land managers and target species: the reserve (cardinal aspect, vegetation type) and foodplant patch scale (foodplant height and density). We investigated whether ecological traits (habitat specialism, as defined at a national-scale, and overwintering life stage) influenced the strength of associations. At the reserve scale, we found variation in associations with habitat characteristics across species, with species that overwinter at non-adult life stages having more restricted associations, indicating that they may be more vulnerable to environmental change. Associations were generally stronger with vegetation type than aspect, which can be manipulated more easily by land managers. Seven species had similar associations with habitat characteristics to their foodplants, implying that management to benefit foodplants will also benefit larvae. However, the remaining four species had different associations to their foodplants, and may require alternative management approaches. At the foodplant patch scale, four species were associated with foodplant characteristics, which could be used to inform effective fine-scale management.The research was funded by a Cambridge Conservation Initiative/Evolution Education Trust (CCI/EET) grant to EAJ. We thank the Isaac Newton Trust / Wellcome Trust ISSF / University of Cambridge Joint Research Grant (RG89529) for funding ECT and AJB to establish the larger research project, within which this study was based. AJB was supported by a NERC Highlight topic grant (NE/V007173/1) to the GLiTRS Project. JA and SW were supported by the Balfour-Browne Fund, and JA was supported by Kings College, University of Cambridge

Thermoregulatory ability and mechanism do not differ consistently between neotropical and temperate butterflies.

Climate change is a major threat to species worldwide, yet it remains uncertain whether tropical or temperate species are more vulnerable to changing temperatures. To further our understanding of this, we used a standardised field protocol to (1) study the buffering ability (ability to regulate body temperature relative to surrounding air temperature) of neotropical (Panama) and temperate (the United Kingdom, Czech Republic and Austria) butterflies at the assemblage and family level, (2) determine if any differences in buffering ability were driven by morphological characteristics and (3) used ecologically relevant temperature measurements to investigate how butterflies use microclimates and behaviour to thermoregulate. We hypothesised that temperate butterflies would be better at buffering than neotropical butterflies as temperate species naturally experience a wider range of temperatures than their tropical counterparts. Contrary to our hypothesis, at the assemblage level, neotropical species (especially Nymphalidae) were better at buffering than temperate species, driven primarily by neotropical individuals cooling themselves more at higher air temperatures. Morphology was the main driver of differences in buffering ability between neotropical and temperate species as opposed to the thermal environment butterflies experienced. Temperate butterflies used postural thermoregulation to raise their body temperature more than neotropical butterflies, probably as an adaptation to temperate climates, but the selection of microclimates did not differ between regions. Our findings demonstrate that butterfly species have unique thermoregulatory strategies driven by behaviour and morphology, and that neotropical species are not likely to be more inherently vulnerable to warming than temperate species.The research was supported by an ERC Starting Grant BABE 805189 (BLH, IF, IK and KS), Smithsonian Tropical Research Institute short-term fellowship (BLH), the Czech Science Foundation (GAČR 19-15645Y GPAL and 20-31295S YB), a Cambridge Conservation Initiative/Evolution Education Trust (CCI/EET) studentship (EAJ), the NERC Highlight topic GLiTRS project NE/V007173/1 (AJB), a Isaac Newton Trust/Wellcome Trust ISSF/University of Cambridge Joint Research Grants Scheme grant (RG89529) (AJB and ECT) and the Sistema Nacional de Investigación, SENACYT Panama (YB and GPAL)

Research data supporting "Thermoregulatory ability and mechanism does not differ consistently between neotropical and temperate butterflies".

A dataset of tropical and temperate butterflies. Methods of data collection: Neotropical data were collected in Panama from February to June 2020 and from October 2021 to March 2022 during both wet (May to December) and dry (January to April) seasons (Supplementary Fig. 1, Supplementary Table 1) (Leigh, 1999). Temperate data were collected in the Czech Republic and Austria between April and August 2021 and in the UK between April and September 2009 and May and September 2018 (Supplementary Fig. 1, Supplementary Table 1) (Bladon et al., 2020). Data collection took place between 7:30 and 17:30. Neotropical field sites included lowland scrub and managed urban green spaces, secondary semi-deciduous lowland tropical forest, mountain rainforest and management agroforestry (Supplementary Table 1). Temperate field sites included calcareous meadows, grassland meadows, alpine/montane grassland, encroaching scrub, secondary forest, and exposed ground (Supplementary Table 1). Butterfly body temperature and morphological measurements Butterflies were captured with butterfly nets when encountered (without chasing) and data were collected following the protocol used by Bladon et al. (2020), as follows. Once in the net, and within 10 seconds, a temperature reading of the butterfly’s thorax (body temperature, Tb) was taken using a thermocouple (0.5 mm diameter) and handheld indicator (Tecpel Thermometer 305B, TC Direct, Uxbridge, UK). Air temperature (Ta) was taken at waist height where the butterfly was caught, with the thermocouple shaded from the sun. If the butterfly was resting on a substrate before capture, the temperature of the air 1 cm above where it was sat was recorded with the thermocouple (microclimate temperature, Tm). The butterfly was identified to species or subspecies. In the case of butterflies from the tropical Calephelis genus it was not possible to identify individuals to species, so data from these butterflies were aggregated to genus level. Forewing length (in mm) from the tip of the wing to the point where it meets the thorax was measured using callipers (at the Panama and UK sites only). Description of each column: Species: species name Site: location of capture of the butterfly Date: date of capture of the butterfly Family: family the butterfly belongs to Activity: what the butterfly was doing when it was first encountered (nectaring, flying, resting, basking, interacting with other/same species). Tair.perch: if the butterfly was first encountered while on a perch, this is the temperature 1cm above the perch. All temperatures are in Celcius. Tbody: temperature of the thorax of the butterfly within 10 seconds of capture Tair: air temperature recorded at waist height in shade in the location the butterfly was first encountered Tperch: if the butterfly was first encountered while on a perch, this is the temperature of the surface of the perch Region: tropical (from Panama) or temperate (from Europe) Mean.winglength.mm: mean wing length of the species (one value per species) in mm Colour: the dominant wing colour of the butterfly Colour.value: the wing colour converted to a scale from 1 (white) to 6 (black) Sexual.dimorphism.in.colour: A Y (yes) or N (no) for whether that species has males and females having different dominant wing colours (so that their colour would be different between sexes) Migratory: A Y (yes) or N (no) for whether in the area of capture that butterfly species is known to be migratory Average.forewing.aspect.ratio: the average aspect ratio for the forewing of the butterfly (wing length divided by wing width) Subfamily: the subfamily the species belongs to Tribe: the tribe the species belongs toThe research was supported by an ERC Starting Grant BABE 805189 (BLH, IF, IK and KS), Smithsonian Tropical Research Institute short-term fellowship (BLH), the Czech Science Foundation (GAČR 19-15645Y GPAL and 20-31295S YB), a Cambridge Conservation Initiative/Evolution Education Trust (CCI/EET) studentship (EAJ), the NERC Highlight topic GLiTRS project NE/V007173/1 (AJB), a Isaac Newton Trust/Wellcome Trust ISSF/University of Cambridge Joint Research Grants Scheme grant (RG89529) (AJB and ECT) and the Sistema Nacional de Investigación, SENACYT Panama (YB and GPAL)