STUDIES ON THE FLORA OF YEMEN: 2-FLORA OF TOOR AL-BAHA DISTRICT, LAHEJ GOVERNORATE, YEMEN دراسات على فلورة اليمن : 2 - محافظة لحج- اليمن

STUDIES ON THE FLORA OF YEMEN:

2-FLORA OF TOOR AL-BAHA DISTRICT, LAHEJ
GOVERNORATE, YEMEN

Abdo, M. A. Dahmash^*; Othman S. S. Hamood^**
and Salah, M. I. El-Naggar^***

*Biology Department, Faculty of science, Sana^, a Uuiversity, Yemen

**Biology Department, Faculty of Education, Aden Uuiversity, Yemen

***Botany Department , Faculty of science, Assiut Uuiversity, Egypt

INTRODUCTION:

The Republic of Yemen lies in the southwestern corner of the Arabian Peninsula. It extends between latitudes 12° 40` to 19° 00` N. and longitudes 42° 30` to 53° 05` E. It is bordered by Kingdom of Saudi Arabia in the north, the Arabian Sea and the Gulf of Aden in the south, Sultanate of Oman in the east, and the Red Sea in the west (Fig. 1). Yemen contains one of the most diverse floras of the Arabian Peninsula region (Wood, 1997 and Al-Dubai, 1998). The flora of this country is characterized by its high diversity and density, particularly in the South and West regions, that makes it a complex one. This flora having affinities with the floras of the Tropical African, Sudanese region, the Saharo-Arabian region, the Mediterranean countries and the Irano-Turanian region (Zohary, 1973; Al-Hubaishi & Muller-Hohenstein, 1984; Takhtajan, 1986; White & Léonard, 1991; Akhan, 2007).

The flora of Yemen is very rich and diverse. Species diversity is a result of considerable climatic changes in former periods, which enabled different species to survive in the different ecological habitats. Previous studies reported that, there are about 2810 plant species belong to 1006 genera and 173 families in Yemen. Of these about 2559 are naturalized, 121 cultivated and 111 introduced (Al-Khulaidi, 2000). On the other hand, Yemen is rich in the endemic plants, with estimated to be 415 plant species (236 in Socotra). The majority of endemic taxa in Yemen are associated with mountainous areas, which provides a rich variety of ecological niches and offers a degree of environmental stability during periods of climate changes. Endemism is generally very high among the succulent plants. The largest numbers of endemic species are found within the Asteraceae, Euphorbiaceae, Acanthaceae, Boraginaceae and Apocynaceae taking into account the Stapeliad genera (Caralluma, Duvalia, Huernia and Rhytidocaulon) (Al-Khulaidi, 2000; Ministry of Water and Environment, 2010).

The study area is a district of Lahej governorate, located at the southwestern part of Yemen. This governorate is bounded in the east by Abyan governorate, in the west by Taiz governorate, in the north by Al-Bayda, Al-Dhalaa governorates and some parts of Taiz governorate, in the south by Aden governorate and the Gulf of Aden (Fig.1). Lahej governorate consists of 15 districts. Toor Al-Baha district is one of them. It extends between latitudes 12° 58` - 13° 20` of the North Latitude and 44° 11` - 44° 39`of the East Longitude, with an area of about 1883 sq km. It represents about 14.4 % of total area of the governorate. The central of this district distances from Al-Hawtah district (the capital of Lahej governorate) about 68 km east. Toor Al-Baha district is bordered by Al-Qubaytah district in the north, Al-Maqatrah district, Al-Madaribah and Ras Al-Aarah district in the west, Tuban district in the east and by Gulf of Aden and parts of Aden governorate in the south (Fig. 1).

The topography of the study area comprises different habitats. Of these are: mountains, intermountain basins (Wadis), alluvial plains, hills, slopes and sandy dunes, with altitudinal ranging between 200-1488 m a. s. l. The geology of study area is characterized by exposures of rock units from the Paleozoic ages (Proterozoic) to the Quaternary. The oldest units are of basement rocks composed in dominant from metamorphic rocks of schist and gneiss which intruded by granite, diorite and grano-diorite bodies, this type of rocks exposed particularly in the most northern part of the studied area (Strojexport Foreign Trade Corporation, 1988).

