Past, present, and future geographic range of the relict Mediterranean and Macaronesian Juniperus phoenicea complex

Abstract Aim The aim of this study is to model the past, current, and future distribution of J. phoenicea s.s., J. turbinata, and J. canariensis, based on bioclimatic variables using a maximum entropy model (Maxent) in the Mediterranean and Macaronesian regions. Location Mediterranean and Macaronesian. Taxon Cupressaceae, Juniperus. Methods Data on the occurrence of the J. phoenicea complex were obtained from the Global Biodiversity Information Facility (GBIF.org), the literature, herbaria, and the authors’ field notes. Bioclimatic variables were obtained from the WorldClim database and Paleoclim. The climate data related to species localities were used for predictions of niches by implementation of Maxent, and the model was evaluated with ENMeval. Results The potential niches of Juniperus phoenicea during the Last Interglacial period (LIG), Last Glacial Maximum climate (LGM), and Mid‐Holocene (MH) covered 30%, 10%, and almost 100%, respectively, of the current potential niche. Climate warming may reduce potential niches by 30% in RCP2.6 and by 90% in RCP8.5. The potential niches of Juniperus turbinata had a broad circum‐Mediterranean and Canarian distribution during the LIG and the MH; its distribution extended during the LGM when it was found in more areas than at present. The predicted warming in scenarios RCP2.6 and RCP8.5 could reduce the current potential niche by 30% and 50%, respectively. The model did not find suitable niches for J. canariensis during the LIG and the LGM, but during the MH its potential niche was 30% larger than at present. The climate warming scenario RCP2.6 indicates a reduction in the potential niche by 30%, while RCP8.5 so indicates a reduction of almost 60%. Main conclusions This research can provide information for increasing the protection of the juniper forest and for counteracting the phenomenon of local extinctions caused by anthropic pressure and climate changes.

Ecological Niche Models (ENMs) are predictive tools that assume that species distribution is determined by climate conditions (Di Pasquale et al., 2020;Franklin et al., 2009;Li et al., 2020;Rodríguez-Sánchez & Arroyo, 2008;Walas et al., 2019) and use their current geographic ranges and climate conditions to predict past and future distribution. The use of georeferenced species localities together with bioclimatic data allows the retro-and prospective analysis of their potential niches (Phillips et al., 2006. Retrospective and prospective niche modeling has been used only occasionally for circum-Mediterranean and Macaronesian species (Di Pasquale et al., 2020;Rodríguez-Sánchez & Arroyo, 2008), and also for species occurring within the region (Arar et al., 2020;Benítez-Benítez et al., 2018;Hajar et al., 2010;Stephan et al., 2020;Taib et al., 2020;Walas et al., 2019). Mediterranean and Macaronesian regions are important biodiversity hotspots at the global scale. However, they have been greatly modified by human activity for millennia and they are vulnerable to current and future climate change (Otto et al., 2012;Thompson, 2005).

| Data
Data on the occurrence of the J. phoenicea complex were obtained from the Global Biodiversity Information Facility (GBIF.org), the literature, herbaria, and the authors' field notes. The data originally did not distinguish J. phoenicea s.s from J. turbinata, and thus, taxa were segregated using published results of biochemical (Lebreton & Pérez de Paz, 2001;Lebreton & Rivera, 1989), genetic (Adams et al., 2002(Adams et al., , 2009(Adams et al., , 2014Boratyński et al., 2009;Dzialuk et al., 2011;Jiménez et al., 2017;Sánchez-Gómez et al., 2018), and biometric (Mazur et al., 2010(Mazur et al., , 2016(Mazur et al., , 2018 research. Additionally, their taxonomic status was reviewed according to geographic and ecological criteria. All data were carefully verified to eliminate possible outliers. For Andalusia, the data regarding J. phoenicea s.s. and J. turbinata distribution were included after reviewing herbaria and the literature, in which these two species were clearly distinguished (Cabezudo et al., 2003;Díez-Garretas et al., 1996;Pérez Latorre & Cabezudo, 2009;Pérez Latorre et al., 2006. We examined the realized, retrospective, and predicted niches separately for J. phoenicea s.s., J. turbinata, and J. canariensis and for the entire J. phoenicea complex. Additionally, we analyzed separately the data from the groups of localities of J. turbinata detected in the genetic study (Sánchez-Gómez et al., 2018:7 Latitude, longitude, and elevation for each locality were obtained from the source data; when this was not possible, they were retrieved from Google Earth. Localities with insufficiently precise descriptions were excluded from the analyses. In total, we gathered more than 10,000 location data, although the majority of them replicated the same information. From this set of data, we selected an exact and precise description for 4,852 localities: 3,254 for J. phoenicea, 1,303 for J. turbinata, and 295 for J. canariensis, respectively (Figure 1). For J. turbinata, the numbers of localities were 529, 38, 404, and 32 for TURAT, TURCM, TUREM, and TURAR, respectively (Table S1).

