Unravelling the Web of Life: Incomplete Lineage Sorting and Hybridisation as Primary Mechanisms Over Polyploidisation in the Evolutionary Dynamics of Pear Species

Zetao Jin,Xiao-Hua Lin,Daikun Ma,Siyu Xie,Jia-Xin Huang,Chen Ren,Liang Zhao,Lei Duan,Chao Xu,Richard G. J. Hodel,Junyao Wu,Bin-Bin Liu

Published 2025 in Molecular Ecology Resources

ABSTRACT

The traditional Tree of Life (ToL) model is increasingly challenged by the Web of Life (WoL) paradigm, which offers a more accurate depiction of organismal phylogeny, particularly in light of the incongruences often observed between gene and species trees. However, the absence of a standardised method for resolving evolutionary mechanisms – such as Incomplete Lineage Sorting (ILS), hybridisation, introgression, polyploidisation, and whole‐genome duplication – remains a significant obstacle in defining the WoL. Characterised by extensive hybridisation events, the pear genus Pyrus provides an ideal model for exploring these complexities. In this study, we present a Step‐by‐Step Exclusion (SSE) approach for investigating the evolutionary pathways of Pyrus, based on Whole Genome Sequencing (WGS) and Deep Genome Skimming (DGS) data, and our results demonstrate that: (1) ILS, rather than polyploidisation, plays a dominant role in the origination of Pyrus; (2) the two subgenera of Pyrus followed independent evolutionary paths, influenced by geographical barriers formed through the uplift of the Tibetan Plateau and increased aridity in Central Asia; (3) both ILS and hybridisation have driven the diversification of subg. Pashia, while hybridisation alone has shaped the reticulate evolution of subg. Pyrus; (4) the establishment of the Silk Road during the Han Dynasty facilitated genetic exchange between subg. Pyrus and subg. Pashia. The SSE approach offers a versatile framework for studying the evolutionary mechanisms underlying the WoL paradigm.

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