Lynda F. Delph

Professor and Associate Chair of Biology

Department of Biology, Jordan Hall, 1001 E. Third Street,
Indiana University, Bloomington, IN 47405 USA
Office phone: 812-855-1831, Biology Fax: 812-855-6705, email: ldelph@indiana.edu

DEGREES
1979          B.S. (Honors), University of Arizona
1983          M.S., University of Arizona
1988          Ph.D., University of Canterbury

APPOINTMENTS
1989          Busch Postdoctoral Fellow at Rutgers University with Dr. T. Meagher
1989-96    Assistant Professor, Department of Biology, Indiana University
1996-02    Associate Professor, Department of Biology, Indiana University
1998-        Associate Chair, Department of Biology, Indiana University
2001-        Senior Fellow, Indiana Molecular Biology Institute
2002-       Professor, Department of Biology, Indiana University

FELLOWSHIPS AND AWARDS
1983-84    Fulbright Fellowship
1994-95    Outstanding Junior Faculty Award, IU
1995          Senior Class Award for Teaching Excellence in Biology, IU
1997          Fulbright Fellowship
2000        Teaching Excellence Recognition Award, IU
2005         Trustees’ Teaching Award, IU
2005         Guggenheim Fellowship

I am interested in evolutionarily based questions concerning reproductive strategies in plants. This involves looking at morphology, genetics, physiology, life histories, how they are interrelated and how they affect fitness. My work includes field, greenhouse, and lab work, and I use a combination of manipulative experiments, comparative approaches, artificial selection, and genetic approaches. Past research includes: (1) an investigation of the forces that select for gender dimorphism, and how this separation of gender affects other plant traits, (2) the evolution of sexual dimorphism, (3) how inbreeding affects inbreeding depression within populations, (4) how plant vigor affects male fitness, (5) mating-system evolution, (6) how traits such as flower size and number affect plant fitness, and (7) the evolution of sex chromosomes.

Current research by me and my postdocs involves two main lines of investigation, and numerous smaller projects. Note that my graduate students often pursue their own research questions using their own systems (see the People page for the titles of past graduate student theses and the Organisms page for pictures of their study systems), and consequently my graduate students have many sole-authored publications. I have room for additional graduate students and am also interested in talking to anyone who might want to do a postdoc in the lab.

SEXUAL DIMORPHISM - The first major project concerns the evolution of sexual dimorphism and sex-chromosome evolution in the dioecious species, Silene latifolia. The two sexes of this species have remarkably different life histories, which appear to be influenced by the sexual dimorphism in flower number - males make 17 times as many flowers as females over the same time period. Although females have a greater reproductive effort because of the high cost of producing fruit, males have higher costs of reproduction in the life-history trade-off sense. By artificially selecting on flower number (to both increase and decrease the sexual dimorphism) we have uncovered correlated responses in morphological and physiological traits that have given us insights into why males pay a higher cost of reproduction and why males make smaller flowers than females.

Silene latifolia - Pistillate flower from a female on the left and staminate flower from a male on the right.

A QTL-mapping project is complete, which involved crosses between the divergent selection lines to investigate the genetic architecture of sexually dimorphic traits.  We have found that several QTL of major affect are only expressed when they are on the Y-chromosome, an unexpected and exciting result.
We planted artificial-selection lines out in the field to investigate how the divergent lines acquire fitness via two pathways - the pathway involved with mate acquisition (sexual selection) and the pathway involved with life history (fecundity and viability selection). This experiment is now complete and Chris Herlihy is in the process of writing up the results.
We also performed a cross-classified breeding design to estimate the G matrix for both males and females. We found that the two sexes have different G matrices and that traits are highly intercorrelated. This means that even if selection were the same in both sexes for certain traits sexual dimorphism would evolve and could include traits not directly under selection.
We also undertook two additional artificial selection experiments to investigate whether genetic correlations can be broken by correlational selection. The results of one of these experiments, in which we tried to break the between-sex genetic correlation for calyx width, revealed that the correlation could be broken in only 4 generations. We are following this up with an experiment to test whether the correlation was actually broken by selecting only on one sex and seeing if the other sex responds. If we really did break the correlation, then little or no response should be seen in the sex not under selection.
Lastly, we are investigating among-population differentiation in morphological and physiological traits that are sexually dimorphic via phenotypic selection analysis in natural populations in Europe that differ in floral and leaf traits.
To date, several of my postdocs (Steve Carroll, Jan Gehring, Maureen Levri, Michele Arntz, Janet Steven, Ivan Scotti, Chris Herlihy, Daniela Bell, and Maia Bailey), one of my graduate students (Frank Frey), and around 18 undergraduates have worked with me on various aspects of this system. The correlational selection work is in collaboration with my colleague Butch Brodie.

GYNODIOECY - The second main avenue of investigation involves the study of gynodioecy, in which both females and hermaphrodites coexist in populations. We are currently working on characterizing costs of restoration, both with simulation models and empirically, as well as investigating mitochondrial gene sequence polymorphism (see text below).
    Our main natural study species for our work on gynodioecy is the cushion plant Silene acaulis, which is circumpolar in the northern hemisphere in arctic and alpine habitats. Our field work on this species has taken place in the mountains of Colorado and in northern Finland (furthermore, we are growing plants from all over the world, including Alaska, Colorado, Iceland, Greenland, Norway, and Finland in the greenhouses at IU).
    We started out using S. acaulis to evaluate mechanisms that might be responsible for why outcrossed seeds from female seed-parents outperformed those from hermaphrodite seed-parents. Once we had shown that seeds from females are not better provisioned than those from hermaphrodites, we turned to alternative hypotheses. These hypotheses (which aren't mutually exclusive) deal with pollen-tube competition, pleiotropic affects of genes, and biparental inbreeding. Results indirectly support the idea that nuclear restorer alleles have negative pleiotropic affects (or costs of restoration).
    Past work with this species also includes an investigation of population structure, which revealed positive spatial autocorrelation within 1-3 m, and panmixia past that. In addition, we are investigating the genetic basis of sex determination in this species, using both crossing designs and molecular markers for mitochondrial genes.
    We have found remarkable sequence polymorphism in a mitochondrial gene of this species (22 substitutions over 3 geographic regions), and these are combined within a small number of haplotypes per population, indicating that either selection or demographic forces have perpetuated a small number of very ancient haplotypes.  Pascal Touzet (University of Lille) and I have followed up on this line of investigation in other Silene species, as this level of polymorphism is unprecendented. We have found that sequence polymorphism in mitochondrial genes is abundant in gynodioecious species, but absent or nearly absent in hermaphroditic or dioecious species.
    We have also begun work on Brassica napus with regard to the cost of restoration. We are making use of the fact that individuals can be characterized as having a male-fertile cytoplasm or one of two male-sterility genes together with one of two restorer genes. In other words, we have individuals whose genotype is known for the mitochondrial genes causing male sterility and the nuclear genes restoring male sterility and can therefore directly measure the cost of the restorers. One of the restorers, Rfp, should act in a silent manner, while the other, Rfn, should act more constitutively, and we hope to be able to compare the cost of these two types of restorers.
    To date, several of my postdocs (Steve Carroll, Jan Gehring, Ben Montgomery, Pia Mutikainen, Molly Nepokroeff, and Thomas Städler), three of my graduate students (Debbie Marr, Maia Bailey, and Dana Dudle), and several undergraduates have worked with me on various aspects of gynodioecy.

  
Silene acaulis from Pennsylvania Mtn. in Colorado - pistillate flowers from a female plant on the left and perfect flowers from a hermaphrodite plant on the right.

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