Spore variability in Hepaticae: a case study on four short-lived Riccia L. species

ABSTRACT

Introduction

In the present study, we tested the variability of spore morphology in freshly collected plants of Riccia bifurca Hoffm., R. glauca L., R. sorocarpa Bisch. and R. warnstorfii Limpr. ex Warnst. at the individual and population scale, and examined the taxonomical power of distinct characters that are used in the literature for species delimitation in the genus Riccia.

Methods

Spore size, number of areolae across the distal spore side, and wing width were determined from permanent preparations of spores, using three individuals of each of the four tested species. Statistical analyses, including power analyses, were carried out, in addition to evaluation using light microscopy images.

Key results

Our results suggest that individual spore characteristics are subject to high variability at the individual and population level. Owing to the high dispersion of the collected data, the boundaries for these characteristics are obscured across different species.

Conclusions

Generally, although the specific morphology of the spores does differ across Riccia species, several characters are too strongly specified in the literature and should be used only in a statistical context and in combination with additional, often qualitative, characters.

KEYWORDS:

• Bioimaging
• diagnostic characters
• liverworts
• Marchantiophyta
• measurements
• species delimitation
• spores

Acknowledgement

We are grateful for all collaborators in the Austrian Riccia Morphology and Sequencing Project, especially those who provided us with fresh Riccia samples.

Disclosure statement

No potential conflict of interest was reported by the authors.

Supplemental material

Supplemental material for this article can be accessed here: https://doi.org/10.1080/03736687.2024.2353408

Supplemental material 1. Single values of measured spore sizes (μm) for the four tested Riccia species.

Supplemental material 2. Spore IDs for each image in Figures 8–11.

Supplemental material 3. Regression results.

Additional information

Notes on contributors

Martina Pöltl

Martina Pöltl curates the bryological collection at the herbarium of the Universalmuseum Joanneum (GJO) in Graz. She is also a Ph.D. student carrying out research on bryophytes, especially Riccia, at the University of Graz.

Adam Thomas Clark

Adam Thomas Clark is an assistant professor at the Institute of Biology at the University of Graz.

Thomas Stadlober

Thomas Stadlober is a masters student of plant science at the Institute of Biology at the University of Graz.

Christian Berg

Christian Berg is the scientific head of the Botanical Garden in Graz. His research at the University of Graz is focused on the phytogeography and ecology of bryophytes and vascular plants.