 There are a few studies on the flora and vegetation of Toor Al-Baha, as a distinct area, were carried out, of these are: White & Sloane (1937); Albers & Meve (2002) and McCoy (2003). Some other scholars studied the flora of Toor Al-Baha among the southern governorates of Yemen such as: Gabali & Al-Gifri (1990);
 Al-Gifri & Gabali (1991).

Fig. 1: Map of Yemen (modified afterhttp://www.worldatlas. com/web image/ country's/ asia/ye.htm), showing political map of Lahej governorate with browsing the location of study area -Toor Al-Baha
(modified after Ministry of the Local administration)

The present study aims to carry out a comprehensive survey of the natural flora of the selected area, to analysis the floral composition of the studied area and to give an annotated checklist of the flora of the studied area as a step towards understanding the flora of Yemen as a whole.

MATERIALS AND METHODS:

The field studies were carried out through several trips during the different seasons between 2008 and 2011. About 4-8 (-10), trips per month were conducted. One hundred sites and 280 quadrates were selected to cover all the different habitats and floral composition of the studied area. For each taxon at least three duplicates of representative plant specimens were collected, with respect to their coordinates (latitude, longitude and altitude using GPS systen).

The collected specimens (un-diseased, and not seriously damaged by insects or other agencies) including flowers and or fruits as well as leaves and stems (Plants of small or moderate size, herbs and small shrubs), were dug up carefully and collected as a whole, including the underground parts (roots, rhizomes, tubers and bulbs).

The plant specimens were pressed in the field and transported to be continued in the laboratory. When the specimens were completely dried, each individual specimen was mounted on a herbarium sheet. For each taxon collected at least three dried specimen were mounted on herbarium sheet and labeled.

Arrangement of the families in the present work was followed the system proposed by Cronquist, 1981, while the genera and species within each family were arranged alphabetically. Voucher specimens for each taxon reported are kept in each of: Herbarium of Biology Department, Faculty of Science, Sanaa University, Herbarium of Biology Departement, Faculty of Education, Aden University (Yemen) and the Herbarium of Assiut Universty, Egypt (ASTU).

RESULTS AND DISCUSSION:

A total number of the vascular plant which has been recorded from the studied area is 560 taxa related to 288 genera and 89 families
(Fig.2). These numbers are very high comparing with those have been recorded from other regions or governorates of Yemen, even their climates are humid arid. If we have a look at the previous results of the floristic composition in other governorates of Yemen, we can note that, the flora of the studied district is very rich and diverse.

Based on the data from the literature, Gabali and Al Gifri (1990), recorded only 467 taxa from the whole southern governorates of Yemen. Also Boulos in 1988 visited the southern governorates (Abyan, Aden, Hadhramout, Lahej and Shabwah) with other Yemenis botanists and they recorded 378 taxa of all these governorates. On the other governorates even the climate is humid arid, wetter, (high rainfall and low temperate) as in Ibb, Al-Mahweet, Hadhramout and Hauf district (Al-Mahrah) the number of the collected taxa was less than that collected from Toor Al-Baha. Aqlan in 2008 reported that about 416 taxa from Ibb governorate. Ibrahim (2006) recorded about 385 taxa from Al-Mahweet governorate. While, from Hadhramout governorate, Al Khulaidi (2010) recorded about 469 taxa of the whole governorate. After different studies on the vegetation of Hauf district, Hussein (2006) recorded 236 taxa only.

As we usually state that the flora of Toor
Al-Baha district is very rich floristically, since it comprises about 560 taxa. This number represents about 22% of the whole flora of Yemen (2559 species) (Al-Khulaidi, 2000). Also the present results proved that the flora of Toor Al-Baha is rich in the genera since its genera represent about 29% of the total genera in the whole flora of Yemen (288/1006). The number of the families in the flora of Toor Al-Baha is constituted about 51% of the families in the flora of Yemen as a whole (89/173). This means that the flora of Toor Al-Baha is relatively the richest part of Yemen in its floristic composition till now. Thus, it may be owing to the biotic, climatic and topographic factors.

