Integrating genome-wide traits and multi-loci phylogeny to investigate orchid evolution—A case study on Pleurothallidinae

Abstract

Rapidly radiated groups are usually accompanied by unclear lineage and taxa delineation, which complicates their better understanding in terms of biodiversity, evolutionary processes, and taxonomic treatment. The most species-rich orchid subtribe, Pleurothallidinae, exemplifies an extremely diverse group with a complex evolutionary history associated with Andean orography. Here we combined multi-loci phylogeny reconstruction (HybSeq), genome-wide traits (inferred by flow cytometry), spatial analyses, and biogeography to investigate the evolutionary intricacy of one clade of Pleurothallidinae orchids. To achieve deep insights, we performed multiple species tree reconstruction approaches with the implementation of custom scripts to reveal sources of topological discrepancies and alternative evolutionary scenarios. The phylogeny clearly resolves the delimitation of the main evolutionary lineages corresponding to the accepted genera, with the exception of the genus Specklinia, which is divided into three distinct monophyletic lineages whose taxonomic treatment is proposed. Genome-wide characters (especially genome size) show an association with precipitation seasonality in a geographical context, and partial endoreplication, a unique character of orchids, is geographically restricted to the Andes, Central America, and the Caribbean. Specifically, the Andean region exemplifies the prevalence of bigger genome size and higher GC content, resulting from a higher proportion of species with partial endoreplication. The Andean origin of the clade was also revealed by biogeographic analysis. Our comprehensive approach has provided deep insights into the evolution of this clade and may be a useful tool for unraveling the intricate evolutionary history of similarly complex lineages.