Intra-specic phylogeny of the native Patagonian grass Festuca pallescens

Abstract

Drylands constitute the largest terrestrial biomes, highly sensitive to climate changeand desertication, and known for their environmental heterogeneity. Widely distributedspecies are usually adapted to these heterogeneous environments characterizedby climatic gradients which promote the expression of phenotypic variabilityand hybridization processes. The Patagonian native grass Festuca pallescens has abroad geographic distribution, occurring at highly diverse environments. Because ofthe broad phenotypic plasticity of this species, it can be hard to identify individualson the eld, particularly in extreme suboptimal habitats where repeated exposureto stressful conditions might enhance phenotypic variation or local adaptations. Inaddition, its ecological niche partly overlaps with other native grasses like Festucaargentina and F. gracillima, which also show morphological variability. Given thescarce information about the genetic variation of F. pallescens, and the possible hybridizationand speciation processes at suboptimal conditions, the objective of thisstudy was to reconstruct the phylogenetic relationships between populations of thisforage grass. We included the sympatric species F. argentina and F. gracillima, aswell as other fescues of the genus. A total of 20 populations along the distributionrange of the species, which encompasses around 1.800 km of Patagonia, were sampled.Sequences from the ITS region, which allows phylogenetic reconstructions,were obtained and complemented with sequences of the chloroplast marker trnL-F.Sequences of species from other regions were retrieved from NCBI. The variationdetected with these two markers allowed us to identify four variants with a cleargeographic distribution. Edge populations were distinctly dierent from most of thepopulations noticing a northern, a north-eastern and two southern variants. Fromthese, the north-eastern variant resembles F. argentina, and the southern variant wasclosely related with F. gracillima. These results constitute the rst reconstructionof Patagonian fescues phylogeny and highlight the relevance of suboptimal regionsfor possible speciation and hybridization processes.