Ethnobotanical Study on Plant Used by Semi-Nomad Descendants’ Community in Ouled Dabbeb—Southern Tunisia

Thanks to its geographic location between two bioclimatic belts (arid and Saharan) and the ancestral nomadic roots of its inhabitants, the sector of Ouled Dabbeb (Southern Tunisia) represents a rich source of plant biodiversity and wide ranging of ethnobotanical knowledge. This work aims to (1) explore and compile the unique diversity of floristic and ethnobotanical information on different folk use of plants in this sector and (2) provide a novel insight into the degree of knowledge transmission between the current population and their semi-nomadic forefathers. Ethnobotanical interviews and vegetation inventories were undertaken during 2014–2019. Thirty informants aged from 27 to 84 were interviewed. The ethnobotanical study revealed that the local community of Ouled Dabbeb perceived the use of 70 plant species belonging to 59 genera from 31 families for therapeutic (83%), food (49%), domestic (15%), ethnoveterinary (12%), cosmetic (5%), and ritual purposes (3%). Moreover, they were knowledgeable about the toxicity of eight taxa. Nearly 73% of reported ethnospecies were freely gathered from the wild. The most commonly used plant parts were leaves (41%) followed by flowers and inflorescence (16%). We reported the use and collection of non-renewable parts (underground storage organs and roots) for 20 ethnospecies. Interestingly, a comparison with the available literature in Tunisia and neighboring countries reveals 13 new useful plants as well as 17 plants with new uses and demonstrates an important reservoir of traditional ethnobotanical heritage that is still sustained by respondents stemming from the semi-nomadic lifestyle of their ancestors (74% of cited taxa). These data could set a basis for further phytochemical and pharmacological research and conservative approach of the most relevant plant species including endemic overused and endangered taxa.


Introduction
Since times immemorial, wild, naturalized, or non-cultivated plants provide a "green social security" to hundreds of millions of people throughout the world, namely in the form of low-cost building materials, fuel, food supplements, herbal medicines (80% of people in the world [1]), basketry containers for storage, processing or preparation of food crops, or as a source of income [2,3].
A recent bibliometric study of all works listed in the Scopus database until 2019 (analysis of more than 100,000 publications) has underlined that global research is focused more on bioprospection rather than cultivation or domestication of plants with known biological potential [4]. This could pose a threat to the future of these natural resources. In this regard, Harshberger underlined the fact that ethnobotanical findings should not deserti Coss. & Durieu endemic to North Africa, Searsia tripartita (Ucria) Moffett to northern Sahara, Astragalus armatus Willd., Calligonum azel Maire, Thymus a Boiss. & Reut., Artemisia saharae Pomel, Rhanterium suaveolens Desf., and A. halimu five latter taxa are endemic to Maghreb. Although using endemic taxa highlights inality of traditional ethnobotanical knowledge maintained by respondents, an e exploration of these taxa might lead to their extinction. Thus, awareness is need raised among the local population of Ouled Dabbeb focusing on the sustainable ut and management of these plant resources.

Source of the Plants Used
The majority of reported ethnospecies was freely gathered from the wild ( some cases (7%), they were later domesticated. However, some exotic or difficult taxa were even cultivated (7%) or bought from herbalists (9%) on the Tataouine Such results revealed the interesting role of spontaneous plants in the livelihoo local communities. These trends regarding harvesting plants from a natural envi can be linked to the nomadic lifestyle rooted in local populations of the area. Sim ings were recorded in the Algerian steppe where 60% of used plants by the noma munity were sourced from the wild [23].

Revelance of Wild Used Plants in the Sector of Ouled Dabbeb
The obtained Ethnobotanicity Index (EI) in this study area was 36.96%. Th that almost 37% of the available plants in the area are considered useful by local nities of which 35% are known to be medicinal plants, 15% are known to be ed

Source of the Plants Used
The majority of reported ethnospecies was freely gathered from the wild (73%); in some cases (7%), they were later domesticated. However, some exotic or difficult-to-reach taxa were even cultivated (7%) or bought from herbalists (9%) on the Tataouine market. Such results revealed the interesting role of spontaneous plants in the livelihood of the local communities. These trends regarding harvesting plants from a natural environment can be linked to the nomadic lifestyle rooted in local populations of the area. Similar findings were recorded in the Algerian steppe where 60% of used plants by the nomadic community were sourced from the wild [23].

Revelance of Wild Used Plants in the Sector of Ouled Dabbeb
The obtained Ethnobotanicity Index (EI) in this study area was 36.96%. This means that almost 37% of the available plants in the area are considered useful by local communities of which 35% are known to be medicinal plants, 15% are known to be edible, and 4% are known to be toxic. The EI registered in our work seems to be higher than those reported 4% are known to be toxic. The EI registered in our work seems to be higher than those reported in other Mediterranean studies such as 12.7% in Sicily, Italy [27], and about 27.6% in Caurel, Spain [28]. However, this ascertainment could be related to the small size of the investigated area in this study. Considering the EI of endemic taxa, the calculated value was 22.2%, which confirms the richness of local ethnobotanical knowledge maintained by the indigenous population.

