Evolutionary Ecology

, Volume 31, Issue 3, pp 363–386 | Cite as

Maintenance of the sexes and persistence of a clonal organism in spatially complex metapopulations

  • Christopher Stieha
  • Gisela García-Ramos
  • D. Nicholas McLetchie
  • Philip Crowley
Original Paper


Clonal organisms persist at a range of population sex ratios, from equal numbers of males and females to single-sex systems. When intersexual competition is strong enough to drive one sex locally extinct, the maintenance of the sexes is facilitated by the semi-independent dynamics of populations within a metapopulation. These semi-independent dynamics are influenced by dispersal and recolonization rates, which are affected by the spatial arrangement of populations. To establish the quantitative relationship between spatially complex metapopulations and the maintenance of the sexes, we used a mathematical model of the liverwort Marchantia inflexa. This clonal organism is found in discrete patches on rocks and along the banks of streams, which form single-sex and two-sex metapopulations. In this system, asexual propagules mainly disperse short distances. Long-distance between-patch dispersal and recolonization mainly occurs via sexual propagules, which require both sexes to be present. Dispersal of these two types of propagules could interact with the spatial arrangement of populations to affect the maintenance of the sexes. With our mathematical model, we found that at intermediate distances between populations, metapopulations maintained both sexes, and the spatial arrangement of populations changed the threshold at which one sex was lost. On the other hand, when populations were close to one another, one sex was lost and the single-sex metapopulation persisted through dispersal of asexual propagules. When populations were far apart, one sex was lost, and the metapopulation either went extinct due to lack of recolonization by asexual propagules or persisted because clumped populations facilitated recolonization. These idealized spatial arrangements help clarify the effects of the spatial arrangement on the maintenance of the sexes and the persistence of metapopulations of clonal organisms, which can help explain geographic parthenogenesis and the distribution of asexual populations, the persistence of asexual species, and inform the conservation of clonal organisms.


Competition Dispersal Geographic parthenogenesis Mathematical model Two-sex model 



We thank Karen Abbott, Samantha Catella, Sara Cilles, Katie Dixon, Scott Gleeson, Allyssa Kilanowski, Daehyun Kim, Brian Lerch, Christopher Moore, Ben Nolting, the Ecology Journal Club at Case Western Reserve University, and two anonymous reviewers for commenting on earlier versions of this paper. Funding for the research was provided by the US National Science Foundation (DEB 9974086-DNM [PI] and PHC [co-PI]); the US Department of State, the Institute of International Education Fulbright Program 2006–2007 (CRS); the University of Kentucky Graduate School (CRS); the University of Kentucky Biology Department (CRS); and the Gertrude Flora Ribble Fund (CRS). CRS was partially supported by a Scholar Award in Complex systems to Karen C. Abbott from the James S. McDonnell Foundation. This work was part of a PhD dissertation project by CRS in Biology at the University of Kentucky, advised by DNM and PHC.


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Copyright information

© Springer International Publishing Switzerland 2016

Authors and Affiliations

  1. 1.Department of BiologyCase Western Reserve UniversityClevelandUSA
  2. 2.Department of BiologyUniversity of KentuckyLexingtonUSA

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