Does plant allometry predict biased sex allocation in Triadica sebifera (L.) small (Euphorbiaceae)?

Abstract

Early seed production by non-native plants may be important to their successful establishment and spread. Understanding the mechanisms underlying age- or size-biased seed production in introduced plants may also identify factors that contribute to propagule pressure and their success as invaders. Here, we asked whether differences in male and female reproductive allocation among individuals of the invasive woody plant species Triadica sebifera (L.) Small (Euphorbiaceae), a monoecious prolific seed producer, were consistent with a life-history trade-off involving sex allocation. We also asked if the quality of seeds produced by trees of different size differed in terms of seed size and germinability. We found no evidence that biomass allocation to either male or female function was related to plant size. Trees varied in ratio of female:male investment from 0.6 to 15.8, but investment ratio was also unrelated to plant size. We also found no relationship between plant size and seed size or mean germination time, and a weak negative relationship between percent seed germination and plant size. Overall, the results do not support the idea that patterns of reproductive sex allocation are the result of a life-history trade-off and are instead most consistent with local resource tracking by individual trees.