̽��ֱ�� of Cambridge - Esme Ashe-Jepson

Small-winged and lighter coloured butterflies likely to be at greatest threat from climate change

cg605 — Thu, 13 Jul 2023 04:05:05 +0000

Butterflies with smaller or lighter coloured wings are likely to be ‘losers’ when it comes to climate change, with the Lycaenidae family, which contains over 6,000 species of butterflies, the majority of which live in the tropics, found to be particularly vulnerable.

Butterflies with larger or darker coloured wings are likely to fare better under increasing temperatures, but only to a point. Researchers say these butterflies could still experience dramatic declines if there were sudden heatwaves or if cool microclimates were lost through deforestation.

̽��ֱ��results are published today in the Journal of Animal Ecology.

Butterflies rely on the sun’s warmth to give them the energy they need to function. They use ‘thermoregulation’ strategies to maintain a balanced body temperature against changing air temperatures.

Generally, strategies to keep cool involve adaptive behaviours like flying to a shady spot or angling wings away from the sun (thermal buffering). But when this is not possible or temperatures become too hot, species have to rely on physiological mechanisms such as the production of heat shock proteins to withstand high temperatures (thermal tolerance). Both of these strategies are needed to cope with climate change.

Researchers collaborated with the Smithsonian Tropical Research Institute (STRI) to study the thermal buffering and thermal tolerance strategies of tropical butterflies. They collected data from multiple habitats in Panama.

Equipped with hand-held nets, ecologists took the temperature of over 1,000 butterflies using a tiny thermometer-like probe. They compared each butterfly’s temperature to that of the surrounding air or the vegetation it was perched on. This gave a measurement of thermal buffering – the ability to maintain a steady body temperature against fluctuating air temperatures.

A second experiment was conducted at STRI Gamboa facilities and involved assessing butterflies’ thermal tolerance – their ability to withstand extreme temperatures, such as those they may experience during a heatwave. This was assessed by capturing a subset of butterflies and placing them in glass jars within a water bath – the temperature of which was steadily increased. Thermal tolerance was assessed as the temperature at which butterflies could no longer function.

Butterflies that had large wings tended to have greater thermal buffering ability but less thermal tolerance than smaller butterflies. Indeed, in a further study conducted by the same research team, butterflies with larger, longer and narrower wings were found to be better at thermal buffering.

Thermal buffering abilities were found to be stronger in darker-winged butterflies who could also tolerate higher temperatures than paler-winged butterflies.

Butterflies from the Lycaenidae family which have small, bright, and often iridescent, wings had the poorest thermal buffering and low thermal tolerance. If temperatures continue to rise at the current rate, forests continue to be cut down, and cool microclimates are lost, there is a very real threat that we could lose many species in this family in the future, say the researchers.

A trade-off in terms of butterflies’ cooling strategies was observed: those that were good at thermal buffering were less good at thermal tolerance and vice versa.

Scientists say this suggests that tropical butterflies have evolved to cope with temperature changes using one of these strategies at the expense of the other, and that this is likely to be due to selective pressures.

Lead author Esme Ashe-Jepson, a PhD student at Cambridge’s Department of Zoology, said: “Butterflies with physical characteristics that may help them to avoid the sun’s heat, like having large wings that enable them to fly quickly into shade, rarely experience high temperatures, and so have not evolved to cope with them. On the other hand, species which can cope with higher temperatures physiologically have experienced less selective pressure to evolve heat-avoiding behaviours.

“As temperatures continue to rise, and forest fragments get smaller and further apart because of deforestation, butterflies which rely on their surroundings to avoid high temperatures may not be able to travel between forest fragments, or cope with increasingly common heatwaves.”

̽��ֱ��researchers say this means that species with large dark wings that are good at thermal buffering may initially be unaffected by warming temperatures, as they can continue to thermoregulate effectively using behaviour and microclimates, but their survival could be at risk if there are sudden heatwaves, or they can no longer escape to cool vegetation.

“Ultimately all insects, including butterflies, the world over are likely to be affected by climate change,” said Ashe-Jepson. “Adaptation to climate change is complex and can be impacted by other factors such as habitat destruction. We need to address these two global challenges together.”

Further research is needed to investigate the effect a warming climate may have on other life stages of butterflies, such as caterpillars and eggs, and other insect groups.

Senior author Greg Lamarre, at the Czech Academy of Science and Research Associate at STRI said: “Worldwide, most entomologists are observing drastic declines in insect biodiversity. Understanding the causes and consequences of insect decline has become an important goal in ecology, particularly in the tropics, where most of terrestrial diversity occurs.”

̽��ֱ��research was funded by the GACR Czech Science Foundation, an ERC Starting Grant, a Smithsonian Tropical Research Institute short-term fellowship, and the Sistema Nacional de Investigación (SENACYT), Panama.

