The Gulf of Mexico oil leak offers an unprecedented opportunity to study rapid evolution in a well-studied system: the eastern mosquitofish (Gambusia holbrooki). This species has a rare, black form that persists at about 1% in nature. Oil contamination is likely to change the background coloration of its habitat and the conspicuousness to predators of the silver form, potentially favoring the black form. The goal of this work is to sample Florida populations before the oil hits them, and just after, so as to assess black and silver fish frequencies as the habitat changes. This work will be followed by additional surveys of long-term changes.
The results of this study may be profound for scientists, college students and the general public as this may be an example of selection in action that parallels the rise in frequency of the peppered moth during the Industrial Revolution. Few opportunities arise for the public to see natural selection occurring on a grand scale at a rapid pace such as is predicted under these extenuating circumstances. In addition, a graduate student will be trained in the course of this study.
After the Deepwater Horizon Gulf of Mexico oil spill, there was a high likelihood of hurricanes in the area and a lack of knowledge about when the oil leak would be capped. Mosquitofish live in the freshwater regions north and east of the Gulf. Most mosquitofish are sandy colored but the rare ones are mottled black (see two images included here). We posited that if oil continued to leak and hurricanes passed through the area, oil droplets would mottle otherwise white sandy substrate in the freshwater habitats near the Gulf where mosquitofish live. This would allow the rare mottled-black individuals to increase in frequency because they would match the background and predators would not see them as easily. While the spill was capped and the hurricanes did not move though during this particular spill, the images of sandy beach and mottled substrate (included here) demonstrate the match in the two types of habitat with the two color morphs. We estimated the frequency of mottled black fish across 12 unique habitats around the Gulf over one year. We are processing our data now to evaluate whether frequency of mottled black fish is associated with background coloration and/or other water quality data parameters that we collected. The funding for this research allowed an MS student and a returning undergraduate student to be trained in field research and to learn valuable skills that they would not otherwise have had the opportunity to learn on our urban campus ( Old Dominion University). A follow-up grant to assess these populations from a genetic perspective is allowing five undergraduate women (two minority) to gain molecular genetic research experience, which will increase their graduate opportunities substantially. This work has been very valuable as a research training tool at a university where few students gain actual field and laboratory experience. While this research was ongoing, it was discussed in a large Evolution course and a population genetics course. The PI received an invitation to discuss this work at the biology honors society at the university and did this in the spring of 2011. The graduate student presented a talk on these fish at the Virginia Academy of Sciences, a regional science meeting, also in the spring of 2011. The work is being printed on scientific posters to be presented at the VA Zoo and in the FL park system so that the general public can better understand possibilities for rapid evolution in natural ecosystems when anthropogenic effects are present. When the work is complete, it will be presented at a national scientific conference in 2012.
