How Daphnia safely catch some rays: Adaptation to UV radiation exposure in subalpine ponds
March 18, 2012
Academic Building A G008, 5:00 PM
Understanding the mechanisms by which populations of organisms have evolved to tolerate environmental stressors in the recent past is critical to predicting responses to changing environments in the future. In lake and pond ecosystems, water transparency determines the degree to which organisms are exposed to UV radiation from the sun, which is harmful because it damages DNA. I study a group of neighboring populations of the freshwater microcrustacean Daphnia melanica, or “water flea,” that inhabit subalpine ponds of widely differing transparency to UV radiation. Daphnia from ponds with more UV radiation survive better under UV in laboratory experiments, illustrating that they have evolved to tolerate this critical environmental stressor. The question is, how do they do it? I conducted a thorough exploration of the possible physiological mechanisms to explain differences in UV tolerance among these populations. Although protective pigments and behavioral escape were not sufficient explanations, I show evidence for an elevated rate of repair of UV-induced DNA damage in the most tolerant Daphnia populations. I infer that this DNA repair mechanism, mediated by the DNA sequence and expression of a single gene, is responsible for observed differences in UV radiation tolerance among natural populations inhabiting differing UV environments.
Brooks Miner was born and raised in Anchorage, Alaska, and received undergraduate and PhD degrees from the University of Washington in Seattle. His dissertation research explored adaptation to UV radiation exposure in subalpine Daphnia, and he continues to investigate the molecular basis of these adaptations. Currently Dr. Miner is an NSF postdoctoral research fellow at Cornell University, where he is exploring the ecological and ecosystem-level consequences of evolutionary change in critical aquatic species using both model laboratory ecosystems and outdoor experimental ponds.
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