Conservation of threatened relict trees through living ex situ collections: lessons from the global survey of the genus Zelkova (Ulmaceae)

Abstract

Maintaining living ex situ collections is one of the key conservation methods in botanic gardens worldwide. Despite of the existence of many other conservation approaches used nowadays, it offers for many endangered plants an important insurance policy for the future, especially for rare and threatened relict trees. The aim of this research was to investigate the global extent of living ex situ collections, to assess and discuss their viability and inform the development of conservation approaches that respond to latest global conservation challenges. We used as a model taxon the tree genus Zelkova (Ulmaceae). The genus includes six prominent Tertiary relict trees which survived the last glaciation in disjunct and isolated refugial regions. Our comprehensive worldwide survey shows that the majority of botanic institutions with Zelkova collections are in countries with a strong horticultural tradition and not in locations of their origin. More importantly, the acutely threatened Zelkova species are not the most represented in collections, and thus safeguarded through ex situ conservation. Less than 20% of the ex situ collections surveyed Published in which should be cited to refer to this work.http://doc.rero.ch contain plant material of known wild provenance while the majority (90%) of collections are generally very small (1-10 trees). Botanic gardens and arboreta particularly in regions where iconic relict trees naturally occur should play a vital role in the conservation of these species. The coordination of conservation efforts between gardens has to be enhanced to prioritise action for the most threatened relict trees. Large scale genetic studies should be undertaken, ideally at genus level, in order to verify or clarify the provenance of ex situ collections of relict trees in cultivation. For the most threatened relict tree genera, wellcoordinated specialist groups should be created.

Geographic analysis of Red List Rhododendron (Ericaceae) taxa by country of origin identifies priorities for ex situ conservation

“…Other challenges for ex situ conservation include accurate identification of specimens, appropriate documentation of collections, development of collections from wild-source material, acquisition of Red List taxa rather than common taxa, securing sufficient accessions at enough sites, and achieving adequate genetic representation (Lopez-Pujol et al 2011, Pritchard et al 2011, Rae 2011, Kozlowski et al 2012, Cires et al 2013, Ensslin et al 2015. Of particular concern is insufficient capacity to house every rare taxon in a botanical collection (Heywood 2009, Lopez-Pujol et al 2011, Ma et al 2014, indicating that robust processes are needed to identify ex situ conservation priorities.…”

Analysis of geographic and taxonomic groups informs conservation of Rhododendron subgenus Vireya (Ericaceae)

“…GSPC Target 2 calls for an assessment of the conservation status of all known plants (as far as possible), to guide conservation action, and thus providing an overview of the 'conservation problem' and indicating initial priorities (Heywood & Iriondo 2003, Newton & Oldfield 2008, Kozlowski et al 2012, Cavender et al 2015, while ex situ conservation action is further focused by Target 8, which has the goal of having 75 % of threatened plant taxa in ex situ collections by 2020 (IUCN 2011). Such collections are usually found in botanic gardens, whose role in ex situ conservation is well known (Heywood & Iriondo 2003, Maunder & Byers 2005, Oldfield 2009, Blackmore et al 2011, Pritchard et al 2011, and has been recognised for many years (Given 1987).…”

“…Collections should contain wild-source material; however, this is often limited and documentation is poor (Maunder et al 2000, 2001a, Kozlowski et al 2012, Christe et al 2014. Correct identity is a fundamental principle of ex situ conservation (Leadlay et al 2006), yet accessions are not always correctly identified (Goodall-Copestake et al 2005, Paton 2009, Christe et al 2014.…”

“…Correct identity is a fundamental principle of ex situ conservation (Leadlay et al 2006), yet accessions are not always correctly identified (Goodall-Copestake et al 2005, Paton 2009, Christe et al 2014. Representation of taxonomic and geographic groups in collections is uneven (Maunder et al 2001b, Kozlowski et al 2012, Cavender et al 2015, and the majority of collections are not in the country of origin (Maunder et al 2001a, b, Kozlowski et al 2012. Genetic diversity of most ex situ populations is unknown and is likely to be low (Maunder et al 2001a, Cavender et al 2015.…”

“…the 201 vireya taxa that were Red Listed 4 , or the 60 taxa assessed as Vulnerable. While the Red List categories create an initial hierarchy, other factors such as geographic hotspots, endemism and taxonomic distinctiveness have also been used to shape priorities (Farnsworth et al 2006, Kozlowski et al 2012, Castañeda-Álvarez et al 2015, Cavender et al 2015. Identifying taxonomic distinctiveness can be problematic in 'big genera' because of their complex taxonomic structures with many subgroups, large numbers of taxonomic queries, frequent hybridisation and active speciation (Crutwell 1988, Frodin 2004, Ennos et al 2005, Milne et al 2010, Argent 2015; a comprehensive taxonomy is required to underpin any conservation assessment that considers taxonomic groups.…”