An Assessment of Biodiversity in Tabuk Region of Saudi Arabia: A Comprehensive Review

: Biodiversity refers to all the type of species in one geographical region or ecosystem. It consists of plants, animals, bacteria, and other life forms. As an estimate, around 1.7 million species are on record globally and approximately 15,000–18,000 new species are added each year. Global climate change is accelerating species extinction due to habitat destruction. Further, various abiotic and biotic environmental factors are limiting the pattern of biodiversity in a geographical region. A change in species category from endangered to extinction occurs due to their physiological, morphological, and life history pattern, which limits them to a speciﬁc niche. Biodiversity is very important for energy production and ﬂow, bioremediation, and biogeochemical cycling of nutrients in terrestrial to aquatic ecosystems and vice versa. It is further required for human existence in the form of food, ﬁbers, medicines, and biological control. Therefore, consistent monitoring, assessment, and conservation of ecological habitats and diversity of ﬂora and fauna of aquatic and terrestrial ecosystems is the need of the hour. In this article, we are presenting an assessment based upon the literature survey on the biodiversity of Tabuk region of Kingdom of Saudi Arabia. A comprehensive study on the biodiversity of plants, animals and microorganisms of the Tabuk region (Tabuk city, Tayma, Haql, Sharma, Duba, Al Wajh and Umluj, Al Zetah, Al Beda’a, etc.) are included in this review. This study will be a landmark as it is conducted at the inception of NEOM project in Tabuk region. It will help the authorities to enhance the native green cover, decrease desertiﬁcation, regenerate biodiversity in natural environments, and advance the quality of life, to achieve the objectives of the Saudi Green Initiative and VISION 2030. However, studies and investigations on Tabuk biodiversity are still limited and need further exploration. Recently, a joint work between King Salman Royal Natural Reserve (KSRNR) and Department of Biology of University of Tabuk is underway to monitor the baseline data of ﬂora and fauna of this region.


