title: Prezygotic resource-allocation dynamics and reproductive trade-offs in Calymperaceae (Bryophyta).
abstract: OBJECTIVE
  Resource allocation is difficult to characterize in plants because of the challenges of quantifying gametes and propagules. We surveyed six sympatric, unisexual species in the family Calymperaceae (Bryophyta) to test for trade-offs in prezygotic sexual and asexual expression and density-dependent survivorship of female gametangia.
  
  
  METHODS
  We tallied gametangial and asexual propagule output for 1820 shoots from 17 populations of six species at monthly intervals during one year (2010-2011) in a central Amazonian forest. Generalized linear mixed models were used to test for trade-offs in sexual and asexual expression and density-dependent senescence probability of gametangia. Precipitation and microsite variables were also included in the model.
  
  
  RESULTS
  For all species, sexual and asexual expression were positively correlated with mean monthly precipitation. Asexually expressing shoots produced significantly fewer gametangia than nonexpressing ones, and the probability of senescence increased with shoot density. Archegonium density per shoot was also consistently lower than the modeled optimum to maximize the number of receptive archegonia.
  
  
  CONCLUSIONS
  Trade-offs among reproductive strategies and positive density-dependent senescence of female gametangia suggest that prezygotic sexual and asexual expression come at a tangible investment. However, the apparently inefficient resource-allocation dynamics in the production of female gametangia makes the possible advantages of squandering such investments unclear. One possibility is that the study populations, like those of many dioicous mosses, are skewed toward expressing females with low sporophyte production, which would suggest that asexual reproduction predominates and upstages efficient resource allocation in prezygotic investment.
authors.affiliation: National Institute for Amazonian Research, Department of Biodiversity, Av. André Araújo, 2936, Petrópolis, CEP 69060-001, Manaus, Amazonas, Brazil.
authors.forename: Marta R
authors.initials: MR
authors.lastname: Pereira
authors.affiliation: Department of Biology, University of Vermont, 120A Marsh Life Sciences, 109 Carrigan Drive, Burlington, Vermont 05405, USA.
authors.forename: Cristian S
authors.initials: CS
authors.lastname: Dambros
authors.affiliation: National Institute for Amazonian Research, Department of Biodiversity, Av. André Araújo, 2936, Petrópolis, CEP 69060-001, Manaus, Amazonas, Brazil chaszartman@gmail.com.
authors.forename: Charles E
authors.initials: CE
authors.lastname: Zartman
mesh_terms: D005075:Biological Evolution; D001938:Brazil; D019068:Bryopsida / Q000502:physiology*; D065947:Rainforest; D012098:Reproduction; D012100:Reproduction, Asexual; D012621:Seasons; D013045:Species Specificity
keywords: Amazon; gametangia; moss; rainforest; reproduction; resource allocation