Introduction

Myers et al. (2000) have recognized the Mediterranean basin to be one of 25 global biodiversity hotspots. As reported by Lopez-Alvarado and Farris (2022), it is considered the world’s second largest biodiversity hotspot. It covers more than 30 states and includes key terrestrial habitats such forests, maquis, garrigues, pastures, wetlands, coastal areas, and transitional to desert zones. Moreover, it includes more than 25,000 species of flowering plants in the world (Zahran 2010). Being the meeting ground between Europe, Asia and Africa makes the Mediterranean basin surrounded by the temperate, arid and tropical biogeographical regions in comparison to the more homogeneous areas to the north and south (Zahran 2010). Consequently, the edaphic, climatic and topographical intricacy of the Mediterranean basin makes it exceptionally rich in biodiversity (Thompson 2020). Moreover, according to the Med-Checklist, about 63.5% of species are endemic to the region (Heywood 2002). Many Mediterranean species are restricted to a single or few localities in sandy areas, isolated mountain ranges, or islands of unusual soils or rocky grounds, thus this region is characterized by a high degree of endemism compared to other regions (Zahran 2010).

Endemism is an integral component of plant diversity in the Mediterranean region (Fois et al. 2022). A characteristic element of this endemism is that of all the species endemic to the Mediterranean region, 60% are narrow endemic species, i.e., they have a distribution that is restricted to a single well-defined area within a small part of the Mediterranean region (Thompson 2020). The Mediterranean flora is thus replete with narrow endemic taxa. A characteristic feature of this region is the spatial isolation, where there are several islands, peninsulas, and high mountains (Vargas 2020). Over 10,000 islands and islets are distributed across the Mediterranean Basin. Good examples of this are Sicily and Sardinia that are the largest islands in the region, followed by Cyprus, Crete, Aegean Islands, Corsica, and Balearic Islands (Médail 2021). Altitudinal species isolation is also remarkable. Mountain environments in particular offer good opportunities to study how plant species richness fluctuates in response to environmental conditions within geographically confined areas because of the progressive changes in many parameters, such as temperature, precipitation, and soil properties with the altitudinal changes (Di Biase et al. 2021). At mid elevations, European and Euro-Asiatic distributions prevail due to temperate climate conditions. Whereas, Mediterranean species dominate the lowest elevation, but decrease with altitude as the temperature declines. Mountain regions are ecological archipelagos that promote evolutionary processes, consequently the proportion of endemics increases by about 20–25%with altitude (Fattorini et al. 2020). The plate collisions between the Eurasian and the African plates in the Tertiary period resulted in mountains rising to around 2000 m a.s.l. mainly located in the three main peninsulas (Iberian, Italian, and Balkan) in southern Europe (Vargas 2020). In addition, the largest mountain range in North Africa is the Atlas, which was raised in the Miocene because of orogenic movements (Babault et al. 2008). Further, except for land proximity on the straits of Gibraltar and Tunisia–Sicily, the Mediterranean Sea’s east-west orientation itself has been a substantial geographical barrier for plant dispersal between North Africa and Europe (Rodríguez-Sánchez and Arroyo 2011; Vargas 2020). Consequently, most narrow endemics are found in southern Europe and North Africa either on islands or medium-high mountains.

Two significant geo-climatic events, the Pleistocene Ice Ages (2.6 Ma) and the Messinian Salinity Crisis (MSC) at the end of the Miocene, 5.97–5.33 Ma, have frequently been used to explain contemporary patterns of distribution and molecular diversity of Mediterranean flora. The MSC was brought on by tectonic movements that isolated the Mediterranean Sea from the Atlantic Ocean. These movements were also accompanied by climatic changes that caused a number of cycles of evaporation, gradually lowering the sea level until it was almost completely desiccated. During this phase, extensive land links between Europe and North Africa were created, serving as land bridges for the exchange of plant species between the two continents. At 5.33 Ma, the Mediterranean basin was dramatically refilled through the Gibraltar Strait corridor, breaking these connections. This event, which began in the Pliocene, initiated differentiation on each side of the strait, formed a maritime barrier for poorly dispersive biota, and it also caused the high endemism currently seen in this biodiversity hotspot (Costa et al. 2022). According to UNEP (2022), the Mediterranean is one of the most vulnerable regions in the world to the impacts of global warming. In fact, the Mediterranean region is warming 20% faster than the global average. 2 °C global warming will reduce precipitation by ~ 10 to 15%. Further, water temperature is expected to rise by between 1.8 and 3.5 °C by 2100 with hotspots in the Eastern Mediterranean and northern parts of the Western Mediterranean. Sea level is expected to rise between 0.43 and 2.5 m by 2100. Consequently, these events will result in increased heat waves, coastal erosion, fires, invasive species, floods, acidification of the sea, and the risk of extinction of certain species in the region (UNEP, 2022).

Considering all the geological and palaeoclimatic events which shaped the Mediterranean basin geography and influenced plant evolution and diversity as described above (Thompson 2020; Médail 2021; Costa 2022), the delimitation of the Mediterranean biogeographic region has been controversial and debated. One strategy to specifically delimit the floristic regions is by using the distribution of the key species (Vargas 2020). Paleobotanists believe the olive tree (Olea europaea L. subsp. europaea), the holm oak (Quercus ilex) and its relatives (Q. rotundifolia, Q. calliprinus, Q. coccifera) can be considered as good indicators of mediterraneity in natural habitats of the Mediterranean Basin (Takhtajan 1986; Vargas 2020). Although the Mediterranean region is well-defined geographically, it is not well spatially delimited (Zohary 1973). In that sense, Macaronesia was included in the Mediterranean floristic region by Drude (1890) and Tolmatchev (1974). Regarding the eastern boundaries, Engler (1879–1882) and Drude (1890) were among those who included inner Anatolia, Iraq, Afghanistan, Baluchistan, and parts of Iran within the region. Moreover, Rikli (1913, 1943, 1948) included the entire Sinai Peninsula, all of Anatolia, Caucasus and Ciscaucasia, Crimea, and the Black Sea steppes within the Mediterranean region.

To overcome the previously outlined conflicts, Greuter in 1989 adopted the political boundaries of the region as the only practicable limits. He included all the countries bordering the Mediterranean Sea, plus Portugal, Bulgaria, Crimea, and Jordan in a large database, termed ‘the Med-Checklist’ and comprising 27 territories (Greuter et al. 1984–1989; Greuter and von Raab-Straube 2008; Med-Checklist 2016).). Doubtlessly, the Med-Checklist has shocked many phytogeographical purists, especially from the countries where the Mediterranean coast represents only a little portion. For instance, he excluded only Gebel Elba and Gebel Uweinat and considered the rest of Egypt (including the Sahara deserts) as Mediterranean.