Introduction
The Northwest region of Saudi Arabia is administratively part of the Tabuk Province and is the current hotspot for agricultural activities in the region.Traditionally, this region is known as Midyan (Midian or Madyan) and has an area of almost 135,000-km 2 [1].It includes diverse terrain such as deserts, valleys, sprawling mountains, coasts of the Red Sea, and natural springs.Long shoreline of Tabuk Province is one of the most important geographical characteristics that contributes about 38% of the western shoreline of Saudi Arabia.It covers coastal cities, such as Haql, Sharma, Duba, Al Wajh and Umluj, with pristine beaches of clear waters (Figure 1).The province of Tabuk contains five major habitats, namely, mountains, coastal and islands, water bodies, plains and valleys with scattered trees, and agricultural and urban environment.The Tabuk region hosts several unique natural attractions occupying considerable natural resources.Tabuk is a desert with relatively little rain, the average temperature is 21.7 °C and precipitation is about 15 mm per year.In 30-year investigations on temperature between 1984 and 2013, trends have shown significant increase in warming of the atmosphere of about 1.93 °C [2].The unique terrains of the Tabuk region and the distinctive climatic condition from extremely low to extremely high results in diverse terrestrial and aquatic ecosystems, which harbor a remarkable biological diversity [1,[3][4][5][6][7][8].
Biodiversity refers to all of the types of species in one geographical region or ecosystem.It consists of plants, animals, bacteria, and other life forms.As per Catalogue of Life-2018 Annual Checklist [9], around 1.7 million species are on record globally and approximately 15,000-18,000 new species are added each year [10].Broadly, biodiversity can be observed at three levels, namely, ecosystem, species and genetic level (Figure 2).The biodiversity is a crucial and a vital environmental component for a functional ecosystem.It is very important for energy production and flow, bioremediation, and biogeochemical cycling of nutrients in terrestrial to aquatic ecosystems and vice versa [11].Since the dawn of civilization, it has been very active in offering humanity with food security, medical care, and goods and materials for various industries, and allows humans to live a comfortable life [12].However, in the modern world, due to increases in various anthropogenic activities, a surge in global climate change is observed.It affected almost all kinds of habitat globally and resulted in a huge decline in plant diversity.The decline in producer community compels a change in the fauna of the affected habitat [13][14][15].The species extinction across the globe is mainly governed by changing environmental conditions The province of Tabuk contains five major habitats, namely, mountains, coastal and islands, water bodies, plains and valleys with scattered trees, and agricultural and urban environment.The Tabuk region hosts several unique natural attractions occupying considerable natural resources.Tabuk is a desert with relatively little rain, the average temperature is 21.7 • C and precipitation is about 15 mm per year.In 30-year investigations on temperature between 1984 and 2013, trends have shown significant increase in warming of the atmosphere of about 1.93 • C [2].The unique terrains of the Tabuk region and the distinctive climatic condition from extremely low to extremely high results in diverse terrestrial and aquatic ecosystems, which harbor a remarkable biological diversity [1,[3][4][5][6][7][8].
Biodiversity refers to all of the types of species in one geographical region or ecosystem.It consists of plants, animals, bacteria, and other life forms.As per Catalogue of Life-2018 Annual Checklist [9], around 1.7 million species are on record globally and approximately 15,000-18,000 new species are added each year [10].Broadly, biodiversity can be observed at three levels, namely, ecosystem, species and genetic level (Figure 2).The biodiversity is a crucial and a vital environmental component for a functional ecosystem.It is very important for energy production and flow, bioremediation, and biogeochemical cycling of nutrients in terrestrial to aquatic ecosystems and vice versa [11].Since the dawn of civilization, it has been very active in offering humanity with food security, medical care, and goods and materials for various industries, and allows humans to live a comfortable life [12].However, in the modern world, due to increases in various anthropogenic activities, a surge in global climate change is observed.It affected almost all kinds of habitat globally and resulted in a huge decline in plant diversity.The decline in producer community compels a change in the fauna of the affected habitat [13][14][15].The species extinction across the globe is mainly governed by changing environmental conditions due to habitat destruction.Various abiotic environmental factors, such as nutrients, pH, water availability, soil quality, temperature, and many other climatic changes, and biotic factors, such as primary producers (green plants, consumers (herbivores, carnivores, and omnivores) and decomposers (microorganisms), are limiting to biodiversity patterns.Any species can be shifted to endangered or extinction due to their physiological, morphological, and life history pattern, which limit each species to a specific niche.In order to conserve the biodiversity of Saudi Arabia, legislation was enacted and The Saudi Wildlife Authority (SWA) was established in 1986.Its task was to develop a national network of protected areas and to pursue the restoration of native endangered species.The Wildlife Protected Areas Act was issued in 1995 to facilitate conservation activities and the establishment of protected areas in Saudi Arabia.Since its inception, SWA has identified 16 protected areas covering 86,582.4km 2 and a further 22 areas planned, covering a total area of 208,356 km 2 , 10.42% of the KSA [16].In 1996, the Government of Saudi Arabia joined CITES, which regulates international trade in listed species and CITES implementing legislation (The Act on Trade in Endangered Wildlife Species and their Products 2000) was introduced in 2001 in KSA.The fauna was protected from poaching and illegal trades by enacting The Wild Animals and Birds Hunting Act 1999.As per this law, hunting was banned without a license, regulations were defined, and penalties were listed in case of violations.An Environmental Code 2002 was also formulated for the protection of the environment [17,18].Later, the Government of Saudi Arabia joins the Convention on Biological Diversity [17].Since joining the Convention, Saudi Arabia has made remarkable and significant progress in addressing biodiversity conservation and its related challenges [19].included in this review.The latest published data of the last decade was collected using Science Direct, Springer, MDPI, Google, Google Scholar, etc.The articles, reviews, short communication, and reports were studied thoroughly and grouped based on plants, animals, and microorganisms.This study will be a landmark as it is done at the inception of mega developmental projects like NEOM, LINE, Red Sea Development Company, AMAALA, etc., in Tabuk region and can be taken as a baseline knowledge of biodiversity of Tabuk region.It will help the authorities to understand the basic diversity of organism of Tabuk and helps in the enhancement of the native green cover.This will decrease desertification, regenerate biodiversity in natural environments, and advance the quality of life, to achieve the objectives of the Saudi Green Initiative and VISION 2030.This article also assesses the gaps in biodiversity research and suggest biodiversity surveys and studies.