In the flora of Yemen the number of genera in proportion to that of species are 2.54, according to (Al-Khulaidi, 2000). This is very low figure comparing with the global average proportion, which are about 13.6. The present studies indicate that the flora of Toor Al-Baha goes below the average level of the Yemenis flora where the number of species per genus is 1.94. This means that the flora of Toor Al-Baha district is more diverse floristically than that of Yemenis flora, as the region that has a certain numbers of species each of which belongs to a different genus is relatively more diverse than that a region with the same number of species but belong to a few number of genera (Hawksworth, 1995; Khedr et al., 2002).

From the recorded 89 families in the present investigation, there are only three families of Pteridophyta which represent 3.37% of the recorded families, while only one family of the Gymnospermae was recorded, which represent 1.12% of the total number of the recorded families, thus indicates that the flora of this region is poor in the vascular non flowering plants (Pteridophyta and Gymnospermae). The above results are natural and agree with the global floral composition (Cronquist, 1981). The remaining families are 85 are belonging to the Angiospermae which divided into two main groups: Dicots (71 families) and Monocots (14 families). The number of dicots families represents 79.78%, while the number of the monocots represents 15.73% of the total number of the recorded families (Fig. 2).

At the generic level the Pteridophyta comprise six genera (2.08%), while Angiospermae comprise 281 genera (97.57%). Of these the dicots comprise about 237genera (82.29%), while the monocots are represented by 44 genera (15.28%). At the specific level, the Pteridophyta comprise eight species (1.43%). while the rest 551 species (98.39%) belong to Angiospermae. Of these the dicots are represented by 470 species (83.93%), and
the monocots comprise 81species (14.46%)
(Fig. 2).

Fig. 2: Numbers of families, genera and species in the flora of Toor Al-Baha by major plant groups (Species including infraspecific taxa), (The numbers are inserted above the columns)

On the other hand from the present results of the flora of Toor Al-Baha, the largest families of the dicots are: Asteraceae (39 sp., 26 g.), Ascl-epiadaceae (34 sp., 21 g.), Euphorbiaceae (34sp., 9g.), Fabaceae (30sp., 10g.), Acanthaceae (28 sp., 13 g.), Capparaceae (19 sp., 6 g.), Lamiaceae (18 sp., 9 g.), Boraginaceae (18 sp., 6g.), Malvaceae (17 sp., 7 g.), Solanaceae (15 sp., 6 g.), Mimosaceae (14 sp., 2 g.), Tiliaceae (13 sp., 2 g.), Amaranthaceae (12 sp., 8 g.), Cucurbitaceae (12 sp., 7 g.), Convolvulaceae (12 sp., 5 g.) and Scrophulariaceae (11sp., 6 g.) while, the largest family of the monocots is Poaceae (49 species and 27 genera) (Figs. 3 & 4). Regarding the number of taxa belong the families the present results are in agreement with those of Ghazanfar, 1992 and Al Khulaidi, 2000. These families represent a high percentage (about 66%) of the total genera and species of the studied area.

The present results revealed that, the largest genera are: Euphorbia (19 species), followed by Acacia (12 species), Grewia, Heliotropium and Indigofera (10 species for each), Barleria and Eragrostis (8 species for each), Aloe, Hibiscus, Solanum and Tephrosia (7 species for each), Cadaba, Crenulluma, Ficus, Justicia, and Senna (6 species for each) (Fig. 5). The analysis of the present data proved that, there are sixteen genera have number of species represent about 24.11% of the total species recorded in the studied area, about 181 genera in Toor Al-Baha are represented by only one species, 46 genera have only two species and 22 genera represented by 3 species. It was also noted that the generic index 560/288 was 1.94. From the present results we can emphasis the high diversity of the flora of the selected area. The present results agree with those of Ghazanfar, 1992.