Another conflict is obvious in the inner and east Anatolian flora that has a tendency toward the Asiatic Irano-Turanian region. Therefore, we consider it is better to adhere to the boundaries previously outlined by Alphonse de Candolle and Edmond Boissier (De Candolle 1855; Boissier 1867),and specified by many authors as well such as Zohary (1973), Good (1974), Wickens (1976) and Takhtajan (1986).

Indeed, it’s crucial to clearly delimit the Mediterranean boundary in national contexts where the Mediterranean biogeographical region takes contact with other regions like the temperate to the north (Gachet et al. 2005) or the Saharan to the south (Cole 1977; Takhtajan 1986). On the national scale, over the years, there have been some issues associated with the delimitation of phytogeographical regions, especially the Mediterranean floristic region in Egypt. Muschler (1912), Täckholm and Drar (1950–1969), Hassib (1951)d ckholm (1956, 1974) have demonstrated that the Mediterranean region in Egypt comprises two sub-regions: The Western Mediterranean coastal region (which stretches from Sallum to Alexandria, including Rosetta); and the Eastern Mediterranean coastal region (which stretches from Port Said to Rafah). Zohary (1973) and Takhtajan (1986) promoted that there are two gaps in the Mediterranean territory along the North African sub-region: the first gap is in northern Egypt from Omayed to Rafah, and the second one is in Libya along the Great Syrte between Tripoli and Benghazi. Hence the Saharo-Arabian vegetation advances quite close to the coast. Wickens (1976) restricted the north African gap to only the Mediterranean coast of Sinai (between Port Said and Rafah).

The borderlines of the Mediterranean coastal strip in Egypt were then modified by Boulos (1999–2005) to be stretched from the border with Libya near Sallum to Port Said. However, to the authors’ best knowledge, very few publications are available in the literature addressing the presence of Mediterranean territory from Rosetta to Rafah.

Although Tadros (1953), Boulos (1975), Ayyad et al. (1986), Rivas-Martínez (2009), and Djamali et al. (2012) sustain that Egypt is not part of the Mediterranean climate nor of the Mediterranean biogeographic region, due to the lack of any native arboreal Mediterranean species in Egypt; Wickens (1977) argued for the possibility of the presence of steppe maquis vegetation of the Ceratonia-Pistacion lentisci alliance (described by Zohary (1973)) along the Egyptian Mediterranean coast, which is considered evidence of the presence of a Mediterranean territory in Egypt. Moreover, Egypt is so close to floristically Mediterranean-rich areas both to the west (Cyrenaic) and to the east, which could be an interesting place to study the interaction among the Mediterranean, the Tropical and the Saharo-Sindic floristic contingents. This geographic location allowed the interesting role as a melting pot among the three contingents (if not four if we consider also the Turanic). Nevertheless, the currently available data provide enough evidence for extending the Mediterranean territory in Egypt from Sallum on the Egyptian-Libyan border to Rafah on the Egyptian-Palestinian border as was elucidated by Zahran et al. (1985). Generally, coastal sectors and subsectors are richer in plant endemism than inland areas in Egypt (Abdelaal et al. 2020).

Indeed, Egypt has a long history in vegetation research, dating back to 1930s (Ahmed 2009; Shaltout et al. 2010; Hatim et al. 2021) The last two decades witnessed intensive studies in the west Mediterranean coastal land, to cope with the devastation associated with the urbanization in this coastal strip (e.g., Halmy 2012; Halmy et al. 2015a, b; Halmy and Gessler 2015; Halmy 2019; Halmy et al. 2019). It is unfortunate to report that Egypt had already lost over one hundred kilometers of its Mediterranean territory due to climate change, and human activities, especially the establishment of tourist summer resorts. As a result, it is now difficult to find any traces of the natural vegetation reported earlier in this region (El-Hadidi and Hosni 2000; Halmy 2012, 2019; Halmy et al. 2015a, b, 2019). Although several regional studies on plant communities have been carried out, there has never been compiled a complete classification overview and vegetation map of the Mediterranean region in Egypt. Consequently, it’s crucial to provide an up-to-date exact demarcation of the Mediterranean floristic region and shed the light on the Mediterranean endemics under the thought-provoking devastating impact of rapid anthropogenic and climate changes on the coastal strip of Egypt. Therefore, the main objectives of this study were to: (1) provide a new contribution to the delimitation of the Mediterranean biogeographic region in Egypt, (2) present an updated dynamic checklist of the Mediterranean endemic plants distributed along the Mediterranean coast of Egypt, (3) summarize the main habitats of these taxa; and (4) interpret their geographic distribution patterns and biogeography.

Materials and methods

Study area delimitation

Delimitation of the Mediterranean region in Egypt in this study was mainly assessed according to the system of Good (1974). Geographic Information Systems (GIS) was used to create a vector layer of the biogeographical regionalization of the study area by converting the map by Good (1973) to a polygon shapefile that can be used in further analyses. We used ArcMap software (ESRI 2012) to import the original map (Good 1974) as a TIFF format. The process was then conducted as follows: (1) using a previously georeferenced shapefile to define the geographic location; (2) creating polygons across sub-regions boundaries; and (3) adding information about provinces to the shapefile attribute table (Fig. 1).

Fig. 1
figure 1

Map of the study area showing the delimitation of the Mediterranean floristic region and the sub-divisions of the Mediterranean region in Egypt

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In Egypt, the Mediterranean territory stretches for about 970 km from Sallum on the Egyptian-Libyan border to Rafah on the Egyptian-Palestinian border with an average width 15–20 km in north-south direction and a total area of 16,500 km2. Zahran et al. (1985) extended the Mediterranean territory in Egypt from Sallum on the Egyptian-Libyan border to Rafah on the Egyptian-Palestinian border and distinguished between three subsectors for the Mediterranean coastal land: (i) western (the Mareotis, extending for 550 km between Sallum and Alexandria, with an annual rainfall between 220 − 150 mm), (ii) middle (Deltaic extending for 180 km between Alexandria and Port Said with about 12 km wide), and (iii) east (Sinaitic, extending for 220 km between Port Said and Rafah, with an annual rainfall between 150 − 100 mm).

List justification

We considered a taxon a Mediterranean endemic when its distribution was confined to the Mediterranean floristic region determined by Good (1974). Undoubtedly, in this study, we focused only on Mediterranean endemics distributed along the Mediterranean coast of Egypt.

An initial list of Mediterranean endemics in Egypt was compiled based on Täckholm (1974), Boulos (1999–2005), Greuter et al. (1984–1989), Greuter and von Raab-Straube (2008), Ahmed (2009), Shaltout et al. (2010) and El-Khalafy (2018).