Plant Biodiversity of Tabuk Region
Tabuk and the surrounding area are composed of metamorphic and igneous rocks.The western part of the region is surrounded by a series of hills and mountains, including Jabal al Lauz, Hijaz mountains.The terrain is similar to that of central Najd and consists of wadi, hills, and plains.Wadi are generally filled with muddy sand and gravel and plain soil sediments range from silt to sand to coarse rocks.Some of the most important agricultural centers are also found on the eastern and southeastern sides of Tabuk City [26].The pioneer work to identify the plant biodiversity of Saudi Arabia was conducted by Recently, the hunting regulation for wildlife terrestrial species (2020) [20] was implemented by The Ministry of Environment, Water and Agriculture, represented by the National Center for Wildlife Development.The ministry prohibited the hunting of Arabian oryx, deer, and ibex; predators, such as the Arabian tiger, lynx, wolf, and hyena; and other endangered species of animals and birds, as well as birds of prey.The ministry further laid down the prohibition of hunting of all kinds of animals or birds within the boundaries of cities, villages, towns, farms and rest houses, or any inhabited places, or near cities and military, industrial, and vital installations.Moreover, hunting is not allowed within the boundaries of natural reserves and giant development projects, such as NEOM, the Red Sea, Amaala, Al Qiddiya, the Al-Soudah Reserve, and the Royal Commission for Al-Ula [21].The approved regulations for trafficking fungal organisms (2020) [22] prohibits hunting wild fungi organisms, endangered species, and overfishing.The law ensures a safe and protected environment without harming the balance of the natural ecosystem [23].
In view of VISION 2030, Royal Commission for Al-Ula was established in 2017 for conservation and sustainable development of Al-Ula, a leading global destination for cultural and natural heritage in Tabuk province.Royal Commission for Al-Ula granted a government membership status by International Union for Conservation of Nature (IUCN).Together, they will conserve nature and wildlife by creating and activating nature reserves.It will protect degraded ecosystems, ecological processes, fragile habitats, biodiversity, and reintroducing native species [24].Similarly, the KSA government launched Saudi Green Initiative (2022) [25]; its main goals are to reduce annual CO 2 emissions by 278 million tonnes by 2030, plant 10 million trees nationwide, and protect 30% of land and sea by developing creative solutions to tackle climate change.
Despite establishment and implementation of various laws and regulations for wildlife protection, there are many reports for the illegal trade and violations from different regions of in Saudi Arabia, particularly from Tabuk region.There is an urgent need to strengthen the law enforcement, as well establishing an awareness campaign to conserve threatened species especially birds, reptiles, and carnivorous animals in Saudi Arabia.In this review, an analysis of published literature is done that can provide a comprehensive data on the biodiversity of Tabuk region of Kingdom of Saudi Arabia.A wide-ranging study on the biodiversity of plants, animals, and microorganisms of the Tabuk region are included in this review.The latest published data of the last decade was collected using Science Direct, Springer, MDPI, Google, Google Scholar, etc.The articles, reviews, short communication, and reports were studied thoroughly and grouped based on plants, animals, and microorganisms.This study will be a landmark as it is done at the inception of mega developmental projects like NEOM, LINE, Red Sea Development Company, AMAALA, etc., in Tabuk region and can be taken as a baseline knowledge of biodiversity of Tabuk region.It will help the authorities to understand the basic diversity of organism of Tabuk and helps in the enhancement of the native green cover.This will decrease desertification, regenerate biodiversity in natural environments, and advance the quality of life, to achieve the objectives of the Saudi Green Initiative and VISION 2030.This article also assesses the gaps in biodiversity research and suggest biodiversity surveys and studies.

Plant Biodiversity of Tabuk Region
Tabuk and the surrounding area are composed of metamorphic and igneous rocks.The western part of the region is surrounded by a series of hills and mountains, including Jabal al Lauz, Hijaz mountains.The terrain is similar to that of central Najd and consists of wadi, hills, and plains.Wadi are generally filled with muddy sand and gravel and plain soil sediments range from silt to sand to coarse rocks.Some of the most important agricultural centers are also found on the eastern and southeastern sides of Tabuk City [26].The pioneer work to identify the plant biodiversity of Saudi Arabia was conducted by [27,28] in the form of an Illustrated Guide to the Flowers of Saudi Arabia and Wild Flowers of Saudi Arabia.Moreover, Migahid (1989) [29] and Chaudhary (2001) [30] completed the Flora of Saudi Arabia.Since then, there is a need to update the Flora of Saudi Arabia in general and Flora of Tabuk in particular due to the inception of megaprojects like NEOM, LINE, Red Sea Development Company, AMAALA etc. Nowadays, a field survey project for the baseline data for vegetation and wildlife life of King Salman Royal Natural Reserve is in its final phase.After the completion of this project, a clear picture will appear regarding the biodiversity of Tabuk region [31].In the following paragraph, an attempt is made to collect the available information about the plant biodiversity of Tabuk region.

