Aneil Flett Agrawal
anagrawa@indiana.edu

Indiana University
Department of Biology
1001 E. Third Street
Bloomington, IN 47405
USA

Advisors:
Dr. Edmund Brodie III, Evolution, Ecology, and Behavior, IU
Dr. Curt Lively, Evolution, Ecology, and Behavior, IU
Dr. Loren Rieseberg, Evolution, Ecology, and Behavior, IU
Dr. Mike Wade, Evolution, Ecology, and Behavior, IU

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Research Interests

I am interested in evolutionary interactions at various levels, from within loci to between coevolving species. My primary efforts include both empirical and theoretical approaches to better understand the genetic properties of social interactions. My second research area focuses on understanding the evolutionary forces affecting the maintenance of sex. My theoretical efforts in this area have considered selective forces generated by both ecological and genetic sources.

Indirect Genetic Effects and Social Evolution 

For complex social traits (e.g., mother-offspring interactions), the phenotype of a focal individual depends not only on its own genes but also on the genes of its social partners. Indirect genetic effects occur whenever the phenotype of one individual depends, at least in part, on the genotype of its social partner(s). Because indirect genetics effects create new sources of genetic (co)variation, they can change the rate and direction of evolution. In addition to my empirical work that evaluates predictions (described below), I also build mathematical models to extend this theory. For example, I have shown that indirect genetic effects are more powerful (and less dependent on genetic correlations) when populations are genetically structured (Agrawal et al., Am. Nat. 2001). My empirical research, in collaboration with Dr. E. D. Brodie III, focuses on a North American hemipteran, the burrower bug, Sehirus cinctus. In this system, mothers guard egg clutches until hatching. Upon hatching, mothers collect small mint fruit that they provision to their offspring. These behaviours are readily observed and measured in the lab. My goal is to identify and quantify factors controlling the complex social trait of maternal care. In particular, I am interested in how this phenotype is controlled by genetic properties of mothers as well as their offspring (Agrawal et al., Science 2001). I use experimental and genetic manipulations as well as quantitative genetics to study this system.

The Maintenance of Sexual Reproduction

Two major classes of theories dominate current thoughts on the maintenance of sex: mutation-based models and host-parasite coevolution models. I am interested in both types of models and use analytical and numerical approaches to examine them. Perhaps the most well known mutation-based model is A. Kondrashov's mutational deterministic hypothesis, which postulates that sexual populations suffer substantially less genetic load than their asexual counterparts. This hypothesis relies on the crucial assumption of synergistic interactions between deleterious mutations. This assumption has not been supported by empirical tests. Based on the notion that dominance within a locus is conceptually similar to epistasis among loci, I have been able to show that sexual populations suffer substantially less load than asexuals if mutations are recessive and populations are slightly structured (Agrawal & Chasnov, Genetics 2001). This model is bolstered by empirical evidence that (i) deleterious mutations usually are recessive and (ii) natural populations are somewhat structured. A second model is based around the idea that sexual selection is an extremely powerful force that does not exist in asexual populations. Because sexual selection is primarily experienced by males, this force can efficiently purge deleterious mutations from sexual populations without reducing the productivity of females. Consequently, the genetic load of sexual females is reduced relative to that of asexuals (Agrawal, Nature 2001). Host-parasite coevolution models, collectively known as the Red Queen hypothesis, postulate that sex is required to prevent complete exploitation by coevolving parasites. While the Red Queen has traditionally been applied to sex vs. asex, I recently showed that it can also help maintain outcrossing in populations where self-fertilization also exists (Agrawal & Lively, Evolution 2001). My interest in the Red Queen has also led to a series of models examining how the genetic basis of infection influences gene- frequency dynamics of host-parasite coevolution (e.g., Agrawal & Lively, Evol. Ecol. Res. 2002).

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Publications

• Agrawal, A. F. (2001) Sexual selection and the maintenance of sexual reproduction. Nature 411:692-695.
• Agrawal, A. F., E. D. Brodie III, and J. Brown.  (2001) Parent-offspring coadaptation and the dual genetic control of maternal care. Science 292: 1710-1712.
• Agrawal, A. F., E. D. Brodie III, and M. J. Wade. (2001) On indirect genetic effects in structured populations. American Naturalist 158: 308-322.
• Agrawal, A. F. and J. R. Chasnov.   (2001)   Recessive mutations and the maintenance of sex in structured populations. Genetics 158: 913-917.
• Agrawal, A. F. and C. M. Lively. (2001) Parasites and the evolution of self-fertilization. Evolution 55: 869-879.
• Agrawal, A. F. and C. M. Lively. (2002) Infection genetics: gene-for-gene versus matching-allele models, and all points in between. Evolutionary Ecology Research  4:79-90.