E. Imbert et al., ACHENE DIMORPHISM AND AMONG-POPULATION VARIATION IN CREPIS-SANCTA (ASTERACEAE), International journal of plant sciences, 157(3), 1996, pp. 309-315
Crepis sancta is an annual composite that colonizes abandoned agricult
ural land and shows achene dimorphism. The achenes on the periphery of
the capitulum are heavy (0.27 mg) and are without a pappus, whereas t
hose in the center are light (0.10 mg), more numerous, and bear a papp
us. Several studies of other species of Asteraceae have shown that the
se morphological differentiations are accompanied by biological differ
ences, but few studies have tested whether these differences are const
ant between populations. We compared the germination, growth, phenolog
y, and reproductive effort of plants derived from these two types of a
chenes from three populations that had been established for 3, 13, and
36 yr. The peripheral achenes from the young population germinated fa
stest and gave rise to the most vigorous individuals. The differences
in the two other populations were slight or nonexistent. By comparing
the morphs between populations, pregermination dormancy and plant vigo
r were found to be different among populations for the central achenes
, whereas the characteristics of the peripheral achenes remained almos
t unchanged. It is often hypothesized that achene dimorphism is due to
developmental constraints. Our results indicate that these constraint
s may be regulated by environmental conditions.