The Texas sleepy daisy
Xanthisma texanum DC. includes herbaceous annuals native to the prairies of Texas, Oklahoma and a small area of eastern New Mexico. It is the only species in Xanthisma sect. Xanthisma.
The species includes two subspecies (ssp. drummondii and ssp. texanum with two varieties; var. orientalis and var. texanum confined to southern Texas). The plants are usually less than 0.5 m tall but a "giant" plant was found in 1972.
J.C. Semple, 1972, Texas
The species has been offered in the past in seed catalogues and collections of escaped cultivated plants have been made from areas greatly out of the range of distribution (e.g., Northern California and North Africa).
The species is notable for its accessory B chromosome first discovered and investigated by Witkus and co-workers in the 1950's and 1960's. More recent studies done by John C. Semple are listed below.
Plants usually have 4 pairs of chromosomes (2n=8) but some have 1 to several extra chromosomes whose inheritance, morphology, meiotic behaviour and distribution in wild populations at the regional and local level were investigated in a series of studies conducted over 20 years by JCS.
A fourteen year long study of variation in the frequency of plants with and without B chromosomes was conducted in southwestern Oklahoma in and around Quartz Mt. State Park. More than a thousand individuals were sampled. The conclusion of all the research was that these extra chromosomes were "endo-parasitic" containing genes for their own propagation but otherwise being of little or no value to the the "host" plant. The B chromosomes may be the remnants of the ancestral fifth pair of chromosomes.
Publications by J.C. Semple on Xanthisma
SEMPLE, J.C. 1972. The behavior of B-chromosomes in Xanthisma texanum DC.: a non-random phenomenon. Science 175: 666.
SEMPLE, J.C. 1972. The cytology, flavonoid chemistry and systematics of the Texas Sleepy Daisy Xanthisma texanum DC. (Asteraceae). Ph.D. Doctoral Dissertation, Washington University - St. Louis.
SEMPLE, J.C. 1973. Chiasma formation in the sub-metacentric B-chromosome of Xanthisma texanum DC. Canad. J. Genet. Cytol. 15: 871-873.
SEMPLE, J.C. 1974a. The phytogeography and systematics of Xanthisma texanum DC. (Asteraceae): proper usage of infraspecific categories. Rhodora 76: 1-19.
SEMPLE, J.C. 1974b. The geographical distribution of B-chromosomes of Xanthisma texanum DC. (Asteraceae). I. Survey of the range. Amer. J.Bot. 61:995-1001.
SEMPLE, J.C., and J.E. AVERRETT. 1975. Flavonoid variation in Xanthisma texanum: infrapopulation and interpopulation variation. Biochem. Syst. Ecol. 3: 11-14.
SEMPLE, J.C. 1976. The cytogenetics of Xanthisma texanum DC. (Asteraceae) and its B-chromosomes. Amer. J. Bot. 63: 388-398.
SEMPLE, J.C. 1989. Geographical distribution of B chromosomes of Xanthisma texanum (Compositae: Astereae). II. Local variation within and between populations and frequency variations through time. Amer. J. Bot. 76: 769-776.
SEMPLE, J.C., and J.G. CHMIELEWSKI. 1989. Studies on the effects, or lack thereof, of B chromosomes on the morphology and pollen viability in wild and cultivated plants of Xanthisma texanum (Compositae: Astereae). Canad. J. Bot. 67: 1157-1160.
Last updated 14 November 2013 by J.C. Semple
© 2013 J.C. Semple, including all photographs unless otherwise indicated