McCauley, Ross A. , Cortés-Palomec, Aurea C. , Oyama, Ken .
A range-wide population genetic study of Guaiacum coulteri (Zygophyllaceae), a threatened tree endemic to the Pacific coast of Mexico.
Guaiacum coulteri is a shrub to small tree endemic to the seasonally dry forests of the Pacific Coast of Mexico ranging from Sonora to Oaxaca. Overexploitation for timber in conjunction with habitat loss and a slow rate of regeneration has left G. coulteri threatened and led to its listing on the IUCN Red List of Threatened Species and protection under CITES. Using microsatellite markers we surveyed the genetic structure and levels of genetic diversity among 40 populations throughout the species range to asses a series of questions important for conservation. In various portions of its range greater levels of extraction and habitat loss have led to large reductions in population sizes and/or the persistence of only young individuals due to the removal of marketable size trees. It is not known however if these reductions in population size or changes in demographic structure have affected the levels of genetic diversity within particular regions, which if identified could be highlighted as areas of special conservation concern. Additionally, morphological variation within two portions of the range has complicated clear species recognition. Variation in floral structure extending from portions of central Sinaloa to the northern limit of the species distribution in Sonora have led to the occasional recognition of the variety G. coulteri var. palmeri, however it has been unclear if this represents a unique genetic distinction. Further variation in vegetative form centered within the region of Huatulco in Oaxaca has suggested the sympatric occurrence of G. coulteri with G. sanctum, a species with a distribution further south and east into the Yucatan Peninsula. Preliminary analysis has indicated that the variation in form may be due to a variation in cytotype within this suspected polyploid complex, however further genetic evidence is needed to verify the affinity of these divergent forms.
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1 - Fort Lewis College, Department of Biology, 1000 Rim Dr., Durango, Colorado, 81301, USA
2 - Universidad Nacional Autónoma de México, Centro de Investigaciones en Ecosistemas, Antigua Carretera a Pátzcuaro No. 8701, Col. Ex-Hacienda de San José de la Huerta, Morelia, Michoacán, 58190, México
Presentation Type: Oral Paper:Papers for Topics
Location: Cottonwood D/Snowbird Center
Date: Tuesday, July 28th, 2009
Time: 11:00 AM