7 research outputs found
Spatial covariance of herbivorous and predatory guilds of forest canopy arthropods along a latitudinal gradient
In arthropod community ecology, species richness studies tend to be prioritised over those investigating patterns of abundance. Consequently, the biotic and abiotic drivers of arboreal arthropod abundance are still relatively poorly known. In this cross-continental study, we employ a theoretical framework in order to examine patterns of covariance among herbivorous and predatory arthropod guilds. Leaf-chewing and leaf-mining herbivores, and predatory ants and spiders, were censused on > 1000 trees in nine 0.1 ha forest plots. After controlling for tree size and season, we found no negative pairwise correlations between guild abundances per plot, suggestive of weak signals of both inter-guild competition and top-down regulation of herbivores by predators. Inter-guild interaction strengths did not vary with mean annual temperature, thus opposing the hypothesis that biotic interactions intensify towards the equator. We find evidence for the bottom-up limitation of arthropod abundances via resources and abiotic factors, rather than for competition and predation.publishedVersio
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Research data supporting "Tropical butterflies use thermal buffering and thermal tolerance as alternative strategies to cope with temperature change".
Data is in two parts, firstly field recordings of the body temperature of 54 species of tropical butterflies and ambient air conditions. Secondly, a subset of these species (24 species) used in upper thermal maxima experiments in the lab.
Methods:
Butterflies were sampled from multiple habitats in Panama from February 2020 to March 2022, across both wet and dry seasons. Data were collected in multiple locations: Gamboa (lowland managed urban green spaces) [9°6'59.13"N, 79°41'47.41"W] (elevation = 28 m), “Pipeline road” in SoberanĂa National Park (secondary semi-deciduous lowland tropical wet forest) [9° 7'39.04"N, 79°42'17.80"W] (elevation = 92 m), Campana in the Capira District (pre-montane wet encroaching scrub and secondary forest) [8°40’54.97”N, 79°55’25.08”W] (elevation = 327 m), Sajalices in the Chame District (lowland tropical wet encroaching scrub and secondary forest) [8°40’53.55”N, 79°51’57.90”W] (elevation = 150 m), El Valle (lowland tropical wet encroaching scrub) [8°37’04.7”N, 80°0656.5”W] (elevation = 674 m), Mount Totumas (lower mountain rainforest and management agroforestry) [8°52’58.6”N, 82°41’01.3”W] (elevation = 1877 m), and San Lorenzo National Park (secondary lowland tropical wet forest) [9°14’49.2”N, 79°58’44.2”W] (elevation = 185 m). This range of sites allowed the collection of a wide variety of species across a range of air temperatures (minimum = 17.4°C, mean = 28.5°C, maximum = 39.7°C). Butterflies were identified to species level using identification guides and with the help of a local expert (ACZ). The only exception was Calephelis spp., which due to their complex taxonomy, were identified only to the genus level and treated as a single species during analyses.
Thermal buffering ability
Surveys were undertaken in all weather conditions except rain, between 07:30 and 16:00 hours, and we attempted to capture any butterflies seen. Butterflies were caught in hand nets without chasing (to avoid raising butterfly body temperature). Immediately after capture, butterfly body temperature was recorded using a thermocouple with a handheld indicator (Tecpel Thermometer 305B, Tecpel Co. Ltd., Taiwan), by gently pressing the probe through the net against the butterfly’s thorax, without handling or touching the butterfly. Body temperature was recorded within 10 seconds of capture, followed by air temperature, taken with the thermocouple held at waist height in the shade. We then identified individual butterflies to species, and recorded wing length (with callipers, from the joint in the thorax to the tip of the forewing), and wing colour (ranked from: 1, almost white; 2, yellow-green; 3, orange; 4; orange-brown or blue; 5, brown; to 6, almost black; as established by Bladon et al. 2020). In species with multiple colours, colour values were averaged (for example, an equally black and white butterfly species would have the values for black (6) and white (1) averaged (giving 3.5)). Butterflies were marked and retained in a small cage until the end of the survey (up to a maximum of 6 hours, in shade with access to water and sugar solution) to prevent re-recording the same individuals, before being released.
