Tests of hybrid origin of two Californian larkspurs (Delphinium, Ranunculaceae)

Hybridization's role in evolution has been debated for decades. However, additional examples of putative hybrid origin must be evaluated to clarify the role of hybridization in species formation. This work tests the putative hybrid origins of Delphinium gypsophilum from D. recurvatum and D. hesperium and D. luteum , an endangered species, from D. decorum and D. nudicaule. These hypotheses of hybrid origin were tested using population-level and phylogenetic analyses. Patterns of allozyme, RAPD, and AFLP markers in these species, their putative parents, and other close relatives were compared, with the expectation that species of hybrid origin will combine the genetic markers of their parents. Furthermore, because a hybrid species should appear in a clade with one or both of its parents, phylogenetic analysis of the putative hybrids and parents plus other species were also used to test the putative hybrid origins. The phylogeny of Delphinium section Diedropetala, which contains D. gypsophilum, D. luteum, and their putative parents, was reconstructed using sequences of the Internal Transcribed Spacer (ITS) regions of nuclear ribosomal DNA and the chloroplast spacer region trnL-trnF. Because D. gypsophilum exists as diploid and tetraploid populations, the ploidy of several populations was assessed and mapped, and a crossing experiment was designed to determine the inheritance of allozyme markers.; The population-level data indicate that neither D. luteum nor D. gypsophilum is of hybrid origin. The phylogenetic analyses indicate that D. luteum is closely related to both D. nudicaule and D. decorum, and that D. gypsophilum is closely related to D. recurvatum. Ploidy in D. gypsophilum is not geographically structured, and the inheritance of the allozyme markers are more consistent with tetrasomic models.; Genetic data indicate that both cultivated populations of D. luteum represent sources of diversity that could be used to establish new populations of D. luteum or enhance the diversity and size of the wild population.