Numerical Densities of Algal Cells and Growth in the Lichen Genus Cladonia

Abstract

This study relates population density patterns of the phycobiont Trebouxia throughout the mycobiont during different seasons in very similar species of Cladonia that occupy granitic rock outcrops. Algal cells were most abundant near the tips of the thalli; they were most abundant also on the S and W sides of each mound-like clump of thalli; and they were more abundant within the clump in May than in February. Densities of the phycobiont in each of three species of Cladonia were essentially similar at the same places in the thalli and in the same seasons, and densities decreased with distance from the edges of the clumps.