Assistant Professor
Ph.D., Duke University, 2002
Center for Population Biology Research Fellow, U. C. Davis, 2002-2004
CPB Postdoctoral Associate, U. C. Davis, 2004-2005

Program Affiliation: Evolution, Ecology and Behavior | Plant Biology

Research Groups Affiliation: Ecology | Evo-Devo | Evolution | Genetics |Genomics & Bioinformatics | Plant Biology

Moyle lab website

I am interested in the genetic basis of adaptation and speciation, and the evolutionary forces responsible for these processes.  Despite more than a century and a half of research, we still understand little about Darwin’s ‘mystery of mysteries’ – the origin of new species. Many basic questions remain:  What drives diversification and speciation in natural systems?  What is the genetic basis of reproductive incompatibility? How important are adaptive processes in the evolution of reproductive barriers? Do dominant modes of speciation differ among diverse biological systems?

Genomic locations of hybrid incompatibility QTL for pollen and seed sterility between L. esculentum and L. hirsutum (adapted from Moyle and Graham 2005). Morphological and ecological diversity within Lycopersicon. (Photo: TGRC, U. C. Davis) Variation in floral morphology between populations of S. rotundifolia .

Our approaches to these questions include empirical studies of micro-evolutionary divergence, detailed genetic analyses of trait variation and interspecific sterility, and comparative analyses of macro-evolutionary patterns between genera. Past and current research has included both model (e.g. Lycopersicon, Arabidopsis) and non-model (e.g. Silene, Collinsia) plant groups, and new promising systems are always welcome. Some current research interests include:

Genetics of Reproductive Barriers and Hybrid Sterility:
Using QTL (Quantitative Trait Locus) mapping, we have been identifying genomic regions that are responsible for hybrid sterility and other ecologically important trait differences between species. This research primarily focuses on the plant group that includes the domesticated tomato – Lycopersicon. Because of its genetic and genomic resources, and its many ecologically diverse wild species, this is a great system to examine ecological and evolutionary questions. One of the goals of this work is to identify and isolate individual genes responsible for adaptation and for hybrid barriers (so-called ‘speciation genes’), and to understand the forces that have shaped the evolution of these genes.

Comparative Genomics of Adaptation and Speciation:
Combining data from several QTL mapping studies, we are examining the genetic changes responsible for differences between multiple closely-related species in Lycopersicon, with the aim of identifying general patterns of adaptation and the evolution of reproductive barriers. Some of our key questions in this research include: What is the connection between genes underlying adaptation and genes causing reproductive barriers between species? Are the same genetic changes, classes of genes, or regions of the genome, repeatedly involved in adaptation and speciation? How does the accumulation of species differences change with increasing evolutionary divergence?

Evolution of Incipient Reproductive Isolation Within Species:
Because speciation is an intraspecific process, we also analyze patterns of divergence within species to examine the first stages of development of reproductive isolation. For example, we have found evidence for reduced crossability between geographically-distant populations of Silene rotundifolia--a rare Appalachian wildflower.  By comparing patterns of population differentiation in many different genetic traits, our analyses indicate that these reproductive barriers likely result from the gradual accumulation of divergent alleles between isolated populations, rather than being associated with one or more morphological traits that are diverging via selection.  In contrast, in Collinsia sparsiflora (an endemic Californian annual), we have shown that F1 hybrids between adjacent non-serpentine and serpentine populations are partially reproductively isolated, but this hybrid sterility is associated with differences in soil type. In this case, our results suggest a direct connection between the early evolution of intrinsic reproductive isolation and the most classical example of adaptation in plants - edaphic (soil) adaptation.

Comparative Patterns of Reproductive Isolation:
We also use comparative approaches to understand patterns of reproductive isolation, and the genetic and evolutionary mechanisms that may underlie them. For example, we have examined patterns of change in reproductive incompatibility over time (measured as genetic distance) within three angiosperm genera (Glycine, Silene, Streptanthus). Variation in these patterns among different genera may indicate differences in the predominant mechanisms of speciation, and in the number and kinds of genetic change that cause reproductive isolation between species in each group.

Genetic and Environmental Effects on Whole-Genome Gene Expression:
Using microarrays, we have been comparing whole-genome gene expression patterns between natural plant ecotypes grown in different environments.  By examining how gene expression changes with genotype and environment, we aim to identify the genes involved in adaptation, to examine environmental effects on the regulation of gene expression, and to better understand the genetic constraints on adaptive responses to environmental change.

Moyle, L.C. 2008. Ecological and evolutionary genomics in the wild tomatoes (Solanum Section Lycopersicon). Evolution in press.

Moyle, L.C. and T. Nakazato. 2008. Comparative genetics of hybrid incompatibility: Sterility in two Solanum species crosses. Genetics 179: 1437-1453.

Nakazato, T., M. Bogonovich, and L. C. Moyle. 2008. Climatic and environmental factors predict adaptive phenotypic differentiation within and between two wild Andean tomatoes. Evolution 62: 774-792.

Turelli, M., and L.C. Moyle. 2007. Asymmetric postmating isolation: Darwin's Corollary to Haldane's Rule. Genetics 176: 1059-1088.

Moyle, L.C. 2007. Comparative genetics of potential prezygotic and postzygtic isolating barriers in a Lycopersicon species cross. Journal of Heredity 98: 123-235.

Moyle, L.C. and E. B. Graham. 2006. Genome-wide associations between hybrid sterility QTL and marker transmission ratio distortion. Molecular Biology and Evolution 23(5): 973-980.

Moyle, L.C. 2006. Correlates of genetic differentiation and isolation by distance in 17 congeneric Silene species. Molecular Ecology 15(4): 1067-1081.

Moyle, L.C., and E. B. Graham. 2005. Genetics of hybrid incompatibility between Lycopersicon esculentum and L. hirsutum. Genetics 169: 355-373.

Hahn, M. W., J. G. Mezey, D. J. Begun, J. H. Gillespie, A. D. Kern, C. H. Langley and L. C. Moyle. 2005. Natural selection and codon bias on single genomes. Nature 433: E5-E6 (20 Jan 2005).

Moyle, L.C., M. Olson and P. L. Tiffin. 2004. Patterns of reproductive isolation in three angiosperm genera. Evolution. 58: 1195-1208.