Abstract Detail



Population Genetics/Genomics

Zumwalde, Bethany [1], McCauley, Ross [2], Fullinwider, Ian [2], Hoban, Sean [1].

Genetic and morphometric analysis of shinnery oak (Quercus havardii), an arid adapted species with a disjunct distribution.

Quercus havardii is a shrubby oak native to the western USA.  It is currently listed as Endangered on the IUCN Red List due to decreasing population size projections and loss of habitat. It occurs in highly arid environments, where its extensive root systems play a vital role in stabilizing deep, loose sand. It is a keystone species that defines the sand shinnery ecosystem and provides habitat to vulnerable species such as the lesser prairie chicken and dunes sagebrush lizard.  Little is known about Q. havardii’s evolutionary dynamics or life history.  The species exists in two separate regions: from western Oklahoma through west Texas and eastern New Mexico (East region), and in the Navajo Basin in northeastern Arizona and southeastern Utah (West region).  Few if any populations occur in the broad disjunction in central New Mexico. In both regions, populations are fragmented, as the species is naturally restricted to sandy habitats and due to high agriculture and gas drilling activities in the Permian Basin.  In addition, the species is known to propagate clonally, but the size and number of clones in a population is difficult to distinguish visually as stems may be connected underground. We used 21 directly measured and 5 composite morphological variables on leaves and 13 microsatellite DNA markers taken from 631 plants across 36 locations to investigate range-wide phenotypic and biogeographic structure of the species. Morphological and genetic evidence both showed clear differentiation between eastern and western regions using principal component analyses and population assignment tests.  After removing clones, we tested population differentiation between the two regions and among populations within each region and found highest pairwise population FST between regions (mean FST=0.12) and higher FST among western than eastern populations (FSTeast=0.029, FSTwest=0.048). Expected heterozygosity was lower than in most oaks (within populations minimum 0.43, maximum 0.79, mean 0.67) which are wind pollinated and usually highly outcrossing. Lastly, morphological data suggests possible hybridization with local Quercus turbinella.  The observed differentiation between east and west supports the hypothesis that these regions are now differentiated after having once been a continuous distribution. The relatively low heterozygosity may be a result of inbreeding due to relatively small population sizes in an extreme environment.  Additional hypotheses regarding evolutionary history and conservation status will be further discussed.


Related Links:
Range-wide population structure of Quercus havardii, a Western sand dune oak


1 - The Morton Arboretum, Center for Tree Science, 4100 Illinois 53, Lisle, IL, 60532, USA
2 - Fort Lewis College, Department Of Biology, 1000 Rim Drive, Durango, CO, 81301, United States

Keywords:
Quercus
population genetics
Morphometrics
clonality.

Presentation Type: Oral Paper
Number:
Abstract ID:471
Candidate for Awards:Margaret Menzel Award


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