Premium
VERBESINA SECTION XIMENESIA (COMPOSITAE): BIOSYSTEMATICS AND ADAPTIVE VARIATION
Author(s) -
Coleman James R.
Publication year - 1974
Publication title -
american journal of botany
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.218
H-Index - 151
eISSN - 1537-2197
pISSN - 0002-9122
DOI - 10.1002/j.1537-2197.1974.tb06024.x
Subject(s) - biology , subspecies , taxon , arid , botany , adaptation (eye) , ploidy , ecology , biochemistry , neuroscience , gene
Section Ximenesia is native to the southwestern United States and northern Mexico. Two of its taxa, Verbesina encelioides subsp. exauriculata and V. nana , are more western and occur in arid or semiarid regions, whereas the third taxon, V. encelioides subsp. encelioides , is more eastern and occurs in relatively moist regions. A crossing program revealed the absence of isolating barriers between the subspecies of V. encelioides . It is suggested that V. encelioides and V. nana are effectively isolated genetically by differences in ploidy. The study of several morphological characters of both field‐collected and garden‐grown populations indicates that differential adaptation for aridity has been of primary importance in the evolution of section Ximenesia . The taxa occupying arid regions show a reduction of transpiring surface, reduced reproductive capacity, and reduced dispersibility.