Mating system of pachycereus pringlei: An autotetraploid cactus

Abstract

The mating system of the Mexican subdioecious columnar cactus, Pachycereus pringlei (Cardon), was examined by allozyme analysis. Tetrasomic patterns of inheritance were found for all polymorphic loci, indicating that the species is an autotetraploid. A model is presented that expands Ritland’s (1990a) mixed mating model for autotetraploids to incorporate an arbitrary number of alleles per locus. This model is applied to the progeny arrays of several female and hermaphroditic individuals of P. pringlei. P. pringlei exhibited a complex breeding system; the multilocus estimate of outcrossing, tm, for female cacti was 0.949 and for hermaphrodites was 0.301. These results are discussed in the context of inbreeding depression and the evolution of the breeding system of this species. © 1994 The Genetical Society of Great Britain.