The African Paleotropical floristic ……….Hassan The African Paleotropical floristic categories links to the Flora of highland plains in Yemen

About 222 plant species (two Ferns, one Gymnosperm, 219 Angiosperms: 169 Dicotyledons and 50 Monocotyledons) from the total 249 species were recorded from the Highland plains in Yemen, showing a distribution relationship with three African paleotropical floristic regions and 10 African paleotropical floristic elements. The distribution relationship among the African paleotropical floristic elements was subjected to numerical analysis: the African paleotropical floristic region with the highest number of species is Sudano-Zambezian, with 207 (83.1 %) species; while the African paleotropical floristic element, with the highest number of species, is the Afro-Montane Archipelago-Like Regional Centre of Endemism, with 184 (73.9 %) species.


Introduction
Based on the physiography of Yemen; eight main vegetation land scope units have been identified: Coastal plains, Low altitude mountains, Medium altitude mountains, High altitude mountains, Highland plains, Eastern and northern east mountains, Eastern desert and Soqotra Archipelago (2) ; seven of them (Coastal plains, Low altitude mountains, Medium altitude mountains, High altitude mountains, Highland plains, Eastern and northern east mountains, Eastern desert) are represented in the western part of Yemen (2&34) ; while the large part of the eastern side of Yemen is represented by the Eastern desert (2) . However, Highland plains of Yemen consist of a series of intermountain plains (45) most of them located in the Eastern and Northern east mountains (34) . Moreover, Highland plains are divided into two elements according to elevation; High altitude plains located over 1800m asl and low altitude plains located lower than 1800m asl (2) .
In this respect White (44) illustrated seven ecological regions in north and center Africa; while Zohary (49) classified Africa as a part of the Paleotropic kingdom except its northern part (Mediterranean region) that was classified as a part of the Holarctic Kingdom. In addition, he placed Yemen within the Eriterio-Arabian province which is a meeting point between the Sudanese region and Saharo-Arabian region.
Furthermore, White (45) renewed the classical phytogeographical definitions such as Kingdom, Regions, Provinces, Sections, Districts, etc. by establishing a new system based on the richness of endemic flora in such a region, thus he classified Africa into 18 Phytogeographical regions, including nine regional centres of endemism parted by six regional transitional zones and three regional mosacics. Following White's system (44) , a chorological map covering southwest of Asia and a part of Africa has been obtained by Leonard (29&30) .
Based on the previous studies, a phytogeographical map of Africa and southwest of Asia was modified by White & Leonard (45) where they classified the African Paleotropical Kingdom into 10 phytogeographical elements; namely: Sahara Regional Subzone (SS1); Sudanian Regional Centre of Endemism (S), Sahel Regional Transition Zone (Sa), Somalia-Masai Regional Centre of Endemism (SM), Afro -Montane Archipelago-Like Regional Centre of Endemism (Af), Zambezi Regional Centre of Endemism (Z) & Zanzibar-Inhambane Regional Mosaic (ZI); Guineo-Congolian Centre of Endemism (GC) Guinea-Congolian / Sudania Regional Transition Zone (GCS), and finally, Guinea-Congolian / Zambezia Regional Transition Zone (GCZ). Furthermore, they suggested that Yemen is a meeting point of two regional centres of endemism (Somalia-Masai Regional Centre of Endemism (SM) and Afro -Montane Archipelago-Like Regional Centre of Endemism) and one regional subzone (Arabian Region subzone).
Recently, Al Khulaidi (2) revealed that the flora of Yemen is a combination of Tropical African Sudanese plant region (west mountains and part of highland plains of Yemen) and Saharo-Arabian plant region (coastal plains, eastern mountains, eastern and northern east desert plains). He also mentioned that the Tropical African Sudanian plant region is highly presented in the flora of Yemen. On the other hand, about 249 plant species (three Ferns, one Gymnosperm, 56 Monocotyledoneae and 189 Dicotyledoneae) were recorded from the Highland plains in Yemen (1; 2; 3; 4 &47) . The present study seeks to investigate the links between the African paleotropical floristic elements and the flora of highlands in Yemen.
Moreover, the distribution of 222 plant species, among the African paleotropical floristic elements, was subjected to numerical analysis (UPGMA method) to investigate the links between the 10 African paleotropical floristic elements.

Felicia dentata (A. Rich.) Dandy
Group I includes the Saharo-Sindian Region element (Saharan Regional Subzone) and 4 elements of the Sudano-Zambezian Region (Sahel Regional Transition Zone, Sudanese Regional. Centre of Endemism, Somalia-Masai Regional Centre of Endemism & Afro-Montane Archipelago-Like Regional Centre of Endemism) which are located north and north east of the Equator; while Group II includes the two remaining elements of the Sudano-Zambezian Region (Zambezi Regional Centre of Endemism & Zanzibar-Inhambane Regional Mosaic) which are located south of the Equator and all the elements of the Guinean Region (Guineo-Congolian Centre of Endemism, Guinea-Congolian / Sudania Regional Transition Zone & Guinea-Congolian / Zambezia Regional Transition Zone). Furthermore, Group I & Group II are divided in two *For abbreviations see Table 1. subgroups; A&B at relative similarity level of 76.59% and C&D at relative similarity level of 76.61% respectively.
Subgroup A includes the Saharo-Sindian Region element (Saharan Regional Subzone); while Subgroup B includes two clusters (1&2) at relative similarity level of 83.63%, cluster1 includes Somalia-Masai Regional Centre of Endemism & Afro-Montane Archipelago-Like Regional Centre of Endemism at relative similarity level of 90.25%, while cluster 2 includes Sahel Regional Transition Zone, Sudanese Regional Centre of Endemism at relative similarity level of 90%. Moreover, subgroup C includes Zambezi Regional Centre of Endemism & Zanzibar-Inhambane Regional Mosaic at relative similarity level of 90.41%. On the other hand, subgroup D includes two clusters (3&4) at relative similarity level of 83.39%; cluster 3 includes the Guinea-Congolian / Sudania Regional Transition Zone; while cluster 4 includes Guineo-Congolian Centre of Endemism & Guinea-Congolian / Zambezia Regional Transition Zone at relative similarity level of 90.45% (Fig. 2).

Discussion
According to the previous phytogegraphical analysis, 207 (83.1%) species from the flora of Yemen highland plains of show more distribution relationships with the Sudano-Zambezian Region then other two African paleotropical floristic regions although about 184 (73.9 %) plant species show more distribution relationships with Afro-Montane Archipelago-Like Regional Centre of Endemism more than the other nine African paleotropical floristic elements. Then, the flora of highland plains of Yemen is more like Afro-Montane Archipelago-Like Regional Centre of Endemism than Somalia-Masai Regional Centre of Endemism and Saharo-Sindian Region which boarded the mountains of Yemen (including of highland plains of Yemen) from the south and the east respectively. This corresponds to the findings of White and Leonard (46) , which placed the southwestern mountains of the Arabian Peninsula (including mountains & highland plains of Yemen) within the Afro-Montane Archipelago-Like Regional Centre of Endemism.  Table 1.