Previous-year reproduction reduces photosynthetic capacity and slows lifetime growth in females of a neotropical tree

Abstract

Females of dioecious plant species typically invest more in reproduction than males because they produce seeds, fruits, and associated structures in addition to flowers. If females are unable to compensate by up-regulating rates of photosynthesis or by reproducing less frequently than males, their greater reproductive investment may result in reduced growth or higher mortality. Here we provide evidence of the cost of reproduction in Ocotea tenera (Lauraceae), a dioecious neotropical tree common in lower montane forests of Monteverde, Costa Rica. Over periods of 12-21 years, females grew more slowly than males in a natural population and in two experimental plots where we were able to control for genotype, age, habitat, and reproductive history. Simultaneous measurements of 10 matched pairs of sibling trees of the opposite sex but same age demonstrated that the photosynthetic capacities of females were 13% lower than those of males. Among females, photosynthetic capacity was negatively correlated with fruit production during the most recent reproductive season but not with lifetime fruit production. Sexual size dimorphism in adult O. tenera trees appears to be a nonadaptive consequence of trading off recent reproduction against maintenance of the photosynthetic apparatus, with long-term negative effects on growth.D ioecious plants, species in which male and female flowers are borne on separate individuals, offer an opportunity to assess the costs of reproduction by examining how sexual differences in reproductive effort affect physiology, growth, and life history traits (1, 2). Greater allocation of resources toward reproduction by one sex (typically females) may result in sexspecific differences in the production and consumption of fixed carbon at the whole-plant level, with both short-term consequences (e.g., photosynthetic acclimation) and long-term consequences (e.g., fecundity, growth, and survival). In some dioecious species, the costs of reproduction are reflected in the fact that females are less likely to survive in stressful habitats, which results in spatial segregation of the sexes (3, 4). In other species (5, 6), females can co-occur with males but must defray the costs of reproduction by delaying reproductive maturity or by reproducing less frequently than males (7,8).Although it is now well established that females of many dioecious plant species invest more carbon, nitrogen, and other resources in reproduction than males (2), few studies have linked physiological performance with morphological or demographic consequences or taken into account the influence of recent reproductive effort, much less lifetime reproductive effort, particularly in long-lived trees (9). Moreover, it has been difficult to generalize about the sex-specific costs of reproduction because of differences in the results of laboratory versus field studies and between studies of herbaceous versus woody plants. For example, females tend to be larger than males in herbaceous plants grown in greenhouse experiments (10). In contrast,...

Sex-specific carbon and nitrogen partitioning under N deposition in Populus cathayana

“…Our results also suggested that there exists a sex-specific N requirement, showing that females have a higher N demand and a higher critical level of saturation N than males. Females' higher resource requirements usually are considered to be related to more reproductive investment in comparison with males (Dawson and Ehleringer 1993;Wheelwright and Logan 2004). 0 (P \ 0.05) according to the result of a one-way ANCOVA with P n or PNUE as dependent variable, sex as fixed factor, and the fraction of water-soluble proteins or the fraction of detergent-insoluble proteins as covariate, respectively.…”

Global Cost of Land Degradation

“…Poor land users are less likely to invest in restoration of high value biomes that take long time to mature. For example, trees take about 4-6 years to reach maturity (Wheelwright and Logan 2004). Given this we assume a 6 year maturity for trees.…”

Sex-Specific Flowering Patterns and Demography of the Understorey Rain Forest TreeIryanthera Hostmannii(Myristicaceae)

“…Unfortunately, the currently available data cover too short a period of many species' life cycles, and good estimates of long-term growth and mortality are difficult to obtain [49]. There is good evidence from some species, however, that female physiological processes cannot increase output, and that photosynthesis and growth rates decrease with increased costs of fruit production [10]. The true long-term costs of reproduction in many species remain unknown.…”

“…For example, males often flower more frequently than females [4,5], flower earlier (both in terms of phenology and size or age) [6,7,8,9], and have faster growth and lower mortality [7,10]. These strategies in turn usually give rise to male-biased sex ratios [11].…”

“…Dioecious species not only provide a natural experiment to examine how resource allocation patterns differ between the sexes, but also allow us to examine how selection acts differently on males and females to maximise their reproductive fitness [10,21]. These selection pressures, in turn, may influence allocation patterns.…”