ECOLOGICALLY‐LINKED VARIATION IN MORPHOLOGY, ACETYLENE REDUCTION, AND WATER RELATIONS IN PSEUDOCYPHELLARIA DISSIMILIS

Abstract

Pseudocyphellaria dissimilis (Nyl.) D. Gall and P. James in litt populations were shown to possess different morphologies which correlated with the evaporative demand of their environment. The variations in morphology consisted of increased thallus thickness, mostly from increased medulla thickness, and increased rhizine length in the more exposed population. These changes confer a decreased surface/volume ratio and increased water storage in the form of external water that could be removed by blotting but not shaking. A consequence of these changes was a slower drying down rate. No differences in water loss rate per unit area were found between populations indicating that no morphological modifications exist to decrease water loss. Preliminary work on the acetylene reduction rates of the populations demonstrated a considerable difference in rates between the individual populations' and indicated that acetylene reduction could be another useful indicator of physiological adaptation. Copyright © 1981, Wiley Blackwell. All rights reserved