Abstract
The IUCN Red List is recognised as a robust system for assessing the risk of extinction to organisms, but there are difficulties in applying the criteria to bryophytes and other clonal and colonial organisms. Three critical terms are addressed – generation length, mature individual and severe fragmentation – and definitions given in order to facilitate the use of the IUCN Red List criteria for bryophytes. These recommendations provide a pragmatic and effective way of using the IUCN Red List process for bryophytes and may have a wider application to other clonal organisms.
Highlights
The IUCN Red List of threatened species is widely recognised as an objective system to assess the extinction risk of animals, plants and fungi, as a global indicator of the threats to biodiversity and as an authoritative tool to catalyse conservation actions (Rodrigues et al 2006, Mace et al 2008)
To date, Red Lists according to the red-listing system of IUCN (2012a) have been established for many different taxonomic groups at various geographical scales () they were originally designed for application at the global level (IUCN 2012b)
A number of terms and concepts are necessary in order to reach conclusions about the various factors employed in the criteria, notably ‘mature individuals’, ‘generation length’ and ‘severe fragmentation’
Summary
Generation length is notoriously difficult to estimate in perennial plants, including bryophytes. IUCN (2012a) defines generation length as ‘the average age of parents of the current cohort (i.e. new born individuals in the population)’. The Red List Guidelines (IUCN SPSC 2017) present several different methods for the estimation of generation length, and clonal organisms are addressed : ‘for partially clonal taxa, generation length should be averaged over asexually and sexually reproducing individuals in the population, weighted according to their relative frequency’ For the estimation of generation length according to these guidelines, knowledge on the age of first reproduction, the length of the reproductive period or adult mortality is required. Perennial stayers (Brachythecium rutabulum, Long-lived shuttles (Hedwigia ciliata), Ctenidium molluscum)
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