Variable demography in relation to germination time in the annual plant Tagetes micrantha Cav. (Asteraceae)

This study tests whether variability in a life history trait such as emergence time has: ecological and evolutionary significance in seasonal environments due to their relationship with fitness components. The population dynamics of nine different cohorts of seedlings emergence were analyzed in a natural population of the annual herb Tagetes micrantha Cav. (Asteraceae). Temporal variation in seedling emergence was related to the pattern of precipitation, while spatial variation could be related to topographical heterogeneity. Plants that emerged at the beginning of the season (early germination) had lower probabilities of survivorship than those that emerged at the end of the season (late germination). In contrast, plants that emerged early had, on average, higher fecundity than those that emerged late. The net result of three contrasting patterns of survival and fecundity constitute a life history trade-off in T. micrantha.