Clonal and genetic structure of two Mexican oaks: Quercus eduardii and Quercus potosina (Fagaceae)

Abstract

Quercus eduardii and Q. potosina are dominant oak species in Sierra Frı´a, Aguascalientes, Mexico. These species have been exploited for multiple purposes since the 16th century. Both species produce clonal offspring through root suckering and acorns through sexual reproduction. To understand clonality for the implementation of the most adequate actions for the conservation of these species, we addressed the following questions: (a) what is the spatial clonal structure of both species? (b) How much clonal and genetic diversity is maintained in these species? Random Amplified Polymorphic DNAs (RAPDs) were used as molecular markers for these analyses. Genets of both species have few ramets and these grow close the parent tree. Autocorrelation analyses at the ramet level showed an aggregated distribution at short distances and a random spatial distribution at larger distances. Also, at the genet level the autocorrelation analyses showed a random distribution. Clonal diversity was high in both species (Q. eduardii: D ¼ 0.963, G/N ¼ 0.60; Q. potosina: D ¼ 0.985, G/N ¼ 0.65). Genetic diversity was high within populations (Q. eduardii: H e ¼ 0.33 ± 0.11; Q. potosina: H e ¼ 0.35 ± 0.11). Low levels of genetic differentiation among populations were observed (Q. eduardii: / st ¼ 0.19, P < 0.002; Q. potosina: / st ¼ 0.13, P < 0.002). Both species maintain high levels of clonal and genetic diversity, probably due to successful sexual reproduction, which allows gene flow among populations. Conservation and/or reforestation programs must include seed collections and germplasm banks. Due to the small genet size and the high clonal diversity of these species, seeds can be collected in any place in Sierra Frı´a, Aguascalientes.

Demography and management of two clonal oaks: Quercus eduardii and Q. potosina (Fagaceae) in central México

“…Although elasticity values show that clonal propagation is more important than sexual reproduction in terms of recruitment of these species, populations of Q. eduardii and Q. potosina also regenerate by means of sexual reproduction. A genetic study carried out with populations of Q. eduardii and Q. potosina in the same plots of this study in Sierra Fría, using random polymorphic amplified DNA (RAPDs) molecular marker, showed that almost 50% of the sampled individual plants of both species had a sexual origin (Alfonso-Corrado et al, 2004). These results suggest that seedling recruitment occurs sporadically in populations of both species, when a good crop is produced followed by specific environmental conditions such as winter rains.…”

Ecological-Genetic Studies and Conservation of Endemic &lt;i&gt;Quercus sideroxyla&lt;/i&gt; (Trel.) in Central Mexico

“…The clonal regenerative capability of Q. sideroxyla allows the undisturbed preservation of genotypes, a phenomenon that was also found in Q. eduardii and Q. potosina in the study zone [5] [8]. These typical life histories could be responsible for the preservation of the genetic diversity of a species, despite the prolonged years of intensive extraction and the changes in soil use that have occurred in the Sierra Fría during the 20th century [16] [17], and could have served as a damping capability against earlier disturbances at the local scale [8] [40].…”

“…The gravity seed dispersal system of Q. sideroxyla, common in Sierra Fría oaks [8] [9], could be responsible for the formation of family groups. Family groups in oaks generally occur at short distances (less than 20 meters) from the progenitor tree [39].…”

Genetic Diversity of Two Evergreen Oaks [Quercus suber (L.) and Quercus ilex subsp. rotundifolia (Lam.)] in Portugal using AFLP Markers

“…The value of AMOVA obtained for the genetic differentiation among populations in Q. suber in Portugal (Φst = 0.036) is within the range of values reported for those species (0.044 -0.030 for oaks over a large European range, 0.021 for Flemish oaks, 0.106 to 0.342 for California red oaks). KREMER and PETIT (1993) reported values from 0.02 to 0.17 for 33 oak species using allozymes markers, HAMRICK et al (1992) found a mean value of 0.11 for 28 oak species and ALFONSO-CORRADO et al (2004) values of 0.13 and 0.19 for two Mexican oaks, using RAPD's markers.…”

“…Genetic diversity has also been assessed in Q. robur and Q. petrae using microsatellites and Amplified Fragment Length Polymorphism (AFLP) markers (COTTRELL et al, 2003;MARI-ETTE et al, 2002;COART et al, 2002), in California red oaks (DODD and KASHANI, 2003) using AFLP, and in Mexican oaks using RAPD's markers (ALFONSO-CORRADO et al, 2004). Conservation policies will depend to a large extent on our knowledge of historic and genetic relationship among these species.…”