No differential consequences of reproduction according to sex in Juniperus communis var. depressa (Cupressaceae)

• Published in: American Journal of Botany
• Main Authors: Marion, Christine, Houle, Gilles
• Other Authors: Natural Sciences and Engineering Research Council
• Format: Article in Journal/Newspaper
• Language: English
• Published: Wiley 1996
• Subjects: Plant Science; Genetics; Ecology, Evolution, Behavior and Systematics; Canada; Hudson; Hudson Bay; Subarctic
• Online Access: http://dx.doi.org/10.1002/j.1537-2197.1996.tb12729.x; https://api.wiley.com/onlinelibrary/tdm/v1/articles/10.1002%2Fj.1537-2197.1996.tb12729.x; http://onlinelibrary.wiley.com/wol1/doi/10.1002/j.1537-2197.1996.tb12729.x/fullpdf

In dioecious plant species, males and females are thought to have dissimilar allocation patterns. Females are believed to invest more in reproduction and less in growth and maintenance than males. This differential investment between sexes could result in distinct growth patterns and contrasting survival rates, thereby affecting the sex ratio of a population and the age and size distribution of males and females, possibly leading to habitat segregation according to sex. These effects might become more apparent under particularly limiting conditions, such as in nutrient‐deficient soils or in climatically stressed environments. To verify these predictions, growth patterns, microsite characteristics, and age and size distribution of male and female individuals were compared, and population sex ratio was determined in three populations of the dioecious shrub Juniperus communis var. depressa (Cupressaceae, Pinophyta) along a short latitudinal gradient on the eastern coast of Hudson Bay (Northern Québec, Canada). We found that the northernmost population had a male‐biased sex ratio, but that the southernmost one had a higher proportion of females. Our results failed to reveal any significant differences in radial growth patterns, mean sensitivity, annual elongation of the main axis, and size and age frequency distribution between males and females in any population. Furthermore, there was no evidence of microhabitat segregation according to sex as indicated by the lack of differences in the physicochemical characteristics of the substrate under males and females. Clearly, the expected ecological consequences of a presumed greater investment of females in reproduction were not apparent even under the very stressful conditions prevailing on subarctic dunes. Many factors could reduce differences in the cost of reproduction between males and females, such as the number and quality of reproductive structures produced annually by individuals of each sex, the possible photosynthetic activity of the immature female cones, and ...