| Environmental variables
Temperature, precipitation, and altitude data have been identified as the most influential elements for current ecological niches (Bradie & Leung, 2017). In this study, however, altitude was not used in the models as we did not have these data for all projections.
We built ENMs with 19 bioclimatic variables (  (Brown et al., 2018) and F I G U R E 1 Geographic distribution of Juniperus phoenicea complex, J. phoenicea s.s., J. turbinata, and J. canariensis on the background of the mountain systems had a spatial resolution of 30 arc-seconds (~1 km). To delineate potential niches during the Last Interglacial period (LIG 120-140 ka BP), WC used the climate data from the CAPE project (Otto-Bliesner et al., 2006) and data from the Community Climate System Model (CCSM, Gent et al., 2011 (Fick & Hijmans, 2017). For future predictions, we used scenarios of climate change with two representative concentration pathways (RCPs), RCP 2.6 and RCP 8.5 (Collins et al., 2013).
The first predicts an increase in radiative forcing by 2.6 W/m 2 and an increase in temperature of 1°C before 2070 (average for 2061-2080), and the second by 8.5 W/m 2 and 2°C during the same period. Both are climate projections from GCMs that were downscaled and calibrated using WorldClim 1.4 as the baseline climate.

| Ecological niche modeling
The climate data related to species localities were used for predictions of niches by implementation of Maxent 3.4.1. (Phillips, 2017;Phillips et al., 2020). Maximum entropy modeling was used to estimate species probability distributions outside their known area of distribution (Raffini et al., 2020;Yan et al., 2020). Firstly, we evaluated the model with ENMeval R software (Ancillotto et al., 2020;Muscarella et al., 2014). We used 10 k-fold spatial partitions for each species presence record and evaluated models with the following feature classes: linear, quadratic, hinge, product and threshold, and the following values of regularization multipliers: 0.5, 1, 1.5, 2, 2.5, 3, 3.5, and 4 (Table S2). The parameters used in Maxent were as follows: different features and regularization, bias file, maximum F I G U R E 2 Percentage of georeferenced localities of Juniperus canariensis (CAN), J. turbinata (TUR), and J. phoenicea s.s. (PHO) depending on elevation number of iterations at 1,000, convergence threshold 10 -5 , with 10 replicates, cloglog output format, number of background points at 10,000, and replicated run type as cross-validate.
Receiver Operating Characteristic (ROC) curves were used to evaluate the results of models (Mas et al., 2013;Wang et al., 2007).
Area Under the Curve (AUC) values below 0.6 indicated that the results of the predictions were close to random, while 1.0 showed excellent predictions (Table S2)  and high potential (0.6-1) (Yang et al., 2013). We calculated the potential distribution area of the Juniperus phoenicea complex based on high-potential niches (0.6-1).

| Present niche range (1970-2020)
The    (Table 1). Precipitation-associated climate factors are responsible for about 55% of the potential niche delimitations, while temperature factors are responsible for over 45%. The jackknife of AUC, however, found that temperature factors are more important in determining the current niche, with annual temperature range and annual mean temperature (BIO7 and BIO1, respectively) having the strongest influence on distribution (Fig. S2).
Juniperus canariensis has a narrow geographic range, being found only on the Canary Islands (excluding Lanzarote and Fuerteventura) and Madeira and Porto Santo islands ( Figure 1). These localities provide a good reflection of the realized niche, which goes slightly beyond the Canary Islands. The species altitudinal range extends from about 100 to 1,400 m, with about 80% of localities being between 400 and 1,000 m ( Figure 2). The potential niche of the species is determined mostly by annual precipitation and precipitation in the wettest month (BIO12 and BIO13, respectively; Table 1).
Precipitation-associated bioclimatic factors determine more than 70% of the potential niche of the species. The jackknife of AUC confirmed this, indicating precipitation as the most important variable, especially during the wettest month and the wettest quarter (BIO13 and BIO16, respectively; Fig. S3).

