Ethiopians have lived at high altitudes for thousands of years, providing a natural experiment for studying human adaptations to low oxygen, a condition known as hypoxia. One factor that may enable Ethiopians to tolerate high altitudes and hypoxia is the endothelin receptor type B (EDNRB) gene. Researchers at University of California, San Diego School of Medicine now find that mice with lower-than-normal levels of EDNRB protein are remarkably tolerant to hypoxia. The study, published this week by the Proceedings of the National Academy of Sciences, provides a mechanism for the gene's role in adaptation to life at high altitudes and suggests that EDNRB could be targeted to treat sea level diseases that stem from lack of oxygen.
High up in the high Andes mountains of Argentina, researchers have identified the first-ever evidence of a population uniquely adapted to tolerate the toxic chemical arsenic.
For thousands of years, in some regions of the Andes, people have been exposed to high levels of arsenic, a naturally occurring phenomenon that happens when arsenic in the volcanic bedrock is released into the groundwater. How could this population adapt to tolerate arsenic, a potent killer of such ill repute that it's often the overused plot-driver of many murder mysteries?
In a new study published in the advanced online edition of Molecular Biology and Evolution, a Swedish research team led by Karolinska Institutet and Uppsala University professor Karin Broberg, performed a genome wide survey from a group of 124 Andean women screened for the ability to metabolize arsenic (measured by levels in the urine). The study pinpointed a key set of nucleotide variants in a gene, AS3MT, which were at much lower frequencies in control populations from Columbia and Peru. The researchers estimate that the increase in frequency of these variants occurred recently, between 10,000-7,000 years ago, based on the age of a recently excavated mummy that was found to have high arsenic levels in its hair.
Is adaptation to climate change really constrained in niche specialists?
Authors:
van Heerwaarden et al
Abstract:
Species with restricted distributions make up the vast majority of biodiversity. Recent evidence suggests that Drosophila species with restricted tropical distributions lack genetic variation in the key trait of desiccation resistance. It has therefore been predicted that tropically restricted species will be limited in their evolutionary response to future climatic changes and will face higher risks of extinction. However, these assessments have been made using extreme levels of desiccation stress (less than 10% relative humidity (RH)) that extend well beyond the changes projected for the wet tropics under climate change scenarios over the next 30 years. Here, we show that significant evolutionary responses to less extreme (35% RH) but more ecologically realistic levels of climatic change and desiccation stress are in fact possible in two species of rainforest restricted Drosophila. Evolution may indeed be an important means by which sensitive rainforest-restricted species are able to mitigate the effects of climate change.
Reining in the Red Queen: the dynamics of adaptation and extinction reexamined
Authors:
Geerat J. Vermeij and Peter D. Roopnarine
Abstract:
One of the most enduring evolutionary metaphors is Van Valen's (1973) Red Queen. According to this metaphor, as one species in a community adapts by becoming better able to acquire and defend resources, species with which it interacts are adversely affected. If those other species do not continuously adapt to compensate for this biotically caused deterioration, they will be driven to extinction. Continuous adaptation of all species in a community prevents any single species from gaining a long-term advantage; this amounts to the Red Queen running in place. We have critically examined the assumptions on which the Red Queen metaphor was founded. We argue that the Red Queen embodies three demonstrably false assumptions: (1) evolutionary adaptation is continuous; (2) organisms are important agents of extinction; and (3) evolution is a zero-sum process in which living things divide up an unchanging quantity of resources. Changes in the selective regime need not always elicit adaptation, because most organisms function adequately under many “suboptimal” conditions and often compensate by demonstrating adaptive flexibility. Likewise, ecosystems are organized in such a way that they tend to be robust and capable of absorbing invasions and extinctions, at least up to a point. With a simple evolutionary game involving three species, we show that Red Queen dynamics (continuous adaptation by all interacting species) apply in only a very small minority of possible outcomes. Importantly, cooperation and facilitation among species enable competitors to increase ecosystem productivity and therefore to enlarge the pool and turnover of resources. The Red Queen reigns only under a few unusual circumstances.
