Reproductive allocation and compensation mechanism for reproductive costs of dioecious shrub Rhamnus davurica

Objective The trade-offs between reproductive and vegetative processes have an important role in the life-history theory. Dioecious species afford an excellent opportunity to detect the trade-offs in resource allocation.

Method This research selected the dioecious shrub Rhamnus davurica to examine trade-offs between reproduction and vegetative growth, and determine whether females reduce vegetative growth with the higher reproductive allocation. If female hadn’t showed less vegetative growth than male, whether compensation mechanism led to that or not. The investigated R.davurica was divided into 4 groups based on genders and DBH. The differences of reproductive allocation between genders were compared by ANOVA and multiple comparisons. We did photosynthetic experiment of R.davurica on early June 2012 using LI-6400 portable photosynthesis system.

Result The main results were showed as: diameter level was positively correlated with reproductive biomass and foliage biomass (P < 0.05). In the same diameter level, the reproductive biomass (including flower and fruit biomass) was significantly different between genders (P < 0.05), but there was no significant difference between genders regarding the foliage biomass (P > 0.05). Photosynthetic capacity and the estimated light photosynthetic curves were different between the male and female.

Conclusion We conclude that the relationship between vegetative growth and reproductive growth does not agree with trade-off theory, this is a result of difference in the total available resources, R.davurica in large diameter-class has more total available resources. Although in the same diameter level, females do not show less vegetative growth than males. It is due to their higher photosynthetic efficiency and carbon fixation capacity. This higher photosynthetic capacity is a compensatory mechanism for females whit higher reproductive pressure.