Algal Biodiversity
Algae is a group of different organisms capable of producing oxygen through photosynthesis.However, though these organisms are not closely related, they share some common features with the major group of photosynthetic organisms, plants.The coastline of Tabuk region along the Red Sea is the harbor for marine algae.As per the literature survey and the published reports in Tabuk region, seasonal dynamics and ecological parameters of marine algae are recorded by various workers [5,[32][33][34][35][36].However, Al Solami (2020) [37] studied the comparative response of red and green algae in relation to the quality of coastal waters of Red Sea at Haql region.Recently, Menaa et al. (2021) [38] reviewed the marine algae derived bioactive compounds as a source of Nanodrugs.Alshehri et al. (2021) [39] worked for the molecular characterization of some algae collected from the Gulf of Aqaba using protein banding pattern and ISSR markers.There are various genera of algae reported from Tabuk region listed in Table 1.Ibraheem et al. (2014) [40] reported some algal species from Umluj coasts of the Red Sea, namely, Enteromorpha intestinalis, Padina pavonia, Cystoseira myrica, Cystoseira trinodis, Colpomenia sinuosa, Turbinaria ornate, Sargassum latifolium, Laurencia majuscule, Laurencia catarinensis, Laurencia papillosa, Laurencia sp., Laurencia sp., Liagora hawaiiana Butters, Hypnea bryoides Børgesen, Palmaria palmate, Galaxaura rugose, Gracilaria arcuate, Acanthophora spicifera, and Digenia simplex.Ansari et al. (2015) [5] studied eutrophication in coastal waters, and floral and faunal density in relation to the seasonal dynamics of some selected coastal areas at Haql, Sharma and Duba of the Red Sea in Tabuk region.Only few coastal sites showed eutrophic characteristics.Water samples from these sites were more turbid, alkaline, and with higher nutrient and low dissolved oxygen contents compared to other sampling sites.A variation in relative densities of coastal flora and fauna were recorded and correlated with coastal water quality.The authors concluded that the fish markets, boating clubs, and touristic and human settlements at the coastal areas may be the prime reason of run-offs and nutrient loading rains aggravate the problem.
Ansari (2016) [32] studied the relative density of aquatic flora in relation to the seasonal dynamics and concluded that the summer season (April, May, June, and July) of Tabuk can be considered as the most suitable period for the collection of aquatic plants for medicinal purpose and ecological studies.Ansari and Ghanem (2017) [33] studied seasonal variation in growth responses and antioxidant activities of Ulva lactuca, Enteromorpha flexuoca, Cladophora prolifera, Chaetomorpha linum).
In July and October, significantly higher accumulation of NPK, carbohydrates, total protein, photosynthetic, and accessory pigments was recorded; however, a significant decrease in January was observed for the same parameters (Ansari and Ghanem 2017).Significant antioxidant activities in all the species were observed in January, which may be due to low temperature stress as compared to the other months.Various Biotic factors (plants, animals, and microorganisms) and abiotic factors (nutrients, soil quality, water, temperature, pH, salinity, and light) are the limiting factors for the production of primary and secondary metabolites.Ansari and Ghanem (2019) [34] also studied the growth attributes and biochemical composition of a brown alga Padina pavonica (L.) from the Red Sea at Haql in different seasons.The carbohydrate, protein and lipids, mineral ashes, macronutrients, and dietary fibers were high in July.The antioxidant enzymatic activities and proline accumulation showed a response to abiotic stress (low temperature) in January.A quantitative analysis on the diversity of algal flora revealed that the frequency, density, and abundance of Sargassum sp. was highest whereas of Ulva sp. was least at the six different study sites of Haql [35].Five common algal species, namely, Padina, Sargassum, Dictyota, Polysiphonia, and Ulva were reported in their study.Mazen & Solami (2020) [37] compared the responses of Red algae (Gracilaria salicornia