Overgrowth competition, fragmentation and sex-ratio dynamics: A spatially explicit, sub-individual-based model

Philip H. Crowley, Christopher R. Stieha, D. Nicholas McLetchie

Research output: Contribution to journalArticlepeer-review

25 Scopus citations


Sessile organisms that compete for access to resources by overgrowing each other may risk the local elimination of one sex or the other, as frequently happens within clumps of the dioecious liverwort Marchantia inflexa. A multi-stage, spatially implicit differential-equation model of M. inflexa growing in an isolated patch, analysed in a previous study, indicated that long-term coexistence of the sexes within such patches may be only temporary. Here we derive a spatially explicit, sub-individual-based model to reconsider this interpretation when much more ecological realism is taken into account, including the process of fragmentation. The model tracks temporally discrete growth increments in continuous space, representing growth architecture and the overgrowth process in significant geometric detail. Results remain generally consistent with the absence of long-term coexistence of the sexes in individual patches of Marchantia. Dynamics of sex-specific growth qualitatively resemble those generated by differential-equation models, suggesting that this much simpler framework may be adequate for multi-patch metapopulation models. Direct competition between fragmenting and non-fragmenting clones demonstrates the importance of fragmentation in overgrowth competition. The results emphasize the need for empirical work on mechanisms of overgrowth and for modeling and empirical studies of life history tradeoffs and sex-ratio dynamics in multi-patch systems.

Original languageEnglish
Pages (from-to)25-42
Number of pages18
JournalJournal of Theoretical Biology
Issue number1
StatePublished - Mar 7 2005

Bibliographical note

Funding Information:
We thank Heinjo During and the UK Wort Group (particularly Linda Fuselier, Gisela García-Ramos, Charles Richardson, Carey Snyder, and Nicole Sudler) for helpful suggestions during this study and Gisela García-Ramos for insightful comments on an earlier draft of the manuscript. PHC gratefully acknowledges the hospitality of Isabelle Olivieri, Ophelie Ronce and colleagues for hosting his visit to the Institute of Evolution at the Université de Montpellier, France, during May, 2002, where this work and many related ideas were discussed to good effect. We acknowledge support for this project from NSF grant DEB 9974086.


  • Clonal plant populations
  • Liverworts
  • Maintenance of sex
  • Marchantia inflexa
  • Simulation modeling

ASJC Scopus subject areas

  • Statistics and Probability
  • Modeling and Simulation
  • General Biochemistry, Genetics and Molecular Biology
  • General Immunology and Microbiology
  • General Agricultural and Biological Sciences
  • Applied Mathematics


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