The Parts Used and Harvest Impact
As shown in Figure 2, the most commonly used plant part was the leaves (41%) followed by flowers and inflorescence (16%) and then fruits, stems, and roots (7% for each). This prevalence of ethnobotanical use of leaves is observed in previous studies in Tunisia [17] as well as in other neighboring countries such as Algeria [21,23] and Morocco [29]. This can be explained by the fact that leaves require less effort to be obtained compared with other parts, especially underground organs, and plant exudates (gums, resins). They are also the main photosynthetic organs in the plants; therefore, they might be considered as rich sources of bioactive compounds [2]. In light of this, a recent study led by Sicari et al. [30] recommended even the consumption of blanching water of some leafy vegetable as a good source of bioactive compounds.
Since different plant resources can be grouped according to their potential for sustainable harvest, from high potential (leaves, flowers, fruits) to low potential (bark, roots, or the whole plant), information about used plant parts ( Figure 2) can lead us to have a preliminary idea about yield impact and then sift out taxa that are likely considered to be more vulnerable to overharvesting [2].
In this study, debarking or the collection of non-renewable parts (underground storage organs and roots) was reported for 20 ethnospecies (17%), including two edible geophytes: A. roseum and Scorzonera undulata Vahl, which were picked up for their bulbs and fleshy roots, respectively, F. tunetana for its rhizome, and S. tripartita, Periploca angustifolia Labill. for their roots. It may cause enormous strain and increase mortality in taxa, thus making them vulnerable to overexploitation. This vulnerability can be more and more alarming when it concerns endemic taxa such as F. tunetana and S. tripartita. Above all, these last two do not benefit currently from any conservation action either in situ (nature reserves) or ex situ (seed banks) [31]. This vulnerability can be more and more alarming when it concerns endemic taxa such as F. tunetana and S. tripartita. Above all, these last two do not benefit currently from any conservation action either in situ (nature reserves) or ex situ (seed banks) [31].

Stems Leaves Flowers
Med: It is used to treat gas trouble (leaves infusions) and also used as antidiabetic (aerial part decoction) and to relieve hepatitis (infusion or water decoction of leaves and flowers). Dom: It is used as odor control, and a deterrent against tadpoles in 'Magel' (hanging a bunch of stems). It is also against insects and plant pests (incorporating stems' powder into the soil).

Leaves Flowers Roots
Med: Leaves decoction is used to relieve stomach pains, gas trouble, ulcers, and constipation. Leaves and flowers' infusion is used as hypotensive and antidiabetic. Compress with roots water infusion is used to relieve dermatoses Al/Med: Leaves and flowers are freshly cooked as part of a traditional dish (a sort of thick soup) often prepared by local people of Tataouine in spring which is considered as a panacea, to increase immunity, to treat or prevent the development of cancer **.

Med:
The poultice is applied locally on the skin for wounds healing and as hemostatic. It is also used as a disinfectant (washing with water leaves infusion) and as collyrium (fresh twigs' water infusion). Ethnovet: Water infusion is applied locally on the skin of livestock against scabies and as disinfectants after mowing, infusion (drink) as appetizer, and digestive. Dom: It is used to prepare snuff powder 'neffa' to which it owes its degradation.

Sociodemographic Profile of Respondents
The demographic characteristics of informants (n = 30) are summarized in Table 2. A preponderance of females (53.3%) and elders (over 60 years old) (46.6%) was noted with the majority being rural residents (80%) and illiterate (46.6%).
The number of cited ethnospecies correlated with the user's age (Kruskal-Wallis chi-, p-value = 0.048) ( Figure 3A) and education level (Kruskal-Wallis chi-, p-value = 0.046) ( Figure 3B). In contrast, it was predisposed neither by gender (Kruskal-Wallis chi-, p-value = 0.060) nor location (Kruskal-Wallis chi-, p-value = 0.133). Thus, age and education are the main factors that seem to influence the local ethnobotanical knowledge of respondents. Illiterates and elderly people exhibit a more significant understanding of the ethnobotanical properties of the local flora compared to the educated and youngsters.
This can be attributed to their personal experience stemming from the semi-nomadic lifestyle of their younger years [32]. On the other hand, modernization and the exotic culture acquired by education can influence the younger generation's unwillingness to learn. Similar results were found in another study in Morocco [21].

Sociodemographic Profile of Respondents
The demographic characteristics of informants (n = 30) are summarized in Table 2. A preponderance of females (53.3%) and elders (over 60 years old) (46.6%) was noted with the majority being rural residents (80%) and illiterate (46.6%).
The number of cited ethnospecies correlated with the user's age (Kruskal-Wallis chi-, p-value = 0.048) ( Figure 3A) and education level (Kruskal-Wallis chi-, p-value = 0.046) ( Figure 3B). In contrast, it was predisposed neither by gender (Kruskal-Wallis chi-, pvalue = 0.060) nor location (Kruskal-Wallis chi-, p-value = 0.133). Thus, age and education are the main factors that seem to influence the local ethnobotanical knowledge of respondents. Illiterates and elderly people exhibit a more significant understanding of the ethnobotanical properties of the local flora compared to the educated and youngsters.
This can be attributed to their personal experience stemming from the semi-nomadic lifestyle of their younger years [32]. On the other hand, modernization and the exotic culture acquired by education can influence the younger generation's unwillingness to learn. Similar results were found in another study in Morocco [21].  Although results indicated that women and men sustain a roughly similar level of ethnobotanical knowledge ( Figure 4A), it was significantly patterned by the use category Although results indicated that women and men sustain a roughly similar level of ethnobotanical knowledge ( Figure 4A), it was significantly patterned by the use category (F = 33.11, p = 2.2 × 10 −16 ) and also by the interaction between gender and use categories (F = 3.0556, p = 0.007019).
men were more knowledgeable about ethnoveterinary plants. Such difference can be linked to gender roles among the local community of the studied area where women are considered as primary health care and food providers for their families, and livestock keeping is the main source of income for men. Finally, it cannot be ruled out that the size of our sample (30 participants to the interviews) may have failed to disclose a highly significant variability. However, the size of the village population in itself constituted the main restraint to our sample.

