Population Dynamic Consequences of Dispersal and Between-year Dormancy

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Theoretical models have been developed to investigate the consequences that delayed germination and seed dispersal have for the ecology and evolution of plants in variable environments. These models suggest that dormancy and dispersal are important mechanisms for coping with, and exploiting environmental variation. There has been, however, virtually no experimental calibration of those models or tests of their predictions in natural populations due to the difficulty of quantifying the population dynamics of seed dispersal and dormancy. New research will apply new procedures, which facilitate the estimation of the magnitudes of dispersal and delayed germination for plant populations, to determine the relative importance of within- habitat reproduction, between-year seed bank, and seed dispersal in natural populations of desert annuals. The study will be performed at the Desert Laboratory of the University of Arizona, which has the oldest ongoing permanent plot studies of desert plants, 88 years of accurate weather data, and 9 years of demographic data collected on the proposed study organisms. Desertification and increasing levels of human disturbance to natural ecosystems are now commonplace. It is important to know to what extent our theoretical concepts regarding the ecological and evolutionary consequences of variation are actually predictive of what goes on in nature. With specific respect to desert annuals, a large fraction of the flora of desert regions are annual plants (frequently 30-100%). Investigations of their life-cycles, ecology and evolution not only provide a basis for general understanding, but may provide some insights regarding their conservation and rational exploitation (e.g. in arid land grazing).