Climate change threatens small and light-colored Butterflies: Study

A group of ecologists from the University of Cambridge have led a study indicating that within a family of tropical butterflies, wing length and colour are crucial factors in how well they can adapt to rising temperatures. The researchers believe this study could play a crucial role in identifying species that are particularly vulnerable due to the impacts of climate change.

Small-winged butterflies struggle in climate change

These findings have been detailed in the Journal of Animal Ecology. The research claims that when faced with climate change, butterflies with smaller or lighter-coloured wings struggle to adapt effectively. In particular, the family Lycaenidae, home to more than 6,000 species of butterflies, which mainly inhabit tropical regions, faces significant risks.

Butterflies with darker or larger wings show better resistance to rising temperatures, but this advantage has its limits. The researchers warn that if cold microclimates, created by shade or vegetation, disappear due to sudden heat waves or deforestation, these butterflies could also face drastic population declines.

Butterflies rely heavily on solar heat for energy, employing 'thermoregulation' strategies to balance body temperature against changes in air temperature. These strategies include behaviors such as seeking shade or turning the wings away from the sun (thermal damping) to keep cool.

However, when these options run out or temperatures become unreasonably high, species must resort to physiological mechanisms such as the generation of heat shock proteins to cope. Both strategies are essential to combat the challenges of climate change.

In collaboration with the Smithsonian Tropical Research Institute (STRI), the researchers investigated thermal buffering strategies and heat tolerance in tropical butterflies. They collected data from various habitats in Panama.

Thermometer probes gauge butterfly temperatures

The environmentalists measured the temperatures of more than 1,000 butterflies using thermometer-like probes, comparing their temperatures to those of the air or the plants on which they rested. This established a measure of thermal damping, the ability to maintain a constant temperature despite fluctuations in air temperature.

A second experiment, conducted at the STRI Gamboa facility, tested the butterflies' heat tolerance: how well they tolerated extreme temperatures, such as those experienced during heat waves. The butterflies were placed in a jar of water with increasing temperatures until they were no longer functional, defining their heat tolerance threshold.

The larger-winged butterflies exhibited greater thermal buffering capacity but lower heat tolerance than their smaller counterparts. Another study by the same team revealed that butterflies with larger, longer and narrower wings coped better in the heat.

The darker-winged butterflies showed greater heat tolerance, enduring higher temperatures compared to their lighter-winged counterparts.

Lycaenidae butterflies face danger due to heat

For butterflies in the family Lycaenidae, characterized by small, brightly colored, often iridescent wings, their heat tolerance was the lowest. The researchers warn that at the current rate of temperature rise, deforestation, and loss of cold microclimates, many species in this family could be in danger.

The study suggests that tropical butterflies have evolved to cope with changes in temperature by focusing on one strategy at the expense of the other, influenced by selective pressures.

Butterflies with morphological traits that help avoid heat, such as larger wings that facilitate rapid movement into shade, rarely experience high temperatures and therefore have not evolved heat coping mechanisms. Conversely, species capable of withstanding higher temperatures have found themselves under less pressure to develop heat-avoidance behaviors.

As temperatures rise and forests shrink due to deforestation, butterflies that rely on external conditions to withstand the heat may find it difficult to navigate between fragmented forested areas. They might have a hard time withstanding higher temperatures or heat stress.

Big-winged species adapt, heat waves peril

The researchers propose that large-winged species with strong heat tolerance may not be immediately affected by warmer temperatures, as they effectively regulate temperature through behavior and microclimate. However, sudden heat waves could threaten their survival or interrupt migration to cooler habitats.

The researchers stress that all insects, including butterflies around the world, will face the impacts of climate change. Adaptation to climate change is complex and can be influenced by factors such as habitat loss. Addressing these twin global challenges is vital.

More research is needed to assess the impact of age on other life stages of butterflies, such as caterpillars and eggs, as well as other groups of insects.

Globally, entomologists have witnessed a significant drop in insect biodiversity. Understanding the causes and consequences of this decline has become fundamental in ecology, especially in tropical regions, where terrestrial diversity is more abundant.

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