The succulent plants are of a great ecological significance, particularly in arid and semi-arid parts of Yemen or the Arabian Peninsula. They store water in their stems, leaves or roots, a characteristic feature adopted by several plants to withstand high temperature and low precipitation. In Yemen, the succulents are usually seen in shallow depressions and dry places with low altitudes and along the Aden Gulf and the Red Sea coasts. In the study area, approximately, 68 species belonging to 18 families are generally recognized as succulent. Some of the families, which are rich in succulent species, are Aizoaceae, Aloaceae, Asclepia-daceae, Crassulaceae, Euphorbiaceae, and Vitaceae. These results are in agreement with those of (McCoy, 2003). The succulent habit of the plants may be reflect the dominant climatic factors in this region since the plants modify their parts leaves, stems and inflorescences to storage the available water in the wet rainy seasons to survive in the dry seasons.

There are three species viz.: Cucumis dipsaceus Ehrenb. ex Spach (Cucurbitaceae), Dactyloctenium robecchii (Chiov.) Chiov. (Poaceae) and Helichrysum glumaceum DC. (Asteraceae) are recorded here, for the first time in Toor Al-Baha. Previously, these three species were reported, that they are found in Socotra Island only (Al-Khulaidi, 2000).

One of the most distinct features of the flora of Yemen is the high percentage of the endemic plants among its components (Al-Hubaishi & Muller-Hohenstein, 1984; Wood, 1997;
Al-Khulaidi, 2000).

The present results revealed that there are about 28 species belong to 22 genera and 14 families are endemic to the flora of Yemen. In addition to the endemic species to the flora of Yemen there are also about 34 species belong to 27 genera and 20 families are near endemic to Yemen (endemic to Saudi Arabia Oman and Yemen) Appendix (1).

The present results of the flora of Toor Al-Baha has revealed the importance of this region in terms of plant biodiversity, and particularly of endemic and near-endemic species, which urgently require further management and conservation activities.

REFERENCES:

Akhan, H. (2007): Diversity biogeography and photosynthetic pathways of Argusia and Heliotropium (Boraginaceae) in South-West Asia with an analysis of phytogeo-graphical units. Bot. J. Linn. Soc., 155: 401-425.

Albers, F. & Meve, U. (2002): Illustrated handbook of succulent plants: Asclepiad-aceae. Springer Verlag, Heidelberg, Berlin, Germany, 318 pp .

Al-Dubaie, A. S. (1998): Vegetation degradation and desertification in Yemen. Taiz Univ. Research J. Vol. 1: 44-59.

Al-Gifri, A. N. & Gabali, S. A. (1991): Notes on the distribution of shrubs and trees in Aden (Republic of Yemen). Fragm. Flor. Geobot. , Vol. 35(1-2): 89-95.

Al-Hubaishi, A. A. & Muller-Hohenstein, K. (1984): An Introduction to the vegetation of Yemen: Ecological basis, floristic composition and human influence. Published by Deutsche Gesellschaft Technische Zusammenarbeit (GTZ), Eschborn, West Germany.

Al-Khulaidi, A. A. (2000): Flora of Yemen. (SEMP, YEM/97/100) EPC, Sana’a, Yemen.

Al-Khulaidi, A. A. (2010): The vegetation of the Hadhramout. Abstracts Compendium of Seventh Scientific Conference of the Yemeni Biological Society, Sana'a.

Aqlan, E. M. K. (2008): Studies on the flora of Ibb governorate, Republic of Yemen. Unpublished M. Sc. Thesis, Fac. of Sci. Sana'a Univ. .

Boulos, L. (1988): A contribution to the flora of South Yemen (PDRY). Candollea, Vol. 43: 549-585.

Cronquist, A. (1981): An integrated system of classification of flowering plants. Colu-mbia Univ. Press, New York, NY, USA.

Gabali, S. A. & Al-Gifri, A. N. (1990): Flora of South Yemen-Angiospermae A provisi-onal checklist. Feddes Repert. Berlin, Vol.101 (7-8): 373-383.

