Two butterfly species, the small heath (left) and common blue (right), have become more likely since 1980 to have multiple generations in Central Europe in the same year, as a long-term warming trend has picked up pace:
Ecologist Florian Altermatt of the University of California, Davis has studied 44 species of moths and butterflies in Central Europe. He published the results December 22 in the science journal, Proceedings of the Royal Society B article, “Climatic warming increases voltinism in European butterflies and moths” (which is available online for free for a few more days). “Voltinism” refers to the number of breeding cycles in a year.
As the region has warmed since the 1980s, some of these species have added an extra generation during the summer for the first time on record in that location. Among the 263 species already known to have a second or third generation there during toasty times, 190 have grown more likely to do so since 1980.
Since the journal article is a tough read, I’m excerpting the Science News story (which is also the source of the pictures):
Only a rough third or so of all the species Altermatt reviewed show the capacity to breed more than once a year. What warming is probably doing for them, he speculates, is jolting the insects’ overwintering form into action early and also speeding up insect development. These head starts may allow time for a bonus generation before a non-temperature cue, atumnal day length, plays its role in shutting down insects for winter.
“From a pest perspective it’s an important issue,” says population ecologist Patrick Tobin based in Morgantown, W.Va., for the Forest Service Northern Research Station. Tobin has studied a warmth-related extra generation in a North American pest, the grape berry moth. He points out that an extra surge of attacking pests in the growing season means yet another headache, expense and round of damage for farmers.
Extra insect generations are important for ecosystems too, Tobin says, though predicting those ripples of consequences will be “extraordinarily complex.” An additional generation of insects might boost a population of the predators that feed on them and thus make life tougher for the other species the predators attack. Or an extra annual generation of an endangered insect might give the species an extra push toward recovery.
When creatures manage an extra generation in a year, evolutionary processes happen faster, Altermatt says. Those species that do get an extra, successful generation win a little uptick in their chances of adapting. He’s not predicting that the effect will be enough for species to cope with widespread habitat loss or climate change, but, he says, “It’s maybe a little hope.”
Finally, some climate-changed-boosted insect population explosions are worse than others (see “Memo to Baucus: Your state’s trees are being ravaged by warming-driven pests now and Montana faces 175% to 400% increase in wildfire burn area.”
h/t Wired Science.