When temperatures rise even a modest amount, insects' ability to reproduce is affected, according to a new study from UK researchers at the University of Sheffield.
Scientists there exposed a species of fruit fly (Drosophila subobscura) collected from both Spain and Sweden to a mild increase of 5.5 C. (9.9 F.) above temperatures considered environmentally normal for the species in each location.
What happened when the heat rose? The researchers say, in the Journal of Evolutionary Biology, that juveniles exposed to the temperature boost saw reduced chances of producing offspring as adults.
The insect's location seemed to play a role, the study found. The flies from the lower latitude of Spain fared better with the temperature increase than did those from Sweden.
"Our study is unique, as we only exposed the insects to mild heat but tested the long-term impact this had on them as both juveniles and when they reached adulthood," explained the study's lead researcher Rhonda Snook in a statement.
"The results show that even small increases in temperature may still cause populations to decline because, while these insects don't die because of the mild heat, they produce fewer offspring," she added.
Shook pointed out that juvenile insects are generally more susceptible to changes in their environment because at that age they are either larvae or too young yet to have wings that would allow them to fly away and seek relief.
Because the flies from a lower latitude country fared better in the study, the scientists say insects from higher-latitude countries are more vulnerable to climate change and could suffer declining populations.
"We already knew that insects are feeling the effect of climate change," Snook said, "but we now know they are felt at much lower temperatures."
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The researchers noted that their experiments were performed only on fruit flies. However, they wrote: "This may be common in other organisms with complex life cycles, and current models predicting population responses to climate change, which do not take into account the impact of juvenile heat stress on reproductive performance, may be too conservative."
Next up, the University of Sheffield team plans to have a closer look at the genetics of the flies from Spain and Sweden to see if they can discern why those from Spain fared better at reproduction after the juvenile heat exposure.
"Identifying genes that are linked to increased and decreased reproduction is something which may be very useful not only in understanding how insects will cope with climate change but from the perspective of controlling insect pests," said Snook.
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