Dr. Joseph Travis
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Robert O. Lawton Distinguished Professor
Ph.D., Duke University, 1980
Graduate Faculty Status
Research and Professional Interests:
My research revolves around understanding how ecological processes drive evolutionary ones and, sometimes, vice-versa. My research is focused on variation among local populations of the same species, which represents the earliest stage in the adaptive generation of biodiversity.
For example, local populations of the least killifish, Heterandria formosa, that exhibit consistently higher numerical densities have different life histories than those at consistently lower numerical densities. Variation in density is driven by variation in predation pressure and so local adaptation trades off features well-suited to predation risk against those well-suited to coping with chronic crowding. In another example, populations of Trinidadian guppies (Poecilia reticulata) occur across an elevational gradient and it appears that here also predation pressure interacts with numerical density to maintain many of the distinctions among local populations in their life histories.
As the examples suggest, my interest runs to situations in which different agents of selection combine to challenge local populations in different ways. I am particularly interested in density-dependent selection because it adds an interesting challenge to understanding local adaptation. For example, changes in predation pressure from one population to another usually produce changes in numerical density as well, which makes untangling the role of each potential agent of selection more challenging. Density-dependent selection has a long history as a topic that links ecology and evolutionary biology; while the history is rich with theory, it remains unclear how pervasive density-dependent adaptation might be in nature.
With one foot in ecology and another in evolutionary biology, I have guided students in a diversity of research projects. My graduate students have studied topics from the community ecology of Amazonian frogs to the population genetics of gag grouper, from the development of personalities in bluefin killifish to the prenatal conflict between mothers and offspring in the least killifish. The common element in all of these projects is an immense curiosity about nature and the determination to find answers to important questions regardless of the path to those answers.Selected Publications:
Bassar, R., D. Reznick, A. Lopez-Sepulcre, and J. Travis. 2013. Experimental evidence for density-dependent regulation and selection on Trinidadian guppy life histories. Am. Nat. 181:25- 38.
Travis, J., J. Leips, and F. H. Rodd. 2013. Evolution in population parameters: density- dependent selection or density-dependent fitness? Am. Nat 181:S9-S20.
Apodaca, J. J., J. C. Trexler, N. Jue, M. Schrader, and J. Travis. 2013. Large-scale natural disturbance alters genetic population structure of the sailfin molly, Poecilia latipinna. Am. Nat. 181:254-263.
Macrae, P.S.D and J. Travis. 2013 The contribution of abiotic and biotic factors to spatial and temporal variation in population density of the least killifish, Heterandria formosa. Env. Biol. Fishes (in press). doi:10.1007/s10641-013-0117-7.
Travis, J. and K. E. Lotterhos. 2013. Using experiments and models to untangle direct and indirect effects: is there hope for understanding fishery systems? Bull. Mar. Sci. 89:317- 336.
McGhee, K. and J. Travis. 2013. Heritable variation underlies behavioural types in the mating context in male bluefin killifish. Animal Behaviour (in press). doi:10.1016/j.anbehav.2013.05.044.
Schrader, M, R. C. Fuller, and J. Travis. 2013. Differences in offspring size predict the direction of isolation asymmetry between populations of a placental fish. Biology Letters 9:20130327. doi:10.1098/rsbl.203.0327.
Bagley, J. C., M. Sandel, J. Travis, M. deL. Lozano Vilano, and J. B. Johnson. 2013. Paleoclimatic modeling and phylogeography of least killifish Heterandria formosa: insights into Pleistocene expansion-contraction dynamics and evolutionary history of North American Coastal Plain freshwater biota. BMC Evolutionary Biology (in press).
Bassar, R., R. Ferriere, A. Lopez-Sepulcre, M. Marshall, J. Travis, C. Pringle, and D. Reznick. 2012. Direct and indirect effects of evolutionary adaptation in the Trinidadian guppy (Poecilia reticulata). Am. Nat. 180:167-185. 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. 2012. Widespread intraspecific organismal stoichiometry among populations of the Trinidadian guppy (Poecilia reticulata). Functional Ecology 26:666-676.
Reznick, D. N., R. D. Bassar, J. Travis, and F. H. Rodd. 2012. Life history evolution in guppies VIII: the demographics of density regulation in guppies (Poecilia reticulata). Evolution 66:2903-2915.
Schrader, M. and J. Travis. 2012. Embryonic IGF2 expression is not associated with offspring size among populations of a placental fish. PLoS ONE 7(9):e45463. doi:10.1371/journal.pone.0045463.