We are delighted to announce the publication of our first Sprent Review in Journal of Ecology, by Julie Ardley and Janet Sprent on the “Evolution and biogeography of actinorhizal plants and legumes.”

Here our Senior Editors, Richard Bardgett and David Gibson, introduce the Sprent Reviews series, discusses the career of Janet Sprent and highlights the importance of this inaugural review paper!

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Janet has also written several books on legume nodulation, nitrogen fixing organisms, and the ecology of the nitrogen cycle, which have guided and inspired many students and researchers in the field. She also founded the International Database of Legume Nodulation (ILDON), which is a database of publications of nodulation data for all legume genera and species.  Janet has spent most of her career at the University of Dundee, where she is now Emeritus Professor of Plant Biology and Nodulation in Legumes, and in recognition of her contributions to ecology, she was awarded Honorary Membership of the British Ecological Society, the highest honour the Society can give.   

Nitrogen availability is arguably the most limiting factor for primary production in terrestrial ecosystems. The symbiosis between plants and nitrogen fixing bacteria allows a source of fixed nitrogen for the host plants offering them an advantage in low nitrogen habitats. This symbiosis is, with a few exceptions, restricted to legumes (Fabaceae family) and actinorhizal plants (Angiosperms in 24 genera in 8 families) within the nitrogen-fixing root nodule (NFN) Rosid 1 clade. In their review, Julie Ardley and Janet Sprent provide an authoritative evolutionary and biogeographic overview of the NFN symbiosis. They ask why the evolution of NFN symbiosis led to several bursts of speciation in legumes – but not in actinorhizal plants where the symbiosis has been lost in most lineages.  

Derived from a common symbiotic ancestor, the energetically expensive N-fixing symbiosis was lost in most actinorhizal lineages but retained in most legumes. Ardley and Sprent argue that the legume-rhizobia symbiosis allows large flexibility of a wide range of rhizobial microsymbiont partners, whereas actinorhizal plants are restricted to a symbiosis with the actinobacteria Frankia. They point out that legumes have a greater control of the microsymbiont, and enhanced efficiency of N fixation compared with actinorhizal symbioses. This control of the symbiont aided legume radiation allowing them to be highly competitive against non-nitrogen fixing plants through enhanced N₂fixation efficiency. Overall, this review by Ardley and Sprent documents fascinating and important insights into the evolutionary and ecological success of nodulated legumes.  

Richard Bardgett Executive Editor, Journal of Ecology
David Gibson Senior Editor, Journal of Ecology

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We very much hope that you enjoy our first Sprent Review by Ardley and Sprent and we look forward to letting you know about future reviews in this exciting new series!