Evidence of Relic Genotypes Persisting in the Texas Hybrid Swarm of Quercus Series Virentes

Abstract

Quercus series Virentes (live oaks) are many independent populations of semi-evergreen trees common from the southeastern United States to Texas, California, and Mexico. Southern live oak (Q. virginiana Mill.) and Texas live oak (Q. fusiformis Small) are species valued in native, and urban landscapes. In Texas, morphological similarities between the standards for these species have complicated classification of individual populations. Classification is further confounded by populations which interact reproductively. Hybrid progeny create opportunity for phenotypic and genotypic diverse Virentes series populations. A putative population of Quercus series Virentes located near Lake Alan Henry, TX was identified. This population is highlighted by a relic individual which appears to be the progenitor of the population. The phylogeny of this specimen was analyzed, and compared to other Texas native oak species. Native Quercus accessions were sampled from known locations of Q. fusiformis, the hybrid swarm of Q. virginiana and Q. fusiformis, and other Quercus species. Genetic diversity analysis was conducted using 70 expressed sequence tags. Four genetic clusters were found which represent populations in different terrestrial regions of Texas. Results indicate the Lake Alan Henry, TX specimen, and a second individual located in Elmendorf, TX are relictual trees of Quercus series Virentes populations.