Water use traits within Australian alpine plants
The Australian alpine ecosystem is particularly vulnerable to the effects of climate change. In part, because it covers such a small area, <1% of mainland Australia, and also has a limited elevational range. Alpine plants have limited options for range migration, therefore response to climate change is expected to be primarily determined by their ability to survive in-situ through local adaptations or phenotypic plasticity. Models project increasingly variable precipitation and snow cover, thus we expect efficient water use to become increasingly important. Plants from lower elevations experience a more variable environment as earlier snow melt results in more frequent frosts, greater temperature extremes, and higher evapotranspiration. It is commonly held that individuals from more variable environments exhibit greater phenotypic plasticity. However, the opposite has also been proposed. We investigated the extent of plasticity and intraspecific variation in water use traits in three Australian alpine herbs; Wahlenbergia ceracea, Aciphylla glacialis and Oreomyrrhis eriopoda. Specifically, we assessed whether patterns of morphological and physiological plasticity differed between species, or between elevations within species under two contrasting glasshouse water treatments. Based on previous studies in this environment, we hypothesised that plants from lower elevations would exhibit greater plasticity in water use traits.
Plastic response to water availability was widespread in most traits we measured. Previous work in the same environment and for two of the same species demonstrated greater plasticity in response to temperature for low elevation populations. Preliminary results from this study, investigating response to water availability, do not reveal the same pattern. We found few differences between high and low elevation populations within species, and elevation-by-treatment interactions were rare. In each of these cases, responses were not consistent with respect to trait, species, elevation, nor direction of plasticity. Our results suggest that patterns of plasticity, and within species differentiation, vary greatly depending on the resource under consideration and generalising a response based on one environmental variable is not possible. Furthermore, the low intra-specific variation displayed by these study species may limit the adaptive evolution under environmental changes.