Plant Taxa Use and Frequency
Considering that one single ethnospecies could be useful for various purposes, the results shown in Table 1 revealed that the reported ethnospecies were mainly used for therapeutic (83%) and food (49%) practices. Furthermore, informants acknowledged the use of some taxa for domestic (15%), ethnoveterinary (12%), cosmetic (5%), and ritual (3%) purposes, highlighting the wealth and wide range of ethnobotanical knowledge that is still sustained by local people. As shown in Figure 4B, women knew more about medicinal and food taxa, whereas men were more knowledgeable about ethnoveterinary plants. Such difference can be linked to gender roles among the local community of the studied area where women are considered as primary health care and food providers for their families, and livestock keeping is the main source of income for men. Finally, it cannot be ruled out that the size of our sample (30 participants to the interviews) may have failed to disclose a highly significant variability. However, the size of the village population in itself constituted the main restraint to our sample.

Plant Taxa Use and Frequency
Considering that one single ethnospecies could be useful for various purposes, the results shown in Table 1 revealed that the reported ethnospecies were mainly used for therapeutic (83%) and food (49%) practices. Furthermore, informants acknowledged the use of some taxa for domestic (15%), ethnoveterinary (12%), cosmetic (5%), and ritual (3%) purposes, highlighting the wealth and wide range of ethnobotanical knowledge that is still sustained by local people.
Ten taxa were reported to be utilized for various household uses. Some of them, such as Deverra denudata (Viv.) Pfiesterer & Podlech, Deverra tortuosa DC., and A. saharae were used for odor control, as repellent and deterrent against tadpoles in "Magel" (a sort of Tunisian cistern made for the collection and storage of rainwater). Another interesting use concerned S. tripartita (root bark), R. suaveolens (flowers), Olea europaea L. (black fruit), and Punica granatum L. (flowers and fruit set) that seem to be used for tinting wool in light brown, yellow, pinkish white, and orange, respectively. The coloring attributes of these plant taxa were reported previously by [13] in southern Tunisia. Informants were also knowledgeable about the biopesticidal utilization of plants-namely the case of the powdered aerial part of D. tortuosa incorporated in the soil before sowing carrots for soil-borne pest management.
Eight taxa were used for livestock health care, intended mainly to treat skin diseases, digestive disorders, and to correct fractures. Some plants were administered to treat the same syndromes for which they are recommended in human medicine such as R. suaveolens and Plantago albicans L. that were used for their diuretic properties. Such similarity was reported in previous studies in Saudi Arabia and Palestine [33] suggesting that humans may have tried these remedies on animals before they used them for their medical problems.
Ajuga iva (L.) Schreb., Lavandula coronopifolia Poir., and Myrtus communis L. are three aromatic taxa that were widely used by women for cosmetic purposes, mostly for hair care and to concoct perfume commonly homemade for the brides in this region. The uses of these three species were also reported by Ghrabi-Gammar et al. [34].
The interviewees seldom referred to religious and ritual customs. Only two ethnospecies were reported for this type of use: the fruits of Ziziphus lotus Lam. were used for washing and shrouding the deceased thanks to their saponifying properties, and Ruta chalepensis L. was used to ward off the evil eye and spirits by inhalation of burned leaves. The same practice was reported by Le Floc'h [13] in Tunisia.

Relative Frequency of Citation (RFC)
The RFC of the reported taxa ranged from 0.03 to 1 ( Table 1)

Human Medicine
Our surveys stated the use of 54 ethnospecies for various therapeutic purposes that fall into 17 ailment categories (Table 3). Among them, 22 taxa (40.7%) were devoted to treat digestive disorders (hemorrhoids, constipation, diarrhea, ulcers, bloating) with 72 citations. Eleven taxa (20.4%) were used to relieve dermatological problems (wounds, irritations, dermatoses, furunculosis, eczema, spots) with 49 citations, while nine taxa (16.7%) were revealed as remedies for cold, respiratory diseases (bronchitis, cough, asthma, sore throat) and fever with 42 citations. To treat either urogenital disorders (urinary incontinence) or cardiovascular disorders, the local population described the use of 10 taxa (18.5%) for each ailment category. Six taxa (11.1%) were mentioned as remedies for each case of headaches, endocrine system disease (diabetes), and sexual reproductive problems while only five taxa (9.3%) were used to relieve muscular/skeletal diseases (rheumatism, arthritis, and joint pain). Four taxa (7.4%) were reported for treating fractures, toothache, and mouth inflammation. Two ethnospecies (3.7%) were used to soothe nervous system diseases as a tonic or as calming and sedative taxa, whereas two other ones were used for the ear-nose and throat (ENT) conditions. Finally, the interviewees stated the use employment of one taxon for eye care and another for cancer treatment. In line with these observations, previous studies underlined that the local people of the northwest of the governorate of Kef in Tunisia [17] and also nomadic peoples in the Algerian steppe [23] were mainly informed about plants that relieve digestive system disorders, skin diseases, and respiratory system diseases.

