L. Allphin et Kt. Harper, DEMOGRAPHY AND LIFE-HISTORY CHARACTERISTICS OF THE RARE KACHINA DAISY(ERIGERON KACHINENSIS, ASTERACEAE), The American midland naturalist, 138(1), 1997, pp. 109-120
Erigeron kachinensis is a rare endemic of the Colorado Plateau regions
of southeastern Utah and southwestern Colorado. It occurs in small, i
solated alcoves (recessed areas in canyon walls) at seeps arising alon
g canyon walls in sandstone substrates. One hundred randomly selected
individuals of E. kachinensis within each of six alcoves in Natural Br
idges National Monument, San Juan County, Utah, were monitored for 5 y
r (1990-1994). Survival of the 600 individuals was followed over the m
onitoring interval. Vegetative and reproductive parameters were assess
ed for the survivors each year. Mortality varied among the study alcov
es and individual size-classes. Mortality was heavily concentrated in
the smaller size-classes. Growth rate accelerated with increasing size
-class. Survival rate also increased with increasing size-class. Plant
s are long-lived; however, longevity is still unknown since mortality
was not observed in the largest size-class. Fecundity was greatest for
the largest size-classes, yet over 80% of the annual seed production
came from the three smallest size-classes due to abundance of individu
als in these size-classes. Populations varied with respect to plant si
ze and resistance to environmental stressors. Matrix analysis demonstr
ated a finite rate of population growth of 0.75. However, observed siz
e-class distributions of the six study populations over 5 yr of observ
ation have never been stable. Maintenance of viable populations of the
Kachina daisy is dependent on management actions that minimize distur
bances (natural or anthropogenic) in the fragile hanging gardens that
support the species.