One of the greatest challenges in biology is to explain observed
levels and patterns of species diversity. My research focuses on pieces
of this puzzle on a variety of organizational levels from the physiology
of individuals to the large scale temporal and spatial dynamics of assemblages.
I use freshwater fishes as model organisms to address some of these problems.
Much of my recent work has focused on fishes in the Fundulus notatus
species complex. These species are ecologically and morphologically very
similar and found throughout the Mississippi basin and Southern United
States. The two most widely distributed members of this complex, F.
notatus and F. olivaceus, occur throughout much of the Mississippi
River drainage as well as the coastal drainages of the Gulf of Mexico.
Throughout this range, the species encounter one another and hybridize
in numerous contact zones. These contact zones are ecological and evolutionary
replicates, making them an ideal study system for some basic questions:
- Are contact zones structured along predictable ecological gradients?
- Are the contact zones temporally stable?
- What is the nature of the reproductive barriers among these species?
A third member of the F. notatus complex, F. euryzonus, is more
narrowly distributed and endemic to the Pontchartrain drainage in Louisiana
and southwestern Mississippi. This species is again ecologically and morphologically
very similar, leading one to ask why its range is so limited in comparison
to its sister species.
- What factors explain the different distributional patterns observed broadly
distributed and narrowly endemic sister species?
- Are there physiological or life history differences that have limited
the distribution of F. euryzonus?
Selected Recent Publications
For a complete list, see my C.V.
- Schaefer, J.F., B.K. Kresier, P. Mickle, C. Champagne and D.
Duvernell. 2009. Patterns of co-existence and hybridization among
two topminnows (Fundulus euryzonus and F. olivaceus)
in a riverine contact zone. In press, Ecology of Freshwater
Fish.
- Gido, K.B., J.F. Schaefer and J.A. Falke. 2009. Convergence of
littoral zone fish communities in reservoirs. In press, Freshwater
Biology.
- Matamoros, W.A., P. Mickle, J. Schaefer, W. Arthurs, J. Ikoma,
R. Ragsdale. 2009. First record of Agonostomus monticola (Family:
Mugilidae) in Mississippi freshwaters with notes of its distribution
in the southern USA. In press, The Southeastern Naturalist.
- Vigueira, P., Schaefer,
J.F., Kreiser, B.R., Duvernell, D. 2008. Tests of reproductive isolation
among species in the Fundulus notatus (Cyprinodontiformes:
Fundulidae) species complex. Evolutionary Ecology 22(1) 55-70.
- Bowen, B.R., B. Kreiser, P. F. Mickle, J. Schaefer, and S. B.
Adams. 2008. Phylogenetic relationships among North American Alosa
species (Clupeidae). Journal of Fish Biology 72: 1188-1201.
- Duvernell, D., Schaefer,
J.F. and Ravenelli, A. 2007. Hybridization and Introgression Among
Syntopic Populations of the Topminnows Fundulus notatus
and F. olivaceus in Southern Illinois. Journal of
Evolutionary Biology 20: 152-164
- Meadows, D., Adams, S.B. and Schaefer, J.F. 2007. Threatened fishes
of the world: Alosa alabamae Jordan and Everman, 1896 (Clupeidae).
Environmental Biology of Fishes 82:173-174.
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Fundulus notatus, the blackstripe topminnow.
Three Fundulus olivaceus (identified via mtDNA haplotype) sampled from a contact zone. Note the variability in the spot phenotype.
Geographic ranges of fishes in the Fundulus notatus species complex.
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