Fossil records indicate that Cycadales emerged during the Permian period and experienced an increase in both abundance and diversity during the Mesozoic era. Despite the ancient origins of Cycads, most extant species have evolved more recently. It is possible that climate played a significant role in Cycad differentiation and speciation, however, physiological data for these species remains scarce and the extent to which climate has played a role in the evolution of species functional traits remains largely unexplored. Australian cycad species in particular have witnessed large-scale climate changes. For example, central Australia, which is now highly arid, was once cooler and dominated by rainforests. To understand the genetic basis for trait variation (as opposed to variation due to phenotypic plasticity) a common garden of Australian Cycad species (majority grown from wild-collected seeds) was utilized at Montgomery Botanical Center in Miami, FL. Traits such as specific leaf area (SLA), photosynthetic rate (Aa), and elemental compositions were measured and correlated with environmental variables associated with species’ native habitats. We hypothesized that SLA and photosynthetic rate would correlate strongly with environmental variables such as potential evapotranspiration (PET), soil water content (SWC), and aridity.
Results/Conclusions
Our preliminary findings suggest that SLA and photosynthetic rate are highly correlated with native habitat, water availability and evapotranspiration variables. We found a negative relationship between photosynthetic rate and soil water capacity (R= -0.88). Additionally, there is a strong negative correlation between maximum PET and SLA (R= -0.68). These findings suggest that there are significant environmental drivers behind functional trait diversification in Cycads, and could give us insight regarding the ecophysiological histories of these plants.