Authentication of the taxa was considered based on floras of countries of the Mediterranean basin including Zohary (1966, 1987), Feinbrun-Dothan (1978, 1986), Jafri and El-Gadi (1977–1988), Pottier-Alapetite (1979–1981), Cuénod et al. (1954), Meikle (1977–1985), Guinochet and De Vilmorin (1973–1984), Zangheri (1976), Mouterde (1966–1984), Franco and Amaral (1971–1984), Smythies (1984–1986), Davis (1965–1985), Davis et al. (1988), Güner et al. (2000), Beck-Mannagetta (1967–1983), Boissier (1867), Duvigneaud (1979), Hayek (1924–1933), Quézel and Santa (1962–1963), Briquet (1910–1913), Haslam et al. (1977), Halácsy (1900–1912), Tutin et al. (1964–1980), and Castroviejo (1986–2012).

The following databases were also considered to check the recorded plants: Med-Checklist (2016), Euro + Med (2006), Flora of Libya (2022), Flora of Turkey (2022), Flora of Cyprus (2022), eflora Maghreb (2021), POWO (2022), WCSP (2022), Hassler (2004–2022), GBIF (2022), JSTOR (2022), Danin and Fragman- Sapir (2016), Flowers in Israel (2005–2022), African Plant Database (2022), Dimopoulos et al. (2020), EPPO (2022), VicFlora (2022), and Chikhali (2022).

Other information was collected from field visits and the herbaria of Real Jardín Botánico de Madrid (MA), Tanta University (TANE), Alexandria University (ALEX), Cairo University (CAI), Assiut University (ASTU), Agricultural Research Center (CAIM), Desert Research Center (CAIH), National Research Centre (CAIRC) and National Registry for Egyptian Herbaria (2022). Information was also gathered from available literature (papers, books, M.Sc. and Ph.D. Theses, and scientific reports).

The recorded taxa were arranged alphabetically according to Angiosperm Phylogeny Group IV (2016). The accepted names followed the International Plant Names Index (IPNI 2022), World Flora Online (WFO 2022), World Checklist of Selected Plant Families (WCSP 2022) and Plants of the World Online (POWO 2022).

Since the taxonomy and distribution of several taxa are still not certain, taxa were included in the final checklist as includenda (i.e., surely Mediterranean endemic taxa), excludenda (i.e., taxa that are natively distributed outside the Mediterranean region), inquirenda (i.e., taxa doubtfully reported to Egypt, whose presence in Egypt was reported at only one time but not recognized by further research and/or never confirmed in the field in the last 50 years: taxa belonging to this category should be better searched in the future), and extendenda (i.e., taxa mainly distributed in the Mediterranean basin but having extensions to neighboring areas). Therefore, we produced a dynamic checklist for the Mediterranean flora of Egypt, following some recent examples such as Fois et al. (2022). Undoubtedly, this dynamic checklist should be progressively updated in the near and the far future as more field data will be collected.

Habitat types

Habitat classification in this study follows an Authors’ scheme (previously published by Shaltout et al. (2015) and Bedair et al. (2022c). Fifteen major habitats have been considered: eleven are natural habitats (they are coastal dunes, sand formations, Sallum plateau, salt marshes, saline depressions, non-saline depressions, inland ridges, inland plateaus, plains and wadis, alluvial soils, and rocky ground), and four are anthropogenic (they are roadsides, wastelands, cultivated lands and Lake Mariut). Habitats of the recorded plants were determined by the authors in the field and the missing information was completed based on the following publications: Täckholm and Drar (1950–1969), Täckholm (1974), Zohary (1966, 1987), Jafri and El-Gadi (1977–1988), Feinbrun-Dothan (1978, 1986), El-Hadidi and Hosni (2000), Seif El-Nasr and Bidak (2006a, 2006b), Ahmed (2009), Boulos (1999–2005, 2009), Shaltout et al. (2010), El-Khalafy (2018), Bedair (2020), Mushtaq et al. (2020), Bedair et al. (2020), Ghosh et al. (2021), Bedair et al. (2022a & 2022b), Ghosh et al. (2022), Abdelsalam et al. (2022), and Shaltout and Bedair (2022, 2023)

Geographical distribution

Phytogeographical sectors in this study were identified according to Zahran et al. (1985) who extended the Mediterranean territory in Egypt from Sallum on the Egyptian-Libyan border to Rafah on the Egyptian-Palestinian border and divided it into 3 subsectors: western (from Sallum to Alexandria), middle (between Alexandria and Port Said) and eastern (between Port Said and Rafah). Whereas the global distribution of the recorded taxa (i.e., floristic regions) was assessed according to the system of Good (1974). The global distribution was checked in the following references: Zohary (1966, 1987), Feinbrun-Dothan (1978, 1986), Boulos (1999–2005), Ahmed (2009) and Shaltout et al. (2010). The distribution of the recorded taxa in countries of the Mediterranean basin was also checked in some databases such as Med-Checklist (2016), Euro + Med (2006), Flora of Libya (2022), POWO (2022), WCSP (2022), Hassler (2004–2022), GBIF (2022) and JSTOR (2022).

Both two-way indicator species analysis (TWINSPAN) and detrended correspondence analysis (DECORANA) were carried out for estimations of the 65 species recorded in 22 countries in the Mediterranean basin (Gauch and Whittaker 1981) to divide the countries into groups according to the common species among them. All the analysis was carried out using the Community Analysis Package (CAP 4) Statistics program. Shapefile of the Mediterranean Basin countries was extracted from the TM_WORLD_BORDERS-SIMPL_0.3 dataset (source: https://thematicmapping.org/downloads/world_borders.php) within the framework of ArcMap 10.1 software.

Results

List justification

A preliminary list of 402 Mediterranean endemic taxa in Egypt was prepared. Boulos (1999–2005) recorded two hundred and seventy-five (about 68.4% of the preliminary list) Mediterranean endemic taxa in the Egyptian flora. From which, one hundred and six (26.4%) Mediterranean endemics were recorded in the western Mediterranean region of Egypt by Ahmed (2009). On the other hand, three hundred and one (74.9%) Mediterranean endemics were recorded in Egypt (including Sinai) in the four published volumes of Med-Checklist (Greuter et al. 1984–1989, Greuter and von Raab-Straube 2008). Indeed, the present study has reduced this number to be sixty-five (16.2%) surely Mediterranean endemics in Egypt (i.e., includenda; Appendix 1). 13 taxa (20% of the total 65 Mediterranean endemics in the present study) were recorded as Mediterranean endemics in the present study and by Boulos (1999–2005), 16 (24.6%) in the present study as well as Boulos (1999–2005) and the Med-Checklist, 13 (20%) in the present study, Boulos, 1999–2005 and Ahmed 2009; and 23 (35.4%) in the present study, as well as the 3 prior studies namely Boulos (1999–2005), Med-Checklist, and Ahmed (2009).

