## 4 Winners and Losers of Mediterranean Species under Climate Change  
The relative behaviour (i.e., physiological performances, growth, reproduction) and resistance of different Mediterranean species under increasing drought and temperature has been compared in researches by means of long-term field experiments [53]. Many papers explored the physiological drivers of the greater resistance of _P.__latifolia_ and _P.__lentiscus_ in comparison with _Q.__ilex_ and _A.__unedo_, as reported in field observations [51; 54] (Figure 1), and the ecological consequences of such differences in terms of species competitiveness, community composition and vegetational dynamics. From a physiological point of view, _P.__latifolia_ and _P.__lentiscus_ showed higher photosynthetic rates and lower stomatal conductance than _Q.__ilex_ in water stress conditions, thus exhibiting higher instantaneous plant water use efficiencies [55]. _Phillyrea latifolia_ survived under severe short-term drought events, whereas _Q.__ilex_ did not [55; 56; 57]. These findings were confirmed by [58] by comparing the behavior of _P.__latifolia_ and _Q.__ilex_ in field and experimental conditions. These authors found that _P.__latifolia_ can take advantage on _Q.__ilex_ by maintaining higher sap flow rates during dry periods. _Phillyrea latifolia_,  
Figure 1: Quercus _ilex_ L. (holm oak) forest stands in the Regional Park of Maremma (Tuscany, Central Italy). Trees of holm oak are completed defoliated, while _Phillyrea latifolia_ L. trees show green canopy (photo by [PERSON], 20 January 2020). moreover, is better performing than _Q.__ilex_ in drier soils: whereas _Q.__ilex_ assimilation rates increased with soil humidity; in _P.__latifolia_, assimilation rates did not increase above 17% of soil humidity, showing no water availability response above such threshold [59]. Under severe drought stress, the optimal temperature for photosynthesis is 20-30% lower than in wetter conditions. This condition can overpass the high acclimatory capacity of Mediterranean trees to high air temperatures, which could provoke growth reduction rise in leaf shedding and, for some species such as _A.__unedo_, increase mortality risk [60]. Lower water potentials in _P.__latifolia_ were not clearly associated with higher risk of hydraulic failure. Differently, hydraulic failure remains the most likely cause of death in _Q.__ilex_ under extreme drought [61]. The vulnerability to xylem embolism has been assessed by [62; 63] in a number of Mediterranean species and a pattern was proposed from the most to the lesser vulnerable: _Quercus ilex_ = _Acer nonspessulanum_ L. = _Arbutus unedo_ = _Sorbus torminalis_ L. = _Cistus laurifolia_ L. > _Cistus albidus_ L. = _Ilex aquifolium_ L. > _Phillyrea latifolia_ > _Juniperus oxycedrus_ L.  
Concerning the reproductive processes [64], reporting the results of an experimental drought suggest that in a drier environment drought-resistant species such as _P.__latifolia_ could present greater ability to produce reproductive structures than less-resistant species, such as _Q.__ilex_ or _A.__unedo_. In _Q.__ilex_ and _A.__unedo_, flower and specifically fruit production were strongly correlated with annual rainfall, but not in _P.__latifolia_. Experimental drought, tested by [65], reduced flower and fruit production in _Q.__ilex_ by 30% and 45%, respectively, whereas they were not significant in _A.__unedo_ and _P.__latifolia_. Overall results induced [66; 67; 68] speculation that in the drier conditions predicted in Mediterranean area, a relevant reduction of tree growth rates can be expected, combined with an increase of diffusion of drought-tolerant species, such as _P.__latifolia_, in detriment of more mesic species, such as _Q.__ilex_. In a 14-year-long field experiment, [69; 70] observed that _A.__unedo_ was the only species showing a significant reduction in basal area increment (BAI) under drought.