Intraspecific and phylogenetic density-dependent seedling recruitment in a subtropical evergreen forest
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Recent evidence suggests that plant performance can be influenced by the phylogenetic diversity of neighboring plants. However, no study to date has examined the effect of such phylogenetic density dependence on the transition from seed to seedling. Using 6 years of data on seedling recruitment and seed rain of 13 species from 130 stations (one 0.5 m2 seed trap and three adjacent 1 m2 seedling plots) in a subtropical evergreen forest, we asked: (1) Does negative density dependence act across seed to seedling stages? (2) Is there evidence for phylogenetic density dependence during the seed to seedling transition? (3) Does the strength of density dependence vary among years? Generalized linear mixed-effects models were used to model seed to seedling transition as a function of conspecific seed and seedling densities, heterospecific seed and seedling densities, and mean phylogenetic distance of heterospecific seeds and seedling. Conspecific seed density had a significant negative effect on seedling transition rates for 12 of 13 focal species. In contrast, conspecific seedling density had a positive effect for 7 species, suggesting species-specific habitat preferences. Few species were significantly affected by the density or phylogenetic relatedness of heterospecific seeds and seedlings. Only conspecific seed density effects varied among years for most focal species. Overall, our results reveal that conspecific seed and seedling densities play a more important role than the density or relatedness of heterospecific seeds and seedlings during the seed to seedling stage, suggesting that species-specific seed predators, along with habitat preferences, may contribute to diversity maintenance in this forest.
KeywordsJanzen–Connell hypothesis Phylogenetic relatedness Seed Seedling Species coexistence
We thank Dr. Lebrija-Trejos for sharing R code for calculating phylodiversity and Jinlong Zhang for building the phylogenetic tree. Yanjun Du was financially supported by Research Division of Biodiversity and Conservation Ecology (80006F2005) and National Natural Science Foundation of China (Y32H3A1001). Yanjun Du is appreciative of the visiting scholar program at Yale University and the China Scholarship Council, which supported his visit.
Author contribution statement
YJD, KPM and LSC developed the original idea; LC, XCM and YJD conducted the fieldwork. YJD, YQW, and LSC analyzed the data. YJD, SAQ, LSC and KPM wrote the manuscript.
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