Reference:

Esme Ashe-Jepson et al. Tropical butterflies use thermal buffering and thermal tolerance as alternative strategies to cope with temperature increase. Journal of Animal Ecology DOI: 10.1111/1365-2656.13970

̽��ֱ��family, wing length and wing colour of tropical butterflies all influence their ability to withstand rising temperatures, say a team led by ecologists at the ̽��ֱ�� of Cambridge. ̽��ֱ��researchers believe this could help identify species whose survival is under threat from climate change.

Ultimately all insects, including butterflies, the world over are likely to be affected by climate change.

Esme Ashe-Jepson

Esme Ashe-Jepson conducing fieldwork in Panama, with a Juditha caucana butterfly from the Riodinidae family.

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Tropical butterflies’ wings could help them withstand climate change, study suggests

cg605 — Wed, 14 Jun 2023 09:15:24 +0000

In fact, tropical species’ ability to keep cool at higher air temperatures mean they are more able to “thermoregulate” and keep a balanced body temperature compared to their evolutionary cousins in milder climates.

Scientists say that the strategies of butterflies from Central America to stay cool mean they could actually be better equipped to deal with global warming than previously thought.

̽��ֱ��team behind the latest study argue that conservation researchers should be careful not to assume creatures in hotter parts of the world will suffer most under rising temperatures – rather, some butterflies in temperate regions, such as Western and central Europe, could be at greater risk.

Equipped with hand-held nets, ecologists took the temperature of over 6,800 butterflies in Panama, Austria, the Czech Republic and the UK using a tiny thermometer-like probe. They compared the butterfly’s temperature to that of the surrounding air or the vegetation it was perched on.

They found that tropical butterflies were able to maintain a lower body temperature at higher air temperatures than butterflies from milder climates. ̽��ֱ��results are published today in the journal Global Change Biology.

Researchers from the ̽��ֱ�� of Cambridge and the Czech Academy of Sciences spent nine months, over the course of two trips, in the tropical lowland forests of Central Panama, working with collaborators at the Smithsonian Tropical Research Institute. Working for nine hours a day they assessed 54 species of butterflies and surrounding temperatures. They compared these measurements with those of butterflies from alpine meadows in Austria, pastures in the Czech Republic and chalk grasslands in the UK.

Researchers discovered that butterflies from different climates used specialised strategies to warm up or cool down. But physical factors – particularly wing size and shape – were key to keeping body temperature at an optimal level for butterflies across both climates studied.

Senior author Dr Andrew Bladon from the Department of Zoology, ̽��ֱ�� of Cambridge, said: “We were surprised to see that it was physical differences like wing size and shape that drove a butterfly species’ ability to keep their temperature constant in both regions, rather than an inherent difference between species adapted to tropical and temperate climates. We expected to find that tropical species would be more sensitive to temperature changes, but this may not be the case.”

̽��ֱ��team say that when it comes to butterflies’ ability to buffer against changing temperatures – and ultimately survive – bigger appears to be better. For tropical butterflies, bigger wings mean they are more mobile and can fly quicker to cooler areas. And for butterflies who live in mild climates, bigger wings allow them to warm up faster when basking in the sun, giving them the energy boost they need to fly.

“Our results have highlighted how unique these species are – they’re using different strategies to cool down or warm up,” said co-lead author Esme Ashe-Jepson, ̽��ֱ�� of Cambridge. “What’s exciting is that these results suggest that physiological measures could be used to make predictions about how species might respond to climate change.”

“We showed that changes in size and wing shape are important for coping with temperature change,” said co-lead Benita Laird-Hopkins, ̽��ֱ�� of South Bohemia. “For example, small butterflies, regardless of where they are from, are likely to be more impacted by climate change than big butterflies.”

While the current study suggests a note of optimism in terms of the ability of some butterfly species to live in hot temperatures, what is not known is how butterflies may cope with dramatic shifts in temperature like heatwaves, or what effect a warming climate will have on other life stages, such as caterpillars and eggs.

Bladon says more research is needed to understand how other insect groups, as well as butterflies, respond to temperature change. “ ̽��ֱ��dual threats of climate and habitat change threaten to push many insects to their physiological limits. Understanding how and where this happens is crucial for designing conservation mitigation strategies, but we also need to act fast to protect and restore diverse habitats.”

Paper reference:

Laird-Hopkins B, Ashe-Jepson E et al. Thermoregulatory ability and mechanism does not differ consistently between neotropical and temperate butterflies. Global Change Biology DOI: 10.1111/gcb.16797

Tropical butterflies with bigger, longer and narrower wings are better able to stay cool when temperatures get too hot.

We showed that changes in size and wing shape are important for coping with temperature change.

Benita Laird-Hopkins

Marius Klotz

Looking for butterflies in forest in Panama

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