Allometry of within-fruit reproductive allocation in subtropical dicot woody species.

Angiosperm fruits typically consist of pericarp and seed, which collectively function to maximize plant reproductive success. Within-fruit reproductive allocation has been scarcely examined across a wide range of fruit types and taxa although it is critical to the understanding of the evolution of fruit size and seed size. We investigated seed size, fruit size, seed number per fruit (SNF), and within-fruit biomass allocation between seed mass and pericarp mass for 62 dicot woody species (27 deciduous and 35 evergreen species) of a subtropical evergreen forest in southwest China. At the fruit level, total pericarp mass (TPM) isometrically scaled with increasing total seed mass (TSM) in the evergreen species and in the pooled data set, while TPM increased faster than TSM in the deciduous species. The slope difference is possibly due to the difference in the timing of fruit development between the two species groups. At the seed level, seed package (pericarp mass per seed) isometrically scaled with increasing seed size in the deciduous group, but less than isometrically in the evergreens and in the pooled data set. SNF was negatively correlated with seed size but positively correlated with the proportion of pericarp within fruits. In conclusion, within-fruit biomass allocation is significantly affected by seed size, fruit size, and SNF in both deciduous and evergreen species. The implications of the observed scaling relationships are discussed in relation to seed size evolution and global patterns of seed size variation.