Climate change modifying animal genes: study

Evidence is piling up that climate change has led to genetic modifications in a diverse range of animals including birds, squirrels and mosquitoes, scientists said on Thursday.

These genetic changes are a result of altered seasonal events, not to the expected direct effects of increasing temperatures, according to William Bradshaw, a professor at the University of Oregon, and Christina Holzapfel, a research associate at the university.

Their findings were published on the June 9 issue of the journal Science.

Global warming is proceeding fastest at the most northern latitudes, resulting in longer growing seasons while simultaneously alleviating winter cold stress without imposing summer heat stress.

In short, northern climates are becoming more like those in the south, the researchers said. Because of this, animal species are extending their range toward the poles and populations have been migrating, developing or reproducing earlier, they said.

These expansions and changes have often been attributed to "phenotypic plasticity," or the ability of individuals to modify their behavior, morphology or physiology in response to altered environmental conditions.

However, "phenotypic plasticity" is not the whole story. Over the past several decades, rapid climate change has led to heritable, genetic changes in animal populations, they said.

The researchers provided a number of examples of these changes: Canadian red squirrels reproducing earlier in the year; German blackcaps are migrating and arriving earlier to their nesting grounds; and North American mosquitoes living in the water-filled leaves of carnivorous plants are using shorter day lengths to cue the initiation of larval dormancy.

No studies have found genetic changes in animal populations due to the generally expected direct effects of increasing temperature, said the researchers, but over evolutionary time such changes should appear, following the genetic shifts in the timing of seasonal events, the researchers added.

Small animals with short life cycles and large population sizes will probably adapt to longer growing seasons and be able to persist, they predicted. But many large animals with longer life cycles and smaller population sizes will decline in population or be replaced by more southern species.

"It is clear that unless the long-term magnitude of rapid climate change is widely acknowledged and effective steps are taken to mitigate its effects, natural communities that we are familiar with will cease to exist," they wrote in the Science paper.

Source: Xinhua