Gender-related traits in the dioecious shrub Empetrum rubrum in two plant communities, in the Magellanic steppe

Following the theory on costs of reproduction, sexually dimorphic plants may exhibit several trade-offs in energy and resources that can determine gender dimorphism in morphological or physiological traits, especially during the reproductive period. In this study we assess whether the sexes of the dioecious species Empetrum rubrum differ in morphological and ecophysiological traits related to water economy and photochemical efficiency and whether these differences change in nearby populations with contrasting plant communities. We conducted physiological, morphological, sex ratio, and cover measurements in E. rubrum plants in the Magellanic steppe, North-Eastern part of Tierra del Fuego (Argentina), from two types of heathlands with differing community composition. We found differences between sites in soil pH and wind speed at the canopy level. E. rubrum plants exhibited lower photosynthetic height and higher LAI (leaf area index), lower RWC (relative water content) and higher water-use efficiency (lower Delta C-13) in the heathland with harsher environmental conditions. Gender dimorphism in the physiological response was patent for photochemical efficiency and water use (RWC and Delta C-13 discrimination), with males showing a more conservative strategy in relation to females. Accordingly, male-biased sex ratio in the stress-prone community suggested a better performance of male plants under stressful environmental conditions. The integrated analysis of all variables (photochemical efficiency, RWC, leaf dry matter content (LDMC), pigments, and Delta C-13) indicated an interaction between gender and heathland community effects in the physiological response. We suggest that female plants may exhibit compensatory mechanisms to face their higher reproductive costs. (C) 2014 Elsevier Masson SAS. All rights reserved.