 |
 |
 |
 |
 |
 |
 |
 |
 |
 |
| . |  |
. |
Major Mutations, Not Small Changes, May Lead
To New Species
Hummingbirds visited nearly 70 times more often after scientists altered the color of a kind of monkeyflower from pink � beloved by bees but virtually ignored by hummingbirds � to a hummer-attractive yellow-orange. Researchers writing in the Nov. 13 issue of Nature say perhaps it was a major change or two, such as petal color, that first forged the fork in the evolutionary road that led to today's species of monkeyflowers that are attractive to and pollinated by hummingbirds and separate species of monkeyflowers that are pollinated by bees. The color change is the result, it appears, of mutation in a single gene, according to H.D. "Toby" Bradshaw, a professor of biology at the University of Washington and lead author of the Nature piece. He says the resulting quick change in pollinator preferences adds to the debate over whether new species arise according to the classic, 150-year-old Darwin theory of evolution that says it may take a hundred small genetic changes, each with mounting effect, or might speciation be kick-started by a few mutations that cause large effects. "It could be that the first adaptations require a few big changes, sort of like taking a watch that has stopped ticking and banging it a few times before making the small tweaks to restore its optimal performance," says Douglas Schemske, professor of plant biology at Michigan State University and co-author of the letter in Nature. There are 123 species of monkeyflowers, a wildflower found around the world. Mimulus lewisii appeals to bees with forward-thrusting petals that serve as a landing platform and yellow nectar guides that contrast with the pale pink flowers. The closely related M. cardinalis, on the other hand, has a deep, tubular shape that excludes bees but is easily probed by the slender beaks of hummingbirds, and has red or deep yellow-orange petals, colors bees can't see. These and other differences make the species of monkeyflowers distinct and nearly eliminates crossbreeding in the wild. In an experiment funded by the National Science Foundation, the researchers changed the region of a chromosome, thought to be a single gene, that affects the concentration of yellow pigment in petals of monkeyflowers. M. lewisii, the normal favorite of bees, responded with petals of yellow-orange instead of the usual pink. Although its other features � flower size, petal shape and amount of nectar � were unchanged, the resulting flowers were suddenly being visited 68 times more often by hummingbirds. The flowers were actually shunned by bees, probably because orange is in the spectrum of light they don't see. In another alteration as part of the experiment, M. cardinalis, usually favored by hummingbirds, responded with petals that were dark pink rather than deep red. These flowers appealed equally to hummingbirds and bees. Bradshaw and Schemske say altering just the genetic region responsible for the concentration of yellow pigment is much like what might happen during a naturally occurring mutation. "Perhaps a single mutation having to do with color changed the pollinator milieu back when there was only a single species," Bradshaw says. That one big evolutionary step may then have been followed by many smaller steps triggered by pollinator preferences that led ultimately to different species. Monkeyflowers, so-called because someone once imagined the face of a monkey in the markings on the blossoms, have been used by researchers interested in ecology and evolution for more than 50 years. The plants readily reveal the effects of crossbreeding and can be planted in native settings so they are useful for experiments. "A unique aspect of out work is that it combines ecological observations with molecular genetic techniques to elucidate the process of adaptation in natural populations," Schemske says. Related Links University of Washington SpaceDaily Search SpaceDaily Subscribe To SpaceDaily Express 
Mass Extinctions May Promote Longevity Of New Species
Cincinnati - Nov 10, 2003With the economy, we talk about cycles of boom and bust. Make that "bust and boom" when it comes to the geological record in the post-Paleozoic world, University of Cincinnati geologist Arnold Miller suggests, after his analysis of marine fossil genera and what happens after mass extinction events.
|
|
| |||||||||
| The content herein, unless otherwise known to be public domain, are Copyright 1995-2016 - Space Media Network. All websites are published in Australia and are solely subject to Australian law and governed by Fair Use principals for news reporting and research purposes. AFP, UPI and IANS news wire stories are copyright Agence France-Presse, United Press International and Indo-Asia News Service. ESA news reports are copyright European Space Agency. All NASA sourced material is public domain. Additional copyrights may apply in whole or part to other bona fide parties. Advertising does not imply endorsement, agreement or approval of any opinions, statements or information provided by Space Media Network on any Web page published or hosted by Space Media Network. Privacy Statement All images and articles appearing on Space Media Network have been edited or digitally altered in some way. Any requests to remove copyright material will be acted upon in a timely and appropriate manner. Any attempt to extort money from Space Media Network will be ignored and reported to Australian Law Enforcement Agencies as a potential case of financial fraud involving the use of a telephonic carriage device or postal service. |