Ghazanfar, S. A. (1992): Quantitative and biogeographic analysis of the flora of
the Sultanate of Oman. Global Ecology Biogeography letters, Vol. 2(6): 189-
195.

Hawksworth, D.L. (1995): Biodiversity: measur-ement and estimation. Chapman and Hall, London. 140 pp .

Hussein, M. A. (2006): Natural wild flora and vegetative composition of Hauf forest. Univ. Aden J. of Nat. and Appl. Sci., Vol. 10(2): 277- 289.

Ibrahim, H. M. (2006): Studies on the flora of Al-Mahweet governorate, Republic of Yemen. Unpublished M. Sc. Thesis, Fac. of Sci. Sana'a Univ.

Khedr, A. A.; Cadotte, M. W.; El-Keblawy, A. & Loveti-Doust, J. (2002): Phytogentic diversity and ecological feature in the Egyptian flora. Biodiversity and Conser-vation, 11: 1809-1824.

McCoy, T. A. (2003): Rhytidocaulon splendid-um McCoy A new species from southwestern Yemen. Cact. and Succ. J. (U.S.), Vol. 75(4):154-157.

Ministry of Water and Environment (2010): Fourth national report, Assessing Progress towards Target-the 4th national CBD report July, 2009 .Environment Protection Authority, Ministry of water and environment, Republic of Yemen, 100 pp.

Strojexport Foreign Trade Corporation (1988): Final report on the integrated Geological mapping of the western part of the former P.D.R. Yemen. Strojexport Foreign Trade Corporation: Czechosl-ovakia Prague, 517 pp.

Takhtajan, A. (1986): Floristic Regions of the World. University of California Press, California.

White, A. & Sloane, B.L. (1937): The Stapelieae. 3 vols. Abbes San Encino Press, Pasadena, California, USA, 1185 pp.

White, F. & Léonard, J. (1991): Phytogeo-graphical links between Africa and Southwest Asia. Flora et Vegetatio Muhndi, Vol. 9: 229-246.

Wood, J. R. I. (1997): A handbook of the Yemen flora. Royal Botanic Gardens, Kew, UK, 434 pp .

Zohary, M. (1973): Geobotanical foundations of the Middle East. 2 Vols. Gustav Fischer Verlag, Stuttgart. 739 pp .

STUDIES ON THE FLORA OF YEMEN:

2-FLORA OF TOOR AL-BAHA DISTRICT, LAHEJ
GOVERNORATE, YEMEN

Abdo, M. A. Dahmash^*; Othman S. S. Hamood^**
and Salah, M. I. El-Naggar^***

*Biology Department, Faculty of science, Sana^, a Uuiversity, Yemen

**Biology Department, Faculty of Education, Aden Uuiversity, Yemen

***Botany Department , Faculty of science, Assiut Uuiversity, Egypt

INTRODUCTION:

The Republic of Yemen lies in the southwestern corner of the Arabian Peninsula. It extends between latitudes 12° 40` to 19° 00` N. and longitudes 42° 30` to 53° 05` E. It is bordered by Kingdom of Saudi Arabia in the north, the Arabian Sea and the Gulf of Aden in the south, Sultanate of Oman in the east, and the Red Sea in the west (Fig. 1). Yemen contains one of the most diverse floras of the Arabian Peninsula region (Wood, 1997 and Al-Dubai, 1998). The flora of this country is characterized by its high diversity and density, particularly in the South and West regions, that makes it a complex one. This flora having affinities with the floras of the Tropical African, Sudanese region, the Saharo-Arabian region, the Mediterranean countries and the Irano-Turanian region (Zohary, 1973; Al-Hubaishi & Muller-Hohenstein, 1984; Takhtajan, 1986; White & Léonard, 1991; Akhan, 2007).

