The species pool concept applied to forests in a fragmented landscape: dispersal limitation versus habitat limitation

Abstract

The species pool concept has been used as a theo- retical framework for understanding local community rich- ness. A significant problem in putting the concept into practice is the lack of methods for determining the size of the species pool. We tested the hypothesis that species composition of recent forests is primarily determined by the species composi- tion of neighbouring older forests against the null-hypothesis that species are a random sample of the species occurring in the study area. Forest plant species composition of recently established fragments was significantly correlated with spe- cies composition in neighbouring older forests (i.e. the local species pool). When older forest within a neighbourhood of 1000m radius is considered, seed dispersal sources can be found for 91% of the flora in the recent forests. For an individual fragment, dispersal is a much more important deter- minant of species presence than the environment, with an average of 46% of the total pool excluded from local pools by dispersal limitation and only 8% excluded by environmental limitations. The species richness of recent forests is on aver- age 23% of the local species pool. Several hypotheses are proposed for this low percentage, such as asymmetric compe- tition due to the early successional state or the limited coloni- zation period.