A further 209 taxa have been excluded (i.e., taxa excludenda). Thirty-six taxa were excluded from the endemism (17.2% of the total 209 excluded taxa), unlike the three prior studies (Boulos, 1999–2005, Med-Checklist, and Ahmed 2009). Whereas 6 taxa (22.9%) were excluded from the present study as well as Boulos (1999–2005), 25 (12%) from the present study as well as Med-Checklist, 104 (49.8%) from the present study and Ahmed (2009), 45 (21.5%) from the present study as well as Med-Checklist and Ahmed (2009), and 118 (56.5%) from the present study as well as Boulos (1999–2005) and Ahmed (2009).

On the other hand, 92 taxa (22.9% of the total checklist) have some extended populations in neighboring areas (i.e., extendenda), while 36 (9%) are doubtfully reported in Egypt (i.e., inquirenda).

Taxonomic diversity

There are 73 taxa recorded in this study (65 species, 6 subspecies and 2 varieties) belonging to 49 genera and 22 families. The most represented genera are Allium and Fumaria (4 taxa); Bellevalia (4 taxa); Muscari, Centaurea and Limonium (2 taxa). Gymnosperms are not represented by any taxon, while angiosperms are represented by 3 clades. Monocot families are 4 (Amaryllidaceae, Asparagaceae, Poaceae and Posidoniaceae), represented by 10 genera and 18 species, while Eudicots are represented by only Papaveraceae (Table 1).

Table 1 Major taxonomic groups of the Mediterranean endemics in Egypt
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Core Eudicots are the most represented by 17 families (5 Superrosids and 12 Superasterids). The highly represented families are Asteraceae (13 species), Fabaceae (10 species), Asparagaceae (8 species), and Amaryllidaceae (5 species). On the other hand, 12 families are represented by only one species (Posidoniaceae, Convolvulaceae, Euphorbiaceae, Resedaceae, Apiaceae, Caprifoliaceae, Caryophyllaceae, Rubiaceae, Santalaceae, Solanaceae and Scrophulariaceae) (Table 2). The diversity of the major taxonomic groups indicates that the Superasterids are the most diverse in terms of families, genera, species, subspecies and varieties, whereas Eudicots are the least. The ratio of genus to family (G/F) has a maximum value in Monocots and a minimum in Eudicots. The ratio of species to genus (S/G) has a maximum in Eudicots (3) and a minimum in Superrosids (1.1), while the ratio of subspecies to species is very low in all the major taxonomic groups.

Table 2 Taxic diversity of the Mediterranean endemics in Egypt. Ac: actual number and Re: relative number (%)
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Habitats

Fifteen major habitats support the Mediterranean endemics in Egypt: eleven are natural habitats and four are anthropogenic habitats. The most represented habitat is the non-saline depressions (20 taxa = 30.8%) followed by the coastal dunes (19 taxa = 29.2%), whereas alluvial soils (only one taxon: Bellevalia warburgii) and wastelands (2 taxa = 3.1%) are the least represented habitats (Fig. 2).

Fig. 2
figure 2

Number of the Mediterranean endemics in Egypt in relation to their habitat. Habitats are abbreviated as follows: IR: Inland ridges, CL: Cultivated lands, PW: plains and wadis, SF: Sand formations, NS: Non-saline depressions, CD: Coastal dunes, RO: Roadsides, SD: Saline depressions, IP: Inland plateaus, SM: Salt marshes, RG: Rocky ground, LA: Lake Mariut, SP: Sallum plateau, WL: Waste lands and AL: Alluvial soils

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Geographical distribution

National geographic distribution

Mareotis (west) subsector is the richest with 57 taxa = 87.7% (e.g., Allium mareoticum, Muscari albiflorum and Scilla peruviana), followed by the Sinaitic (east) subsector with 19 taxa = 29.2% (e.g., Bellevalia warburgii, Coronilla repanda and Vicia sinaica). Whereas, the Deltaic (middle) subsector is occupied by only 5 taxa = 7.7% (Fig. 3).

Fig. 3
figure 3

Number of Mediterranean endemics in Egypt in relation to the national geographical distribution

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Global geographical distribution

All the recorded species belong to the Mediterranean region in the Boreal kingdom, which is divided into four sub-regions: North African sub-region (52 taxa = 91.2%), Eastern (levant) sub-region (36 taxa = 63.2%), Balkans sub-region (21 taxa = 36.8%) and North-western sub-region (16 taxa = 28.1%). The Mediterranean endemics in Egypt are recorded in 22 Mediterranean basin countries out of 25. The highest number of taxa are recorded in Libya (29 taxa = 50.9%), followed by Palestine (24 taxa = 42.1%) then Syria and Lebanon (22 taxa each = 38.6%). Whilst the least number of taxa are present in Gibraltar, San Marino, Slovenia, Bosnia and Herzegovina (one taxon each = 1.8%). On the other hand, no taxa are recorded in Malta, Monaco and Holy See (Vatican City). Interestingly, 47 Mediterranean endemics (82.5%) are recorded in Egypt (excluding Sinai Peninsula) that belongs to North African sub-region, and 15 (26.3%) in Sinai Peninsula belonging to Eastern sub-region.

Remarkably, there are 11 (19.3% of the total Mediterranean endemics) steno-endemics exclusive to Egypt and Sinai: Allium mareoticum, Anthemis microsperma, Bellevalia salah-eidii, Echinops taeckholmianus, Fumaria microstachys, Limonium sinuatum subsp. romanum, Muscari albiflorum, Pancratium arabicum, Thesium humile var. maritima in Egypt (excluding Sinai), and both Muscari salah-eidii and Vicia sinaica in Sinai. Whereas, 11 steno near-endemic taxa (9 in Egypt-Libya: Allium barthianum, Allium blomfieldianum, Ebenus armitagei, Euphorbia parvula, Helianthemum crassifolium subsp. sphaerocalyx, Herniaria cyrenaica, Valantia columella, Valerianella petrovitchii and Verbascum letourneuxii; and 2 in Egypt-Palestine: Lycium schweinfurthii var. aschersonii and Linaria joppensis)) are recorded. Indeed, Thymbra capitata, Posidonia oceanica and Lotus cytisoides are widely distributed in the Mediterranean basin.

