Systematics and biogeography of Guaiacum and allied genera of Larreoideae (Zygophyllaceae).

摘要

Guaiacum (Zygophyllaceae) is a genus of neotropical hardwood trees and shrubs, many of which are considered endangered in their natural habitats. A multi-gene phylogenetic analysis of multiple accessions of Guaiacum spp. was conducted to resolve infrageneric evolutionary relationships and attempt to delimit species boundaries. Statistical parsimony networks were implemented to resolve relationships within and among closely related species that lacked resolution in maximum parsimony analyses.;Differences in genetic signatures (haplotypes) of chloroplast markers among populations of Guaiacum sanctum L. were characterized and interpreted as evidence of an ancient genetic divergence within this species. A mixed haplotype composition of the G. sanctum population on Lignumvitae Key, Florida is best interpreted as the result of dual colonization and mixing of haplotypes subsequent to genetic divergence and consistent with the geologic history of the region.;Putative taxonomic positions within Guaiacum were resolved, and a novel genetic intermediate was characterized in accessions collected from Chiapas, Mexico. Chiapas accessions possess a chloroplast haplotype that is intermediate between haplotypes found in accessions of G. sanctum and G. coulteri, which corresponds with the geographic position between the ranges of G. sanctum and G. coulteri. The phylogenetic reconstruction of Guaiacum spp. also resolved the proper taxonomic status of G. palmeri, and G. unijugum.;Phylogenetic analysis was also conducted to resolve relationships among Guaiacum and its allied genera in Larreoideae (i.e., Porlieria, Bulnesia, Larrea, Pintoa). This study utilized multiple genetic markers and a broader sampling of taxa than previous studies of this group. Incongruent tree topologies between chloroplast and nuclear markers were identified, and interpreted as indicators of ancient hybridization events among Larreoid taxa.;A paraphyletic relationship among species of Bulnesia was also characterized, which supports a taxonomic revision raising the subgeneric divisions within Bulnesia to full genus status.