Thermal tolerance
From January to March 2022, a subset of butterflies, captured to record their thermal buffering ability, were used for thermal tolerance experiments. Species (n = 24) were chosen based on high abundance. The selected individuals were retained in glassine envelopes with moistened cotton and kept outdoors in the shade at ambient temperature before measurement of thermal tolerance (within six hours of capture). To measure critical thermal maximum (CTmax), butterflies were placed individually into six glass jars with moistened filter paper (to prevent dehydration) in a water bath (Huber CC-K20 with Pilot ONE, Huber Kältemaschinenbau AG, Germany) at 28°C for five minutes to acclimatise. This starting temperature was chosen as it was the average ambient air temperature recorded during capture across all butterflies. A thermocouple with a hand-held indicator (Tecpel Thermometer 305B, Tecpel Co. Ltd., Taiwan) was placed into a control jar to monitor and record in-jar temperatures. After acclimatisation, the water bath was set to ramp up temperature steadily, at a rate of 0.5°C/min to a maximum of 70°C. By maintaining high humidity throughout the experiment and ramping temperature at an ecologically relevant rate (Terblanche et al. 2007), we aimed to simulate features of climate change in the tropics, for example a high temperature weather event, where temperature increases and humidity remains high. During the experiment, water bath internal temperatures (recorded using the water bath internal thermometer) and actual in-jar temperatures (recorded using the thermocouple) were recorded every five minutes to ensure the set ramping rate was achieved. To prevent inter-run differences affecting results, no more than three individuals of a single species were placed into a single run. The temperature at which each butterfly lost motor control (“knockdown”, assessed as the temperature at which the butterfly fell down and, after being poked, did not right itself) and time to knockdown were recorded (Huey, Crill, Kingsolver, & Weber, 1992). Ambient laboratory temperatures during the experiments ranged from 23-25°C. Before being placed in the water bath, wing length (measured with callipers) (Ribeiro et al. 2012) and condition (on a scale of 1-5, following Bladon et al. 2020, where 1 is perfect, 2 is scale loss but no physical damage to wings, 3 is heavy scale loss and/or light damage to wing edges, 4 is damage to multiple (but not all) wings, and 5 is significant damage on all wings) of each butterfly was recorded again. Only butterflies of conditions 1-3 were used (assessed beforehand) to prevent senescence or poor condition affecting the results. Exposure duration (including starting temperature and rate of temperature change) is known to influence critical thermal limits recorded (Terblanche et al. 2007). As the butterflies were wild-caught, temperature variation experienced throughout the life cycle, and therefore their thermal history, may have influenced our results (Kellermann et al. 2017). However, as all individuals were randomly caught in the same season of the same year for this experiment, this effect is likely to be minimal.
Descriptions of columns in datasets:
New_buffering_4
Family: family the butterfly species belongs to
Genus_sp: Species name in the format "Genus species"
Air.temp: Air temperature recorded at waist height in shade in the location the butterfly was first encountered
Body.temp: Body temperature of the butterfly (recorded from the thorax within 10 seconds of capture)
Size_mm: Individual wing lengths of each butterfly, recorded with callipers in mm
Colour: Colour is on a scale (following the same protocol as Bladon et al 2020) from 1 (white) to 6 (black).
Target_sp_only
Date: data of experiment
Round.num: unique number (integer starting from 1) for each experimental run in the water bath
Jar: number from 1-5 representing the individual jar butterflies occupied within the waterbath
Family: family that butterfly species belongs to
Species: species name in the format "Genus_species"
Sex: M (male) or F (female)
Condition: condition of the butterfly, ranging from 1 (perfect condition) to 3 (minor damage)
Time.start: Time the experiment was started at
Set.end: The temperature the ramping program recorded as the final temperature the butterfly was knocked down at
Int.end: The internal thermometer reading from the water bath as to the temperature the butterfly was knocked down at
Act.end: The actual temperature (recorded using a thermocouple within a control jar in every waterbath run) the butterfly was knocked down at
Time.end: the time it took from the Time.start in minutes and seconds for the butterfly be knocked down
Recovery: Whether or not the butterfly recovered from the experiment after 1 hour at room temperature after knockdown (A = alive, D = dead)
Wing.length: individual wing lengths in cm (recorded with callipers)
A_1: A column of only 1's, required for the coding
Buffering: The buffering ability (species-specific) of the butterfly species
Colour: The colour value of the species, ranging from 1 (white) to 6 (black). See Bladon et al 2020 for further information on this scale.
