Polyphyly, gene-duplication and extensive allopolyploidy framed the evolution of the ephemeral Vulpia grasses and other fine-leaved Loliinae (Poaceae)

Abstract

The fine-leaved Loliinae is one of the temperate grass lineages that is richest in number of evolutionary switches from perennial to annual life-cycle, and also shows one of the most complex reticulate patterns involving distinct diploid and allopolyploid lineages. Eight distinct annual lineages, that have traditionally been placed in the genus Vulpia and in other fine-leaved ephemeral genera, have apparently emerged from different perennial Festuca ancestors. The phenotypically similar Vulpia taxa have been reconstructed as polyphyletic, with polyploid lineages showing unclear relationships to their purported diploid relatives. Interspecific and intergeneric hybridization is, however, rampant across different lineages. An evolutionary analysis based on cloned nuclear low-copy GBSSI (Granule-Bound Starch Synthase I) and multicopy ITS (Internal Transcribed Spacer) sequences has been conducted on representatives of most Vulpia species and other fine-leaved lineages, using Bayesian consensus and agreement trees, networking split graphs and species tree-based approaches, to disentangle their phylogenetic relationships and to identify the parental genome donors of the allopolyploids. Both data sets were able to reconstruct a congruent phylogeny in which Vulpia was resolved as polyphyletic from at least three main ancestral diploid lineages. These, in turn, participated in the origin of the derived allopolyploid Vulpia lineages together with other Festuca-like, Psilurus-like and some unknown genome donors. Long-distance dispersal events were inferred to explain the polytopic origin of the Mediterranean and American Vulpia lineages.