Factors influencing the fruit crops and seed fates ofPistacia chinensis: the results of structural equation modeling

Abstract

Seed production and quality are important factors influencing population regeneration in many seed plants. We used structural equation modeling to investigate how plant and fruit traits interact with each other to influence the fruit crops and seed fates of Pistacia chinensis. From May to September 2009, we sampled 45 fruiting female trees and measured plant traits (height, DBH and crown area), fruit traits (infructescence size, fruit size) and the fruit crop of each sampled tree in Jiyuan City of Henan Province, Central China. The fruit crops of P. chinensis were positively correlated with tree height, crown area and infructescence size but not significantly correlated with DBH or fruit size. The fruit crop of an individual tree had no negative direct effect on the infestation of seeds by wasps (Eurytoma plotnikovi). Such a direct effect would be predicted by the predator satiation hypothesis. Tree height and fruit size had a positive direct effect on the seed predation rate, but a significant negative correlation was found between the seed predation rate and the rate of seedlessness. Our results indicate that seedless fruits may serve as a defensive mechanism against insect seed predators. In addition, both seedless and insect-infested fruits had a negative direct effect on seed survival, and DBH, infructescence size and fruit crop had a positive indirect effect on seed survival. However, tree height and fruit size had negative indirect effects on seed survival. In conclusion, we have shown 第 2期 郭洪岭等: 应用结构方程模型解析影响黄连木果实产量和种子命运的因素 175 that both plant and fruit traits can strongly influence fruit crops and insect seed predation and subsequently determine the seed quality and population regeneration of P. chinensis.