Heterotopy remastered with a quantitative tool: the case study of the European beech (Fagus sylvatica L. subsp. sylvatica) in peninsular Italy and Sicily

The term “heterotopic” was applied to phytogeography referring to those populations found on soils apparently different from those typically occurring across the distribution range of a given species. In Italy, it was also applied to European beech populations generally occurring at an altitude below 800 m a.s.l. Based on a multivariate analysis using climatic and altitudinal data, we propose a method to apply reliably this concept to the European beech occurring in peninsular Italy and Sicily. Our results suggest that beech populations located at an altitude ≤ 600 m a.s.l. can be defined as “quantitatively heterotopic” in Italy. These populations mainly occur on the Tyrrhenian side, marked by high oceanicity. Most of them are located outside of the natural vegetation series with European beech and, some are more than 20 km outside. Our method could be applied to other species in order to quantify the level of heterotopy by defining ad hoc thresholds, resulting from multivariate analysis.