Best Master Prize

The SSS wants to encourage brilliant young scientists in their early career and therefore set up a yearly prize that will reward an excellent contribution in the field of systematics at the level of a Master thesis.

See details in the document below.

Deadline for next submission is September 30 2025

Best Master thesis 2025

Exploration of peristome architecture in the Pottiaceae (Bryophyta) with pattern characterization: what is a ‘pottioid peristome’?

Matilde Nari

Department of Plant Sciences, University of Geneva and Conservatoire et Jardin botaniques de Genève.

In mosses (Bryophyta), the peristome is a structure made up of articulated teeth that enable spore dispersal through hygroscopic movements. Due to their high variability, the shape and structure of the peristome have often been used as criteria in higher-level taxonomic classifications. The Pottiaceae is a highly diverse family, comprising around 1255 species with a worldwide distribution. The taxonomy of the Pottiaceae is known to be difficult, partly due to the small size of the plants and the high variability of the gametophyte characters. The Pottiaceae are characterised by a peristome consisting of a single row of teeth, known as a ‘pottioid peristome’ composed of 16 teeth that divide into 32 twisting filaments. The architecture of the mature peristome of nine species belonging to two subfamilies of Pottiaceae were investigated using structural and histological observations to understand peristome behaviour and characteristics. The shape, structure, and hygroscopic behaviour of the peristome in the nine species were documented and photographed under dry and wet conditions. The internal anatomy of the teeth and the teeth insertion region into the capsule were studied by histological techniques using a protocol for herbarium specimens using Technovit® 7100 resin. All nine species studied exhibited xerochastic behaviour, opening in dry and closing in wet conditions, consistent with previous observations. Histological analysis revealed both shared and variable features among species and distinguished two types of peristomes: typical ‘pottioid peristomes’ and others with short, entire teeth. These observations highlight the diversity of peristomes within the Pottiaceae and question the application of the term ‘pottioid peristome’, underscoring the need to redefine the peristome type in this family.