Dr. Joseph Travis
Robert O. Lawton Distinguished Professor;
My interests are focused on the complex, reciprocal relationship between population dynamics and natural selection. At the simplest level, Im interested in how crowding might act as an agent of natural or sexual selection: which combinations of traits, if any, distinguish individuals that thrive in crowded conditions from those that do not? Im also interested in whether there are trade-offs between those combinations of traits that are most conducive to success at different densities. And given that success at low densities is often caused by successfully coping with agents of selection like predators, Im interested in how predators, which reduce population density, also act as agents of natural selection. At a more complicated level, Im interested in how the spread of useful traits through a population might change that populations ecological relationships: if population size increases because fewer individuals are lost to predation, does the population now face a new challenge in limited resources or susceptibility to different predators? And finally, at the most complicated level, I ask whether such new ecological challenges generate different selection pressures; put another way, how often do successful genotypes, by virtue of their very success, sow the seeds of their eventual eclipse by creating conditions of high density that favor different gentypes?
I approach these problems by studying the contrasts among local populations of the same species. I usually begin with observations of populations that have different levels of population density and that also differ from one another in body size, life history, or sexual behavior patterns. When I find such differences, I ask whether they are genetically based and, if so, whether they are maintained by divergent effects of natural selection. Obtaining the answers to these questions requires a combination of experimental ecology and population genetics, explaining the wide range of subjects that appear in the publications from my laboratory.
Within this general context, I have focused on a number of problems ranging from the differences in inflorescence size among populations of the lily Zigadenus (Amianthium) muscatoxicus in Virginia to the striking divergence in body size in north Florida populations of the sailfin molly, Poecilia latipinna. My current work has two foci. First, some of my students and I have been studying how population density acts as a selective agent in the least killifish, Heterandria formosa. Second, I am part of a large team of scientists, led by David Reznick of the University of California, Riverside, that is investigating how adaptation in Trinidadian guppies (Poecilia reticulata) alters the ecological role of guppies in their aquatic communities, creates cascading effects on energy flow through the mountain stream ecosystem, and appears to alter the selection pressures that the guppies themselves experience.
This type of work makes a contribution in two broader areas. First, it helps us understand the power and precision of evolutionary adaptation by uncovering it on very local scales. Second, it opens up an important window on comparative ecology by helping us understand how species cope with different ecological challenges in different locations. The principles that emerge from this work can be applied to a variety of situations, from understanding how fishery stocks respond evolutionarily to harvesting to understanding how a species role in a community might vary from one location to another. A number of my publications and those of my students reflect these broader applications.
My teaching experience has taken me into a variety of courses at FSU, from undergraduate courses focused on the natural history of fish and amphibians to graduate courses focused on statistical methods in ecology. I have guided the training of 18 doctoral students, whose work has ranged from the community ecology of Amazonian frogs to the population genetics of sex ratios in wasps. The studies being conducted by my current students include the effects of habitat alteration on hybridization in water snakes (Pierson Hill) and the control of variation in shape in male least killifish (Alex Landy). A number of superb postdoctoral scholars have worked in my laboratory; currently, J. J. Apodaca is continuing his work on the conservation biology of the Red Hills salamander (Phaeognathus hubrichti) and developing landscape-scale models for reintroductions of listed species.
More information on some of these projects and my general approach to problems can be found in the materials on my personal home page.
Bassar, R., R. Ferriere, A. Lopez-Sepulcre, M. Marshall, J. Travis, C. Pringle, and D. Reznick. In press. Direct and indirect effects of evolutionary adaptation in the Trinidadian guppy (Poecilia reticulata). American Naturalist.
El-Sabaawi, R., E. Zandona, T. J. Kohler, M. C. Marshall, J. Moslemi, J. Travis, A. Lopez-Sepulcre, R. Ferriere, C. Pringle, and S. N. Thomas. In press. Widespread intraspecific organismal stoichiometry among populations of the Trinidadian guppy (Poecilia reticulata). Functional Ecology.
Schrader, M., and J. Travis. In press. Assessing the roles of population density and predation risk in the evolution of offspring size in populations of a placental fish. Evolution and Ecology.
Reznick, D. N., R. D. Bassar, J. Travis, and F. H. Rodd. In press. Life history evolution in guppies VIII: the demographics of density regulation in guppies (Poecilia reticulata). Evolution.
Schrader, M., and J. Travis. 2012. Variation in offspring size with birth order in a placental fish: a role for asymmetric sib competition? Evolution 66:272-279.
El-Sabaawi, R., T. J. Kohler, E. Zandona, J. Travis, M. C. Marshall, S. N. Thomas, D. Reznick, M. Walsh, J. F. Gilliam, C. Pringle, and A. S. Flecker. 2012. Environmental and organismal predictors of intraspecific variation in stoichiometry of a neotropical freshwater fish. PLoS ONE 7:e32713.
McGhee, K., and J. Travis. 2011. Early food and social environment affect select behaviours but not female choice or male dominance in bluefin killifish. Animal Behaviour 82:139-147.
Schrader, M., J. Travis, and R. C. Fuller. 2011. Do density-driven mating system differences explain reproductive incompatibilities between populations of a placental fish? Molecular Ecology 20:4140-4151.
McGhee, K., and J. Travis. 2010. Repeatable behavioural type and stable dominance rank in the bluefin killifish. Animal Behaviour 79:497-507.
Bassar, R. D., M. C. Marshall, A. Lopez-Sepulchre, E. Zandona, S. K. Auer, J. Travis, C. M. Pringle, A. S. Flecker, S. A. Thomas, D. F. Fraser, D. N. Reznick. 2010. Local adaptation in Trinidadian guppies alters ecosystem processes. Proceedings of the National Academy of Sciences of the USA 107:3616-3621.