The flora of Yemen is very rich and diverse. Species diversity is a result of considerable climatic changes in former periods, which enabled different species to survive in the different ecological habitats. Previous studies reported that, there are about 2810 plant species belong to 1006 genera and 173 families in Yemen. Of these about 2559 are naturalized, 121 cultivated and 111 introduced (Al-Khulaidi, 2000). On the other hand, Yemen is rich in the endemic plants, with estimated to be 415 plant species (236 in Socotra). The majority of endemic taxa in Yemen are associated with mountainous areas, which provides a rich variety of ecological niches and offers a degree of environmental stability during periods of climate changes. Endemism is generally very high among the succulent plants. The largest numbers of endemic species are found within the Asteraceae, Euphorbiaceae, Acanthaceae, Boraginaceae and Apocynaceae taking into account the Stapeliad genera (Caralluma, Duvalia, Huernia and Rhytidocaulon) (Al-Khulaidi, 2000; Ministry of Water and Environment, 2010).

The study area is a district of Lahej governorate, located at the southwestern part of Yemen. This governorate is bounded in the east by Abyan governorate, in the west by Taiz governorate, in the north by Al-Bayda, Al-Dhalaa governorates and some parts of Taiz governorate, in the south by Aden governorate and the Gulf of Aden (Fig.1). Lahej governorate consists of 15 districts. Toor Al-Baha district is one of them. It extends between latitudes 12° 58` - 13° 20` of the North Latitude and 44° 11` - 44° 39`of the East Longitude, with an area of about 1883 sq km. It represents about 14.4 % of total area of the governorate. The central of this district distances from Al-Hawtah district (the capital of Lahej governorate) about 68 km east. Toor Al-Baha district is bordered by Al-Qubaytah district in the north, Al-Maqatrah district, Al-Madaribah and Ras Al-Aarah district in the west, Tuban district in the east and by Gulf of Aden and parts of Aden governorate in the south (Fig. 1).

The topography of the study area comprises different habitats. Of these are: mountains, intermountain basins (Wadis), alluvial plains, hills, slopes and sandy dunes, with altitudinal ranging between 200-1488 m a. s. l. The geology of study area is characterized by exposures of rock units from the Paleozoic ages (Proterozoic) to the Quaternary. The oldest units are of basement rocks composed in dominant from metamorphic rocks of schist and gneiss which intruded by granite, diorite and grano-diorite bodies, this type of rocks exposed particularly in the most northern part of the studied area (Strojexport Foreign Trade Corporation, 1988).

 There are a few studies on the flora and vegetation of Toor Al-Baha, as a distinct area, were carried out, of these are: White & Sloane (1937); Albers & Meve (2002) and McCoy (2003). Some other scholars studied the flora of Toor Al-Baha among the southern governorates of Yemen such as: Gabali & Al-Gifri (1990);
 Al-Gifri & Gabali (1991).

Fig. 1: Map of Yemen (modified afterhttp://www.worldatlas. com/web image/ country's/ asia/ye.htm), showing political map of Lahej governorate with browsing the location of study area -Toor Al-Baha
(modified after Ministry of the Local administration)

The present study aims to carry out a comprehensive survey of the natural flora of the selected area, to analysis the floral composition of the studied area and to give an annotated checklist of the flora of the studied area as a step towards understanding the flora of Yemen as a whole.

MATERIALS AND METHODS:

The field studies were carried out through several trips during the different seasons between 2008 and 2011. About 4-8 (-10), trips per month were conducted. One hundred sites and 280 quadrates were selected to cover all the different habitats and floral composition of the studied area. For each taxon at least three duplicates of representative plant specimens were collected, with respect to their coordinates (latitude, longitude and altitude using GPS systen).

The collected specimens (un-diseased, and not seriously damaged by insects or other agencies) including flowers and or fruits as well as leaves and stems (Plants of small or moderate size, herbs and small shrubs), were dug up carefully and collected as a whole, including the underground parts (roots, rhizomes, tubers and bulbs).

The plant specimens were pressed in the field and transported to be continued in the laboratory. When the specimens were completely dried, each individual specimen was mounted on a herbarium sheet. For each taxon collected at least three dried specimen were mounted on herbarium sheet and labeled.

