The typification of Australasian Plagiochila species (Plagiochilaceae: Jungermanniidae): a review with recommendations

ABSTRACT

Plagiochila is the most diverse genus of liverwort by number of described species, with 1600 validly published names. The typification and application of names within the context of such nomenclatural diversity is therefore critical. Typification statements made over five decades of revisionary study for 95 validly published species names, and two varieties, in Australasian Plagiochilaceae are reviewed with reference to the International Code of Nomenclature for algae, fungi, and plants (Code) and the citation of original material in the protologue, to establish for each the type specimens and their status. This review serves two purposes, firstly to confirm type specimen status given the recent suggestion that type citations by Bonner in Index Hepaticarum Volume 1 not be accepted as effective (if inadvertent) lectotypifications; and secondly to provide a data-based assessment of typification practice with reference to a relatively well-studied bryophyte group. None of the works reviewed were error-free with regards to typification practice. The most common errors were the citation of a holotype when none exists, and neglecting earlier type citation statements and their context. However, no instance where these errors impacted the application of names was found, implying authors are generally conscientious in their identification of original material. Three recommendations to improve typification practice are made: firstly, taxonomists need to utilise available online biodiversity resources to establish for themselves the original material and its context; secondly, greater scrutiny of type statements in existing primary and secondary literature is required; and thirdly, we need proactive education and self-education in the Code’s requirements.

KEYWORDS:

• Nomenclature
• taxonomy
• bryophyte
• Australia
• New Zealand

Acknowledgements

I thank Russell Barrett, Peter de Lange, and Peter Wilson for perspectives on typification as they pertain to Plagiochila and other cases, and for comments on the draft; Lindsey Gray for suggesting improvements to the draft, an anonymous reviewer and especially Anna Monro for critical comments that improved the manuscript. This study received no specific funding.

Disclosure statement

The author declares that this review was conducted in response to Engel and Merrill's (2019) critique of Renner (2018).