Drought susceptibility of southern African C4 grasses: phylogenetically and photosynthetically determined?

Factors that determine C4 grass distributions have been well documented, with evidence in the literature for C4 photosynthetic subtypes displaying varying levels of drought susceptibility. However, the interactions between C4 photosynthetic subtype and phylogeny add complexity and are relatively under-studied.  

We use species distribution modelling to determine the influence of rainfall on distribution patterns of representative C4 grass families and subtypes. Select C4 grass species, representing different photosynthetic subtypes (NADP-Me and NAD-Me) and lineages (Panicoideae and Aristidoideae), were then subjected to a progressive 58-day drought period and recovery phase, to explore drought responses through leaf water relations, gas exchange and chlorophyll fluorescence.
We show Panicoideae NADP-Me species to be more susceptible to drought than both Panicoideae NAD-Me and Aristidoideae NADP-Me species due to apparent greater metabolic impairment. The differences between groups w..., Materials and methods
Species distribution modeling
MaxEnt Species Distribution Models (SDMs) were developed using the maximum entropy algorithm implemented in MaxEnt v.3.3.3k to display the current SDMs for an array of C4 grass species from the Panicoideae and Aristidoideae families. Maximum Entropy Models (MaxEnt) use machine-learning principles to predict the presence/absence of species across geographic space based on the relationship between site-specific environmental conditions and species occurrence records (Elith et al., 2011). From this, MaxEnt models can predict a measure of habitat suitability for a particular species in a particular location. Habitat suitability is a factor of both the density of individuals of a species and the likelihood of the species being present (Elith et al., 2011). Although there are limitations to the chosen method (e.g., using solely presence data as opposed to presence-absence records; Phillips et al., 2009), MaxEnt SDMs provide a good base from ..., The data obtained were analysed using the R language and platform (R Core Team 2020).Â