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How Did Cactuses Evolve

Neoraimondia herzogiana, a member of the leafless, stem-succulent Cactoideae, growing in central Bolivia.
by Staff Writers
Chicago IL (SPX) May 15, 2006
In a groundbreaking new study in the June issue of American Naturalist, Erika J. Edwards (Yale University and University of California, Santa Barbara) and Michael J. Donoghue (Yale University) explore how leafy, "normal" plants evolved into the leafless succulent cactus.

"The cactus form is often heralded as a striking example of the tight relationship between form and function in plants," write the authors. "A succulent, long-lived photosynthetic system allows cacti to survive periods of extreme drought while maintaining well-hydrated tissues."

Recent molecular phylogenetic work has confirmed that Pereskia, a genus that consists of 17 species of leafy shrubs and trees, is where the earliest cactus lineages began. Using field studies and environmental modeling, Edwards and Donoghue found that the Pereskia species already showed water use patterns that are similar to the leafless, stem-succulent cacti.

"[Our] analyses suggest that several key elements of cactus ecological function were established prior to the evolution of the cactus life form," explain the authors. "Such a sequence may be common in evolution, but it has rarely been documented as few studies have incorporated physiological, ecological, anatomical, and phylogenetic data."

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Aberystwyth, Wales (SPX) May 15, 2006
Sexual harassment is a burden that females of many species face, and some may go to extreme lengths to avoid it. In a new paper from the June issue of the American Naturalist, Darren Croft (University of Wales) and a research team from the University of Leeds suggest that female guppies, a popular aquarium fish, may risk their lives to avoid too much attention from males.







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