and Digenea simplex) and Green Algae (Enteromorpha compressa and Sargassum muticum) to the water quality at the coast of Red Sea.A significant variation in physiological and biochemical parameters of algae was observed.Green algae showed higher concentration of Chl a, b, total chlorophyll Chl a:b ratio, and carbohydrates content compared to red algae; whereas, red algae accumulated more carotenoids, phycocyanin, phycoerythrin, and protein compared to green algae.Moreover, low levels of hydrogen peroxide and TBARS were exhibited in red algae G. salicornia and D. simplex, however, proline, glycine betaine, and activities of antioxidant enzymes were high, showing strong defense system than the green algae.
Menaa et al. ( 2021) [38] investigated the bioactive compounds for nanodrugs derived from marine algae.The main compounds from algae are the nutraceuticals, which can be extracted and purified for nanotheranostic purposes.Algal extracts can be utilized for stabilizing/capping and reducing the synthesis of thermodynamically stable nanoparticles (NPs).Varieties of nanotherapeutics have been synthesized through physical, chemical, and biological processing.Marine algae are a promising source of lead theranostics compounds and are important for the development of nanotheranostics, which enhance the drug efficacy and safety [38].Marine algae are considered as biofactories for the nanomaterials as they are easy to handle, capable to absorb and accumulate inorganic metallic ions, cost-effective, and eco-friendly for rapid, healthier synthesis of nanoparticles for various therapies.
DNA fingerprinting is a promising tool for species identification and can be solution for many errors occurred during morphological taxonomy as it requires only a small amount of tissue.To conserve the biodiversity, DNA fingerprinting could also be used for the identification of various invasive and endangered species.DNA fingerprinting is also used for the recognition of high-yielding agar strains of algae as well as for the identification of cryptic species.Alshehri et al. (2021) [39] performed the molecular characterization of some selected algal species (collected from the Gulf of Aqaba) through protein banding pattern and ISSR markers and identified eight algae, namely, Padina pavonica, Turbinaria gracilis, Carpomitra costata, Pterocladiella capillacea, Cladostephus spongiosus, Ulva lactuca, Sporochnus comosus, and Sargassum muticum.The study showed that ISSR marker is more effective than protein banding pattern to measure algal diversity at genetic level.The complied data reflect that the algal biodiversity work is highly reported at Haql shore, whereas the Umluj shore is least explored.The maximum work is about the seasonal dynamics and its floral or faunal density relationship.In all studies, Padina pavonia was the common algal species reported at Tabuk shoreline.The list of algae reported from Tabuk region is summarized in Table 1.Algae are very popular for their high ecological and commercial demand.The most important role of algae to our atmosphere and wellbeing is the generation of oxygen through photosynthesis and as a food for the marine organisms.They are the producer in the aquatic environment.According to an estimate, the worldwide turnover of the seaweed industry is about USD 10 billion per year.Seaweeds have a number of human applications; the principal use of seaweeds as a source of human food and as a source of gums (phycocollides).Phycocolloides like agar agar, alginic acid and carrageenan are primarily constituents of brown and red algal cell walls and are widely used in food industry to thicken a variety of foods (soy milk, chocolate milk, ice cream, yogurt, soups, salad dressings, jellies, etc.) and in molecular biology lab.Marine macroalgae have been used as foods, especially in China and Japan, and crude drugs for treatment of many diseases such as iodine deficiency (goiter, Basedow's disease, and hyperthyroidism).Marine algae are the richest source of bioactive nutraceuticals such as antioxidants, pigments, carbohydrates, proteins, minerals, and fatty acids.Moreover, it can be used as a source of fodder, in fish farming, and as a fertilizer [36,41].

