case study( contiued)ligustica., the ecotype that is characteristic of the Italian peninsula, but they also have genetic influences from a variety of other European ecotypes. The " AFricanized" or " killer" bee is Apis mellifera scutellata, but it has hybirdized with other ecopytes as it has spread through South and Central American and, more recently, into Texas, Arizona, and California.The differences among honeybee eptypes have a genetic basis; this w s wqJl established by beekeepers long before scientists 4 {ached the question, but common garden and controlled crosses of ecotypes by scientists support this conclusion.KEY TERM: Common gardening is a technique in which animals( or plants) are maintained in the same enviroment. if the animals differ in behavior across their native habitats, then keeping them in a common garden helps to separate environmental from genetic influences. If they all behave the same when in the common garden, then the behavioral differences observed across their native habitats likely are due to environment. If the differences persist in a common garden, then a genetic hypothesis is supported.The most striking difference between "Africanized" bees and the honeybees to which most North Americans are accustomed is the heightened defensive response of the "Africanized" bees. With bees of European origins, under most conditions you can walk fo within a few meters of a hive without risk of being stung, and if approaching the hive from behind, you can probably walk up to it and sit on it without risk. In contrast, "Africanized" bees often respond to an animal's movement 50 to 100 meters from their hive by flying and stinging. Each "Africanized" bee sting is no more potent that a European bee sting, but mass stinging can be lethal to the large animals such as humans, dogs, horses, and cattle. A conservative estimate is that severalhundred people have died in South and Central America from mass stinging events since the release of the bees in 1957, "Africanized" bees exhibit extreme responses in all phases of nest defense when compared with their European counterparts; the differences between the ecotypes are largely due to genetics (see Figure 3.1 and Table 3.1).These observations raise the question of why the root African stock from which the "Africanized" bees are derived exhibits such extreme responses: The best hypothesis is that honeybees in Africa have been faced by a combination of predators that includes humans and their evolutionary predecessors.
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