Research

Image One

Evolutionary models of organisms with complex life histories

Clonal reproduction, and the complex life history traits associated with it, is widespread across most higher taxa in plants, in algae, and across metazoan phyla. However, most evolutionary models have focused on sexually reproducing organisms that exhibit approximately determinate development and growth. Our work has extended important concepts in population genetics and evolutionary biology to include clonal reproduction, including developing a coalescent-based method for estimating effective population size, a population genetics model predicting the fate of alleles affecting life history attributes, and a model following phenotypic evolution in organisms with both sexual and clonal reproduction. These models have allowed us to consider effects of clonal reproduction on the evolution of senescence and on evolutionary lag and evolutionary rescue in such organisms.

publications on this topic:

  • Orive, M.E., M. Barfield, C. Fernandez, and R.D. Holt. (2017). Effects of clonal reproduction on evolutionary lag and evolutionary rescue. American Naturalist    https://doi.org/10.1086/693006
  • Orive, M.E. (1995).  Senescence in organisms with clonal reproduction and complex life histories. American Naturalist 145:90 - 108.
  • Orive, M.E. (1993).  Effective population size in organisms with complex life histories.Theoretical Population Biology 44:316 - 340.
Image Two

The interaction of clonal reproduction and mutation

A general assumption regarding the interaction of clonal (asexual) reproduction and mutation is that clonal reproduction should expose organisms to excessive mutation load, due to the additional effects of somatic mutations, in organisms such as plants that do not sequester the germline early in reproduction. We have shown that this initial assumption may be overly simplistic, due to the action of within-individual selection, the shielding of clonal organisms from meiotic mutations in some life cycles, and the preservation of heterozygosity for deleterious recessive alleles in the absence of sexual reproduction.

publications on this topic:

  • Marriage, T. and M.E. Orive. (2012) Mutation-selection balance and mixed mating with asexual reproduction. Journal of Theoretical Biology, 308:25-35.
  • Marriage, T.N., S. Hudman, M.E. Mort, M.E. Orive, R.G. Shaw and J.K. Kelly. (2009) Direct estimation of the mutation rate at dinucleotide microsatellite loci in Arabidopsis thaliana (Brassicaceae). Heredity 103:310-317.
  • Orive, M. E. (2001).  Somatic mutations in organisms with complex life histories.  Theoretical Population Biology, 59:235-249.
  • Otto, S. P. and M. E. Orive (1995).  Evolutionary consequences of mutation and selection within an individual.  Genetics 141:1173 - 1187.
 
Image Three

Models of within- and between-host pathogen and symbiont population dynamics/

For pathogen and symbiont populations, there are important levels of structure both within and between hosts. We developed models that considered the linkages between these two levels, as well as models that allow consideration of multiple host cell types, and multiple tissue types or body compartments coupled via pathogen movement. These studies extended important concepts from population ecology and evolutionary biology to these types of structured host-pathogen and host-symbiont systems.

publications on this topic:

  • Barfield, M., M. E. Orive, and R. D. Holt. (2015) The role of pathogen shedding in linking within- and between-host pathogen dynamics. Mathematical Biosciences 270:249-262, doi:10.1016/j.mbs.2015.04.010
  • Orive, M. E., M.N. Stearns, J. K. Kelly, M. Barfield, M.S. Smith and R. D. Holt.  (2005). Viral infection in internally structured hosts. I. Conditions for persistent infection. Journal of Theoretical Biology 232(4):453-466
  • Kelly, J. K., S. Williamson, M. E. Orive, M. Smith, and R. D. Holt (2003).  Linking dynamical and population genetic models of persistent viral infection. Am. Natur. 162:14-28.
Image Four

Use of multi-locus genetic data in analyzing gene flow and hybrid zones

We have developed models that considered the effects of gene flow on patterns of nuclear and cytonuclear statistical associations between loci (disequilibria), allowing for estimation of asymmetric migration rates. Such asymmetries arise naturally in plant systems with gene flow from both pollen and seed, and in animal systems with different migration rates in males and females.

publications on this topic:

  • Orive, M.E. and N. H. Barton (2002).  Associations between cytoplasmic and nuclear loci in hybridizing populations.  Genetics 162:1469-1485.
  • Asmussen, M. A. and M. E. Orive (2000).  The effects of pollen and seed migration on nuclear-dictyoplasmic systems.  I. Nonrandom associations and equilibrium structure with both maternal and paternal cytoplasmic inheritance. Genetics 155:813-831.
  • Orive, M. E. and M. A. Asmussen (2000). The effects of pollen and seed migration on nuclear-dictyoplasmic systems.  II. A new method for estimating plant gene flow from joint nuclear-cytoplasmic data.  Genetics 155:833-854.