1. Allium tricoccum GAGNON Departement des Sciences biologiques, Universite Montreal, CP 8888, Succ. 'A', Montreal, Quebec, Canada H3C 3P8 du Quebec a a spring study provides precise information northern limits of its distribution is a long-lived perennial, harvested for its edible bulbs. This on vital rates in vulnerable populations at the in southern Quebec. 2. A dense population was studied for 5 years, by mapping 18 1-m x 1-m plots and measuring all ramets to estimate annual mortality, recruitment, status. A stage-classified growth, population trends. Elasticity analyses and simulations were performed of harvests. 3. All vital rates estimated sterile and flowering were closely size-dependent, and differed ramets. The bimodal population structure 4. Most flower scapes died before setting rare. Flowering sexual and asexual reproduction rates. Ramets were classified both by their size and flowering projection matrix model was used to reveal to identify the demographic variables most relevant to population growth and to estimate the effect greatly large sterile ramets showing high survival rates and maintained through recruitment. ramets showed high rates of asexual reproduction. between was dominated by vegetative Seedlings emerged every year, but largely failed to establish. seed. Flowering in consecutive years was At the population level, reproductive patterns were clearly biennial; resource availability (critical size and reproductive determine reproductive 5. Temporal variability cost) and the regulating effect of season length, appear to synchrony. was significant for all demographic for seedling emergence and reproductive behaviour. One exceptionally led to the establishment rate had essentially season was observed during this 5-year study; outstanding flowering, production and seedling recruitment variables, but especially good growth mast seed of new genotypes. 6. Population growth rates (k) estimated were close to the equilibrium value of 100. Elasticity values associated with sexual reproduction less than 1.5% of X. Thus, germination usually contributed no effect growth rate. Clonal development of already-established important pathway to population growth. 7. Simulated harvesting rates of only 5-15% were sufficient growth rates below the equilibrium value, predicting populations, in which recruitment to bring the population a population decline. Bulb harvest represents a threat for population maintenance of these largely clonal northern from seeds is unlikely.
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