Informant Consensus Factor (ICF)
The Informant Consensus Factor (ICF) was calculated for all ailments categories, except ophthalmological diseases, which had only one citation (Table 3) and was found to range from 0.40 to 1.00 with an average of 0.68. Such results demonstrate that knowledge about the therapeutic use of plants seems to be well distributed among the local population of the area of the study.
Cancer had the highest ICF value (ICF = 1.00) due to the use of a single species for its treatment (M. arvensis), demonstrating that local pharmacopoeia could provide species with promising anticancer activities. In this context, a pharmacological study [35] evaluated this species and highlighted the antiproliferative activity of its leaf extract against human cancer cells.
Poisonous animal bites presented the second-highest ICF value (ICF = 0.82) and were reported to be treated using three taxa A. campestris, C. colocynthis, and R. raetam. This may be attributed to frequent reports about scorpions and snakes in Saharan areas or to the paucity of alternative treatments and the long distancing from hospital centers. Similar results were also observed in southern Tunisia [13] and among the nomadic populations in Algerian Sahara [36].
Considerable consensus values were also found for the treatment of dermatological illnesses and bone pains (ICF = 0.79) for each. Other categories were noted with high ICF values such as fever (ICF = 0.75), sexual reproductive problems (ICF = 0.71), and gastrointestinal disorders (ICF = 0.70).

Preparation and Modes of Administration
In our study, decoction was the most commonly applied method of preparation (43% of total used medicinal taxa) followed by infusion (16%), powder (11%), poultice, and maceration (10% for each) ( Figure 5). Similar findings were reported by other studies [21,37]. Regarding direct usage, five cases (6%) were noted in which fresh plant parts were chewed mostly to relieve gastrointestinal ailments. For example, respondents disclosed that tubercles of Erodium glaucophyllum (L.) L'Hér. were directly eaten for their laxative properties.

Preparation and Modes of Administration
In our study, decoction was the most commonly applied method of preparation (43% of total used medicinal taxa) followed by infusion (16%), powder (11%), poultice, and maceration (10% for each) ( Figure 5). Similar findings were reported by other studies [21,37]. Regarding direct usage, five cases (6%) were noted in which fresh plant parts were chewed mostly to relieve gastrointestinal ailments. For example, respondents disclosed that tubercles of Erodium glaucophyllum (L.) L'Hér. were directly eaten for their laxative properties. Once plants have been prepared, the next step is to proceed with the administration. The two main roots of administration recorded in the present work were oral application (64%) and topical applications (36%). Most of the plants were used as they are. However, in some cases, they were mixed with adjuvants such as milk and olive oil to potentiate their effects and facilitate their application. For instance, a decoction in the milk of leaves powder of Nitraria retusa Asch. was used to prepare an ointment to treat leishmaniasis. Few species were used in combination with other plants. Particularly, aerial parts of Cynodon dactylon (L.) Pers. were boiled with leaves of Polygonum equisetiforme Sm. to treat urinary incontinence.

Culinary Uses
Our survey highlights that 32 ethnospecies were reported as being traditionally used for culinary purposes (Table 1). Slightly more than their quarter (26%) are consumed raw. Some are used in salads such as the tubercles of E. glaucophyllum (Tommir) and leaves and flowers of Rumex roseus L. (Homidha). The latter are appreciated for their lemony taste. Others are often eaten directly off the plant as a snack. As examples, we can cite the fruits of jujube Z. lotus (Nbeg) and S. undulata (Guiz), which is a plant consumed for its fleshy root and flowers, which taste similar to chocolate. Nevertheless, the majority of edible reported ethnospecies are consumed freshly cooked as a part of typical savory dishes, such as couscous, vegetable stews, and thick soups. The leaves and bulbs of the two Alliaceae: A. roseum subsp. odoratissimum and Allium ampeloprasum L. are often incorporated Once plants have been prepared, the next step is to proceed with the administration. The two main roots of administration recorded in the present work were oral application (64%) and topical applications (36%). Most of the plants were used as they are. However, in some cases, they were mixed with adjuvants such as milk and olive oil to potentiate their effects and facilitate their application. For instance, a decoction in the milk of leaves powder of Nitraria retusa Asch. was used to prepare an ointment to treat leishmaniasis. Few species were used in combination with other plants. Particularly, aerial parts of Cynodon dactylon (L.) Pers. were boiled with leaves of Polygonum equisetiforme Sm. to treat urinary incontinence.

Culinary Uses
Our survey highlights that 32 ethnospecies were reported as being traditionally used for culinary purposes (Table 1). Slightly more than their quarter (26%) are consumed raw. Some are used in salads such as the tubercles of E. glaucophyllum (Tommir) and leaves and flowers of Rumex roseus L. (Homidha). The latter are appreciated for their lemony taste. Others are often eaten directly off the plant as a snack. As examples, we can cite the fruits of jujube Z. lotus (Nbeg) and S. undulata (Guiz), which is a plant consumed for its fleshy root and flowers, which taste similar to chocolate. Nevertheless, the majority of edible reported ethnospecies are consumed freshly cooked as a part of typical savory dishes, such as couscous, vegetable stews, and thick soups. The leaves and bulbs of the two Alliaceae: A. roseum subsp. odoratissimum and Allium ampeloprasum L. are often incorporated in the traditional flatbread 'Kesra'. Asphodelus tenuifolius Cav. leaves are freshly cooked as an ingredient of the sauce for couscous and also to prepare the traditional soup 'Dchich'. Similar findings were reported in Sidi Bouzid (central Tunisia) where a favorable perception of these same wild edible plants was observed [38]. This could spur their consumption at a national scale as a part of sustainable food systems for good nutrition and health, as several studies cited by the Biodiversity International revealed that the nutritional value of wild and indigenous food is often higher than that of their cultivate counterparts [39].
In addition, we reported the use of some plant taxa either as condiments such as T. algeriensis and R. eriocalyx leaves or as flavoring mainly added to black tea, as is the case of twigs of A sahareae and bark of the roots of P. angustifolia. We recorded also some "cognitive use" and "not-so-active use" regarding some ethnospecies used in times of food insecurity in the past, in the 1940s, as a replacement or complement to barley flour namely grounded dried leaves of A. halimus. This was confirmed by Bouquet's study [40] focusing on food in Tunisia at the beginning of the 20th century.
Several reported edible plant taxa are considered as functional foods that are ingested in a food context as culinary preparations for their assumed health benefits [41]. Powders of F. tunetana (rhizome) and S. tripartita (peeled roots) are added to barley flour to prepare a traditional dish locally named 'Ich' for its mineralizing and anti-inflammatory proprieties as well as to relieve ulcers. Likewise, leaves and flowers of M. arvensis are commonly consumed by local people of Tataouine during spring in thick soup and are perceived as a panacea that boosts the immune system and may treat or prevent the development of cancer.

