Fungi As Focal Species In Conservation

Conservation of biodiversity is a complex task, and it is broadly accepted that means to reduce complexity are necessary if we want to make conservation biology practicable. This is equally relevant in a mega diverse group such as fungi, where global species numbers are estimated to be close to 1.5 million (Hawksworth, 2001). In most cases it will be unrealistic to make complete or even semi-complete species inventories to guide fungal conservation priorities. A way forward is, therefore, to focus on particular species or species groups, commonly termed focal species (Caro and O'Doherty, 1999). Focal species definitions and terminology are confusing and widely different classification systems have been suggested (Heilmann-Clausen, 2003). Often the terms indicator species, surrogate species, umbrella species and focal species are used interchangeably which does not improve clarity. Below, we review two different approaches to reduce complexity in fungal conservation, by focussing on a smaller fraction of the total species diversity: (i) red-listing and (ii) the use of indicators of habitat quality. Both approaches have been widely applied in Europe.

2.1 Applying the IUCN Red-Listing Criteria to Fungi

The aim of red-lists is to ''provide an explicit, objective ... classification of species according to their extinction risk'' (IUCN, 2001). Earlier, red-lists were compiled

Table 1 Threat categories following IUCN criteria

Extinct (EX)

Extinct in the wild (EW) Regionally extinct (RE) Critically endangered (CR) Endangered (EN) Vulnerable (VU) Near threatened (NT) Least concern (LC) Data deficient (DD) Not applicable (NA) Not evaluated (NE)

following a range of different national and regional approaches, but in general, recent national or regional red-lists of fungi follow the guidelines of IUCN (2003). However, national and regional red-lists do show varying interpretations, especially in evaluation of rare species (with limited data). Red-lists for fungi following current IUCN criteria have been published in several countries, e.g. Norway (Brandrud et al., 2006), Sweden (Gardenfors, 2005) and Finland (Kytovuori et al., 2005). Red-list evaluation of major groups of Danish macro-fungi is ongoing, with 1,500 species having been evaluated by 2005 (DMU, 2006), and the discussion following is based mainly on this work.

Basically, evaluating an organism, typically a species, for red-listing involves determining the risk that it may disappear from the region in question. The species is then referred to a threat category (Table 1). Each species is evaluated by four sets of different criteria (Box 1): (A) population decrease; (B) decrease in geographical range; (C) small population size and decline; and (D) very small or restricted population size. Alternatively (criterion E), available data may be used for a so-called population viability analysis that uses an algorithm to estimate risk of extinction. However, to our knowledge the E criterion has not yet been applied to fungi.

The IUCN red-list criteria are not specifically designed for fungi, and applying them to fungi (Box 1) involves a number of challenges, such as defining: (i) what an (mature) individual is; (ii) how population sizes are estimated? (iii) what is the generation time in different fungi; and (iv) how population trends are estimated? These challenges are discussed below.

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