My research is centered in evolutionary ecology and conservation biology, and has concentrated on the evolution of environmentally induced polymorphisms.  These polymorphisms provide useful models for understanding the general mechanisms maintaining phenotypic plasticity, which is a fundamental component of biological systems.

Examples of such polymorphisms include horn and wing dimorphism in insects and trophic polymorphisms in fish.  It is a goal of my research to model the evolution of these polymorphisms, to improve our understanding of the evolutionary mechanisms maintaining them, and to relate our understanding of environmentally induced polymorphisms to the evolution of phenotypic variation and plasticity.

My conservation biology research has focused on amphibians. Amphibians are thought to be important indicators of ecosystem health, because they often spend part of their life in water, and part on land, and thus are exposed to contaminants and habitat loss in both environments. My research is aimed at understanding the mechanisms which affect natural and anthropogenic population fluctuations, and utilizing developmental stability as a biological indicator of stressed populations.  The results of this research may eventually allow biologists to quickly and easily assess populations of amphibians and other wildlife before such populations decline or become extinct.

Much of my research involves the evolution of alternative life histories in salamanders.  In some salamander species, individuals either transform from an aquatic larval stage into a terrestrial "metamorphic adult", or they remain within the aquatic environment as a sexually mature "paedomorphic adult".  This dimorphism, called facultative paedomorphosis, is environmentally induced because environmental conditions experienced as a larva influence whether an individual becomes one morph or the other.

In 1994 I proposed three hypotheses for the maintenance of facultative paedomorphosis (Whiteman 1994).  A literature review revealed that at least two of the three mechanisms are operating in natural populations, suggesting that selection can favor the production of the same adaptive polymorphism for very different evolutionary reasons.

Currently, I am testing these hypotheses in the facultatively paedomorphic tiger salamander, Ambystoma tigrinum nebulosum.  Since 1990 I have studied this species at the Mexican Cut Nature Preserve in Colorado.  Mexican Cut (shown below) is a high-elevation pond system which is owned by The Nature Conservancy and administered by the Rocky Mountain Biological Laboratory (RMBL) in Gothic, Colorado.

My research is aimed at understanding both the environmental factors influencing paedomorphosis and the resultant fitness consequences to each morph.  Thus far, my research supports the idea that selection pressures in the Rocky Mountains maintain paedomorphosis through very different evolutionary processes than those which maintain the dimorphism at lower elevations or in other species (Whiteman et al. 1994, 1996).

Besides confirming the existence of alternative selection mechanisms for the production of paedomorphosis, these results suggest that plasticity in one trait or suite of traits can be adaptive for very different evolutionary reasons in different populations or species.

My Colorado research has also shown that sex plays a strong role in the payoffs to each morph, and may influence the degree to which members of each sex become a certain morph (Whiteman 1997).  This result suggests that other polymorphisms and plastic responses may also have sex-specific payoffs which have been thus far unappreciated.  These findings led me to consider utilizing facultative paedomorphosis as a model system for studying the interaction of natural and sexual selection.

Interaction of Natural and Sexual Selection

Understanding the interaction between natural and sexual selection is one of the most basic problems confronting evolutionary biologists.  Because the expression of facultative paedomorphosis is environmentally induced, yet genetically based (and thus subject to natural selection) and because the two morphs interbreed (and thus are potentially influenced by sexual selection), facultative paedomorphosis provides an unique system in which to test the relative strength of these two evolutionary forces.

I am currently focusing on this question in another facultatively paedomorphic species, the mole salamander, Ambystoma talpoideum.  Mole salamanders, unlike high-elevation populations of tiger salamanders, live in low-elevation Carolina bays and other wetlands of the southeastern U. S.  Thus, the environments experienced by these two species are extremely different, and provide an interesting comparison.  Thus far, I have found that temporal and spatial differences between morphs within breeding ponds affects morph success and that females mate with multiple males of each morph, suggesting that the fitness payoffs to each morph are more complex than initially realized.

I began this study as a postdoctoral research associate at the University of Georgia's Savannah River Ecology Laboratory (SREL), in collaboration with Drs. Raymond Semlitsch (University of Missouri-Columbia) and J. Whitfield Gibbons (SREL), and am currently continuing the work using both South Carolina and Kentucky populations, in collaboration with Drs. Joseph Pechmann (University of New Orleans; see photo above) and John Krenz (University of Minnesota-Mankato).  This study has the potential to elucidate much about the maintenance of facultative paedomorphosis and the interaction of natural and sexual selection.

Evolutionary Ecology of Cannibalistic Polyphenism

I have also expanded my interest in environmentally induced polymorphisms by working on cannibalistic larval morphs in tiger salamanders.  In some populations, two larval morphologies are present: a "typical" morph and a "cannibal" morph.  Cannibal morphs differ from typical morphs in that they have an enlarged head and vomerine ridge ("teeth") which assist them when feeding on conspecifics.  This bizarre morphology is environmentally induced, with a higher frequency of cannibals produced at higher larval densities under laboratory conditions.  However, little is known about the environmental factors influencing the production of cannibal morphs in the field and the fitness consequences of becoming cannibalistic.

