Pollen viability of Scots pine (Pinus sylvestris) in different temperature conditions:: high levels of variation among and within latitudes

We examined the viability of pollen in a widely distributed anemophilous species, Scots pine (Pinus sylvestris L.), along a south-north gradient from 60 up to 69degreesN in Finland. It was hypothesised that problems in the reproduction cycle of Scots pine in northern marginal areas are partly due to the poor adaptedness of pollen at low temperatures. The pollen was collected directly from the male strobili and germinated in vitro at different temperatures. The results revealed marked variation in pollen viability both among and within latitudes and also among different temperature treatments. A contrast between southern and northern pollen was found in each year: in 1997-1999, southern pollen performed better, but an opposite contrast was observed in 1998. Pollen germination at the smaller temperatures was low across all the study areas, but very good at the highest temperature which was 20 degreesC. Variation in pollen viability among stands may lead to differential success of pollen of different origin. Variation among years was also high; thus different pollen might be favoured in different years. Finally, the possibility of gene flow from south to north was assessed. (C) 2002 Elsevier Science B.V. All rights reserved.