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Massimo Pigliucci
Massimo Pigliucci
Department of Botany
University of Tennessee

Research Interests

This laboratory conducts research in the general area of plant ecological and evolutionary genetics. The approach is mostly organismal, although molecular work is done in collaboration with other laboratories. The major types of research employed are field studies of the ecology of natural populations and laboratory / greenhouse studies under controlled environmental conditions. There is an emphasis on sophisticated, computer-assisted, statistical and graphical analyses of the data obtained. Underlying most of our efforts is to arrive at a better understanding of how adaptations evolve and what factors limit their efficacy. The current areas of active research include (but are not limited to) those listed below.

Phenotypic plasticity:
There are many open questions concerning phenotypic plasticity, some of which are directly being pursued in this lab. For example, we would like to know more about natural selection on plasticity under field conditions, which requires extensive field studies of plant populations over several seasons. The long-term evolution of plasticity has also been scarcely addressed, and we are using the comparative method based on molecular phylogenies of plant groups to determine how often plasticity evolves and following which historical patterns. Our interest expands also to the genetic basis of plastic responses, and to the idea of "plasticity genes" proposed by Schlichting and Pigliucci. This direction of our studies is being pursued by a combination of quantitative genetics experiments and experiments using mutants specifically impaired in their ability to respond to environmental conditions.

While the goals of this lab's activities are to pursue fundamental research in the area of genotype-environment interactions, applications of plasticity studies are far-reaching and wide-ranging. In animals, the nature-nurture debate extends to the evolution of complex behaviors, including social behavior and intelligence in mammals, primates, and therefore humans. This has consequences for our discussions of social policies, as well as ethics and morality. Among the economical applications of plasticity studies are the improvement of genetic stocks of commercially important plants and animals, especially as it refers to selective breeding and genetic engineering of varieties capable to withstand an ample range of environmental conditions.

Genetic constraints and phenotypic integration:
Our investigations in the area of constraints utilizes an eminently empirical approach, based on two types of projects. On the one hand, we investigate how easy (or difficult) it is to break a constraint by mutation or recombination. For example, we may focus on a strong genetic correlation between two plant traits, which would make it difficult to select simultaneously on both traits in combinations that lie outside the correlation line. We then induce mutations in the genetic background of a population and see if we can select for individuals with novel combinations of traits. This can also be done by focusing on the effects of recombination. In this case, we cross two lines with different combinations of traits and see if their descendants show transgression, that is novel phenotypes not present in the parents. The second approach to the study of constraints uses the comparative method, and consists in determining how rapidly the genetic variance-covariance matrices of different populations or species change during evolutionary time. This is accomplished by comparing the matrices of different taxa whose phylogenetic relationships are known and plotting the resulting patterns on a cladogram.

An understanding of the genetic architecture of traits and how they evolve leads also to investigate the phenomenon of phenotypic integration, i.e., the way in which multiple characters relate to each other to build the whole multivariate phenotype. Phenotypic integration (and its environmental liability, related to the plasticity discussed above) has been much discussed but little investigated empirically. The same experimental and comparative methods used here to study changes in genetic variance-covariance matrices are useful in order to gain insights into the evolutionary genetics of phenotypic integration.

While again the main focus of this research is at the level of basic understanding of natural processes, the applications are clear: plant and animal breeders (and even genetic engineers) have to deal with the limitations that the genetic machinery of an organism imposes on the response to selection, be that natural or artificial.

Conservation biology, invasives, weeds ecology:
Phenotypic plasticity, genetic constraints, and phenotypic integration can be studied from the point of view of how they affect the invasive abilities of weeds or the inability of rare species to recover or withstand threats of invasion or extinction.

All the concepts discussed above apply, obviously, to both invasive and rare species, and it seems most urgent to find out what differences characterize species with distinct abilities of establishing themselves in novel environments or of maintaining stable population dynamics and demographic parameters.

This is an area of research at the interface between basic and applied population biology which surprisingly few people have pursued so far and which is a new field of interest for our lab.