Waterbath_temps
Round: Round number (same as above)
Time: Time ranging from the start of the experiment (0) to 80 minutes later, at 5 minute intervals
Set temperature: the temperature the water bath was set to at that time
Internal.temp: The temperature recording from the internal thermometer of the water bath at that time
Act.temp: The actual temperature within the jars (recorded using a thermocouple) at each timeThe research was funded by The Czech Science Foundation (GAÄŚR 19-15645Y to GPAL and 20-31295S to YB), ERC Starting Grant BABE 805189 to BLH and KS, Smithsonian Tropical Research Institute short-term fellowship to BLH, Cambridge Conservation Initiative/Evolution Education Trust (CCI/EET) to EAJ, and NERC Highlight topic GLiTRS project NE/V007173/1 to AJB. YB and GPAL were supported by the Sistema Nacional de InvestigaciĂłn, SENACYT, Panama
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Tropical butterflies use thermal buffering and thermal tolerance as alternative strategies to cope with temperature increase
Climate change poses a severe threat to many taxa, with increased mean temperatures and frequency of extreme weather events predicted. Insects can respond to high temperatures using behaviour, such as angling their wings away from the sun or seeking cool local microclimates to thermoregulate, or through physiological tolerance. In a butterfly community in Panama, we compared the ability of adult butterflies from 54 species to control their body temperature across a range of air temperatures (thermal buffering ability), as well as assessing the critical thermal maxima for a subset of 23 species. Thermal buffering ability and tolerance were influenced by family, wing length, and wing colour, with Pieridae, and butterflies that are large or darker in colour having the strongest thermal buffering ability, but Hesperiidae, small, and darker butterflies tolerating the highest temperatures. We identified an interaction between thermal buffering ability and physiological tolerance, where species with stronger thermal buffering abilities had lower thermal tolerance, and vice versa. This interaction implies that species with more stable body temperatures in the field may be more vulnerable to increases in ambient temperatures, for example heat waves associated with ongoing climate change. Our study demonstrates that tropical species employ diverse thermoregulatory strategies, which is also reflected in their sensitivity to temperature extremes.The research was funded by The Czech Science Foundation (GAÄŚR 19-15645Y to GPAL and 20-31295S to YB), ERC Starting Grant BABE 805189 to BLH and KS, Smithsonian Tropical Research Institute short-term fellowship to BLH, Cambridge Conservation Initiative/Evolution Education Trust (CCI/EET) to EAJ, and NERC Highlight topic GLiTRS project NE/V007173/1 to AJB. YB and GPAL were supported by the Sistema Nacional de InvestigaciĂłn, SENACYT, Panama
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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 (GAÄŚR 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 InvestigaciĂłn, SENACYT Panama (YB and GPAL)
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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 (GAÄŚR 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 InvestigaciĂłn, SENACYT Panama (YB and GPAL)
Spatial covariance of herbivorous and predatory guilds of forest canopy arthropods along a latitudinal gradient
In arthropod community ecology, species richness studies tend to be prioritised over those investigating patterns of abundance. Consequently, the biotic and abiotic drivers of arboreal arthropod abundance are still relatively poorly known. In this cross-continental study, we employ a theoretical framework in order to examine patterns of covariance among herbivorous and predatory arthropod guilds. Leaf-chewing and leaf-mining herbivores, and predatory ants and spiders, were censused on > 1000 trees in nine 0.1 ha forest plots. After controlling for tree size and season, we found no negative pairwise correlations between guild abundances per plot, suggestive of weak signals of both inter-guild competition and top-down regulation of herbivores by predators. Inter-guild interaction strengths did not vary with mean annual temperature, thus opposing the hypothesis that biotic interactions intensify towards the equator. We find evidence for the bottom-up limitation of arthropod abundances via resources and abiotic factors, rather than for competition and predation