tailieunhanh - Báo cáo khoa học: "hybridization within the genus Quercus"

Tuyển tập các báo cáo nghiên cứu về lâm nghiệp được đăng trên tạp chí lâm nghiệp quốc tế đề tài: hybridization within the genus Quercus. | 73s Ann Sci For 1993 50 Suppl 1 73S-90S Elsevier INRA Review article Natural hybridization within the genus Quercus L BS Rushton Department of Biological and Biomedical Sciences University of Ulster Coleraine Northern Ireland BT52 ISA UK Summary Hybridization within the genus Quercus L appears to be extensive and reports vary from sightings of individual hybrid trees to small numbers of individual hybrid trees within populations to populations with characteristics of small-scale eg Q robur and Q petraea in Hurepoix France and large-scale introgression eg Q robur and Q petraea in Scotland and in some cases the occurrence of hybrid swarms eg Q douglasii and o turbinella subsp californica in California . This has persuaded some authorities to question the current formal species concept in the genus and to suggest alternatives. The evidence supporting these cases of hybridization is examined in detail. The majority of the reports of hybrids between species of Quercus are based on an analysis of morphological data alone using a variety of univariate bivariate and more effectively multivariate statistics while other forms of evidence such as estimates of fertility in the putative hybrids resynthesis of hybrids habitat characteristics of the putative hybrids and F2 segregation of parental types have only been used occasionally. Data from chemotaxonomic investigations of suspected Quercus hybrids mainly isozymes and phenolic components in some instances support the morphological evidence but in other instances are contradictory chemical data are also shown to be variable and possibly related to environmental variation which will limit their usefulness. It is concluded that before any radical revision of the genus is attempted in which the specific limits are redefined a wider application of the possible techniques for the study of hybrids be applied in order to clarify the true extent of gene flow between Quercus species. natural hybridization introgression chemotaxonomy I