The application of TWINSPAN to the presence of 65 species recorded in 22 countries led to the recognition of 10 groups at the sixth level of classification, and 7 groups at the fourth level (Fig. 4a). The application of DECORANA on the same set of data indicates reasonable segregation among these groups (Fig. 4b). The groups are named after the species with the highest presence percentage (first common species), as follows: I- Posidonia oceanica group. This group includes both Egypt and Libya. The most common species between the 2 countries are Allium barthianum, A.blomfieldianum and Bellevalia sessiliflora; II- Limonium echioides group. This group includes Tunisia, Algeria, Morocco, Spain, Portugal, Italy and France.The most common species are Posidonia oceanica, Thymbra capitata, Hedysarum spinosissimum and Convolvulus humilis; III- Thymbra capitata group that includes both Cyprus and Greece. The most common species are Allium trifoliatum, Fumaria judaica subsp. judaica, Lotus cytisoides and Posidonia oceanica; IV- Hedysarum spinosissimum group that includes Palestine, Syria, Lebanon and Turkey. The most common species are Allium trifoliatum, Fumaria gaillardotii, Lotus cytisoides, Veronica syriaca and Muscari parviflorum; V- Pancratium arabicum group. This group is specific to Sinai Peninsula and is characterized by spectacular endemic species such as Muscari salah-eidii, Anthemis microsperma and Vicia sinaica; VI- Anthemis chia group. It includes Albania and Former Yugoslavia (Bosnia and Herzegovina, Croatia, Montenegro and Slovenia). The most common species are Hyoseris scabra, Posidonia oceanica and Muscari parviflorum; and VII- Muscari parviflorum group which includes Gibraltar and San Marino. This group is only characterized by M. parviflorum.

Fig. 4
figure 4

Dendrogram of the most important 6 groups obtained after application of TWINSPAN classification technique at the fourth level(a). Cluster segregation of the 7 vegetation groups using DECORANA (b). The 6 groups are named after characteristic species, as follows: I- Posidonia oceanica group; II- Limonium echioides group; III- Thymbra capitata group; IV- Hedysarum spinosissimum group; V- Pancratium arabicum; and VI- Anthemis chia and VII Muscari Parviflorum. Countries are coded as: EG = Egypt, AG = Algeria, AL = Albania, BK = Bosnia and Herzegovina, CY = Cyprus, FR = France, GR = Greece, HR = Croatia, IS = Israel, IT = Italy, LE = Lebanon, LY = Libyan Arab Jamahiriya, MO = Morocco, GI = Gibraltar, MJ = Montenegro, PA = Palestine, PO = Portugal, SI = Sinai, Sl = Slovenia, SP = Spain, SY = Syrian Arab Republic, TS = Tunisia, TU = Turkey, and SM = San Marino

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Discussion

The present study has proved the idea that Egypt’s Mediterranean territory extending from Sallum to Rafah is part of the Mediterranean floristic region. Delimitation of the region in Egypt showed that the average width in north-south direction is not equal in the 3 subsectors. It extends to 15–20 km southwardly in the Mareotis subsector, 12 km in the Deltaic, and only 5 km in the Sinaitic subsector. In addition, the region is suffering from huge human impact and is threatened due to the extensive climatic change projections. Consequently, conservation plans to conserve these restricted endemic taxa and plant diversity in the Egyptian Mediterranean territory are required.

Indeed, Boulos (1999–2005) recorded two hundred and seventy-five Mediterranean endemic taxa in the Egyptian flora. From which, one hundred and six Mediterranean endemics were recorded in the western Mediterranean region of Egypt by Ahmed (2009). On the other hand, three hundred and one Mediterranean endemics were recorded in Egypt (including Sinai) in the four published volumes of Med-Checklist (Greuter et al. 1984–1989; Greuter and von Raab-Straube 2008). Indeed, the present analysis has reduced this number to be sixty five Mediterranean endemics in Egypt.

From a list of 402 taxa possibly considered as Mediterranean endemics in Egypt, only 16.2% were left after analysis in this study. Many species have extended to neighbouring regions such as North African Desert region, Macaronesian region, Euro-Siberian region, Western and Central Asiatic region. Doubtlessly, the floras of certain regions, ranging from subarctic to tropical, have been enriched half again by species from other biographic regions. There are also substantial numbers of invading species that have become naturalized, many maintaining large and dominating populations. These invading species are not distributed uniformly in the landscape but are generally associated with ecosystems that have experienced human impact (Mooney 1988).

Further, terrestrial ecosystem distribution and function are likely to shift as a result of human-induced climate change. Terrestrial ecosystems are likely to change from tundra to boreal forests (IPCC 2023), while temperate forests and grasslands might take their place (Zhang et al. 2018). Deserts such as the Saharan Desert have the potential to change in size. Although the future of tropical forests is uncertain, certain climate change scenarios suggest that there could be significant losses (Keenan 2015), and temperate forests in areas subject to drier climates may be more at risk (Choat et al. 2012). The high rate of climate change in the recent decade has exceeded the migration rates of most plant species. Indeed, the spread of a species depends on the dispersal mode and distance of this species. For example, species of wind dispersal modes can spread long distances in the direction of storm tracks under foul weather conditions (Neilson et al. 2005). Moreover, many species could not survive the high temperature rates and went extinct. Even though about 13.000 plant species are endemic to the Mediterranean region (Thompson et al. 2005), only 0.5% of this percentage is present in Egypt. This may be due to the lack of islands and high elevation mountains that are microclimatic hotspots of endemics in the Mediterranean region. Also, the high human impact in the region and the extension of the Saharan Desert towards the Mediterranean region in Egypt are characteristic features in the recent years. Indeed, endemic species in Egypt are concentrated in south Sinai where high mountains do exist and act as natural geographical barriers to species dispersal (El-Khalafy et al. 2021).

In the present study, 36 taxa were excluded from endemism, unlike the three prior studies (Boulos, 1999–2005; Med-Checklist; Ahmed 2009). For example, Tripodion tetraphyllum was recorded in inner Anatolia (Euro + Med, 2006; Hassler 2004-Arenaria deflexa in Arabian Peninsula (POWO 2022), Bryonia cretica in central Europe and Asia (POWO 2022; GBIF 2022; JSTOR 2022), Carlina involucrata in Saharo-Arabian regions of Libya (Jafri and El-Gadi 1977–1988), Crucianella maritima, Limoniastrum monopetalum, Paronychia capitata, Lycium schweinfurthii var. schweinfurthii and Euphorbia dendroides in Canary Islands (JSTOR 2022; African Plant Database 2022; POWO 2022; GBIF 2022; Hassler 2004–2022), Suaeda pruinosa in Djibouti (GBIF 2022, JSTOR 2022), Coris monspeliensis in Somalia and Switzerland (GBIF 2022; POWO 2022) and Limonium narbonense in Azores Islands (Hassler 2004–2022; GBIF 2022). In addition, the Mediterranean element Fumana thymifolia was recorded in Krym (POWO 2022) and the Isthmic desert of Sinai (Täckholm 1974). The Mediterranean Didesmus aegyptius was reported to be in Luxor in Täckholm (1974). Moreover, it was recorded near Farafra Oasis in El-Wadi El-Gadeed in the herbarium of Conservatoire et Jardin botaniques de la Ville de Genève, Genève, Switzerland (G).

