Research

Dr. Schemske received his Ph.D. from the University of Illinois in 1977. The following year he completed a postdoctoral fellowship at the Smithsonian Tropical Research Institute in Balboa, Panama. Before joining the University of Washington Botany Department in 1989, Dr. Schemske was an Associate Professor at the University of Chicago.

Research Interests

'The challenge of studying adaptive variation in nature is that one has to know so much about the biology of the organism. Thus, it would seem that the second phase of the Dobzhanskian project, to show that genetic differentiation has occurred by natural selection, seems to evade us.' Lewontin (1997, p. 353)

The influential studies of Drosophila carried out by Dobzhansky and his colleagues illustrated the existence of adaptive genetic variation both within and between populations (Dobzhansky and Epling 1944; Dobzhansky and Levene 1948). Similarly, experiments conducted by researchers at the Carnegie Institution demonstrated that plant populations display marked local adaptation (Clausen, Keck, and Hiesey, 1940; Hiesey, Nobs, and Björkman 1971). Subsequent studies in both plants and animals provided abundant proof that the morphological and physiological differences observed between species and populations are often ecological adaptations (Antonovics and Bradshaw 1970; Schemske 1984; Endler 1986; Schluter and McPhail 1992).

The goal of my research is to characterize the mechanisms of adaptation. This requires information on both the ecological significance of putative adaptive traits as well as an understanding of their genetic basis. Such comprehensive studies are extremely difficult to accomplish; thus it is perhaps not surprising that our current knowledge of adaptation is inadequate. In a recent review of the literature, Orr and Coyne (1992) found only eight studies that had identified both the adaptive value and the genetic basis of differences between species in nature.

A central theme of my work is the link between temporal and spatial variation in ecological conditions and the adaptive differentiation of populations and species. I rely on ecological and genetic approaches to investigate the origin and maintenance of biological diversity. Such complex problems often require interdisciplinary solutions. I have established a number of rewarding collaborations that have greatly expanded the scope of my research program. For example, my work with Dr. H. D. Bradshaw, Jr. has introduced genetic mapping approaches to the field of population biology, demonstrating a powerful new approach to the study of natural populations. In the future, we plan to establish interdisciplinary training programs that will bring together researchers from a variety of fields. My long-term goal is to promote the study of adaptation at all levels, from the gene to the population. This research agenda takes its cue from the pioneering efforts of Clausen, Keck and Hiesey, whose collaborations in the mid-20th century provided a framework for the field of population biology. I have endeavored to follow their lead, bringing new technology to bear on the same, fundamental questions: How do organisms adapt to their environment?


The following links take you to brief discussions of my specific research interests and the abstracts from selected papers in each area.

I. What is the genetic architecture of adaptation?

a. Pollinator-mediated selection and the evolution of reproductive isolation in monkeyflowers.
                                         


II. What is the role of random genetic drift in adaptation?
a. Fine-Scale Genetic Differentiation in Linanthus: Isolation by Distance or Natural Selection?
III. How does spatial variation in the environment contribute to adaptation and speciation?
a. Environmental variation along an elevation gradient, and the evolution of the niche in monkeyflowers.
b. Local adaptation and the genetics of adaptation in Linanthus parviflorus.

IV. Why are tropical regions so diverse?
a. The Demographic Consequences of Plant-Animal Interactions in a Neotropical herb: Spatio-Temporal Dynamics
Horvitz, C. C. and D. W. Schemske. Leaf herbivory and neighbourhood competition in a neotropical herb: effects on demographic fates. J. Ecology 90:279-290.
b. Plant-Animal Interactions and Adaptive Evolution in Neotropical Costus
c. Deceit pollination and floral mimicry in tropical Begonia
d. Biotic Interactions and the Evolution of Tropical Diversity


"Since the animals and plants which exist in the world are products of the evolutionary development of living matter, any differences between tropical and temperate organisms must be the outcome of differences in evolutionary patterns." (Dobzhansky 1950)


How do we explain the extraordinary biological diversity of tropical regions? Few questions have generated such interest, yet we still struggle to find the answers. One of the greatest obstacles is that the question is multi-faceted, so a single mechanism is unlikely to provide both a necessary and sufficient explanation. Most of the hypotheses put forth to explain tropical diversity are purely ecological, and therefore do not identify the causal mechanisms responsible for diversity gradients. For example, energy is one of the best predictors of diversity, yet the energy hypothesis fails to identify how or why new species are produced in productive sites.


Here I review the major ideas concerning the origins of tropical diversity, with the goal of linking ecological and evolutionary perspectives. I first discuss the papers reprinted in this section, illustrating their individual contributions and their relationship to a general theory of tropical diversity. This is followed by a review of the evidence and explanations for latitudinal diversity gradients, a discussion of the mechanisms that may contribute to the origin and maintenance of diverse communities, and recommendations for future research directions.

Schemske, D. W. Ecological and evolutionary perspectives on the origins of tropical diversity, In R. Chazdon and T. Whitmore (eds.), Foundations of Tropical Biology: Key papers and commentaries. Univ. of Chicago Press. PDF

Schemske, D. W., H. V. Cornell, G. G. Mittelbach, K. Roy and J. M. Sobel. 2009. Is there a latitudinal gradient in the importance of biotic interactions? Annual Review of Ecology, Evolution and Systematics 40: 245-269. PDF

Schemske, D. W. 2009. Biotic interactions and speciation in the tropics. pp. 219-239, In Speciation and patterns of diversity, R. K. Butlin, J. R. Bridle and D. Schluter (eds.). Cambridge University Press, Cambridge. PDF

V. Polyploidy as a mechanism of rapid adaptation and speciation in plants. VI. The ecology and evolution of plant mating systems

VII. Research approaches in plant conservation