J Syst Evol ›› 2019, Vol. 57 ›› Issue (4): 418-430.DOI: 10.1111/jse.12525

• Research Articles • Previous Articles    

Polyploidy does not control all: Lineage‐specific average chromosome length constrains genome size evolution in ferns

Hong-Mei Liu1, Libor Ekrt2, Petr Koutecky2, Jaume Pellicer3, Oriane Hidalgo3,4,5, Jeannine Marquardt4,5,6, Fatima Pustahija7, Atsushi Ebihara8, Sonja Siljak-Yakovlev9, Mary Gibby10, Ilia Leitch3, and Harald Schneider11*   

  1. 1Key Laboratory of Tropical Plant Resources and Sustainable Use, Xishuangbanna Tropical Botanical Garden, Chinese Academy of Sciences, Menglun 666303, China
    2Department of Botany, Faculty of Science, University of South Bohemia, Ceske Budejovice 370 05, Czech Republic
    3Royal Botanic Gardens, Kew, Richmond TW3 3DS, UK
    4Laboratori de Botànica, Unitat associada al CSIC, Facultat de Farmàcia i Ciències de l’Alimentació, Universitat de Barcelona, Barcelona 08028, Spain
    5Department of Life Sciences, Natural History Museum, London SW7 5BD, UK
    6Botanischer Garten und Botanisches Museum Berlin Dahlem & Freie Universität Berlin, Berlin 14195, Germany
    7Faculty of Forestry, University of Sarajevo, Sarajevo 71000, Bosnia and Herzegovina
    8Department of Botany, National Museum of Nature and Science, Tsukuba 305‐0005, Japan
    9Laboratoire d’Ecologie, Systématique et Evolution, Université Paris‐Sud, UPS‐CNRS‐AgroParisTech, Orsay France
    10Royal Botanic Garden Edinburgh, Edinburgh EH3 5LR, UK
    11Center for Integrative Conservation, Xishuangbanna Tropical Botanical Garden, Chinese Academy of Sciences, Menglun 666303, China
  • Received:2019-03-09 Accepted:2019-06-19 Online:2019-08-09 Published:2019-07-01


Recent studies investigating the evolution of genome size diversity in ferns have shown that they have a distinctive genome profile compared with other land plants. Ferns are typically characterized by possessing medium‐sized genomes, although a few lineages have evolved very large genomes. Ferns are different from other vascular plant lineages as they are the only group to show evidence for a correlation between genome size and chromosome number. In this study, we aim to explore whether the evolution of fern genome sizes is not only shaped by chromosome number changes arising from polyploidy but also by constraints on the average amount of DNA per chromosome. We selected the genus Asplenium L. as a model genus to study the question because of the unique combination of a highly conserved base chromosome number and a high frequency of polyploidy. New genome size data for Asplenium taxa were combined with existing data and analyzed within a phylogenetic framework. Genome size varied substantially between diploid species, resulting in overlapping genome sizes among diploid and tetraploid spleenworts. The observed additive pattern indicates the absence of genome downsizing following polyploidy. The genome size of diploids varied non‐randomly and we found evidence for clade‐specific trends towards larger or smaller genomes. The 578‐fold range of fern genome sizes have arisen not only from repeated cycles of polyploidy but also through clade‐specific constraints governing accumulation and/or elimination of DNA.

Key words: chromosome number, DNA‐C value, evolutionary constraint, evolvability, genome evolution, land plant, macroevolution, plant diversity, whole genome duplication