Format: ORAL

Ruche M.1, Pressel S.2, Price M.J.1,3

1 Conservatory and Botanical Garden of the City of Geneva, Geneva, Switzerland 2 Life Sciences Department, Natural History Museum, London, UK 3 Plant Sciences Department, University of Geneva, Geneva, Switzerland

The peristome is considered the most complex and conservative morphological structure in mosses. The arthrodontous peristome is composed of a single, or double, ring of teeth surrounding the opening of the capsule. Peristome characters have long been used for classification at the higher taxonomic ranks, and for understanding evolutionary events across mosses. In the monophyletic Dicranidae, which contain a third of total moss diversity and are characterized by a haplolepidous peristome, the peristome architecture has been found to be informative across the group. A thorough morpho-anatomical investigation of the haplolepidous peristome was carried out across a large sampling in the Dicranidae, using histology and state-of-the-art SEM. The peristome tooth-insertion region, studied with thin longitudinal sections, was delimited, and described. The comparative anatomy of the peristome teeth-insertion region has revealed conserved and variable anatomical features, at the lower levels, that are useful for elucidating relationships in the Dicranidae. The imaging of teeth ornamentations and morphology, using SEM, revealed an unsuspected diversity across the group. The main patterns and traits of ornamentations have been reassessed, and a newly discovered set of shapes and sizes of ornamentations have been redefined. The ornamentations have proven to hold taxon-specific information across and between the various taxonomic ranks. The combination of anatomy and micro-morphology allowed for a global comparison of peristomes in the Dicranidae. This study confirms the taxonomic importance of the peristome at the species, generic and familial level in the Dicranidae. It will allow the use of new diagnostic features for further investigations on the relationships across the Dicranidae, as well as for the establishment of stable characteristics for peristome descriptions.