In the meantime, 6 taxa were excluded from the present study as well as Boulos (1999–2005). These are Echium angustifolium subsp. sericeum that was recorded in Yemen and Arabia (GBIF 2022; Dubaie and Al-Khulaidi 1993; Boulos, 1999–2005), Phlomis floccosa in Russia (GBIF 2022), Reseda pruinosa in Ethiopia and Sudan (POWO 2022), Reseda urnigera, Sonchus macrocarpus and Orobanche ramosa var. schweinfurthii in the Saharo-Arabian deserts of Egypt (Amer et al. 2015; Hassler 2004–2022; El-Khalafy et al. 2021; Boulos, 1999–2005).

In addition, 25 taxa were excluded from the present study as well as Med-Checklist. For example, romana and Didesmus bipinnatuswere recorded in the Netherlands (GBIF 2022; JSTOR 2022; Hassler 2004–2022). Cutandia maritima, Galium verticillatum, Lotus creticus, Prasium majus and Euphorbia terracina were recorded in Macaronesia (POWO 2022). Whereas Echinops spinosissimus and Erodium chium were recorded in Western Sahara (POWO 2022). Scorzoneroides simplex and Limonium sinuatum subsp. bonduellei were recorded in Mauritania (POWO 2022). Although Leiotulus alexandrinus is a Mediterranean element, it was collected along the Gulf of Suez in the eastern desert of Egypt (Abd El-Ghani et al. 2017, Hassler 2004–2022). Therefore, it was excluded from Mediterranean endemics list in this study. Moreover, Plantago crassifolia was recorded in United States of America, Canada and South Africa (JSTOR 2022; GBIF 2022; SANBI 2010–2012; Tropicos 2022). Zygophyllum aegyptium was recorded in Wadi Sudr, south Sinai by Morsy et al. (2015).

In the meantime, 104 taxa were excluded from the present study and Ahmed (2009). For instance, Astragalus kralikii, Astragalus trimestris, Chlamydophora tridentata, Diplotaxis muralis subsp. simplex, Onopordum alexandrinum, Echium glomeratum, Trigonella arabica, Ononis vaginalis, Atractylis serratuloides, Enarthrocarpus strangulatus, Papaver humile, Centaurea furfuracea and Crepis nigricans were reported as Saharo-Arabian elements (Jafri and El-Gadi 1977–1988; Zohary 1966, 1987; Feinbrun-Dothan 1978, 1986; African Plant Database 2022; Flowers in Israel 2005–2022; GBIF 2022). Moreover, Lotus edulis and Euphorbia oxyodonta extend to the Irano-Turanian inner and east Anatolia (Turkey) (Euro + Med, 2006; Hassler 2004–2022; GBIF 2022). Delphinium ambiguum and Ononis variegata were recorded in the Canary Islands (POWO 2022; GBIF 2022; Hassler 2004–2022). Astragalus fruticosus, Astragalus peregrinus, Hippocrepis cyclocarpa, Rhamnus lycioides subsp. oleoides, Salvia dominica, Astragalus sinaicus, Silene schimperiana, Salsola longifolia and Convolvulus spicatus were recorded in the Arabian Peninsula (POWO 2022; Hassler 2004–2022; GBIF 2022). Although, the endemic Brassica deserti was recorded by Kamel et al. (2008) only on the Mediterranean coast of Sinai, it was recorded by El-Khalafy et al. (2021) in Gebel Igma, southern Sinai. Hence, it was excluded from the present study. The same status is noticed for Convolvulus palaestinus that was collected from southern Sinai by El-Husseini et al. (2008). Further, Täckholm (1974) recorded Delphinium bovei, Centaurea postii, Anabasis syriaca, Silene palaestina, Astragalus camelorum, Astragalus macrocarpus subsp. macrocarpus, Astragalus sanctus and Trifolium philistaeum in the Saharo-Arabian Isthmic desert, Sinai. Consequently, they were excluded from the present study.

Furthermore, in the present study, as well as in the Med-Checklist and Ahmed (2009), 45 taxa were excluded. Four of which (Allium aschersonianum, Allium curtum subsp. curtum, Allium curtum subsp. palaestinum and Helianthemum vesicarium) were recorded as Irano-Turanian elements by Feinbrun-Dothan (1978, 1986) and Zohary (1966, 1987). Moreover, Feinbrun-Dothan (1978, 1986) considered Allium roseum var. tourneuxii, Biarum olivieri, Bupleurum nanum, Moraea mediterranea and Avena longiglumis as Saharo-Arabian elements (Danin and Fragman-Sapir 2016; Flowers in Israel 2005–2022; Pokorný and Pokorná 2009–2010). Otherwise, Allium sphaerocephalon subsp. arvense, Astragalus mareoticus, Plantago albicans, Ridolfia segetum, Lathyrus setifolius, Linum decumbens, Euphorbia pterococca and Phalaris aquatica were recorded in the Canary Islands (Euro + Med, 2006; eflora Maghreb 2021; Hassler 2004–2022; POWO 2022). Retama raetam subsp. raetam was recorded in Sudan and Western Sahara, Melilotus elegans in Djibouti and Ethiopia, Reseda phyteuma in Central Europe and Transcaucasus, and Stoibrax dichotomum in Saudi Arabia (POWO 2022; GBIF 2022; African Plant Database 2022).

In addition, in the present study, as well as Boulos (1999–2005) and Ahmed (2009), 118 taxa were excluded. For instance, Echiochilon fruticosum, Adonis dentata, Argyrolobium uniflorum, Astragalus asterias subsp. radiatus, Atriplex leucoclada var. inamoena, Ballota undulata, Bassia arabica, Bituminaria flaccida, Capparis spinosa var. canescens, Centaurium malzacianum, Dianthus sinaicus, Echium longifolium, Helianthemum kahiricum, Hypericum sinaicum, Iphiona mucronata, Paronychia sinaica and Picris asplenioides as they were recorded in Arabian Peninsula (POWO 2022; GBIF 2022; Hassler 2004–2022). Astragalus asterias subsp. radiates, Atriplex leucoclada var. inamoena and Phlomis fruticosa were recorded in Transcaucasus (POWO 2022). Further, Agathophora alopecuroides var. alopecuroides, Euphorbia chamaepeplus, Gypsophila capillaris, Hypecoum littorale, Lathyrus hierosolymitanus, Paronychia arabica subsp. longiseta, Polycarpon succulentum and Silene vivianii subsp. vivianii were recorded in Iraq (POWO 2022). On the other hand, only 3 taxa were recorded as Mediterranean endemics only in Ahmed (2009) and excluded from the other studies as well as the present study. They are Lycium europaeum that was recorded in southwest Asia and Canary Islands (Boulos, 1999–2005; Euro + Med, 2006), Thesium humile var. humile in Canary Islands, Iran and Arabian Peninsula (POWO 2022; Euro + Med, 2006; GBIF 2022; Hassler 2004–2022) and Tordylium aegyptiacum as it was recorded in Iraq (POWO 2022).

