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Reproductive strategies of cacti in the driest desert on Earth

Date: May 11, 2015

About face! We discovered that cactus flowers face the north in the Atacama Desert of the southern hemisphere. Now we are discovering the opposite in the northern hemisphere. Who would have thought?

By definition, deserts are dry, and organisms living there must evolve strategies to cope with the aridity. The Atacama Desert of northern Chile is the driest place on earth, receiving as little as 2 millimeters  (0.08 inches) of annual rainfall, depending on latitude and elevation. During a recent visit, observations were made of several cactus species that successfully occupy the coastal region. We observed that cacti of the genus Eulychnia orient their reproductive structures ubiquitously on the north. With a Chilean colleague from the Universidad de La Serena, Dr. Warren collected data from a large number of individuals of two species in the genus. The data confirm the original observation. The Atacama Desert lies south of the Tropic of Capricorn; the sun is always to the north. By producing reproductive structures on the north side of the plants, they maximize their exposure to sunlight. Next, we plan to next collect fruits, and test the viability of their seeds. The hypothesis is that fruits with northerly exposure will have a greater percentage of viable seeds than fruits with more easterly and westerly exposure. Based on the experiences in the Atacama Desert, we are now discovering similar and previously undescribed adaptations among plants in U.S. deserts.

Principal Investigators: 
External Partners: 
Lorgio Aguilera Jopia, Univesidad de La Serena, Chile