F I G U R E 4
The retrospective analyses did not find suitable habitats for J. canariensis, during either the LIG, or the LGM. Climatically suitable habitats appeared during the MH, but only on Gran Canaria Island and on the western shore of North Africa (Tamri region).
Interestingly, Lanzarote, Fuerteventura, and the Madeira islands did not have climatic conditions suitable for J. canariensis at that time ( Figure 5, Table 2).  Table 2).
The area of the potential niches suitable for J. turbinata in the optimistic scenario would be reduced by 30%. This reduction will mostly involve the mountain area in northwest Africa. Compared with the current geographic range of the species, the marginal southern-most localities in the African and Asian mountain regions would be outside the potential niche. The area of the potential niche in the case of the optimistic scenario will be similar, as detected during the Holocene optimum ( Figure 4). The pessimistic climate change scenario would reduce the potential niche area by more than 50% compared with the present ( Table 2) The RCP8.5 scenario would drastically reduce its potential niche ( Figure 6, Table 2).
The current potential niches of J. phoenicea, J. turbinata, and

| D ISCUSS I ON
Macroremnants of the complex of J. phoenicea from past geological periods are scarce or lacking (Kvaček, 2002;Palamarev, 1989;Palamarev et al., 2005;Stockey et al., 2005;Uzquiano & Arnaz, 1997;Velitzelos et al., 2014). Additionally, juniper pollen has not been distinguished to the species level (Carrión et al., 2001). Therefore, we were only able to use the climate conditions of the current realized

