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Dryad

Independent evolutionary changes in fine-root traits among main clades during the diversification of seed plants

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Jun 04, 2020 version files 126.81 KB

Abstract

Rationale: Changes in fine-root morphology are typically associated with transitions from the ancestral arbuscular mycorrhizal (AM) to the alternative ectomycorrhizal (ECM) or non-mycorrhizal (NM) associations. However, the modifications in root morphology may also coincide with new modifications in leaf hydraulics and growth habit during angiosperm diversification. These hypotheses have not been evaluated concurrently, which limits our understanding of the causes of fine-root evolution.

Methods: To explore the evolution of fine-root systems, we assembled a 600+ species database to reconstruct historical changes in seed plants over time. We utilize ancestral reconstruction approaches together with phylogenetically informed comparative analyses to test whether changes in fine-root traits were most strongly associated with mycorrhizal affiliation, leaf hydraulics or growth form.

Key Results: Our findings show significant shifts in root diameter, specific root length and root tissue density as angiosperms diversified, largely independent from leaf changes or mycorrhizal affiliation. Growth form was the only factor associated with fine-root traits in statistical models including mycorrhizal association and leaf venation, suggesting substantial modifications in fine-root morphology during transitions from woody to non-woody habits.

Conclusion: Divergences in fine-root systems were crucial in the evolution of seed plant lineages, with important implications for ecological processes in terrestrial ecosystems.