title: Genetic variation and population structure of the mixed-mating cactus, Melocactus curvispinus (Cactaceae).
abstract: Genetic diversity was measured in the mixed-mating cactus, Melocactus curvispinus, in Venezuela. Allozyme diversity was surveyed in 19 putative loci over 18 populations. Compared to other plant taxa, this cactus is rich in polymorphic loci (Ps=89.5%), with high numbers of alleles per polymorphic locus (APs=3.82), but moderate levels of heterozygosity (Hes=0.145). Substantial levels of inbreeding were detected across loci and populations at macrogeographic (FIS=0.348) and regional levels (FIS=0.194-0.402). Moderate levels of genetic differentiation among populations were detected at macrogeographical (FST=0.193) and regional (FST=0.084-0.187) scales, suggesting that gene flow is relatively restricted, but increases within regions without topographic barriers. The population genetic structure observed for this cactus was attributed to, at least, three factors: short-distance pollination and seed dispersal, the mixed-mating condition of the species, and genetic drift. High genetic identities between populations (I=0.942) supported the conspecific nature of all populations surveyed. The levels and patterns of genetic structure observed for M. curvispinus were consistent with its mating system and gene dispersal mechanisms.
authors.affiliation: University of Miami, Biology Department, PO Box 249118, Coral Gables, FL 33124, USA. jnassar@oikos.ivic.ve
authors.forename: J M
authors.initials: JM
authors.lastname: Nassar
authors.forename: J L
authors.initials: JL
authors.lastname: Hamrick
authors.forename: T H
authors.initials: TH
authors.lastname: Fleming
mesh_terms: D029421:Cactaceae / Q000201:enzymology / Q000235:genetics*; D005787:Gene Frequency; D014644:Genetic Variation; D007527:Isoenzymes / Q000235:genetics; D010802:Phylogeny; D014687:Venezuela
chemical_list: D007527:Isoenzymes