Much of my cannibalism work has been performed in collaboration with a number of NSF Research Experience for Undergraduates (REU) students at the RMBL.  Together, we have found evidence for geographic variation in the mechanisms that produce cannibals (Sheen and Whiteman 1998) and discovered that large invertebrate prey indirectly affect the production of cannibals, by increasing the body size variation within both natural and laboratory populations (Whiteman et al. in review).  The latter study also suggests that the geographic variation found in Sheen and Whiteman (1998) may be a result of regional differences in large prey types.  Future research is aimed at exploring the sex-specific payoffs of cannibalistic morphs in this species.

Other Evolutionary Ecology Research

Recently I have begun studies of the effects of reservoir fluctuations on the life history and plasticity of benthic invertebrates.  In collaboration with a number of students and faculty in MSU's Watershed Studies Institute and funded by NSF's Collaborative Research at Undergraduate Institutions (C-RUI) program, we are exploring how such water fluctuations affect the ecology and biogeochemistry of Ledbetter embayment on Kentucky Lake.  I currently have two C-RUI students involved in this project.

Amphibian populations have been well documented to fluctuate dramatically, in part because of the high fecundity of females and the dynamic nature of their breeding habitats (e.g., drought, competition, predation).  However, although several studies have documented fluctuations in amphibian populations, no research has examined the ecological causes of such fluctuation in detail.

In 1990 Dr. Scott Wissinger (Allegheny College) and I  began a long-term study of a high-elevation metapopulation of tiger salamanders, Ambystoma tigrinum nebulosum, at the Mexican Cut Nature Preserve.  Our research has elucidated much about the life-history strategies of the salamanders (see above) and the effects of the salamander predators on invertebrate prey (Bohonak and Whiteman 1999, Wissinger et al. 1999a, b).  It has also allowed us to hypothesize the mechanisms that produce the fluctuations evident in this population.  The population experienced a decline phase in the 1980s, which originally was attributed to acidic deposition.  After the population rebounded dramatically in 1988, we found that larval mortality due to pond drying was a more likely explanation for the 1980s decline (Wissinger and Whiteman 1992).

Over the past decade, we have determined a number of other extrinsic and intrinsic variables likely to be important to these population fluctuations, including winter mortality, zooplankton abundance, cannibalism by aquatic adults, and demographic convergence among adults (Whiteman and Wissinger 2001).  Currently, we are creating simple mathematical models of the populationís dynamics, in collaboration with Dr. Ian Billick (Rocky Mountain Biological Laboratory), and plan to finish the parameterization of this model over the next few years.  Our research should help clarify the variables that are most important to understanding amphibian population fluctuations, and thus should be applicable to the management of a variety of species and populations.

An increase in incidence of malformed frogs has been observed throughout parts of North America.  Deformed frogs may be indicators of developmental problems associated with human-induced stress, such as pesticide and herbicide accumulation in wetlands.  Although these disfigured frogs serve as a warning for the management of nearby amphibians as well as human health concerns, they may appear too late to reduce anthropogenic stress to nearby ecosystems.  Proper screening of individuals with a stress indicator may have warned biologists about environmental problems and led to changes in human behavior before the stressor dramatically affected sensitive biota.

Amphibian biologists thus need an early-warning system that could identify stressed animals before the stressor causes population or regional harm.  One such indicator is obtained by measuring developmental stability, one component of the ability of an organism to withstand environmental and genetic disturbances during development to produce a genetically predetermined phenotype.  Under normal conditions, development follows a genetically determined pathway, and minor perturbations are controlled by developmental stability mechanisms.  Under stressful conditions (e.g., increased pollutants), the performance of the stability mechanism may be reduced such that development cannot be restored to the original pathway, resulting in the production of abnormal phenotypes.

One of the most widely used measures of developmental stability is fluctuating asymmetry (FA).  FA is nondirectional differences between the left and right sides of paired bilateral characters.  The underlying assumption of FA is that development of both sides of a bilateral organism is influenced by identical genes, and thus nondirectional differences between sides must be environmental in origin.  Because developmental stability acts to reduce such changes, FA will measure the efficiency of developmental stability and the magnitude of the environmental perturbation.

Because measures of developmental stability, such as FA, can be used to identify stressed populations before significant deleterious effects are observed, and because such measures may also be used to estimate future changes in fitness, developmental stability has the potential to be an important tool for biological conservation.  Surprisingly, although development has been studied extensively in amphibians, FA is only recently being applied to amphibian conservation.

Over the past few years, my students (Amy Benson, above, and Jessica Boynton, right) and I  have begun correlating amphibian FA with: 1. water chemistry parameters known to cause deformities and mortality in amphibians; 2.  land use practices, i.e., undisturbed forested sites, moderately disturbed agricultural sites and highly disturbed industrial sites; 3.  density of larvae, which at high levels can induce stress; and 4.  population size of adults, which may affect FA via inbreeding depression in small populations.  Population estimates will thus allow separation of natural stress levels from those that may be human induced (via water chemistry).

