Earlier this summer, whilst other members of the British Bryological Society headed to Galloway for a week of bryologising in glorious sunshine, I set off on the Eurostar to Belgium to bryologise in the Meise Botanic Garden herbarium. Over the past 15 years I have been working when time allows on a monographic project to describe and document the mosses of the Orthotrichaceae family across tropical Africa. European bryologists will be familiar with the neat cushions of Orthotrichum, Zygodon and Ulota. In the tropics the family has a greater diversity with an additional subfamily Macromitrioideae which includes genera which have a creeping habit.
Macromitrium and Schlotheimia are two particularly diverse genera which had not been critically reviewed across this part of the world and at the start of my project identification of specimens was extremely challenging. Lists of published names were not often accompanied by comprehensive descriptions and illustrations, so working out what plant a particular name referred to would ultimately require examining the original nomenclatural type specimen that is linked to the published name. We often hear about how much species diversity still waits to be described on Earth yet most of my work to date has involved reducing the number of known species! This is because over the last 200 years since taxonomists started to formally describe the natural world, many species have been described more than once. Reviewing this past manuscript of nature and editing it to reflect a more accurate picture of species diversity is a slow and pedantic job yet ultimately crucial in understanding patterns in biodiversity; an accurate checklist being the baseline required for most biodiversity and conservation studies.
In the Meise herbarium I was able to travel across tropical Africa from Cameroon to Uganda, dipping into the Comoros and spending rather a long time puzzling over species in Madagascar. Meise has an extremely rich herbarium of African bryophytes which includes extensive expedition material collected in the 1970s from Madagascar by M. Onraedt and G. Cremers and from Rwanda by botanists including J.L. de Sloover. More recently, there are the extremely detailed surveys and collections of bryophytes made by Theo Arts in the late 1990s to early 2000s from La Réunion in the Mascarenes; a small island which packs a big punch in terms of bryophyte diversity.
The herbarium was easy to navigate so I could quickly find the material of interest and I was able to make use of microscopes in the adjacent working area. The African moss herbarium (sensu lato to include Madagascar and the Indian Ocean islands) is separated as a stand-alone series of cabinets (I didn’t venture downstairs to visit the hepatic collection on this visit!) and I estimated it comprised about 25,000 specimens. All specimen packets were fixed to standard size cards and stored upright in trays with the species name they were filed under clearly marked.
During my three day visit I was able to microscopically examine around 100 specimens in my study group, focusing on particularly tricky taxa. I was able to document features which can help describe the morphological flexibility of a species. In particular, I was keen to examine additional collections from Madagascar as I am starting to put together an overview of Macromitrium to look at diversity and distribution across Madagascar and help people identify these plants. I was also pleased to find a good collection of specimens of the rare Cardotiella species (C. subappendiculata and C. renauldii) and Leoimitrium plicatum, which are endemic to Madagascar and the Mascarenes. Confirming the accurate identification of these specimens combined with their detailed locality data means I can provide a reliable past distribution of these species which is important data for conservation. In total, re-identifying specimens in the Meise herbarium has revealed new country records for six species in Macromitrium, Cardotiella and Zygodon from across six countries. These will need writing up now for a short publication.
I’d like to thank the British Bryological Society for supporting this project with a travel bursary. This work is part of a larger programme of activity supported by the Natural History Museum, London. I am very grateful to the collections staff at Meise herbarium, Petra Ballings and Ann Bogaerts, for hosting my visit.
Jo Wilbraham 14/07/2023