RESUMO
PREMISE: We investigated sex-specific differences in the life-history traits of a metapopulation of the dioicous moss Weissia jamaicensis. Field observations revealed high rates of fertilization, which is uncommon for most dioicous bryophytes. We raised four hypotheses associated with the way the reproductive traits are related to the fertilization rate in this metapopulation. METHODS: We sampled 10 patches of the metapopulation and quantified sexual expression, sex ratio, reproductive success, and reproductive allocation. The ramets were classified as male, non-sporophytic female, sporophytic female, or non-sex-expressing. Thirty ramets from each of the categories expressing sex were placed for regeneration to test the effect of reproductive allocation on this trait. RESULTS: We found greater expression of the female function in all patches, implying a female bias in the metapopulation. The number of male ramets was variable in each patch and did not affect reproductive success. At the prezygotic level, the allocation of resources to the male function was higher. However, the large allocation of resources to sporophyte development in sporophytic females, which exceeded allocations at prezygotic levels, was related to the higher mortality rate of these ramets, suggesting reproductive cost. CONCLUSIONS: The prezygotic ramets that allocated the greatest amount of resources to reproduction expressed sex less frequently, biasing the sex ratio toward the sex that allocated the least amount of resources to reproduction. Overall, the ramets that allocated the greatest amount of resources to reproduction had the lowest regeneration rate, suggesting reproductive cost.
Assuntos
Briófitas , Bryopsida , Características de História de Vida , Animais , Reprodução , Razão de MasculinidadeRESUMO
PREMISE OF THE STUDY: Leaf-inhabiting organisms offer an experimentally tractable model system within which to investigate the influence of alternative reproductive strategies on plant metapopulation dynamics. We conducted a field study to determine whether (1) threshold colony sizes exist for the onset of sexual and asexual expression, and (2) alternative reproductive strategies differentially influence within-patch dynamics of the tropical pleurocarpous moss Crossomitrium patrisiae. METHODS: The growth, reproduction, and fate of 2101 colonies of C. patrisiae were followed over 2 years to investigate threshold size and age for sporophyte and brood branch formation and their influence on within-patch growth rates and longevity. KEY RESULTS: Asexual expression rather than sexual onset was limited by a minimal colony size. Age was uncoupled with threshold sizes. Colonies bearing brood branches survived nearly twice as long as sterile and solely sporophytic colonies. However, no effect of reproductive strategies on colony growth rates was found. CONCLUSIONS: This study is among the few attempts to correlate life history strategies with demographic parameters of terrestrial plants. Specifically, we provide evidence for differential influence of reproductive strategies on metapopulation survivorship.