02716nas a2200145   4500008004100000245011000041210006900151260000900220300001200229490000800241520224700249100001502496700001602511856004302527       2003                        eng d00aMolecular differentiation and diversity among the California red oaks (Fagaceae; Quercus section Lobatae)0 aMolecular differentiation and diversity among the California red  c2003  a884-8920 v1073 aA recent epidemic of Phytopthora (Sudden Oak Death) in coastal woodlands ofCalifornia is causing severe mortality in some oak species belonging to the red oak (Lobatae) group. To predict the risks of spread of this disease, an understanding of the relationships among California’s red oak species and of their population genetic structure is needed. We focus here on relationships among the four species of red oak. Whereas morphological distinction of Quercus wislizeni and Quercus parvula can pose problems, Quercus kelloggii and Quercus agrifolia in pure forms are easily distinguishable from one another and from Q. wislizeni and Q. parvula in the field. However, hybrids among all species combinations are known to occur in nature and these can confound data from ecological studies. Our results revealed greatest differentiation of the deciduous Q. kelloggii, with only weak AFLP fragment differentiation of the three remaining evergreen species. The molecular data suggest a closer affinity of Q. agrifolia with Q. wislizeni and Q. parvula contrary to earlier suggestions that its origins are likely to have been with northern deciduous oaks probably through a common ancestor with Q. kelloggii. Interior and coastal populations of Q. wislizeni separated in dendrograms based on phenetic and genetic distances suggesting probable isolation in different glacial refugia. The position of Q. parvula remains ambiguous, having a closer affinity with interior populations of Q. wislizeni and with Q. agrifolia, than with coastal populations of Q. wislizeni. Mean population differentiation in Q. wislizeni was 0.18, which is somewhat higher than the average for other oak species, suggesting that range fragmentation has occurred in the past, resulting in a metapopulation structure. Our results provide evidence that introgression among these species may be causing reticulation, further confounding species separation. Whereas Phytopthora has been reported on Q. agrifolia, Q. parvula and Q. kelloggii, it has not yet been detected in natural populations of Q. wislizeni. The species relationships that our molecular data show suggest that this is more likely a result of escape due to ecological tolerances than to genetic differences.1 aDodd, R.S.1 aKashani, N.  uhttps://quercus.myspecies.info/node/4402293nas a2200133   4500008004100000245014100041210006900182260000900251300001200260520181300272100001602085700001502101856004302116       2002                        eng d00aGenetic differentiation of two california red oak species, Quercus parvula var. shreveii and Q. wislizeni, based on AFLP genetic markers0 aGenetic differentiation of two california red oak species Quercu  c2002  a417-4263 aOaks are renowned for posing problems in defining species boundaries. One example is the case of the interior live oak complex that is usually taken to include two varieties of Quercus wislizeni from the Coast Ranges of California and the Sierra Nevada, and Q. parvula var. shreveii from the central coast of California. The latter taxon was separated from Q. wislizeni, and was recognized in The Jepson Manual, but still is not fully accepted, since its morphological separation is ambiguous. In an attempt to test differentiation of these two taxa, molecular genetic analysis was carried out using Amplified Fragment Length Polymorphism (AFLP) markers. A total of 202 individuals from 19 populations including Q. parvula var. shreveii, Quercus wislizeni, Q. kelloggii and Q. agrifolia were analyzed. Four primer sets generated 311 polymorphic band classes. Although species-specific markers were observed between Q. kelloggii and other members of the red oak group in California, fixed genetic differences were not apparent among Q. agrifolia, Q. parvula var. shreveii and Q. wislizeni. Cluster analysis and principal coordinate analysis revealed low levels of genetic differentiation among coast live oak, interior live oak and shreve oak. Cluster analysis also suggested that Q. agrifolia populations are more similar to populations of Q. parvula var. shreveii than to coastal populations of Q. wislizeni. This may reflect the relatively short time since divergence of these species. On the other hand, repetitive hybridization and introgression may have acted as a homogenizing factor for these genetic markers. The relatively high genetic similarity between Q. agrifolia and Q. parvula var. shreveii may have implications for the management of Sudden Oak Death in the limited range of the latter taxon.1 aKashani, N.1 aDodd, R.S.  uhttps://quercus.myspecies.info/node/50