Abstract

MCCAULEY, Ross A.; CORTES-PALOMEC, Aurea C.  and  OYAMA, Ken. Distribution, genetic structure, and conservation status of the rare microendemic species, Guaiacum unijugum (Zygophyllaceae) in the Cape Region of Baja California, Mexico. Rev. Mex. Biodiv. [online]. 2010, vol.81, n.3, pp.745-758. ISSN 2007-8706.

Guaiacum unijugum is a rare shrub endemic to a 70 km stretch of coastline extending east from San José del Cabo in Baja California and is the least well-known of the 4 species of Guaiacum in Mexico. To increase our knowledge of this species and assess its conservation status we surveyed the extent of occurrence using both herbarium material and field work, assessed levels of genetic diversity, determined its phylogenetic relationships, and completed an evaluation of risk of extinction (MER). Herbarium material identified 5 known localities of occurrence with field work verifying the continued persistence of 4 of these with an additional site discovered. Genetic analysis across the small range using 17 microsatellite loci showed very low levels of genetic diversity with a mean expected heterozygosity (H_E) of 0.162 over all polymorphic loci. Most loci were found to be monomorphic and genetic divergence was small, maintained by the presence of rare private alleles in widely-separated populations. Phylogenetic analysis indicated a sister group relationship to G. coulteri along the Pacific coast suggesting vicariance for the origin and occurrence of G. unijugum. The unique evolutionary history coupled with current small population sizes warrants increased conservation via listing as a critically endangered species.

Keywords : Baja California Sur; conservation genetics; endemic species; Guaiacum unijugum; MER; Mexico; Zygophyllaceae.