Toxicity of Used Plants
Eight taxa were reported as being toxic for humans and/or livestock. As shown in Table 1, their poisonous effects were manifested by gastrointestinal disorders, skin irritation, and abortifacient effect, and they depended mainly on the consumed quantity. Moreover, serious poisoning cases inducing sometimes death were reported after oral administration of R. raetam and C. colocynthis. In this regard, previous pharmacological studies confirmed the lethal effect of the pulp extract of C. colocynthis received by rabbits [42] and also its toxicity on liver cells which may engender hepatocyte necrosis and liver fibrosis [43]. Likewise, the findings of Algandaby [44] revealed that the repeated administration of excessive doses of methanolic extract of R. raetam in rats could exhibit hepatotoxic, nephrotoxic, and mutagenic effects.
An overlap of five taxa was found between toxic plants reported in this investigation and those referenced by Le Floc'h [13] (Figure 6). Additionally, nine taxa were mentioned in the literature to be poisonous while they were frequently utilized by local communities of Ouled Dabbeb. Four of them were cautiously used for the control of snakebites, insect pests, and many other harmful organisms.
Some experimental studies proved the involvement of endogenous alkaloids of Peganum harmala L. in Parkinson's disease [45] and the potent tetratogenic effect of Nicotiana glauca Graham high in anabasine [46] confirming, thus, their poisonous effect described by Le Floc'h [13]. The ignorance of such possible toxicity may interfere with their biosafety, since the mode of application described by respondents seems to be "unsafe" (Figure 6). Nevertheless, earlier studies proved positively the innocuousness of Diplotaxis harra Boiss., A. tenuifolius [47,48], and C. dactylon [49,50]. Therefore, the complexity of issues drives the need for further research of the phytochemical analyses and toxicological effects of the documented flora to provide a better understanding about the safety and efficacy of their consumption.

Transmission of Ethnobotanical Knowledge over Time (1936-2016)
The comparison of reported data with the ethnobotanical literature revealed that local plant knowledge in the study area may have changed, been lost, or newly developed, but also elements of this knowledge may persist for many generations (Figure 7). We note that the interviewees in this study ignore the use of over 38 taxa available in their surrounding area while they have been widely used by their nomadic and semi-nomadic forefathers in the past (Supplementary Table S2). Among these plants, we find mainly those of critical survival value namely edible ones used in times of food insecurity such as Aizoon canariense L. and Erodium crassifolium (Forssk.) L'Hér. [51]. We also assess taxa with detergent proprieties such as Anabasis articulata (Forssk.) Moq. and Fagonia cretica L. Knowledge on medicinal plants also seems to have reduced especially that on skin healing wound flora as Plantago lanceolata L., Limoniastrum guyonianum Durieu ex Boiss., and Thymelaea microphylla Coss. & Durieu. Some experimental studies proved the involvement of endogenous alkaloids of Peganum harmala L. in Parkinson's disease [45] and the potent tetratogenic effect of Nicotiana glauca Graham high in anabasine [46] confirming, thus, their poisonous effect described by Le Floc'h [13]. The ignorance of such possible toxicity may interfere with their biosafety, since the mode of application described by respondents seems to be "unsafe" (Figure 6). Nevertheless, earlier studies proved positively the innocuousness of Diplotaxis harra Boiss., A. tenuifolius [47,48], and C. dactylon [49,50]. Therefore, the complexity of issues drives the need for further research of the phytochemical analyses and toxicological effects of the documented flora to provide a better understanding about the safety and efficacy of their consumption.

