The Systematic Classification And Floristic Geography Of Ericaceae In Gansu Province

The systematic classification and floristic geography of Ericaceae in Gansu Province were studied in this thesis. The all species of the family Ericaceae were tried to recognize in Gansu province based on herbarium examinations of more than two thousands specimens from five herbaria(abbreviated as PE, WUK, LZU, NWTC, GAUF), literatures and additional filed work, they had also contributed to reveal the main morphological characters and their evolution studies. UPGMA(Unweighted Pair Group Mathematics Average) clustering analysis was applied to discuss the relationship among the taxa of Rhododendron. Based on the materials of systematic classification and geographic distribution, the modern geographic distribution patterns(distribution types) of all species and genera in this region were classified and taken into statistical analysis. And used similarity coefficient analysis to compare with adjacent regions to display the geographical distribution features, floristic elements, the relationship of floristic similarity and the floristic origin of the family Ericaceae in Gansu. The results were summarized as follows:1. 8 genera and 47 species (include 47 species, 4 subspecies and 3 varieties) of the family Ericaceae were recognized in Gansu province; Morphological description, localities, habitats and specimens cite were given in detail and systematic key to the genera and species had been made.2. One was described as a new species, viz. Cassiope zhouquense X. G. Sun et Y. J. Zhang(data unpublished), This species was different from C. selaginoides Hook. f. et Thoms. in membranous margin of leaf and had obvious difference in longer pedicel with C. abbreviata Hand.-Mazz. and C. fastigiata (Wall.) D. Don.3. Cassiope D. Don and Gaultheria Kalm ex Linn. were recognized as tow newly recorded genus in Gansu; the genus Cassiope D. Don, as the arctic & alpine distribution pattern genera, was a instruction group for analysis the possible migration route to south of the flora for the icy weather; and Gaultheria Kalm ex Linn. as one of the distribution pattern genera to the Trop. Asia & Trop. Amer. adjuncted, had contributed to reveal the relation of the flora of lower reaches of the Bailong River, the Baishui River and the Southern Qin Mountains to the tropical flora and the floristic similarity of this area to the Hengduan Mountains Region.And Rhododendron triflorum Hook. f., R. asterochnoum Diels, Enkianthus deflexus (Griff.) Schneid., Gaultheria cuneata (Rehd. et Wils.) Bean, Vaecinium bracteatum Thunb., R. faberi Hemsl. subsp. prattii (Franch.) Chamb ex Cullen et Chamb., R. przewalskii Maxim. subsp. huzhueuse Fang et S. X. Wang, R. priewalskii Maxim. subsp. yushuense Fang et S. X. Wang and Lyonia ovalifolia (Wall.) Drude var. lanceolata (Wall.) Hand.-Mazz. were recognized as new records in geographical distribution from Gansu Province.4. Rhododendron rockii Wils., R. hunnewellianum Rehd. et Wils. subsp. rockii (Will.) Chamb. ex Cullen et Chamb. and R. rufum Batal. var. glaudlulosum G. H. Wang were reduced to the synonymies.5. The results of cluster analysis indicated that the the systematic positions of subgenera were completely correspond to the classical taxonomy, but they were not supported the classification of sections; however, they could be classified into 10 cluster groups at subsection level and the results were consistent with that of the traditional taxonomy. The cluster tree showed: R. invictum Baff. f. et Farrer was closely related with Subsect. Triflora (Hutch.) Sleumer, and it should belong to this section; R. labolengense Ching et H. P. Yang and R. xiguense Ching et H. P. Yang were maybe the same species which had some morphological variation in Subsect. Lapponica (Balf. f.) Sleumer; the R. oreodoxa Franch. shuold be separated from Subsect Fortunea sleumer as a independent group; R. gannanense Z. C. Feng et X. G. Sun belonging to Subsect. Taliensia Sleumer was more reasonably.6. According to different areal division, The geographic distribution ranges of the family in Gansu were divided into 7 regions: among the mountains area in the Middle-upper reaches of Bailong River and the mountains area in southern Qinling were seemed to be the centre of the distribution density and the species diversity of Ericaceae in Gansu province.7. It was abundance in species and diversity in forms of the family Ericaceae in Gansu; the China only and Gansu only species were obvious; and the temperate distribution elements of the flora of Ericaceae in Gansu were absolutely dominant.8. They were higher floristic similarity of genera and species between Gansu and Shanxi, Sichuan, Yunnan as well as Tibet, but the similarity coefficient between Qinhai, Xinjiang, InnerMongolia as well as Ninxia was lower; all of above indicated that the Southwest of China was the distribution center of Ericaceae, the more far form this center the more poor in species of the family Ericaceae.9. Lastly, it can be regarded that the southwest of China was quite possible the location of its origin. The principal reasons of the floristic development and their areal division of the family in Gansu may be summed up in the migration and differentiation of the species. They were also assumed that Hengduan Mountains-Northwest of Sichuan-Southeast of Gansu was the mainly migratory way for the family to the North.