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 emerge nce time has: ecological and evolutionary significance in seasonal environm ents due to their relationship with fitness components. The population dyna mics of nine different cohorts of seedlings emergence were analyzed in a na tural population of the annual herb Tagetes micrantha Cav. (Asteraceae). Te mporal variation in seedling emergence was related to the pattern of precip itation, while spatial variation could be related to topographical heteroge neity. Plants that emerged at the beginning of the season (early germinatio n) had lower probabilities of survivorship than those that emerged at the e nd of the season (late germination). In contrast, plants that emerged early had, on average, higher fecundity than those that emerged late. The net re sult of three contrasting patterns of survival and fecundity constitute a l ife history trade-off in T. micrantha.