Abstract
The contribution of forest generalists and specialists to the dispersal pattern of tree species is not well understood. Specialists are considered low-quality dispersers because their dispersal distance is often short. However, disregard for seed deposition site may result in underestimation of the dispersal quality of specialists. The present study estimated the contribution of generalist and specialist species to the dispersal patterns of the endangered Chinese yew (Taxus chinensis) in a subtropical patchy forest in Southeast China. A relatively diverse assemblage of frugivorous birds visited T. chinensis source trees, and specialist Hypsipetes leucocephalus and generalist Urocissa erythrorhyncha were by far the highest-quantity dispersers. Considering dispersal effectiveness, the quantity aspect of effectiveness differed between the specialist assemblage and generalist assemblage; the contribution of specialists to the quantity part of effectiveness was significantly higher than that of generalists despite the relatively low diversity of specialists. After foraging, both specialist H. leucocephalus and generalist U. erythrorhyncha significantly contributed to the number of seedlings, and their contributions to seedling recruitment did not differ with regard to quality. Our results highlight the ability of T. chinensis to recruit an effective disperser assemblage in patchy habitats, thus increasing its persistence in this disturbed habitat.
Highlights
The contribution of forest generalists and specialists to the dispersal pattern of tree species is not well understood
The quantity aspect is determined by the number of bird disperser visits to the seed source and the number of seeds dispersed per visit, whereas the quality aspect is determined mainly by seed treatment during transport and location of seed deposition[5,6]
An increasing amount of scientific evidence strongly supports the idea that generalization and specialization are more frequent in disperser assemblages than previously thought, with most plant species interacting with both forest generalists and forest specialists in patchy habitats[11,12,13]
Summary
The contribution of forest generalists and specialists to the dispersal pattern of tree species is not well understood. The present study estimated the contribution of generalist and specialist species to the dispersal patterns of the endangered Chinese yew (Taxus chinensis) in a subtropical patchy forest in Southeast China. Considering dispersal effectiveness, the quantity aspect of effectiveness differed between the specialist assemblage and generalist assemblage; the contribution of specialists to the quantity part of effectiveness was significantly higher than that of generalists despite the relatively low diversity of specialists After foraging, both specialist H. leucocephalus and generalist U. erythrorhyncha significantly contributed to the number of seedlings, and their contributions to seedling recruitment did not differ with regard to quality. An increasing amount of scientific evidence strongly supports the idea that generalization and specialization are more frequent in disperser assemblages than previously thought, with most plant species interacting with both forest generalists and forest specialists in patchy habitats[11,12,13]. We examined the following factors: (1) differences between forest specialists and generalists in fruit consumption among individual T. chinensis, and resulting effects on the quantity of seeds dispersed, and (2) the ways in which post-foraging perching among forest specialists and generalists affects their quality of seed dispersal
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