Floral Biodiversity (Angiosperms)
The available literature on floristic diversity of Tabuk region from the last decades (Table 2) mainly focused on their ecological and environmental parameters [1,3,8,18,[42][43][44][45][46][47][48].In the past two decades, Rajasab (2011) [49] carried out the pioneering work in Tabuk region flora.He presented a pictorial guide to the plant diversity of Tabuk region with the description on their traditional uses.The book comprised of three different sections.The first section was on species description, ethno-botanical, and Medicinal uses; the second on plant communities; and the third on plant biodiversity of Tabuk region.In Section I, the author has provided photographs of 115 plant species along with the information on their traditional uses as medicine, food, fodder, agriculture, and horticulture.In Section II, the plant communities in different areas of Tabuk region were described with the help of images of 109 species.Section III contains a list of 198 plant species of 52 families from eight diverse habitats of Tabuk region.Artemisia herba-alba Asso.
Many authors [45,47,50] conducted the study of biodiversity in relation to the regimes of Tabuk environment.The Tabuk region is known for its extremely variable environment where the temperature varies from extreme low to extreme high.These temperature regimes have a profound effect on growth, morphology, physiology, and biochemistry of the plants.Ansari et al. (2014) [51] studied the growth of Lavandula pubescens in relation to the temperature variations, and observed active role of CAT, POD, and SOD in plants to cope with this abiotic stress.Abbas et al. (2017) [50] also observed the ecological variations and an active role of heat shock protein in Artemisia judaica L. to the same abiotic stress.The investigations of Ansari et al. (2014) [51] and Abbas et al. (2017) [50] suggest that April and October are favorable for growth, development, and medicinal uses of plants reported from this region.Recently, Ansari et al. ( 2021) [52] reported five common sea grass species, namely, Cymodocea rotundata, Halodule pinifolia, Thalassodendron ciliatum, Halophila stipulacea, and Thalassia hemprichii, from the Red Sea coast at Haql in Tabuk province.A quantitative analysis, in terms of frequency, density, abundance, and dominance of sea grass diversity was measured.The authors reported a marked difference in the quantitative parameters of sea grass diversity within the species, as well as on different study sites.
However, Mutairi et al. ( 2017) [45] focused on the influence of environmental factors on the taxonomic diversity of plant species in the arid region of Tabuk, which are characterized by a particular floristic composition, and their diversity.Average taxonomic distinctness (∆+) and variation in taxonomic distinctness (Λ+) were the two diversity indices used to calculate the effect of the environment and limiting environmental factors.Anthropogenic factors (woodcutting, pasture, and urbanization) are some of the important factors which significantly affect the floristic diversity [45].In another study, Al-Mutairi et al. ( 2016) [4] discussed the floristic diversity and phytogeographical distribution of plant species along the four Red Sea coastal sites at Sharma, Alqan, Al-Lwaz Mountains, and Alzetah of Tabuk province.The author reported 96 plant species belonging to 75 genera and 38 families, out of which, there were 34 dicots and 4 monocots.Most of the species were from the family Asteraceae (12.5%), followed by Fabaceae (10.42%),Zygophyllaceae (6.25%), and Lamiaceae (5.21%).In terms of life form spectrum, most of the species were theorphytes (37%), followed by chamaephytes (32%), geeophytes (13%), hemicryptophytes (10%), and Phanerophytes (8%).The chorological analysis of the recorded species indicated the predominance of monoregional taxa in this region.Recently, Al Mutairi (2022) [1] studied the plant diversity in five places of Tabuk region along with spatial variables, soil physical and chemical variables.The author reported 163 species of plants belonging to 124 genera of 41 families.The Aldesah site recorded the highest value of beta diversity followed by Sharma.There was no pronounced influence of spatial variables was observed on the plant diversity.However, the soil variables (pH, potassium.organic matter and sodium) show a solid possibility in constructing the plant communities.
Moawed and Ansari (2015) [8] studied the wild plant diversity at the coastal areas of Red Sea in Tabuk province.They reported 30 families, 66 genera, and 82 plant species from this region.Family Asteraceae showed highest abundance (9 species), followed by Fabaceae (8 species), Brassicaceae and Zygophyllaceae (7 species), Amaranthaceae (Chenopodiaceae) and Poacea (6 species), Resedaceae (5 species), Boraginaceae (4 species), and Asclepediaceae and Caryophyllaceae (3 species).The chamaephytes and therophytes are the dominating plant life forms, indicating vegetation of typical desert spectrum.There were 32.92% chamaephytes, and 29.27% therophytes; 57.32% were perennial and 42.68% annual species [8].Al-Qahtani (2018) [46] reported the diversity of weeds species in Citrus farms of Taymma of Tabuk province to find out the invasive species of weeds, which are the critical problem of agroecosystem and a major cause of huge economic losses.They have identified 36 weed species belonging to 20 families from the citrus farms of Taymma.Out of all the reported invasive species, Izoon canariense, Artemisia seiberi, Morettia parviflora, Oxalis corniculata, Setaria viridis, and Salsola imbricata were dominant over these citrus farmlands belonging to the dominant families Poacea, Asteraceae, Brassicaceae, and Amaranthaceae (Chenopodiaceae) [46].The Harrat ArRahah is located in the southern area of Tabuk, which is a solidified lava area.Fakhry and Al-Kenany (2019) [48] reported 135 species belonging to 99 genera and 34 families from the study area.Families Asteraceae, Brassicaceae, and Fabaceae contributed about 38% of total species.Fourteen species (10%) were recognized as endangered, Iris postii and Tulipa biflora were reported as rare endangered species.Although Rheum palaestinum in the flora of Saudi Arabia is recorded as an extinct species, three individuals were recorded in the study area.Astragalus collenettiae was the only endemic species recorded from this area [48].

