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A prevailing theory contends that eastern and western monarchs aregenetically distinct, and that genetic mechanisms trigger theirdivergent migratory paths. An analysis led by Emory University biologists, however, finds thatthe two groups of monarchs are genetically mixed. Their research,published in the journal Molecular Ecology , suggests that environmental factors may be the key to thebutterflies' choice of winter homes, and to where they wind up inthe spring. "Our data gives the strongest signal yet that the eastern andwestern monarchs belong to a single genetic population," saysEmory biologist Jaap de Roode, who led the research. "Thisdistinction is important to help us better understand the behaviorof the organism, and to conserve the monarch flyways." In addition to researchers in the de Roode lab, the study involveda scientist from the Institute of Integrative Biology in Zurich,Switzerland. Biologists have long been fascinated by the innate and learnedbehaviors underlying animal migrations. When monarchs are breeding,for instance, they can live up to four weeks, but when they aremigrating, they can live as long as six months. "As the day length gets shorter, their sexual organs do notfully mature and they don't put energy into reproduction. Thatenables them to fly long distances to warmer zones, and survive thewinter," de Roode says. "It's one of the basic lessons inbiology: Reproduction is very costly, and if you don't use it, youcan live much longer." Mass movements of animals have huge ecological impacts. They arealso visually arresting, from the spectacle of giant herds ofwildebeest trekking across the Serengeti to hundreds of thousandsof sandhill cranes flocking along the banks of Nebraska's PlatteRiver. In the case of long-lived mammals and birds, the younger animalsmay learn some of the behaviors associated with migration. That'snot the case with the monarchs, notes Amanda Pierce, a graduatestudent in Emory's Population Biology, Ecology and Evolutionprogram, and a co-author of the study. "We know there is no learning component for the butterflies,because each migration is separated by two to threegenerations," Pierce says. "To me, that makes the problemeven more interesting. How can these small, delicate animals travelthousands of kilometers and arrive at the same destination as theirgreat-great grandparents?" The question of whether eastern and western monarchs aregenetically the same has been hotly debated, and may be anessential piece to the puzzle of their divergent migrationpatterns. The researchers used 11 genetic markers to compare the geneticstructures of eastern and western monarchs, as well asnon-migratory monarch populations in Hawaii and New Zealand. Theresults showed extensive gene flow between the eastern and westernmonarchs, and a genetic divergence between these North Americanbutterflies and those from Hawaii and New Zealand. "In a sense, the genetic markers provide a DNA 'fingerprint'for the butterflies," de Roode says. "Just by looking atthis fingerprint, you can easily separate the butterflies of NorthAmerica from those in Hawaii and New Zealand, but you can't tellthe difference between the eastern and western monarchs." The Emory researchers have now joined a project headed by Harvard,which also involves the University of Georgia and the University ofMassachusetts, to sequence the full genomes of monarch butterfliesfrom places around the world. That data should rule out geneticdifferences between the eastern and western monarchs, or revealwhether any smaller genetic differences, beyond the 11 markers usedin the study, may be at play between the two groups. The idea that eastern and western monarchs are distinct populationshas been bolstered by tagging-and-tracking efforts based in theUnited States. That data, gathered through citizen science,indicates that the butterflies stay on separate sides of the RockyMountains -- a formidable high-altitude barrier. De Roode, however, theorizes that when spring signals the easternmonarchs to leave the overwintering grounds in Mexico, they maysimply keep radiating out, reproducing and expanding as long asthey find milkweed plants, the food for their caterpillars. "Few people have tagged the monarchs within Mexico to seewhere they go," he says, "because Mexico doesn't have asmuch citizen science as the U.S." If the theory is correct, some of the monarchs leaving Mexico eachspring may wind up in western North America, while others mayfilter into the eastern United States. This influx to the westernU.S. could be crucial to survival of monarchs on that side of thecontinental divide. "There are far fewer monarchs west of the Rockies," deRoode says. He notes that all of the overwintering monarchs on atypical overwintering site along the California coast consist ofabout the same number clustered onto a single big tree in Mexico'sMonarch Butterfly Biosphere Reserve, where hundreds of millions ofmonarchs blanket the landscape in the winter. The monarch butterfly migration has been called an endangeredphenomenon, due to the loss of habitat along the routes. TheMexican overwintering sites, located in the Trans-Mexican VolcanicBelt region northwest of Mexico City, particularly suffer fromdeforestation. Drug trafficking in the region has decimatedeco-tourism and hampered efforts to protect the trees. "We hope our research can aid in the conservation of themonarch flyways," de Roode says. Raising monarchs for release at weddings, memorials and otherevents is a growing industry, but U.S. Department of Agricultureregulations restrict shipping the butterflies across state lines. De Roode stresses that this regulation should remain in force, evenif further research confirms that eastern and western monarchs aregenetically identical, because parasites that the butterflies carrycan differ by region. "It's not a good idea to be shippingparasites around," he says. I am an expert from automobiledvd-players.com, while we provides the quality product, such as China Volvo DVD GPS , Ford DVD GPS, Automobile DVD Players,and more.
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