| Geographic ranges and their climatic determinants
The three species in the J. phoenicea complex have been distinguished from each other during recent decades, and maps of their geographic ranges have been presented either schematically (Adams, 2014;Lebreton & Pérez de Paz, 2001;Lebreton & Rivera, 1989;Mazur et al., 2016) or partially (Otto et al., 2012). The Cabo de Espichel are somewhat surprising but are documented in herbarium materials and by morphometric study (Mazur et al., 2018).
The average yearly precipitation in the distribution area of J. phoenicea s.s. ranges between 350 and ca 500 mm at lower altitudes but increases to 800-1000 mm in the mountain regions Villar et al., 1997;Walter & Lieth, 1964). The average rainfall in the realized potential niche is 490 mm, with ranges between 300 and 1,100 mm (Table S3) In southern France and northern Italy, J. phoenicea s.s. occurs in similar climatic conditions to the Mediterranean region, but also grows in temperate regions at specific sites, such as steep, rocky south-facing slopes in the mountains, or rocky slopes in river ravines (Mandin, 2005). The species is adapted to the Mediterranean climate and to a wide range of bioclimates, from subarid to subhumid or even humid, within the meso-Mediterranean, supra-sub-Mediterranean, and oro-sub-Mediterranean zones (Mazur et al., 2016;Rivas-Martínez et al., 2004).
Juniperus turbinata occurs in the Mediterranean region, mainly on the coast and at low elevations up to about 400 m; in the southernmost localities it can be found in the mountains, up to 2,400 m in the High Atlas, and 1,800-2,000 m in southwest Asia (Boratyński et al., 1992;Browicz & Zieliński, 1982;Charco, 2001;El Bana et al., 2010;Kerfoot & Lavranos, 1984;Lebreton & Rivera, 1989;Quézel & Barbero, 1981;Quézel et al., 1994). At coastal sites, J. turbinata colonizes maritime dunes and/or rocks, growing on either siliceous or calcium substrata (Ayache et al., 2020;Eliçin 1977;Loidi, 2017;Martinis et al., 2018). It forms populations that can be locally extensive. Inland penetration occurs mostly in maquis and pine or oak forests, and also on the calcareous rocks (Albarreal Núñez & Romero Zarco, 2004;Asensi et al., 2007;Bacchetta, 2006;Capelo et al., 1994;Elmahdy & Mohamed, 2016;Gianguzzi et al in the Mediterranean and Atlantic coastal regions exposed to the west or north, with the direct influence of winds carrying humidity . The current potential niche of the species receives an annual average precipitation of more than 600 mm, ranging from 100 to more than 1,250 mm (Table S3).
The climate conditions of the Atlas Mountains and the mountains of southwest Asia are oro-Mediterranean in character, with temperatures close to 0°C during winter (Walter & Lieth, 1964;Zohary 1973). The High and Middle Atlas in Morocco receives relatively high precipitation during winter but suffers prolonged drought during late spring and summer (Born et al., 2008;Emberger, 1955).
Interestingly, several localities of J. turbinata at the top of mountain ridges in northwest Africa remain outside the current potential niche of the species (compare Figures 1 and 4).
The relictual populations of J. turbinata on the Sinai Peninsula have survived in an arid region with annual rainfall ca 100 mm and annual mean temperature above 26°C. The species grows here in the so-called "wetter places," on rocks on mountain tops, in wadis or at the base of rocks (Danin, 1983;El-Bana et al., 2010;Moustafa et al., 2016). Currently, however, there is no regeneration of J. turbinata (Danin, 1983;Moustafa et al., 2016).
The climatic conditions of most localities of the species in the mountains along the Red Sea have a transitory character between the inland continental desert and the coast. In the mountains, at altitudes between 1,000 and 1,600 m, there is a belt with characteristics resembling the Mediterranean climate, with high temperatures during spring and summer, but wet and cold conditions in winter (Kerfoot & Lavranos, 1984;Palmer, 2013;Schyfsma, 1978;Zohary, 1973).
The potential niches for the four groups of J. turbinata (TURAT, TURCM, TUREM, and TURAR) detected during genetic (Sánchez-Gómez et al., 2018) and morphometric studies (Mazur et al., 2018) appeared to be associated with varying climatic conditions. The differences and the specific response to climate change may reflect their spatial isolation from one another, as is the case with a number of populations of J. drupacea (Walas et al., 2019), or even some taxonomic differentiation, as in the case of Quercus ilex L. subsp. ilex and Q. ilex subsp. ballota (Desf.) Samp. (López-Tirado et al., 2018); this hypothesis, however, needs to be tested in further studies.

Juniperus canariensis is native to the Canary Islands and the
Madeira archipelago, although only isolated specimens are found in the latter . It does not grow on the driest Canary Islands, Lanzarote, and Fuerteventura, which are exposed to dry and warm winds (Bechtel, 2016;Cropper, 2013). The climate of the Canary Islands is oceanic, with low temperature amplitudes and high humidity, but J. canariensis forms homogeneous patches and enters shrub communities in places with relatively low rainfall (Fernández-Palacios et al., 2008Luis González et al., 2017;Otto et al., 2010Otto et al., , 2012Romo 2018;Romo et al., 2014;Romo & Salvà-Catarineu, 2013). It grows at elevations mostly between 400 and 1,000 m, higher on the leeward than the windward sides of the islands (Fernández-Palacios et al., 2008;Otto et al., 2012).
The species distribution in the Macaronesian province is associated with a thermo-Mediterranean type of bioclimate (Fernández-Palacios et al., 2008;Rivas-Martínez et al., 2004) with BIO12, BIO13, and BIO18 being the most influential climate factors. The climate conditions of the current potential niche are characterized by low annual precipitation, which reaches about 340 mm on average and does not go above 420 mm. The lack of rain may be compensated by high air humidity (Fernández-Palacios et al., 2008;Otto et al., 2010Otto et al., , 2012.

