Phylogenetic Analysis of Quercus Series Virentes

Quercus series Virentes (live oaks) are many independent populations of semi-evergreen native trees common from the southeastern United States to Texas, California, and Mexico.  The picturesque, wide-spreading canopy of Quercus virginiana (southern live oak) and Quercus fusiformis (Texas live oak) are highly valued for urban landscapes.  In Texas, morphological similarities between the standards for Q. fusiformis and Q. virginiana have complicated the classification of individual populations. Taxonomy is further complicated by populations that are not reproductively isolated but are derived from interspecific hybridization throughout much of Texas. The identification of relic individuals in this hybrid swarm is important to preserve the Texas Q. fusiformis and Q. virginiana species.  A putative relic individual has been located in the northern most adaptive range of the Quercus series Virentes (located just south of Justiceberg, TX).  This old oak has morphological attributes of Q. virginiana in appearance, yet thrives in an environment much farther north and west than previously documented species of Q. fusiformis or Q. virginiana, and in an environment known for drought, high pH soils, and cold seasonal temperatures.  To examine the heredity relationship of this individual with the Texas live oak population a phylogenetic analysis of forty-eight Quercus accessions was conducted.  Quercus accessions were sampled from locations predominantly recognized as Q. virginiana, Q. fusiformis, or a hybrid swarm of both species.  Several other Quercus species, including a group of deciduous hardwoods, which consisted of white oaks (Lepidobalanus) including bur (Q. macrocarpa), chinquapin (Q. muhlenbergii), gambel (Q. gambelii), shinnery (Q. havardii), Post (Q. stellata), and Monterey (Q. polymorpha) and a group of red oaks (Erythrobalanus) including red (Q. rubra), scarlet (Q. coccinea), and Shumard (Q. shumardii), served as outgroups.  Genetic analysis using 12 expressed sequence tags (ESTs) suggests geography may be relevant to population trends.  Four genetic clusters represent populations in different terrestrial regions of Texas. The specimen located in the Justiceberg, TX, population and a second individual located in Elmendorf, TX, appear to be relictual populations of Quercus series Virentes. The physical age, traits, and genetic analysis indicated both specimens predate other Texas Virentes populations.