Partial endoreplication stimulates diversification in the species-richest lineage of orchids

Abstract

Some of the most burning questions in biology in recent years concern differential diversification along the tree of life and its causes. Among others, it could be triggered by the evolution of novel phenotypes accelerating diversification in lineages that bear them. In the Pleurothallidinae, the most species-rich subtribe of plants on Earth with 46 genera and [~]5,500 species, we constructed a completely new phylogeny and mapped on to it the type of endoreplication intending to trace how the phenomenon of partial endoreplication, which is unique to orchids, affects the differential diversification of lineages. We have used NGS based target enrichment HybSeq approach for the reconstruction of the phylogeny and the flow cytometry to estimate the type of endoreplication. The BAMM and BiSSE analyses have been used to assess diversification rates and to trace the phenotype changes. We have found that three of six changes in diversification rates are associated with changes in the endoreplication type and the clades bearing taxa with partial endoreplication showed higher net diversification rates. Our results demonstrate that multiple evolution of partial endoreplication within the subtribe considerably shapes the patterns of diversity and that partial endoreplication is a trait with an evolutionary significance.