| Past and future geographic range
Retrospective analyses indicated the differences between potential climatic niches of J. phoenicea s.s. and J. turbinata during the LIG and the LGM. Both species had potential niches in northern Africa, but there were potential niches for J. phoenicea in the mountains, and for J. turbinata mostly along the Atlantic and Mediterranean shores and the Canary Islands. The current spatial isolation of the geographic ranges of J. phoenicea and J. turbinata supports an early divergence between these two species and their adaptation to different climatic conditions.
High temperatures and low levels of precipitation during May, June, July, and August, and a high diurnal amplitude of temperatures and precipitation seasonality, were identified as important limitations to the current occurrence of J. phoenicea s.s. The same limitations would have restricted potential niches during the LIG and the LGM (Jalut et al., 2009;Zucca et al., 2014). The restricted area of the potential niche of J. phoenicea during the LIG could also be attributed to annual temperatures that were lower than those currently observed (Allen & Huntley, 2009;Zachos et al., 2001). Taking into account the species' humidity requirements, their potential LIG niche on Tenerife and close to the African Atlantic shore may be associated with the more humid at that time (Abrantes et al., 2012).
The potential niche distribution of the species during the LGM overlaps with only one refugial area in the Maritime Alps (Médail & Diadema, 2009:1336, Figure 1). Considering the current climate limitations, the enlargement of the potential niche suitable for J. phoenicea during the MH could have been a response to the increased precipitation and, to some degree, to the higher temperatures at that time (Jalut et al., 2009;Lionello, 2012;Pérez-Obiol et al., 2011;Rensen et al., 2012). The higher precipitation created suitable conditions of the species in the Iberian Peninsula at altitudes higher than the ones it currently occupies. The aridification of the Mediterranean climate, which started after the MH (Jalut et al., 1997), has been a reason for the ongoing restriction of J. phoenicea s.s. and movement of its potential niche to the more moderate climate zone, where it currently grows.
The overlap between the current potential and realized niches of J. phoenicea (Figures 1 and 3) could explain the relatively rapid reaction of the species to past changes in the climate. This can be illustrated by comparing the MH and current potential niches of the species. The reduction in the temperature by approximately 2°C and the fall in precipitation from the MH to the present (Lionello 2012) caused the movement of the species' potential and realized niches.
The expansion of broadleaved trees during the MH could also have contributed to the persistence of J. phoenicea at specific rocky sites where there was less competition from broadleaved trees.
The high demands of J. phoenicea for access to light, its pioneering character (Asensi et al., 2007;Díez-Garretas et al., 1996;Franco, 1986;  theoretically diminish the potential niche of the species by more than 30%. The RCP8.5 scenario, in which temperatures would increase by 2°C and precipitation would decrease by 10%-20% in winter and by 30%-40% in summer (Collins et al., 2013), would restrict the potential niche by more than 90%. The reduction in winter precipitation would have a particularly strong influence on the decline in its geographic range (Table 1). Despite this decline, J. phoenicea is relatively tolerant to high temperatures and aridity and would survive in specific microsites inaccessible to broadleaved tree formations. Nevertheless, such a drastic reduction in potential niche area would make this species severely endangered.
