My research interests involve the ecology and evolutionary biology of fishes and fisheries science. I seek to understand the adaptive significance of reproductive, behavioral, physiological, or life history traits in fishes and to extend this knowledge to fundamental problems in resource management. Species currently under investigation include on the U.S. east coast, the Atlantic silverside (Menidia menidia); and on the Pacific coast, the the grunion Leuresthes tenuis and the topsmelt Atherinops affinis.
One long-standing interest of mine is to understand how the sex ratio evolves. I have been the first to show that sex determination in fishes is influenced by temperature during larval development. Most of this work has involved the Atlantic silverside but the phenomenon is now known to be widespread. These findings are important not only in designing approaches to sex ratio manipulation in aquaculture, but also to understanding the causes of fluctuations in sex ratio among natural populations. Current work is focused on the molecular basis of TSD and also how estrogens released in sewage effluents alter the local sex ratio in silversides.
Another area of investigation concerns how growth rate is adapted to differences in seasonality that occur with latitude. Work in our lab has shown that along the North American east coast high-latitude fish have a much higher genetic capacity for growth than do low-latitude fish within a given species. This "countergradient variation" (CnGV) in growth rate appears to be widespread and suggests that natural populations with the highest capacity for growth may be found where the growing season is shortest. Rapid growth in the north evolves because size-dependent winter mortality affects small fish more severely than larger fish. The existence of genetic variation in growth also implies that there must be evolutionary trade-offs that select for different growth rates at different latitudes. These tradeoffs involve swimming performance: fast growing fish are more susceptible to predators because their size-specific maximum swimming speed is reduced.
Our current NSF project focuses on the temporal and spatial scales of adaptive divergence in Menidia, with special attention to the interplay between gene flow and natural selection along the steep ecological gradient that occurs along the east coast of North America. We are combining common garden experiments to explore fine–scale spatial genetic variation in growth rate, vertebral number, and TSD with molecular genetic analyses to measure gene flow. The molecular work is done in collaboration with Paul Barber’s lab at UCLA. We are also extending this work to the Pacific coast using common garden experiments to test for genetic variation with latitude in two species that are ecologically similar to and from the same family as Menidia: i.e., top smelt and grunion.
Finally, I am very interested in the long term consequences of harvesting as a selective force that alters the evolution of life history traits in fishes. Because most fisheries selectively harvest the largest and fastest growing members of a population, the long term evolutionary response is likely to be slower individual growth and lower population productivity. We recently completed a 10 year empirical simulation experiment wherein captive populations of silversides were selectively harvested by size in different directions, to assess the rate at which life history characters might evolve under size-selective harvest in the wild.
For more information about my research, please visit the Conover Fish Ecology Lab website at http://www.somas.stonybrook.edu/~conover/ or click on the link above.
Conover, D.O., S. B. Munch and Stephen A. Arnott. 2009. Reversal of evolutionary downsizing caused by selective harvest of large fish. Proc. Royal Soc. London B. doi: 10.1098/rspb.2009.0003.
Susumu, C., S.A. Arnott, and D.O. Conover. 2007. Coevolution of foraging behavior with intrinsic growth rate: risk-taking in naturally and artifically selected growth genotypes of Menidia menidia. Oecologia 154: 237-246.
Conover, D.O. and S.B. Munch. 2007. Faith, evolution, and the burden of proof. Fisheries 32(2): 90-91.
Conover, D.O. 2007. Nets versus nature. Nature (London) 450:179-180.
Conover, D.O., L.M. Clarke, S. B. Munch, and G. N. Wagner. 2006. Spatial and temporal scales of adaptive divergence in marine fishes and the implications for conservation. J. Fish Biol. 69:21-47.
Arnott, S.A., S. Chiba, and D.O. Conover. 2006. Evolution of intrinsic growth rate: metabolic costs drive tradeoffs between growth and swimming performance in Menidia menidia. Evolution 60(6): 1269-1278.
Yamahira, K., T.E. Lankford, and D.O. Conover. 2006. Intra- and Interspecific Latitudinal Variation in Vertebral Number of Menidia spp. (Teleostei: Atherinopsidae). Copeia 2006(3): 431-436.
Walsh, M., S. Munch, S. Chiba and D.O. Conover. 2006. Maladaptive changes in multiple traits caused by fishing: impediments to population recovery. Ecology Letters 9(2): 142-148.
Conover, D. O., S.A. Arnott, M.R. Walsh, and S.B. Munch. 2005. Darwinian fishery science: lessons from the Atlantic silverside. Can. J. Fish. Aquat. Sci. 62 (4): 730-737.
Conover, D.O. 2004. Temperature-dependent sex determination in fishes. pp. 11-20 In Temperature-dependent sex determination. N. Valenzuela and V. Lance (eds). Smithsonian Institution Press. (194 p).
Munch S.B. and D.O. Conover. 2004. Nonlinear growth cost in Menidia menidia: Theory and empirical evidence. Evolution 58 (3): 661-664.
Conover, D.O., T. Gilmore, and S. B. Munch. 2003. Estimating the relative contribution of spring and summer-spawned cohorts to the Atlantic coast bluefish stock. Trans. Amer. Fish. Soc. 132 (6): 1117-1124.
Munch, S.B. and D.O. Conover. 2003. Rapid growth results in increased susceptibility to predation in Menidia menidia. Evolution 57 (9): 2119-2127
Conover, D.O. and S.B. Munch. 2002. Sustaining fisheries yields over evolutionary time scales. Science 297 (5578): 94-96.