Thus far, we have found that bullfrog (Kentucky) and tiger salamander (Colorado) FA values were higher in agricultural ponds with poor water quality when compared to forested ponds with moderate or excellent water quality (Whiteman et al. in prep).  Currently we are confirming these results using digital imaging to increase the accuracy of FA estimates.   We are also conducting experiments to determine how asymmetry affects traits related to fitness, such as foraging behavior and growth rate.  In the future, I plan microcosm and mesocosm experiments to determine how various environmental stressors affects asymmetry, and how asymmetry affects amphibian ecology under semi-natural conditions.

I have been involved in other conservation biology research throughout my career.  For example, I have studied conservation genetics of freshwater turtles (Parker and Whiteman 1993), the effects of acidity on amphibian development and behavior (Whiteman et al. 1995a), the conservation of rare amphibian phenotypes (Whiteman and Howard 1998, Whiteman et al. 1998), and the ecological and economic risks of introduced transgenic organisms to marine systems (Gutrich and Whiteman 1998, Gutrich et al. 1998).  I am also currently a Co-PI in the vertebrate modeling component of Kentucky GAP, which is aimed at modeling vertebrate habitats across a landscape scale.  I plan to continue collaborating on similar projects in the future.

Bohonak, A. J. and H. H. Whiteman.  1999.  Dispersal of the fairy shrimp Branchinecta  coloradensis (Anostraca): Effects of hydroperiod and salamanders.  Limnology and  Oceanography 44:487-493.

Gutrich, J. J. and H. H. Whiteman.  1998.  Analysis of the ecological risks associated with  genetically engineered marine macroorganisms. In:  Zilinskas, R. A. and P. J. Balint  (eds.), Genetically Engineered Marine Organisms: Environmental and Economic  Risks  and Benefits.  Kluwer Academic Publishers.

Gutrich, J. J., H. H. Whiteman. and R. A. Zilinskas.  1998.  Characteristics of marine  ecosystems relevant to uncontained applications of genetically engineered organisms.   In: Zilinskas, R. A. and P. J. Balint (eds.), Genetically Engineered Marine Organisms:  Environmental and Economic Risks and Benefits.  Kluwer Academic Publishers.

Parker, P. G. and H. H. Whiteman.  1993.  Genetic diversity in fragmented populations of  Clemmys guttata and Chrysemys picta marginata as shown by DNA fingerprinting.   Copeia  1993:841-846.

Whiteman, H. H.  1994.  Evolution of facultative paedomorphosis in salamanders.   Quarterly Review of Biology 69:205-221.

Whiteman, H. H., R. D. Howard, and K. A. Whitten1.  1995.  Effects of pH on embryo  tolerance and adult behavior in the tiger salamander, Ambystoma tigrinum tigrinum.   Canadian Journal of Zoology 73:1529-1537.

Whiteman, H. H., S. A. Wissinger, and A. J. Bohonak.  1994.  Seasonal movement  patterns in a high-elevation population of the tiger salamander, Ambystoma  tigrinum nebulosum.  Canadian Journal of Zoology 72:1780-1787.

Whiteman, H. H., S. A. Wissinger, and W. S. Brown.  1996.  Growth and foraging  consequences of facultative paedomorphosis in the tiger salamander, Ambystoma  tigrinum nebulosum.  Evolutionary Ecology 10: 429-442.

Whiteman, H. H.  1997.  Maintenance of polymorphism promoted by sex-specific fitness  payoffs.  Evolution 51:2039-2044.

Whiteman, H. H. and R. D. Howard.  1998.  Conserving alternative amphibian  phenotypes: Is there anybody out there?  In:  Lannoo, M. J. (ed.), The Status and  Conservation of Midwestern Amphibians, Iowa University Press.

Whiteman, H. H., R. D. Howard, X. Spray1, and J. McGrady-Steed.  1998.  Facultative  paedomorphosis in an Indiana population of the tiger salamanders, Ambystoma  tigrinum tigrinum. Herpetological Review 29:141-143.

Whiteman, H. H. and S. A. Wissinger.  2001.  Multiple hypotheses for population  fluctuations: the importance of long-term data sets for amphibian conservation.  In:  M. L. Lanoo (ed.), Status and Conservation of U.S. Amphibians, California University  Press (in press).

Wissinger, S. A. and H. H. Whiteman.  1992.  Fluctuation in a Rocky Mountain  population of salamanders: anthropogenic acidification or natural variation? Journal  of Herpetology 26:377-391.

Wissinger, S. A., A. J. Bohonak, H. H. Whiteman, and W. S. Brown.  1999a.  Subalpine  wetlands in Colorado: Habitat permanence, salamander predation and invertebrate  communities.  In: Bazter, D. P., R. B. Rader, and S. A. Wissinger (eds.), Invertebrates  in Freshwater Wetlands of North America: Ecology and Management.  John Wiley  and Sons.

Wissinger, S. A., H. H. Whiteman, G. L. Rouse, G. B. Sparks, and W. S. Brown.  1999b.   Foraging trade-offs along a predator-permanence gradient in subalpine wetlands.   Ecology 80:2102-2116.