Arrangement of the families in the present work was followed the system proposed by Cronquist, 1981, while the genera and species within each family were arranged alphabetically. Voucher specimens for each taxon reported are kept in each of: Herbarium of Biology Department, Faculty of Science, Sanaa University, Herbarium of Biology Departement, Faculty of Education, Aden University (Yemen) and the Herbarium of Assiut Universty, Egypt (ASTU).

RESULTS AND DISCUSSION:

A total number of the vascular plant which has been recorded from the studied area is 560 taxa related to 288 genera and 89 families
(Fig.2). These numbers are very high comparing with those have been recorded from other regions or governorates of Yemen, even their climates are humid arid. If we have a look at the previous results of the floristic composition in other governorates of Yemen, we can note that, the flora of the studied district is very rich and diverse.

Based on the data from the literature, Gabali and Al Gifri (1990), recorded only 467 taxa from the whole southern governorates of Yemen. Also Boulos in 1988 visited the southern governorates (Abyan, Aden, Hadhramout, Lahej and Shabwah) with other Yemenis botanists and they recorded 378 taxa of all these governorates. On the other governorates even the climate is humid arid, wetter, (high rainfall and low temperate) as in Ibb, Al-Mahweet, Hadhramout and Hauf district (Al-Mahrah) the number of the collected taxa was less than that collected from Toor Al-Baha. Aqlan in 2008 reported that about 416 taxa from Ibb governorate. Ibrahim (2006) recorded about 385 taxa from Al-Mahweet governorate. While, from Hadhramout governorate, Al Khulaidi (2010) recorded about 469 taxa of the whole governorate. After different studies on the vegetation of Hauf district, Hussein (2006) recorded 236 taxa only.

As we usually state that the flora of Toor
Al-Baha district is very rich floristically, since it comprises about 560 taxa. This number represents about 22% of the whole flora of Yemen (2559 species) (Al-Khulaidi, 2000). Also the present results proved that the flora of Toor Al-Baha is rich in the genera since its genera represent about 29% of the total genera in the whole flora of Yemen (288/1006). The number of the families in the flora of Toor Al-Baha is constituted about 51% of the families in the flora of Yemen as a whole (89/173). This means that the flora of Toor Al-Baha is relatively the richest part of Yemen in its floristic composition till now. Thus, it may be owing to the biotic, climatic and topographic factors.

In the flora of Yemen the number of genera in proportion to that of species are 2.54, according to (Al-Khulaidi, 2000). This is very low figure comparing with the global average proportion, which are about 13.6. The present studies indicate that the flora of Toor Al-Baha goes below the average level of the Yemenis flora where the number of species per genus is 1.94. This means that the flora of Toor Al-Baha district is more diverse floristically than that of Yemenis flora, as the region that has a certain numbers of species each of which belongs to a different genus is relatively more diverse than that a region with the same number of species but belong to a few number of genera (Hawksworth, 1995; Khedr et al., 2002).

From the recorded 89 families in the present investigation, there are only three families of Pteridophyta which represent 3.37% of the recorded families, while only one family of the Gymnospermae was recorded, which represent 1.12% of the total number of the recorded families, thus indicates that the flora of this region is poor in the vascular non flowering plants (Pteridophyta and Gymnospermae). The above results are natural and agree with the global floral composition (Cronquist, 1981). The remaining families are 85 are belonging to the Angiospermae which divided into two main groups: Dicots (71 families) and Monocots (14 families). The number of dicots families represents 79.78%, while the number of the monocots represents 15.73% of the total number of the recorded families (Fig. 2).

At the generic level the Pteridophyta comprise six genera (2.08%), while Angiospermae comprise 281 genera (97.57%). Of these the dicots comprise about 237genera (82.29%), while the monocots are represented by 44 genera (15.28%). At the specific level, the Pteridophyta comprise eight species (1.43%). while the rest 551 species (98.39%) belong to Angiospermae. Of these the dicots are represented by 470 species (83.93%), and
the monocots comprise 81species (14.46%)
(Fig. 2).

