AOBPreview originally published online on April 8, 2005
Annals of Botany 2005 95(7):1221-1227; doi:10.1093/aob/mci135
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Allozyme Variation in the Endangered Insular Endemic Castilleja grisea
Department of Biology, University of South Dakota, Vermillion, SD 57069, USA
* For correspondence. E-mail helenurm{at}usd.edu
Received: 7 February 2004 Returned for revision: 11 August 2004 Accepted: 18 February 2005 Published electronically: 8 April 2005
Background and Aims Genetic diversity in Castilleja grisea, an endangered, perennial herb endemic to San Clemente Island, California was investigated. Subsequent to the elimination of goats from the island in 1992, many populations of C. grisea have reappeared and have been increasing in size.
Methods Nineteen populations were surveyed for their genotype at 19 allozyme loci.
Key Results At the taxon level, 57·9 % of loci are polymorphic with AP = 3·09 and HE = 0·137. Populations averaged 33·0 % polymorphic loci with AP = 2·43 and HE = 0·099. Most variation is found within rather than among populations (GST = 0·128), although differentiation among populations is significant. Genetic identities range from I = 0·960 to I = 1·000 with mean I = 0·990. There is no significant relationship between genetic and geographic distance. Gene flow among populations is Nm = 2·50 based on private alleles and Nm = 1·70 based on FST. Outcrossing rates based on fixation indices average t = 1·01, indicating a primarily outcrossed mating system.
Conclusions The observed genetic variation is moderately high, unusually so for an insular endemic species, suggesting that C. grisea may not have lost substantial genetic variation during 150 years of overgrazing, and indicating that it is unlikely to be endangered by genetic factors.
Key words: Allozymes, conservation, Castilleja grisea, endangered species, endemic, genetic diversity, Scrophulariaceae, San Clemente Island