Doctoral Dissertations

Date of Award

5-1990

Degree Type

Dissertation

Degree Name

Doctor of Philosophy

Major

Botany

Major Professor

Edward E. Schilling

Committee Members

Arthur Echternacht, A. Murray Evans, B. Eugene Wofford

Abstract

The genus Pappobolus S. F. Blake as circumscribed here includes the taxa previously placed in Pappobolus (sensu Blake 1916), the South American species of Helianthus L. (recently known as Helianthopsis H. Robinson) and one species transferred from Viguiera Kunth, V. acutifolia S. F. Blake. It consists of 45 taxa (38 species) 18 of which are newly described here, P. amoenus, P. andinus, P. cajamarcensis, P. davidii, P. decumbens, P. ecuatorianus, P. ecuatorianus var. lancifolius, P. juncosae, P. matthewsii var. occidentalis, P. matthewsii var. viridifolius, P. microphyllus var. dillonii, P. microphyllus var. liberus, P. microphyllus var. soukupii, P. robinsonii, P. sanchezii, P. schillingii, P. stork-hortonii, and P. youngiorum. The genus is distinguished from closely related genera such as Simsia Pers., Tithonia Desf. ex Gmelin and Viguiera by the deciduous disk achene pappus and a shrubby to arborescent habit. Pappobolus is endemic to the Andes of Colombia, Ecuador and Peru. It occupies habitats ranging from xerophytic and tropical deciduous forests to montane moist forests, and some species also occur in the Paramo or Jalca of northern Peru. The greatest concentration of species is encountered in northern Peru in the basin of the Maranon River. Leaf venation patterns and floral microcharacters such as endothecial cell morphology and style shape are essentially identical among the species of the genus. The genus is characterized by monochasial and dichasial thyrsoid capitulescences, although structural differences are common and apparently are tied to environmental conditions. Chromosome numbers obtained from a majority of the species support a base chromosome number of x = 17 for the genus and indicate a lack of polyploidy. A cladistic analysis of the genus supports the recognition of two subgenera. Pappobolus subg. Apricus subg. nov. with nine species is distinguished by yellow anther thecae and disk flower lobes, large monochasial thyrsoid capitulescences and small heads. Pappobolus subg. Pappobolus with 29 species is distinguished by black anther thecae and disk flower lobes, monochasial and dichasial thyrsoid capitulescences (some associated with few, large heads) densely lanate herbage and sclerified leaves. Keys, distribution maps and illustrations are provided for all the species.

Download
Files over 3MB may be slow to open. For best results, right-click and select "save as..."

Share

COinS