To a large extent, the current potential and realized niches of J. The potential niche of the species during the LGM covered most of the glacial refugial areas (Médail & Diadema, 2009). Several localities of J. turbinata outside the potential niche at the southern limits of the species' geographic range may be a remnant of their broader distribution during the LGM (Pulliam 2000). Surprisingly, the potential niches in the LGM did not cover the mountains in the southern part of the Arabian Peninsula and Sinai. This may indicate that populations in these localities are relicts from the LIG or earlier interglacial periods. If so, the species should be considered as having features that allowed millennial persistence in areas outside its optimal conditions. It is also possible that the climate oscillations during the last glacial period (Van Andel 2002) positively influenced the persistence of the species at specific microsites. Wadis, tops of rocky ridges, or bases of steep slopes were considered to be microsites that would allow J. turbinata to persist in the Sinai Peninsula (Danin 1983;El Bana et al., 2010;Moustafa et al., 2016) and the mountain system of the west Arabian Peninsula (Kerfoot & Lavranos, 1984;Zohary, 1973).
During the MH, the potential niche of J. turbinata in the Mediterranean region was especially strong along the Atlantic coast but was somewhat restricted compared with the LGM niches. Its realized niche during that time may have been further reduced due to competition with broadleaved trees, the distribution of which expanded intensively during the Holocene up to the period of the MH (Calò et al., 2012;Pérez-Obiol et al., 2011). The aridification of the Holocene climate, which started from the MH, in the eastern Mediterranean region (Finné et al., 2011) seems to have stimulated the expansion of the potential niche. This reconstruction is well supported by the pollen diagrams found in southern Sicily (Noti et al., 2009) where only J. turbinata and J. macrocarpa Sm. grow, the former on the inland paleo-dunes and the latter strictly on coastal dunes. These pollen diagrams show the abundant presence of juniper about 6,900 years BP, a progressive decline up to the MH, and then a recovery after the MH but to lower levels, coinciding in time with the abundant presence of Quercus ilex. However, the same aridification due to human influence in the African part of the potential niche was a reason for the strong reduction in the realized niche, starting from the MH (Jaouadi et al., 2016).
The current occurrence of populations of J. turbinata in the Anti-, High and Middle Atlas and the Algerian mountains may also be determined by specific site conditions on the mountain ridges (Arar et al., 2020). There the species grows on slopes exposed to the north and northwest, that is, to the winds carrying humidity from the Atlantic Ocean or the Mediterranean Sea. As a result, rainfall is higher than at other sites, and the deposition of dewdrops during the night may also compensate for the water deficit in the summer (Emberger, 1955).
The reduction in the potential niche of J. turbinata is more apparent in the pessimistic scenario RCP8.5, in which the temperature would increase by approximately 2°C, precipitation would decrease and there would be a general increase in climate aridity (Allen et al., 2010;Born et al., 2008;Díez-Garretas et al., 2019;Giannakopoulos et al., 2009;Giorgi & Lionello, 2008;Panagiotis et al., 2013;Paparrizos et al., 2016;Türkeş 2003). and also on Fuerteventura. From the start of the Holocene about 10,000 years ago, the pollen of Juniperus was reported in La Gomera (Nogué et al., 2013). On the other hand, the lack of potential niches of J. canariensis during the LIG and the LGM would not rule out its presence in places with more suitable site conditions, as occurred in glacial microrefugia of European trees (Bhagwat & Willis, 2008;Magri, 2008). Juniperus canariensis has a lower level of genetic diversity than other species of the J. phoenicea complex (Jiménez et al., 2017;Sánchez-Gómez et al., 2018), but it is still high and comparable to that of other conifers Bou Dagher-Kharrat et al., 2007;Conord et al., 2012;Juan et al., 2012).
This level of genetic diversity of the Canarian juniper may have been sufficient to allow it to adapt to changing environmental conditions in the past (Jump & Peñuelas, 2005;Matías & Jump, 2012).
The present potential niche of J. canariensis is determined mostly by precipitation (BIO13 and BIO18) and annual mean temperature (BIO1). The species currently grows in areas with annual precipitation between 211 and 415 mm (Table S3), but with relatively high air humidity (higher than the other two species). These climate conditions had a similar effect during the LIG and the LGM.