Animal Biodiversity of Tabuk Region
The presence of different kinds of animals in a geographical region is very important for a balanced environment and a functional ecosystem.In the Tabuk region, studies are conducted to identify the biodiversity of insects, snails, fishes, amphibians, reptiles, birds, and mammals in different seasons and year [18,[54][55][56][57][58].In the following passage, a comprehensive account is presented to draw a baseline data from the published reports.

Biodiversity of Terrestrial Animals including Amphibians
Mohammed (2012) [57] reported the animal diversity on agricultural and non-agricultural land areas in different seasons of a year.The author selected a 500 m × 500 m land for this study and collected data using various traps.Several animal species were trapped, identified, and described, and their biodiversity was measured using diversity indices.Relative abundance and species richness was also determined for animal species belonging to different classes.Further, the effect of temperature on animal diversity was studied and animal community was studied using diversity index H =− ΣPi (LnPi).The study showed that H of all classes was 2.02; diversity rate for birds (72 species) H = 3.05, mammals (10 species) H = 1.5, reptiles (18 species) H = 2.3, amphibians (7 species) H =1.4, and freshwater fish (3 species) H = 0.92.Among the invertebrates, eight species of scorpions and five species of spiders, H = 1.78 and H = 0.9, respectively, and insects (93 species) H = 3.86 were recorded [57].
Among all the animal species, insect diversity was dominant throughout the year.However, it showed its maximum in the summer and minimum in the winter.Some reptile species Stenodactylus arabicus and Stenodactylus grandiceps, were highly abundant [57].Among the mammal species, Gerbillus nanus was most abundant, whereas Spalax leucodon was rarely found.A convergent abundance of spiders was recorded, except the Pholcus phalangioide.Scorpions also showed convergent abundance, except Leiurus quinquestraitus and Compsobuthus arabicus.There were 21% amphibians, 25% fishes, 3% insects, and 1% birds among all the species studied.The study recommends that more work has to be conducted to measure the biodiversity and abundance of different animal species in various regions of the Kingdom of Saudi Arabia in general and Tabuk region in particular [57].Aloufi and Amr (2018) [54] Mallon and Budd (2011) [62] In another study, Aloufi, et al. (2016) reported 10 bat species (Table 5) based on their echolocation calls.One new species (Barbastella leucomelas) was identified and added to the list of bat species of Saudi Arabia and Arabian Peninsula.Moreover, occurrence of R. aegyptiacus was observed expanding the distribution range of bat species in northwestern part of Saudi Arabia [55].The diversity and distribution of bats in Saudi Arabia is still unexplored.Further GIS studies can provide more authentic data [63][64][65].Aloufi and Amr (2018) studied the diversity of carnivores from Tabuk Province from 2010 to 2017.Information was collected using camera traps and live traps, and through direct observations.Seven carnivore species representing four families were recorded.There were three felines, Felis margarita and Panthera pardus nimr; a hyaenid, Hyaena hyaena; a mustelid, Mellivora capensis; and three canids, Canis lupus, Vulpes cana, and Vulpes vulpes.For each species, a list of location was given for its current distribution.Unfortunately, poachers or the local community killed many of the reported species.Killing and hanging of various animal species is common practice in this region [54].Carnivores are facing many types of threats, such as shooting, trapping, and poisoning [62].The animal killing shows the level of aggression of poachers or villagers for the carnivores (wolves and hyenas) just as a sign of pride [66].However, the conflict between humans and wildlife and their coexistence is a global issue [42].The diversity of carnivores in Saudi Arabia is very poor and requires an immediate action from Ministry of Environment, Water, and Agriculture for their conservation and sustainability of the region [54].Apart from carnivores, one amphibian and thirty-three reptile species belonging to twelve families (Cheloniidae, Gekkonidae, Agamidae, Chamaeleonidae, Lacertidae, Scincidae, Varanidae, Trogonophidae, Boidae, colubridae, Viperidae, and Elapidae) are also reported form Tabuk region (Table 6).The important part is there were three new species of reptiles (Hemidactylus mendiae, Pseudotrapelus aqabensis, and Phoenicolacerta kulzeri) [67].The reporting of new species is a good indicator of a functional ecosystem.

Biodiversity of Aquatic Animals
The aquatic ecosystem is very rich in fauna at various sites of Tabuk region, namely, Haql, Duba, Sharma, Alwajh, Umluj, etc.The relative densities of aquatic fauna in different seasons of Tabuk were determined and correlated with coastal water quality [56].Lottia limulata, Nerita fulgurans Puncturella longifissa Istiblennius dussumieri and Gerres sp were identified from the coastal sites of the Red Sea.Among all, Lottia limulata was abundant and densely populated at the studied coastal sites in Haql in October 2013, whereas Boleophthalmus was at Duba April 2014 [56].Coastal eutrophication due to anthropogenic inputs of nutrients showed a direct influence on phytoplankton, zooplanktons, macrophytes, and fish diversity.Dominating algal species is the major characteristic of eutrophic ecosystems which affects the diversity of consumers [68,69].
The Red Sea is rich in biodiversity with large varieties of fish and other marine animals that can be identified through DNA barcoding.DNA barcoding is an effective tool for the species identification and assessment of biodiversity.Several studies have been conducted for the sequence diversity in a ~650 bp region near the 5 region of COI gene (cytochrome c oxidase) which provides strong species level resolution for verification of animal groups, such as birds, springtails, spiders, and fishes [58].Six fish species, namely, Epinephelus bleekeri, Siganus sutor, Carangoides sp., Scomberomorus commerson, Lutjanus ehrenbergii, and Pristipomoides filamentosus, reported from Red Sea using COI barcode sequence [58].Further, Rock skipper's diversity was studied in the coastal waters of the Red Sea [47,70].The impact of different environmental factors on coastal biodiversity can be measured by determining the density, frequency, and abundance of rock skippers.The reproduction, life cycle, and some specific physiological and behavioral patterns make them important as ecological indicator for coastal biodiversity [56].
In a study by Amr and Alshammari (2012) [71], 29 species of snails were recorded form Arabian Peninsula.One species, Bulinus beccari, was reported from the Hail region.In the Tabuk region, 75 freshwater aquatic habitats (springs, artificial lakes, swamps, streams, ponds, and irrigation canals) were studied in between 2012 and 2014.Eten smarts Global Position System was used; two freshwater snail species (Melanoides tuberculata and Melanopsis buccinoidea) belonging to families Thiaridae and Melanopsidae, respectively, were reported for the first time from six localities of Tabuk region [72].Moreover, characteristics and distribution of larval habitats of Culex pipiens complex in Tabuk was studied.In total, 116 aquatic habitats were surveyed, 48 were positive for larvae of Culex pipiens L. (76.3%) and Cx.quinquefasciatus (23.7%).Shallow water, mud bottom, and absence of grasses, algae, and predators were the common characteristics of habitats positive for Culex larvae (p < 0.05) [73].

