Global warming affects cultivated cereal crops

New Worlds: Study claims to shed new light on early humans' adaptation to living on the ground.

Wheat 311 (photo credit: Courtesy)
Wheat 311
(photo credit: Courtesy)
Although farmers know better than ever how to grow food, global warming may indirectly affect our diet by diminishing the amount of available nutritients. A 28-year comparative study of wild emmer wheat and wild barley populations has revealed that these progenitors of cultivated wheat and barley, which are the best hope for crop improvement, have been affected by climate changes, which presents a real concern for their being a continued source of crop improvement.
Prof. Eviatar Nevo of the University’s evolution institute, who has studied the phenomenon, notes that wheats and barleys are the staple food for humans and animals around the world. Their wild progenitors have undergone genetic changes over the past three decades that imply a risk for crop improvement and food production, he said. Premature flowering time and genetic changes that are taking place in these important progenitor wild cereals, most likely due to global warming, can negatively affect them and thus indirectly cause food production to decline.
Wheats are the universal cereals of Old World agriculture, he said. The progenitor – wild emmer wheat and wild barley, which originated in the Near East – provide the genetic basis for ameliorating wheat and barley cultivars. Earlier studies have shown that they themselves are under constant genetic erosion and increasing susceptibility to environmental stresses.
Nevo’s new study, published in the Proceedings of the [US] National Academy of Sciences (PNAS) set out to examine whether the wild cereal progenitors are undergoing evolutionary changes due to climate change that would impact future food production.
Ten wild emmer wheat and an equal number of wild barley populations from different climates and habitats across Israel were sampled first in 1980 and then again at the same sites in 2008 and grown in a common greenhouse. The results indicated that over the relatively short period of 28 years, all 20 wild cereal populations examined, without exception, showed a dramatic change in flowering time. All populations sampled in 2008 flowered, on average, about 10 days earlier than those sampled in 1980. These cereal progenitors are adapting their time of flowering to escape the heat, Nevo explains.
The study also found that the genetic diversity of the 2008 sample is for the most part significantly reduced, but that some new drought-adapted variants have appeared that could be used for crop improvement.
Ongoing global warming in Israel is the only likely factor that could have caused earliness in flowering and genetic turnover across the range of wild cereals here, he says.
“This indicates that they are under environmental stress that may erode their future survival. Multiple effects of the global warming phenomenon have been observed in many species of plants and animals,” he adds. “But this study is pioneering in showing its influence on flowering and genetic changes in wild cereals. These changes threaten the best genetic resource for crop improvement and thereby may damage food production.”
A number of species did show positive adaptive changes resulting from global warming, such as earliness in flowering or migration into cooler regions. But overall, says Nevo, the genetic resources of these critical wild cereals are undergoing rapid erosion and cannot be dismissed as a concern for future generations.
“Wild emmer wheat is the world’s most important genetic resource for wheat improvement, and it is up to us to preserve it,” he said. “We are utilizing our institute’s gene bank for transforming genes of interest to the crop. However, a much more extensive effort needs to be made to keep the natural populations thriving, by preventing urbanization and global warming from eliminating them.”
Study claims to shed new light on early humans' adaptation to living on the ground
Birds and squirrels nest in trees – and so do many types of chimpanzees. But now researchers at the University of Cambridge and Kyoto University have published the first study of rarely-documented ground nesting by wild chimpanzees. They suggest it supplies clues about the ancient transition of early hominins from sleeping in trees to sleeping on the ground.
The article, published in the American Journal of Physical Anthropology, focused on a group of wild West African chimpanzees that often shows ground-nesting behavior.
UK primatologist Dr. Kathelijne Koops studied the chimpanzee (Pan troglodytes verus) population in the Nimba Mountains in Guinea, West Africa. All species of great ape build nests to sleep in. Construction of these shelters takes minutes as the apes bend, break and interweave branches into a circular frame, followed by tucking in smaller branches to form a sturdy but comfortable sleeping platform.
“We believe that, like modern apes, the common ancestor of chimpanzees and humans also slept in the trees six million years ago,” said Koops. “However, these nests are not preserved in the fossil or archeological record, so it is impossible to study directly the ancient transition from sleeping in trees to building shelters on the ground. Recording this rare behavior in the chimpanzee, our closest relative, may provide vital clues.”
As the Nimba chimpanzees do not yet tolerate human presence at close range, the team used new molecular genetic techniques to analyze hairs collected from the nests. This allowed the team to establish the sex of chimpanzees displaying the behavior and to identify individuals in the group.
The team showed that as chimpanzees sleep both on the ground and in trees, the transition did not require a special evolutionary adaptation. This suggests that early hominins may have slept on the ground before the emergence of Homo erectus, the first species that was fully adapted to living on the ground.
“This is intriguing as it has long been believed that coming down from the trees was a crucial evolutionary shift,” said Koops. “However, this chimpanzees’ behavior suggests a more deep-seated, gradual transition from tree-to-ground sleep.”
Other theories for the tree-to-ground transition have included the use of fire and the scarcity of trees in open habitats. The team demonstrated that neither is a prerequisite for ground sleeping, as the chimpanzees live in a plentiful evergreen rainforest and do not create fire.
“These chimpanzees offer a rare opportunity to investigate why a population of wild apes choose to sleep on the ground,” concluded Koops. “We showed that ground-nesting was not caused by male mate-guarding behavior, a lack of trees in which to nest, or because of fire. This suggests that our direct ancestors were neither the only, nor the first, species to come down from the trees.”