THE ECOLOGICAL SIGNIFICANCE OF FRUIT HETEROMORPHISM IN THE AMPHICARPIC SPECIES CATANANCHE LUTEA (ASTERBCEAE)

The complex fruit heteromorphism of the amphicarpic annual Catananche lutea (Asteraceae) was studied. This species produces two types of subterranean achenes (amphic-1 and amphic-2) and three types of aerial achenes (peripheral, intermediate, and central). Subterranean achenes are produced in February-April in fewer number than aerial achenes, and they are larger and heavier. Amphic-1 achenes germinate quickly and in high proportions. Amphic-2 achenes exhibit delayed germination, which is spread over time as a result of the inhibitory action of the pericarp, and they germinate in low proportions. Aerial achenes are formed between April and May and have similar germination requirements; while the final proportion and rate of germination are quite high in every case, the time and the way in which achenes disperse differ between types. Peripheral achenes have a scarcely developed pappus and are subtended by the inner bracts of the capitula; they disperse when capitula are released by the dead mother plant (short-range dispersal). Central achenes have a highly developed pappus and are dispersed by wind sooner than peripheral achenes (long-range dispersal). Some intermediate achenes are dispersed like central ones and others are dispersed like peripheral ones. There are no significant viability differences between the different types of achenes. Light has an adverse effect on germination of all the achene types: it slightly lengthens the incubation period and decreases both the percentage and rate of germination. Subterranean achenes produce larger seedlings-at least early in the season-than do aerial achenes: however, those produced by peripheral achenes of the aerial capitula grow at the highest rate. Subterranean achenes spread germination over time; they constitute a very safe means of reproduction and an available achene reserve on soil. Aerial achenes spread germination in space, thereby increasing the distribution of the species.