The presence of Quercus estremadurensis O. Schwarz in Iberian Peninsula - Sintaxonomic and Biogeographic analysis

Following  PhD  thesis  work  surveys  on  Monchiquense  District,  the  presence  of  Quercus estremadurensis  O.  Schwarz was noticed  in  the  catenal  dynamics  of  Avenello  strictae-Quercetum marianicae woodlands, ecologically related to freatic and temporihygrophilous positions. Thenceforth, it has been re-discovered, trough fieldwork and Herbaria research, in several biogeographic territories, namely in the Southwestern and Western part of Iberian Peninsula, following the border between Eurosiberian and Mediterranean macrobioclima-tes, as well as in relictual groves of semi-deciduous woodlands, in humid and hyperoceanic areas.  

Here, we combine the phytosociological methodology with species distribution modelling (SDMs)  to  clarify  the  sintaxonomic  affiliation  of  these rare formations,  and  to present  a spatially-explicit model for its potential distribution. BIOMOD2 ensemble modelling framework was implemented to build Q. estremadurensis potential distribution in the Iberian Peninsula, considering climate, slope, land use and soil, as ecologically relevant determinants, for the species distribution. In the lack of absence data, pseudo-absences have been randomly selected from the studied area excluding available presence points. The predictive 
performance per variable was assessed using a randomization procedure as implemented in BIOMOD2.  
Being present in several biogeographic territories, from Portuguese-Divisorian and Algarvian-Monchiquense Sub-Provinces, passing through Luso-Extremadurean and Carpetanan-Leonese ones, we analyze four possible syntaxons occurring in the frame of Quercion broteroi and Aceri granatensis-Quercion fagineae, deeply related to the biogeographic territories where they occur . Ecologically  prone  to  streams  and  deep  valleys,  normally  in  the  midst  of  Pruno-Rubion dense thorn-bushes, mature and pure woodlands are totally absent in all studied territories, due the heavy landscape transformation, which made this study and interpretation of these formations hard and tricky.  
Also, in the absence of phylogeographic and molecular essays, relating the independence or infra-specific  range  of  Quercus  estremadurensis  O.  Schwarz,  inside  the  broad  sense  of Quercus  robur  L.,  this  taxon  faces  great  menace,  mainly  by  introgression  features  with broad sense Quercus faginea Lam., Q. marianica C. Vicioso / Q. canariensis Willd. and also Q. pyrenaica Willd.