Science 353, 69–71 (2016)

Different sexes often exhibit distinct phenotypes, including varied responses to the environment, which raises an intriguing question — do plants respond to climate change in a sex-specific manner? Studying the dioecious plant Valeriana edulis, William K. Petry, at the University of California, USA and colleagues report a rapid sex-specific response to increasing water scarcity.

Credit: WILL PETRY

V. edulis grows in the Rocky Mountains, where water availability increases with elevation. A survey of sex ratios in 31 populations across the species's elevation range showed that male frequency declined as aridity decreased, resulting in female-biased populations at higher elevations. Data across four decades for nine populations showed that males became more frequent across the species's elevation range with the decrease of precipitation and soil moisture over time. This provides evidence that climate change is driving an upslope shift of male frequency at a rate of 175 metres per decade, a magnitude higher than the hitherto reported rate of species's range shift. The sex-specific climate response is likely to arise from sex-specific reproductive life span and water use efficiency.

The change in male frequency at high elevations elevates seed set and female fitness by increasing pollen availability. Lower down, however, where females are already pollen saturated, the female frequency decrease could lead to widespread effects at multiple levels of ecological organization — such as arthropod communities, which rely more on female than male V. edulis plants.