Niche Partitioning, and Phenological and Morphological Separation Between Two Sunflower Species

ABSTRACT
Two species of sunflower (<em>Helianthus grosseserratus</em> and <em>H. rigidus</em>) were investigated to determine phenological, habitat, and morphological separation between them. The two species had overlapping distributions across a habitat gradient and also over- lapped in flowering times, although <em>H. rigidus</em> flowered earlier than <em>H. grosseserratus</em>. The two species achieved their maximum abundance on different portions of a topographic gradient, with <em>H. rigidus</em> being more abundant than <em>H. grosseserratus</em> on upper and middle slopes and <em>H. grosseserratus</em> being more abundant on lower slopes and depressions. The two species had relatively distinctive morphologies.