Premium
THE SYSTEMATICS OF PHACELIA MACULATA AND P. DUBIA VAR. GEORGIANA, BOTH ENDEMIC TO GRANITE OUTCROP COMMUNITIES
Author(s) -
Murdy William H.
Publication year - 1966
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.1537-2197.1966.tb06870.x
Subject(s) - biology , outcrop , endemism , ecology , taxon , habitat , range (aeronautics) , botany , paleontology , materials science , composite material
Phacelia maculata and P. dubia var. georgiana are endemic to granite outcrop communities in the southeastern Piedmont of Alabama, Georgia, and South Carolina. Data are presented in support of the hypothesis that P. maculata is a relict species, whereas P. dubia var. georgiana is an ecotype recently derived from the Appalachian P. dubia. P. maculata is restricted to undisturbed outcrops of the central and upper Piedmont, and its center of distribution coincides with that of other well‐known, relict endemics. It lacks intraspecific variability and has a narrowly circumscribed habitat which has recently undergone contraction. P. dubia var. georgiana is absent from most of the undisturbed outcrops, but it occurs in abundance at outcrop sites of the lower Piedmont of Alabama and Georgia which have been recently disturbed. It is variable and will successfully compete with well‐established outcrop species in a variety of open habitats. Both its habitat and range are expanding with the increase of man's disturbance of the outcrop habitat, especially in the form of pasturing and cultivation. Each taxon is morphologically distinctive throughout its entire range, and population studies reveal no evidence of introgression in regions where they are sympatric. Reproductive isolation is complete and is effected by means of a postfertilization, incompatibility factor.