The Phenotypic Plasticity of Death Valley's Pupfish
Desert fish are revealing how the environment alters development to modify body shape and behavior
Fighting for a Future
Taken together, these studies of phenotypic plasticity are revealing new insights into how phenotypic differentiation is occurring among Death Valley's pupfishes. This work has uncovered how the environment experienced during development plays an underappreciated role in generating phenotypic variation in the wild. Our findings suggest that population- or species-specific phenotypes can result not only from a population's genomic background but also from the interaction of individuals with that population's unique environment.
Recently, the importance of understanding the plasticity of pupfish has taken on a new urgency. The population in Devil's Hole has been declining gradually since the early 1990s for reasons that remain unclear. In 2003, one of the refuge populations was exterminated, and a second has since hybridized with another species of pupfish. A census in April 2006 revealed only 38 adult pupfish remaining in Devil's Hole. New conservation efforts, including the breeding of Devils Hole pupfish in captivity, are now being undertaken. As the Devils Hole pupfish example illustrates, however, the future of Death Valley's pupfishes remains uncertain. Pupfish in Death Valley, as well as fishes through the desert Southwest, continue to be threatened by new introductions of non-native species and unremitting calls for pumping of the aquifers that nourish their aquatic habitats. How Death Valley's pupfishes will fare in the face of these challenges remains to be seen.
In the meantime, research on pupfish is raising some important questions about the goals of conservation. If the phenotypes of animals can be intimately tied to their environments, what are we trying to preserve—the unique genetic composition of the animal or the unique animal in the context of its distinctive environment? Is it the same species if it is not preserved in the habitat that made it unique?
As awareness grows that phenotypic plasticity can shape the traits of imperiled species, new approaches are surfacing that use knowledge of a species' plasticity to achieve conservation goals. For instance, it has been suggested that managing habitats to generate a specific range of phenotypic variation could be useful for increasing the likelihood that a population or species will persist over the long-term. Such a "phenotype management" approach is based on recognition that the scope of phenotypic variation in a population is linked to the range of environmental variation experienced by members of that population during their lives.
In the case of pupfish, studies of how the environment influences phenotypic development are leading to new insights about how these fish respond to environmental change. Although more research is needed to fully understand how phenotypic plasticity has affected evolution of the pupfish that call Death Valley home, these studies have already revealed that when it comes to understanding the origins of variation in morphology, behavior and the brain, it's not only who you are but where you live.
The author thanks Gabrielle Nevitt, Penny Swanson and Thomas Hahn for their advice and encouragement throughout this research. Gratitude is also extended to James Deacon, Phil Pister and all members of the Desert Fishes Council for their unremitting efforts to preserve the unique native fishes of North America's deserts. The author also thanks Sarah Hamilton for assistance with fish care, and Jennifer DeBose for suggestions that greatly improved this manuscript.
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