Transmission of Ethnobotanical Knowledge Over Time (1936-2016)
The comparison of reported data with the ethnobotanical literature revealed that local plant knowledge in the study area may have changed, been lost, or newly developed, but also elements of this knowledge may persist for many generations (Figure 7). We note that the interviewees in this study ignore the use of over 38 taxa available in their surrounding area while they have been widely used by their nomadic and semi-nomadic forefathers in the past (Supplementary Table S2). Among these plants, we find mainly those of critical survival value namely edible ones used in times of food insecurity such as Aizoon canariense L. and Erodium crassifolium (Forssk.) L'Hér. [51]. We also assess taxa with detergent proprieties such as Anabasis articulata (Forssk.) Moq. and Fagonia cretica L. Knowledge on medicinal plants also seems to have reduced especially that on skin healing wound flora as Plantago lanceolata L., Limoniastrum guyonianum Durieu ex Boiss., and Thymelaea microphylla Coss. & Durieu.
Nonetheless, this comparison demonstrated that an important reservoir of traditional ethnobotanical heritage among respondents is still present. More than 74% of cited taxa in this study were also perceived as usable by nomads and semi-nomads in the past. It Nonetheless, this comparison demonstrated that an important reservoir of traditional ethnobotanical heritage among respondents is still present. More than 74% of cited taxa in this study were also perceived as usable by nomads and semi-nomads in the past. It should be noted that despite decades in decline, local inhabitants of Ouled Dabbeb sustain the same use of 29 taxa, keeping the same method of preparation and administration adopted by their nomadic ancestors. This shared knowledge essentially concerns edible (35%), medicinal (35%), and toxic (17%) plants (Figure 7e').
The data presented here mirror the above-reported wealth and experience of nature gained over generations. Thus, we can talk about indigenous ethnobotanical knowledge, which is defined by Masango as "the totality of all knowledge and practices established on past experiences and observations that is held and used by people", which merits further valorizations.
In addition, some preparations recorded by Le Floc'h [13] were newly developed by the current inhabitants of Ouled Dabbeb in order to meet their present-day needs.
For some taxa such as Haloxylon schmittianum Pomel, P. albicans, and R. chalepensis, the same preparation used in the past for human health care are cited in this study to treat animal diseases. Likewise, for some taxa such as P. granatum L. and Malva aegyptia L., participants merge medicinal knowledge inherited from their immediate ancestor with dietetic knowledge recently acquired to prepare some functional food. These results suggest that some past ethnobootanical knowledge is transmitted from parent to offspring and subsequently expanded upon and incorporated to include a broader pattern of use. the same preparation used in the past for human health care are cited in this study to treat animal diseases. Likewise, for some taxa such as P. granatum L. and Malva aegyptia L., participants merge medicinal knowledge inherited from their immediate ancestor with dietetic knowledge recently acquired to prepare some functional food. These results suggest that some past ethnobootanical knowledge is transmitted from parent to offspring and subsequently expanded upon and incorporated to include a broader pattern of use.

New Plant Reports and Uses
A comparison of reported data with the ethnobotanical literature revealed that 48 of the used taxa in the current study were reported as useful in other regions of Tunisia as

New Plant Reports and Uses
A comparison of reported data with the ethnobotanical literature revealed that 48 of the used taxa in the current study were reported as useful in other regions of Tunisia as well in other neighboring countries (Algeria and Libya). We quoted a considerable similarity concerning plant use and mode of application (34 taxa). Shared plants are mainly cosmopolitan accessible taxa well known in the Mediterranean areas. Compared to ethnobotanical surveys carried out in Sahara Septentrional [52] and among nomadic and Touareg people in the Algerian steppe [23,36], the ethnobotanical knowledge recorded in this study area has an important similarity level with that quoted in Algerian regions. This overlap could be related to the similar Saharan environment in these two regions and also to the similar cultural ancestry that they shared. However, in comparison with Lybia [53], we recorded a huge difference regarding patterns of use and application despite its enormous socio-cultural, geographical, lifestyle, and ethnic similarity with Tunisia. Such a difference could reflect the lack of horizontal transmission of ethnobotanical knowledge between the two neighboring areas.
Finally, this comparative analysis led us to identify 11 new useful plants as well as 16 plants with new uses (marked with asterisks in Table 1) that have not been recorded previously in compared ethnobotanical bibliography. This mainly included endemic taxa such as F. tunetana and R. eriocalyx taxa, whose uses are suggested to be related to the challenges of the 21st century (cancer, stress, pesticide pollution) namely D. tortuosa for its biopesticidal properties and M. arvensis for treating and preventing the development of cancer. This study recorded for the first time the folk use of N. retusa to relieve mucocutaneous leishmaniasis vector-borne disease, which is a vector-borne disease that is highly endemic in Tunisia [54] and particularly in Ouled Dabbeb, where the number of cases recorded has multiplied by at least 20 times since 2011 according to the last study carried out in 2012-2013 [55]. Thus, this taxon may be a promising source for the ongoing research for plant-derived leishmanicidal compound conducted at a national scale [56,57], especially given the high toxicity of the available drug [57]. The data observed here highlighted the originality and uniqueness of the relevant ethnobotanical knowledge sustained by the local population of the Ouled Dabbeb Sector.

