Allozyme variation in the endangered insular endemic Castilleja grisea.
OBJECTIVE
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.


RESULTS
At the taxon level, 57.9 % of loci are polymorphic with A(P) = 3.09 and H(E) = 0.137. Populations averaged 33.0 % polymorphic loci with A(P) = 2.43 and H(E) = 0.099. Most variation is found within rather than among populations (G(ST) = 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 F(ST). Outcrossing rates based on fixation indices average t = 1.01, indicating a primarily out-crossed 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.
Helenurm
Kaius
K
Department of Biology, University of South Dakota, Vermillion, SD 57069, USA. helenurm@usd.edu
West
Rachel
R
Burckhalter
Steven J
SJ
D027901:Acanthaceae / Q000201:enzymology* / Q000235:genetics*; D002140:California; D016000:Cluster Analysis; D003710:Demography; D014644:Genetic Variation; D007527:Isoenzymes / Q000235:genetics; D010802:Phylogeny
D007527:Isoenzymes