LIFE EXPECTANCY IN A TULSA CEMETERY - GROWTH AND POPULATION-STRUCTUREOF THE LICHEN XANTHOPARMELIA-CUMBERLANDIA

The demographics of a population of the foliose lichen Xanthoparmelia cumberlandia growing on gravestones in a Tulsa cemetery are presented. Because of the regular layout of granitic gravestones, the cemetery a cted as a mechanism for generating experimental replicates and as a co ntrol for habitat variability. The lichen population was multi-modal, based on age classes. Thalli within each age class approximated a norm al distribution of size. Age classes were separated by several years. Growth rates of thalli within age classes were independent of size, bu t growth was dependent on age class. Thallus growth varied among the m onths, and was correlated with precipitation but uncorrelated with tem perature. Mortality rate was greatest in age class III, and lowest in class I (I youngest-III oldest thalli). A population model of the spec ies showed that recruitment has been sporadic, yet highly successful w hen it did occur. The model depicts growth rates as independent of siz e within, but not among, the three age classes.