Microbial Biodiversity of Tabuk Region
Soil microorganisms are associated soil quality and productivity.The soil microorganisms are very important for the functionality of the ecosystem of a geographical region.The soil fauna and flora are responsible for the decomposition of organic matter and recycling of nutrients.In the Tabuk region, microbial diversity reports are very few and published in past couple of years.The proper mapping still has a long way to go.We are providing a comprehensive account based on available literature.Ghobashy and Helal (2018) [74] studied wild microbial communities, especially in the un-explored areas and reported Bacillus sp. as the most abundant genus.It contributed about 70.4% of the total isolates of soil microbiota.In another study, microbial (fungi and bacteria) diversity and abundance was investigated by Alotaibi et al. (2020) [75] in Sabkha and desert areas of Saudi Arabia.Soil samples from Al-Aushazia lake, AlQasab, AlKasar, Tabuk, Al-Kharj, Al-Madina, Jubail, Taif, and Abqaiq were analyzed for microbial isolation using molecular techniques (PCR and sequencing).On the basis of 18SrDNA sequencing, 203 fungal species belonging to 33 genera were identified [75].The most common fungi were Fusarium, Alternaria, Chaetomium, Aspergillus, Cochliobolus, and Pencillium.Further, 16S rDNA sequencing revealed 22 bacterial species of two genera, Bacillus and Lactobacillus.The most common bacterial species were Bacillus subtilis and Lactobacillus murinus.Some fungal species, Actinomyces elegans, Fusarium proliferatum, Gymnoascus reesii, and Myzostoma spp., were also isolated, but only from the soil of Al-Aushazia.AlQasab soil had the highest microbial diversity among other areas with abundances of 23.5% and 4.4% of total fungi and bacteria, respectively.The findings of this study reveal that fungal diversity is greater than that of bacteria [75].In another report, 33 marine bacterial species [76] and Enterobacter sp.[77] were isolated and identified from the coastal environment of Haql.These studies are very significant and help us to understand the microbial habitat ecology and diversity.Further, these studies can be linked to the presence of other organisms in a functional ecosystem and developing a model.

Conclusions
Biodiversity defines the variations in living organisms at genetic, species, and ecosystem level at a particular time.Monitoring, assessment, and conservation of biodiversity is the need of the hour and is one of the important global environmental concerns.There are some published reports on the diversity of plants, animal, and microorganisms in the Tabuk Region, but there is still gap in the biodiversity of region and its mapping.In order to create a baseline data this review is compiled that can facilitate the researchers to carry out further studies and investigations on biodiversity of Tabuk region.In our study, 227 species of 157 genus were identified that belongs to 45 families of angiosperms.On comparing the above data with the endangered list of Floa of KSA (2022), we recorded 12 endangered species of plants from Tabuk region, namely, Allium sinaiticum, Astragalus collenettiae, Cerastium dichotomum, Cymbolaena griffithii, Glaucium arabicum, Leopoldia tenuiflorum, Minuartia picta, Salsola lachnantha, Salvia palaestina, Tulipa biflora, Valerianella szovitsiana, and Veronica beccabunga..The biodiversity plays a very significant role in energy production, energy flow, pollutants removal, and biogeochemical cycling of nutrients between aquatic and terrestrial ecosystems, and for a comfortable human life existence.In the interest of protection of the wild flora and fauna from poaching and illegal trades, the Government of Saudi Arabia established several laws and regulations.Moreover, there are reports of human-wildlife conflict that need to be addressed by the Tabuk authority for the conservation of the wildlife.Public awareness, education and law enforcement could be the effective practices that should be adopted and promoted.There are many plant species reported from Tabuk region that are well known for their exceptional medicinal and traditional uses, and are considered as an important natural resources for pharmaceutical products.These plants are widely distributed in Saudi Arabia in general and Tabuk in particular, and need more investigation.Further, in Tabuk, despite rich floristic diversity, there are reports of woodcutting activities and mega developmental projects like NEOM, LINE, Red Sea Development Company, and AMALA etc.The ongoing projects requires a more comprehensive baseline data of the biodiversity of Tabuk region for a long-term sustainability.

Figure 1 .
Figure 1.A map demonstrates locations of Tabuk biodiversity research.

Figure 1 .
Figure 1.A map demonstrates locations of Tabuk biodiversity research.

Figure 2 .
Figure 2. Different levels for the biodiversity assessments.

Figure 2 .
Figure 2. Different levels for the biodiversity assessments.

Table 2 .
List of Angiosperms Reported from Tabuk Region of KSA.

Table 4 .
Mammals reported from the Tabuk region.

Table 5 .
Bats reported from the Tabuk region.

Table 6 .
Amphibian and Reptiles reported from Tabuk region.