Anthemis bornmuelleri was recorded in Suadi Arabia in Boulos (1999–2005). Nevertheless, it is not recorded there in all the consulted databases (POWO 2022; GBIF 2022; JSTOR 2022; Hassler 2004–2022) or in Chaudhary (1999–2001) and E flora of the Kingdom of Saudi Arabia (2020). Also, A. bornmuelleri was excluded from the present study because it’s recorded in the Saharo-Arabian regions of southern Syria (Jbel Druze) (Chikhali 2022; POWO 2022; Hassler 2004–2022). In the meantime, Rostraria berythea was collected by Kamel et al. (2008) and Danin et al. (1985) from the Mediterranean coast of northern Sinai, although it was not included in the Flora of Egypt (Täckholm 1974; Boulos 1999–2005). Nevertheless, it was excluded from the present study as well as the Med-Checklist since it was recorded in the Irano-Turanian regions of Iran, Iraq, inner and east Anatolia (Turkey) and Saharo-Arabian regions of Jordon and Israel (POWO 2022; Hassler 2004–2022).

Notably, some Mediterranean elements were excluded from endemism in the present study because of their extension to adjacent regions (i.e., extendenda). For example, Micromeria nervosa that extends to Saharo-Arabian regions in South Sinai Egypt (CAI; CAIM; Täckholm 1974) and Irano-Turanian region (inner and east Anatolia) (Hassler 2004–2022; Davis, 1965–1985; Flora of Turkey 2022). Aegilops longissima, Astragalus trimestris, Ononis natrix subsp. stenophylla and Trigonella maritima extend into adjacent territories of the Saharo-Arabian region as mentioned by Feinbrun-Dothan (1978, 1986) and Zohary (1966, 1987). Bupleurum nanum extends to Saharo-Arabian deserts of Egypt and Libya (GBIF 2022). Bupleurum nodiflorum was recorded in Irano-Turanian Asiatic Turkey (east Anatolia) and Jbel Druze of Syria (Hassler 2004–2022). Further, Caralluma europaea extends to Saharo-Arabian deserts of Israel (Danin and Fragman-Sapir 2016; Flowers in Israel 2005–2022). Centaurea glomerata grows in Saharo-Arabian Great Southwestern Desert, Nile Valley and Southern Sinai, Egypt (TANE, CAI, GBIF 2022). Moreover, Echium angustifolium subsp. angustifolium extends to SA-AR deserts of Egypt and Libya, Irano-Turanian part of Asiatic Turkey and Euro-Siberian Turkey in Europe (Euro + Med, 2006; Hassler 2004–2022; GBIF 2022; African Plant Database 2022; Rabei and Elgamal 2021; Davis, 1965–1985). Zohary (1966, 1987) reported that Helianthemum vesicarium var. ciliatum and Ononis vaginalis extend to west Irano-Turanian. Lotus edulis, L. peregrinus and Plantago squarrosa extend to Irano-Turanian part of Asiatic Turkey and Euro-Siberian Turkey in Europe (Euro + Med, 2006; Hassler 2004–2022). In addition, Malabaila suaveolens is a Mediterranean species collected along Gulf of Suez in the eastern desert and Great Southwestern Desert of Egypt (Hassler 2004–2022; Abd El-Ghani et al. 2017). Scabiosa eremophila and Moraea mediterranea extend to deserts of Egypt (Great Southwestern Desert) and Palestine (Negev Desert) (Abd El-Ghani et al. 2017; Danin and Fragman-Sapir 2016; Pokorný and Pokorná 2009–2010; Flowers in Israel 2005–2022; Hassler 2004–2022). Limonium tubiflorum varieties. zanonii and tubiflorum extend to the Libyan desert in Egypt (CAI, Boulos, 1999–2005).

Furthermore, 36 taxa were excluded from the present study for their doubtful occurrence in the Egyptian flora (i.e., inquirenda). Of these, 28 taxa were never recorded in Egypt in the Egyptian flora books (Täckholm 1974; Boulos, 1999–2005), Egyptian herbaria, the literature, or the consulted databases. Probably, they have been reported in Egypt in Med-Checklist (Greuter et al. 1984–1989; Greuter and von Raab-Straube 2008; Med-Checklist 2016) in error. Some examples of these taxa are Lotus longisiliquosus, Trifolium constantinopolitanum, Haloxylon tamariscifolium, Rhamnus lycioides subsp. graeca, Daveaua anthemoides, Echinops philistaeus, Onopordum carduiforme, Picris amalecitana, Phlomis fruticosa and Origanum syriacum subsp. syriacum. Although Hippocrepis ciliata was recorded in Täckholm (1974), however, it wasn’t recorded in (Boulos, 1999–2005). Surprisingly, Reseda odorata was not included in the Egyptian flora books but was recorded as naturalized in Egypt in a CAI herbarium sheet and in Med-Checklist (2016), but it no longer exists in Egypt as an alien species. It may have been recorded one time, but couldn’t adapt to the Egyptian environment (El-Beheiry et al. 2020). Anthemis scrobicularis subsp. fungosa was not recorded in the Egyptian flora books, even though it was recorded in Wadi Hamra, south of Abu-Zneima, west of Sinai in Yavin (1972), Frumin and Shammash (2008). Artemisia inculta was not recorded in Boulos (1999–2005), despite being recorded in Täckholm (1974) in the Isthmic desert and the Red Sea, because it no longer exists in Egypt.

On the other hand, 11 taxa were excluded from Egypt in the present study despite being recorded in the Egyptian flora books. They might have been recorded in Boulos (1999–2005) in error. Minuartia mediterranea, Echium sabulicolum var. tenue, Parapholis filiformis and Retama monosperma subsp. bovei were reported as doubtfully present in Egypt in Med-Checklist, WSCSP (2022), and Euro + Med (2006). No records for herbarium specimens or research papers that emphasize their occurrence in Egypt are available (GBIF 2022; JSTOR 2022). Boulos (1999–2005) coincided that Rostraria hispida’s presence in Egypt is unconfirmed. Boulos (1999–2005) reported that Plantago macrorhiza was only found once in Egypt by Ascherson in 1887 and is no longer recorded since that time. Further, no authentically identified specimens of Reichardia picroides have been traced in Egypt, since the only collected five specimens from Mariut were proved to be Launaea fragilis subsp. fragilis (Boulos, 1999–2005). Otherwise, there is only a single collection of Ochthodium aegyptiacum in Egypt kept in Naturalis herbarium (L), Leiden, the Netherlands in 1800 without a location, and there is no other evidence emphasizing its presence in Egypt. In the meantime, there are no authentically identified specimens that confirm Convolvulus secundus occurrence in Egypt (Boulos, 1999–2005; POWO 2022; Med-Checklist 2016; Euro + Med, 2006; GBIF 2022; JSTOR 2022). Centaurea pullata was reported as a casual alien in Egypt in the Med-Checklist and databases like POWO (2022), and Euro + Med (2006), but it has not been recorded since in Egypt. It may have been recorded one time, but couldn’t adapt to the Egyptian environment (El-Beheiry et al. 2020). Moreover, the recording of Crepis clausonis in Egypt was based on only a single collection by Letourneux in 1870 from Mariut (Boulos, 1999–2005). There haven’t been other collections of this species in Egypt since that time. In addition to this, some databases like GBIF (2022), JSTOR (2022), Euro + Med (2006), Hassler (2004–2022) do never mention its occurrence in Egypt. Some taxa were reported as doubtfully present in Egypt in Med-Checklist and Euro + Med (2006) in error. They were authentically proved to be present in Egypt (CAI herbarium sheets). They are Hedysarum coronarium, Lobularia arabica, Euphorbia oxyodonta, and Astragalus sinaicus.