Study Area
The sector of Ouled Dabbeb (32 •  Hanfi [11] shows that the region's economy of the region is based mainly on subsistence agriculture devoted to sporadic cereal crop production and rustic arboriculture (olive and fig) and livestock breeding (sheep, goats, and camels). Although these agropastoral activities reflect a relative adaptation to the environmental conditions, it does not hide the great precariousness of this region, which is notably due to inappropriate use of pasture, which could pose a threat to its biodiversity. For the breeding of livestock, it is desirable to provide a grazing plan to preserve natural habitats [60]. For this reason, the application of some management practices, such as adopting (1) a moderate grazing program that is well known as a tool of managing floristic biodiversity [61], (2) livestock's breeding strategies in family projects well used in arid regions in Tunisia [62], and (3) the deferred grazing, becomes a necessity for optimizing ecosystems' productivity and conserving biodiversity.
Despite ecological harshness (long dry season, soil erosion, wind deflation, strong steady agropastoral activities...), the apparent monotony of the sparse sub-Saharan steppe Enclaved between two Mediterranean bioclimatic domains-the arid-lower bioclimatic stage in its northern, western, and southwestern parts and the upper saharan stages in the southern and southeastern part-the sector of Ouled Dabbeb is characterized by low and spatio-temporal irregular rainfall of around 143 mm/year and a prolonged dry season that extends from April to September. Temperatures can reach a maximum of 49 • C in Aout, while the mean minimum temperature is recorded in December, January, and February (15.5 • C) [11]. This contrasting thermal regime with potential evapotranspiration (peak of 170 mm in July) leads to water deficits that reach 2106 mm [11].
According to the latest census (2014), the number of the population in this study area is 49.137, of which 88.8% are in rural areas.
From the late twentieth century until recently, the region was exploited by nomadic and semi-nomadic herders practicing seasonal livestock movements at the local, regional, and national scale [58]. Villages and houses served as storage for families' grain and wealth and as a meeting point for social events [59]. Nowadays, with the sedentarization of the population and the privatization policy of the rangelands, the steppe area decreased in favor of cropping and arboriculture. A field survey carried out in 2014 by Abaza and Hanfi [11] shows that the region's economy of the region is based mainly on subsistence agriculture devoted to sporadic cereal crop production and rustic arboriculture (olive and fig) and livestock breeding (sheep, goats, and camels).
Although these agropastoral activities reflect a relative adaptation to the environmental conditions, it does not hide the great precariousness of this region, which is notably due to inappropriate use of pasture, which could pose a threat to its biodiversity. For the breeding of livestock, it is desirable to provide a grazing plan to preserve natural habitats [60]. For this reason, the application of some management practices, such as adopting (1) a moderate grazing program that is well known as a tool of managing floristic biodiversity [61], (2) livestock's breeding strategies in family projects well used in arid regions in Tunisia [62], and (3) the deferred grazing, becomes a necessity for optimizing ecosystems' productivity and conserving biodiversity.
Despite ecological harshness (long dry season, soil erosion, wind deflation, strong steady agropastoral activities...), the apparent monotony of the sparse sub-Saharan steppe vegetation in this area hides very rich and diversified flora including rare taxa [63,64] with a great heterogeneity of the landscape and vegetation in a small territory. According to previous studies [11,63], four main plant groupings were outlined: (1) Macrochloa tenacissima (L.) Kunth and Artemisia herba-alba Asso grouping that dominated the surrounding mountains, (2) A. herba-alba and H. scoparium grouping characterized loamy arid piles of the study area, (3) R. suaveolens and A. campestris grouping that defined the sandy plains, and (4) Thymus capitatus Hoffmanns. & Link and A. campestris grouping that marked the wadi beds.

Ethnobotanical and Floristic Surveys
Three ethnobotanical surveys were conducted, each lasting at least six days during May 2014, January 2015, and March 2016 in the district of Tataouine covering mostly all seasons of the year. Folk uses of plants were gathered through interviews and discussions among the knowledgeable persons (lay practitioners, traditional herb sellers, shepherds, and village elders). To ensure a comprehensive representation of the local knowledge and use of plants, the choice of the respondents was heterogeneous in terms of gender, age, and level of education. A total of 30 informants (16 women and 14 men) were interviewed. Their age ranged from 27 to 84 years. Most of the respondents claimed they were born in the region and had lived there all their life.
Researchers adhered to the Code of Ethics of the International Society of Ethnobiology [65] and always explained the purpose of the study and obtained verbal informed consent before conducting interviews.
Surveys were carried out in local inhabitants' houses, in fields, and in herbalists' shops, where informants were requested to show the researchers the taxa used for diverse cited purposes. All interviews were carried out in the Tunisian dialect.
The questionnaire comprised two sections: The first compiled the main demographic and social features of the participants (gender, age, education rate, occupation, etc.), and the second gathered information on local communities' folk knowledge about the plant taxa growing in their surrounding areas namely vernacular names of used taxa, uses (medicinal, food, ethnoveterinary, domestic, ritual, etc.), used plant part(s), methods of preparation, administration procedures (in the case of medical remedies), growth form [16,66,67], and life form [16,19,66,67].
Within the scope of this study, reasonably complete flora surveys were undertaken from May 2014 to April 2019 exploring all sides of the studied territory including desert, mountain plains, and river valleys to compile an exhaustive list of all vegetation types within the study area. Such a complete list constituted a baseline to well estimate the importance of useful plants in this area.

Botanical Identification
Samples of plant taxa either recorded during floristic surveys or mentioned by our informants were collected at the flowering/fruiting stages for the accurate identification and preparation of herbarium specimens. In addition, photos were taken in situ when available. Plant materials were preserved using standard procedures and identified by the authors according to Flora of Tunisia [12,66,67], Flora of North Africa [68], and flora of the Sahara [19]. Taxonomic identification was updated concerning systematics nomenclature and chorology using Commented Synonymic Catalogue of the Flora of Tunisia [8], and the index of the database of North Africa [9]. The herbarium specimens were coded and deposited in the herbarium of the National Agronomic Institute of Tunisia (INAT) [69]. Instances of endemism and hazard categories [9,66,67] were specified as per information availability.