Fig. 2: Numbers of families, genera and species in the flora of Toor Al-Baha by major plant groups (Species including infraspecific taxa), (The numbers are inserted above the columns)

On the other hand from the present results of the flora of Toor Al-Baha, the largest families of the dicots are: Asteraceae (39 sp., 26 g.), Ascl-epiadaceae (34 sp., 21 g.), Euphorbiaceae (34sp., 9g.), Fabaceae (30sp., 10g.), Acanthaceae (28 sp., 13 g.), Capparaceae (19 sp., 6 g.), Lamiaceae (18 sp., 9 g.), Boraginaceae (18 sp., 6g.), Malvaceae (17 sp., 7 g.), Solanaceae (15 sp., 6 g.), Mimosaceae (14 sp., 2 g.), Tiliaceae (13 sp., 2 g.), Amaranthaceae (12 sp., 8 g.), Cucurbitaceae (12 sp., 7 g.), Convolvulaceae (12 sp., 5 g.) and Scrophulariaceae (11sp., 6 g.) while, the largest family of the monocots is Poaceae (49 species and 27 genera) (Figs. 3 & 4). Regarding the number of taxa belong the families the present results are in agreement with those of Ghazanfar, 1992 and Al Khulaidi, 2000. These families represent a high percentage (about 66%) of the total genera and species of the studied area.

The present results revealed that, the largest genera are: Euphorbia (19 species), followed by Acacia (12 species), Grewia, Heliotropium and Indigofera (10 species for each), Barleria and Eragrostis (8 species for each), Aloe, Hibiscus, Solanum and Tephrosia (7 species for each), Cadaba, Crenulluma, Ficus, Justicia, and Senna (6 species for each) (Fig. 5). The analysis of the present data proved that, there are sixteen genera have number of species represent about 24.11% of the total species recorded in the studied area, about 181 genera in Toor Al-Baha are represented by only one species, 46 genera have only two species and 22 genera represented by 3 species. It was also noted that the generic index 560/288 was 1.94. From the present results we can emphasis the high diversity of the flora of the selected area. The present results agree with those of Ghazanfar, 1992.

The succulent plants are of a great ecological significance, particularly in arid and semi-arid parts of Yemen or the Arabian Peninsula. They store water in their stems, leaves or roots, a characteristic feature adopted by several plants to withstand high temperature and low precipitation. In Yemen, the succulents are usually seen in shallow depressions and dry places with low altitudes and along the Aden Gulf and the Red Sea coasts. In the study area, approximately, 68 species belonging to 18 families are generally recognized as succulent. Some of the families, which are rich in succulent species, are Aizoaceae, Aloaceae, Asclepia-daceae, Crassulaceae, Euphorbiaceae, and Vitaceae. These results are in agreement with those of (McCoy, 2003). The succulent habit of the plants may be reflect the dominant climatic factors in this region since the plants modify their parts leaves, stems and inflorescences to storage the available water in the wet rainy seasons to survive in the dry seasons.

There are three species viz.: Cucumis dipsaceus Ehrenb. ex Spach (Cucurbitaceae), Dactyloctenium robecchii (Chiov.) Chiov. (Poaceae) and Helichrysum glumaceum DC. (Asteraceae) are recorded here, for the first time in Toor Al-Baha. Previously, these three species were reported, that they are found in Socotra Island only (Al-Khulaidi, 2000).

One of the most distinct features of the flora of Yemen is the high percentage of the endemic plants among its components (Al-Hubaishi & Muller-Hohenstein, 1984; Wood, 1997;
Al-Khulaidi, 2000).

The present results revealed that there are about 28 species belong to 22 genera and 14 families are endemic to the flora of Yemen. In addition to the endemic species to the flora of Yemen there are also about 34 species belong to 27 genera and 20 families are near endemic to Yemen (endemic to Saudi Arabia Oman and Yemen) Appendix (1).

The present results of the flora of Toor Al-Baha has revealed the importance of this region in terms of plant biodiversity, and particularly of endemic and near-endemic species, which urgently require further management and conservation activities.

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