Evolution of Endosymbiosis in (xylotrophic) Wood-Eating Bivalves

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A grant has been awarded to Dr. Daniel L. Distel of the University of Maine to investigate the evolution of wood-boring clams. Though not well known to the general public, wood-boring clams are destructive species that may be considered the marine equivalent of termites. They include many diverse species that cause more than a billion dollars in damage to wooden structures, boats, and fishing gear annually in marine environments worldwide. The most destructive of these are the "shipworms"; worm-like clams that burrow into and eat wood. These voracious wood eaters can destroy a twelve-inch diameter pier piling in less than one year's time. Though they look like worms, molecular evidence suggests that they are closely related to the common "steamer clam", a staple of New England cuisine. The purpose of this investigation is to use molecular data from several genes to reveal the evolutionary relationships of wood boring clams to other more common bivalves and to use these data to better understand how their destructive habits have evolved, including the role of associated bacteria. Although wood can be treated with broad-spectrum chemical biocides to control wood-borer damage, use of the most effective treatments has recently been restricted or banned in many states and nations due to environmental concerns. New environmentally sound control methods are critically needed, particularly in low-income coastal communities where wood is the only affordable marine construction material. Such control measures must be targeted specifically to wood-boring species to minimize ecological impact. Evolutionary studies will tell us how these nuisance species developed the ability to destroy wood and what makes them different from other more desirable and economically important marine species. This knowledge will be essential for developing control methods that are safe and highly specific to these destructive organisms.