Statistical Analyses and Quantitative Indices
To describe the gathered ethnobotanical information, data were first tabulated into an Excel database and structured in Use Reports (UR, a citation of one plant use by one informant). Then, it was analyzed and assessed using various quantitative indices, including, the Relative Frequency of Citation (RFC), the Informant Consensus Factor (ICF), and the Ethnobotanicity Index (EI).
A bibliographical comparison with ethnobotanical studies conducted in Tunisia and neighboring countries (Algeria, Libya) was performed in order to evaluate the originality and uniqueness of ethnobotanical knowledge sustained by the local population of Ouled Dabbeb and to identify new plant citation and new uses. We collected data available from academic databases including PubMed, Springer, Science Direct, and Scopus, using keywords or combinations of keywords linked to the context of this study: Tunisia, Algeria, Libya, Sahara, ethnobotany, steppe, folk uses of plants, and nomads. Furthermore, [13][14][15] were used to compare fieldwork results with historical texts, as these sources are considered to be the first pioneering works on ethnobotany in Tunisia that provide an interesting background, traditional botanical knowledge present in various Tunisian regions, and more specifically in the southern part of the country. The authors of these studies adopted a documentary analysis as secondary data to attain more complete coverage of historical aspects on the topics covered in their ethnobotanical surveys. They used manuscripts, letters, old books, and documents from government and related organizations that date back to the end of the 19th century.
This comparison can serve as a good basis for evaluating the exchange of knowledge between the current interviewed community and its semi-nomadic ancestors.

Relative Frequency of Citation (RFC)
This index shows the local importance of each species [70], and it is given by the following formula. RFC = FC/N; where FC is the number of informants mentioning the use of the species and N is the total number of respondents participating in the survey.

The Informant Consensus Factor (ICF)
The Informant Consensus Factor (ICF) [70] is used to measure homogeneity on the informant's shared knowledge regarding the use of plants to treat the different health disorder categories. This factor follows this formula ICF = (nur − nt) /(nur − 1) where "nur" mentions the number of use reports for each use and "nt" refers to the number of taxa used to relieve the same ailment.
The value of this factor ranges from 0 to 1. A high value (close to 1) indicates that relatively few species are used by a large proportion of respondents, while a low value indicates that the informants disagree on the taxa to be used in the treatment within an ailment category.
In this study, diseases recorded in our survey were regrouped into 17 main categories reflecting local health problem classification.

Ethnobotanicity Index (EI)
To estimate the importance of the used taxa in the studied territory, we used the Ethnobotanicity Index (EI) postulated by Porteres in [71] that stands for the ratio between the useful reported plant species and the total flora of the study area expressed as a percentage.

Conclusions
The floristic surveys carried out from 2014 to 2019 have enabled us to inventory 165 plant taxa of which three are endemic to Tunisia (T. alopecurus, Teucrium sauvagei Le Houér. and A. campestris subsp. cinerea), 32 are endemic to Maghreb, and/or North Africa, and 18 are widespread plants taxa that shape the main steppe vegetation of the area. Such results outline the richness and diverse flora of Ouled Dabbeb sector despite its small size (100 km 2 ) and ecological harshness.
As regards endemic, rare, or threat wild taxa namely L. coronopifolia, A. roseum subsp. Odoratissimum, and R. eriocalyx, it is suggested to launch specific actions to verify if they are Crop Wild Relatives (CWR) and which is their genetic affinity with the respective parental species [72]. CWR taxa are potential sources of traits beneficial to crops, such as pest or disease resistance, yield improvement, or stability [73], and once identified, there is an imperative to effectively conserve these critical taxa in situ (i.e., in natural habitats managed as genetic reserves) and ex situ (primarily as the seeds in gene banks or as mature individuals in field collections) to underpin future world food [74,75].
Considering the ethnobotanical study, collected data indicated that the age and level of education were the main factors that seem to impact respondents' ethnobotanical knowledge, which was also significantly patterned by the interaction between gender and use categories and well related to gender roles among inhabitants. This points out how traditional knowledge is embedded in social norms despite the challenging threat of being eroded and lost for the posterior.
This study revealed also that the local community of Ouled Dabbeb perceive that 70 plant taxa belonging to 59 genera from 31 families are mainly used for therapeutic (83%), food (49%), domestic (15%), ethnoveterinary (12%), cosmetic (5%), and ritual purposes (3%), bearing in mind that a single taxon could be useful for various purposes. Therefore, this ascertainment highlighted the wealth and wide-ranging of ethnobotanical knowledge that is still sustained by local people. Furthermore, 73% of reported ethnospecies were freely gathered from the wild, which points out the high inhabitant awareness of the ethnobotanical importance of the available surrounding flora. This result underpins local populations' resilience and their adaptive capacity, which should be valued and protected as a part of biocultural diversity conservation strategies.
Interestingly, a high quantitative ethnobotanical index value has confirmed the versatility and widespread use of seven endemic plant taxa namely A. campestris subsp cinerea, F. tunetana, A. saharae, R. suaveolens; S. tripartita; A. armatus, and H. deserti. Such a finding strengthens the originality of the recorded folk knowledge. However, it cannot be ruled out that the proclivity of these endemics makes them more vulnerable to overexploitation, especially those whose non-renewable parts (underground storage organs and roots) are used.
Finally, this work brings out valuable and novel information about 11 new useful plants and 16 taxa with new utilization that have not been recorded previously in Tunisian ethnobotanical bibliography including mainly the use of D. tortuosa as biopesticide, M. ar-vensis as anticancer treatment, and the high use of L. coronopifolia, which is a new species that is reported for the first time in this area. Therefore, this study sets a starting point and basis for subsequent pharmacological, biological, and phytochemical investigations on taxa with high use values and then the discovery of many bioactive principles.
Supplementary Materials: The following are available online at https://www.mdpi.com/article/10 .3390/plants10040642/s1, Table S1. List of plant taxa inventoried in Ouled Dabbeb's Sector (2014-2019); Table S2. Comparison of ethnobotanical knowledge reported by the respondents in the present study and their forefathers reported by Le Floc'h (1987): Lists of the taxa used to make the diagrams in Figure 7.