| TH R E AT S
The predicted increase in temperature and decrease in precipitation (the latter by up to 30%, depending on the region) in the Mediterranean basin (Giorgi & Lionello, 2008) will have a great impact on tree biology. Among the climatic factors, precipitation is considered to be the most important, determining the occurrence of many tree species in the Mediterranean and Macaronesian regions (Allen et al., 2010;Matías & Jump, 2012;Thompson, 2005). In our study, precipitation was found to determine the potential niche ranges of the J. phoenicea complex to a very high degree. The predicted reduction in precipitation during spring and summer will increase aridity (Giannakopoulos et al., 2009;Panagiotis et al., 2013;Paparrizos et al., 2016) and will also raise tree mortality (Walas et al., 2019). Drought during the summer period has previously provoked an increase in the rate of direct die-out of juniper speci- thus represents a potential threat (Pausas, 2004). Aridification influences the direct seedling mortality after germination (De Dato et al., 2009) and intensifies inbreeding resulting from a lower level of cross-pollination (Lloret & García, 2016). Lower seedling recruitment also results from a higher level of seed predation associated with increasing temperatures (Mezquida et al., 2016).
The highest amount of precipitation falls during late autumn and early spring (Walter & Lieth, 1964), and a possible water deficit during winter has been detected as a potential limitation for J. phoenicea s.s. physiology (Baquedano & Castillo, 2007). Drought during the cold period and early spring is recognized as a possible cause of J. phoenicea mortality (Sánchez-Salguero & Camarero, 2020). During the summer period, rainfall is low and associated predominantly with storms . High temperatures in June, July, and August and high evapotranspiration are responsible for drought during this period, an important limitation on J. phoenicea occurrence, as is the high diurnal amplitude of temperatures and the precipitation seasonality (Baquedano & Castillo, 2007;Lloret & García, 2016). In the mountains, the minimum temperature may fall to about −7°C (Table S3); however, this does not influence the potential and realized niches of the species (Table 1).
The potential niche of J. turbinata is determined mostly by annual temperature range (BIO7) and precipitation factors (BIO12, 14 and 16). The species' reaction to the climate warming occurring in the southernmost mountainous part of its geographic range is manifested by a high level of mortality in adult trees and a lack of (or highly reduced) recruitment of new plants (personal observations in the High Atlas). The threat to J. turbinata would result from the limited photosynthetic efficiency due to the lack of water during the dry period (summer), the very high temperatures, and possible intensified UV radiation (Álvarez-Rogel et al., 2007; Rubio-Casal et al., 2010). In the dunes along seashores, it may also be stressed by saltwater infiltration due to high evapotranspiration and the shortage of rainfall resulting from climate warming (Berger & Heurteaux, 1985). The longevity of this species reported to be up to 130 years or more (Martinis et al., 2018) may extend its persistence, but for a relatively short period, mainly due to the frequent rot of the trunks which increases its' susceptibility to wind breakage.
The winter and early spring drought that has occurred during recent decades could be an important factor in J. turbinata dieback (Arar et al., 2020;Sánchez-Salguero & Camarero, 2020). The possible limitation of J. turbinata occurrence could also be associated with the summer water deficit (Armas et al., 2010).
In this context, the localities of J. turbinata on the Sinai Peninsula are the most threatened. Its presence there is conneccted with highly local orographic conditions, with slightly modify the desert climate.
The forecasts of niche reduction and consequently of the distribution range of the Juniperus phoenicea complex do not take into account direct anthropic actions such as fires, felling, changes in land use, and forestry with alien species, etc., which in the past have decimated juniper populations, especially J. turbinata. In the future, human disturbance could aggravate the effects of the scenarios outlined, especially on populations that grow on sandy soils in coastal environments. Those growing in rocky habitats may be less vulnerable. Only decisive action regarding the active protection and strategies to heighten awareness among local populations on the part of the bodies responsible for environmental and biodiversity will be able to counter the phenomenon of local extinctions caused by anthropic pressure.

ACK N OWLED G EM ENTS
The authors would like to acknowledge Manuel Luis González for providing the locations of the species. This research study was conducted within the framework of the JUNITUR + Project fund code no. 22722132113).

CO N FLI C T O F I NTE R E S T
The authors declare that they have no conflicts of interest to report. Writing-original draft (lead); Writing-review & editing (lead).

E TH I C S S TATEM ENT
1. This material is the authors' own original work, which has not been previously published elsewhere.
2. The paper is not currently being considered for publication elsewhere.
3. The paper reflects the authors' own research and analysis in a truthful and complete manner.
4. The paper properly credits the meaningful contributions of coauthors and coresearchers.
5. The results are appropriately placed in the context of prior and existing research.
6. All sources used are properly disclosed (correct citation). Literally copying of text must be indicated as such by using quotation marks and giving proper reference.
7. All authors have been personally and actively involved in substantial work leading to the paper and will take public responsibility for its content. Trafford Publishing Co. Adams, R. P., Altarejos, J., Arista, M., & Schwarzbach, A. E. (2014).

DATA AVA I L A B I L I T Y S TAT E M E N T
Geographic variation in Juniperus phoenicea var. phoenicea from