Regarding includenda, 13 taxa were recorded as Mediterranean endemics in the present study and Boulos (1999–2005) such as Allium barthianum, Apium crassipes, Bellevalia warburgii, Muscari salah-eidii, and Centaurea aegialophila. Even though Trisetaria koelerioides was recorded in Suadi Arabia in POWO (2022), and Hassler (2004–2022), it is recorded as Mediterranean endemic in the present study. It doesn’t exist in Chaudhary (1999–2001). In addition, the identification of T. koelerioides in the literature could have been mistaken for Trisetaria chaudharyana (E flora of the Kingdom of Saudi Arabia 2020). Moreover, 13 taxa were recorded as Mediterranean endemics in the present study, as well as Boulos (1999–2005) and Ahmed (2009). These are Allium blomfieldianum, A. mareoticum, (A) trifoliatum, Bellevalia salah-eidii, (B) sessiliflora, Muscari albiflorum, M. parviflorum, Pancratium arabicum, Posidonia oceanica, and Thesium humile var. maritima.

Furthermore, in the present study, as well as Boulos (1999–2005) and the Med-Checklist, 16 taxa were recorded as Mediterranean endemics. These are Echinops taeckholmianus, Reseda orientalis, Vicia sinaica, Helianthemum crassifolium subsp. sphaerocalyx, Euphorbia parvula, Anchusa undulata subsp. hybrida, Coronilla repanda, Crepis aculeata, Cynara cornigera, Filago mareotica, Helichrysum orientale, Herniaria cyrenaica, Leopoldia bicolor, Linaria joppensis and Teucrium brevifolium. Amazingly, 23 taxa were recorded as Mediterranean endemics in the present study, as well as the 3 prior studies (Boulos, 1999–2005; Med-Checklist 2016; Ahmed 2009). For example, Lycium schweinfurthii var. aschersonii, Limonium sinuatum subsp. romanum, Centaurea pumilio, Anthemis microsperma, Fumaria microstachys and Thymbra capitata. Indeed, Heliotropium hirsutissimum was recorded in Saudi Arabia in Hassler (2004–2022), but Chaudhary (1985) elucidated that most reports of H. hirsutissimum from Saudi Arabia could possibly be a misidentification of H. arbainense. Consequently, it can be considered as an east Mediterranean endemic.

Spectacularly, seven Mediterranean endemics were introduced to other floristic regions in the world. Cynosurus coloratus is a naturalized exotic in the South African kingdom (i.e., Cape region) (EPPO 2022; SANBI 2010–2012). In addition, Helichrysum orientale is an east Mediterranean endemic that was introduced to Macaronesian and Euro-Siberian regions (Canary Islands, Lanzarote with Graciosa and Czechoslovakia) (POWO 2022; GBIF 2022; Euro + Med, 2006; Dimopoulos et al. 2020). The threatened Mediterranean endemic seagrass, Posidonia oceanica was introduced to Australia and United States of America for its high contribution to carbon sequestration, biological productivity, nutrient cycling, and sediment stabilization (Hassler 2004–2022; GBIF 2022; JSTOR 2022). Further, Allium trifoliatum is introduced to Great Britain (POWO 2022). The Portuguese squill or hyacinth-of-Peru in some areas, Scilla peruviana is a west and central Mediterranean endemic that is cultivated as an ornamental plant in Sweden, United Kingdom, Canary Islands, South Australia, Queensland, New Zealand, and Mexico (POWO 2022; JSTOR 2022; GBIF 2022; Hassler 2004–2022; Euro + Med, 2006). Further, Pseudodictamnus mediterraneus is recorded as native to dry Mediterranean regions in Europe and western Asia, including Greece (South Aegean), Egypt, Libya and Turkey. It is also an introduced species in the British Isles and Italy (Sicily) (POWO 2022; JSTOR 2022; GBIF 2022) and Silene fruticosa to Netherlands and Austria (JSTOR 2022; GBIF 2022). The endemic Anthemis microsperma was recorded in Täckholm (1974) in only the western Mediterranean region, but Boulos (1999–2005) recorded it in North Sinai. There are no authentically identified collected specimens or herbarium sheets supporting its occurrence in Sinai. It might have been noticed there only one time, then disappeared or it could have been misidentified with another similar species. The same case is for Anchusa undulata subsp. hybrida that was recorded in the Nile region in Boulos (1999–2005) in error.

Conclusion

The current study is the first attempt since those of Greuter et al. (1984–1989), and Greuter and von Raab-Straube (2008) to provide an up-to-date list of the Mediterranean endemics in Egypt. Furthermore, it sought to provide information about more recognizable boundaries of the Mediterranean floristic region in Egypt, and used the original map provided by Good (1974) to produce an updated spatial layer of the biogeographical regionalization of the Mediterranean area, thus facilitating future analysis in the region. Indeed, the study has revealed that the Egyptian flora includes 65 Mediterranean endemics that are mostly distributed in the Mareotis subsector in the North African Mediterranean sub-region. Thus, the Mareotis region at the northwest coast of Egypt could be considered as an Egyptian hotspot of Mediterranean endemics. Certainly, these taxa are the most common in the Mediterranean territory, a finding that supports the idea that part of Egypt is included in this strip. In addition, the study revealed that the coastal dunes and non-saline depressions are the most supportive habitats for the Mediterranean endemics in Egypt. These outcomes may promote future conservation efforts for these habitats which are currently under eminent threat due to continuous human activities. It is recommended that other countries in the Mediterranean basin conduct inventoriesy of the Mediterranean endemics in their floras, to facilitate future efforts for compiling a complete up-to-date authenticated database of endemics in the whole Mediterranean floristic region.