Phenorhythms and forest refugia

Abstract

Anomalous phenoryhthms such as reiterated anthesis and annual, biennial and intermediate fruiting are recorded for evergreen oaks (Quercus sect. Sclerophyllodrys: Q. ilex, Q. coccifera s.l. and Quercus sect. Cerris: Q. suber) in southern peninsular Italy. The same patterns are known from populations of evergreen oaks of the same sections in the western Himalaya, in areas where climatic conditions are intermediate between mediterranean and monsoons regimes, thus resembling border-line mediterranean climates. This suggests persistence of atavistic adaptations in areas with similar, “relaxed” climatic conditions. In the Italian peninsula, such areas would have acted as small isolates where a less intense climatic deterioration during the Late Quaternary affected the forest stands that survived across pleni-glacial events, preserving the main features of evergreenness with anomalous phenorhythms. These areas are today particularly dense in Arctotertiary taxa of Caucasian affinity, which coexist where oak populations with anomalous phenorhythms have been recorded. This suggests that present-day anomalies in reproductive cycles, along with a rich woody flora and local altitudinal zonations with mixed forest stands of Caucasian affinity, might represent the legacy of cryptic forest refugia during the last pleni-glacial.