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Epiphyte Ecology
Monitoring Change
Species Discovery

Staff
Dr Brian Coppins
Ms Sally Eaton
Dr Christopher Ellis
Ms Louise Olley
Dr Rebecca Yahr

Students
Research Projects

   
   


   

Introduction

Taxonomy is the science that identifies and documents the Earth's species. Systematics understands the evolutionary relationships among these species. Molecular Biology has aided species identification, revolutionised our understanding of species relationships, and created a greater depth of understanding in the diversity of life, including the genetic diversity within species.

These themes are explored below in five sections.

1. The RBGE Herbarium

The fundamental resource for taxonomy is the herbarium, which includes a large collection of examplar lichen specimens. Similar to a world-class museum, which protects and interprets cultural artefacts on behalf of the nation, the herbarium collects and archives specimens for the description and interpretation of the Earth's biodiversity.

The herbarium at RBGE houses an historically important collection of lichens. Among the oldest specimens are those collected during the global voyages of Archibald Menzies during late 18th Century. Additionally, there are important international collections by Joseph Hooker, e.g. from the sub-Antarctic Islands (Figure 1), by Lauder Lindsay from New Zealand and Iceland, and by Alfred Eaton during the 'Transit of Venus' Expedition (1874) to the Southern Ocean including Kerguelan. Among the extensive British and Scottish material are collections by Borrer (included as part of Brodie's material), Greville, McAndrew and Duncan.

2. Species Description

With the appointment of Brian Coppins in the early 1970s (Figure 2), RBGE came to play a leading role in the taxonomy of British lichens. Consequently, the lichen herbarium has an unparalleled reputation for its modern and comprehensive collection of British material. Collections by Brian (> 25,000 specimens) have focussed especially on difficult lichen groups (e.g. Micarea, and sterile crusts), and under Brian's leadership the herbarium at RBGE came to represent a facility which under-pins our current knowledge of the British lichen flora.

Classical taxonomic approaches continue at RBGE; additionally, and with the appointment of Rebecca Yahr, there has been a complimentary focus on molecular biology to further understand lichen diversity. An example of this work includes DNA-barcoding.

3. DNA Bar-Coding

DNA barcoding uses a small number of gene regions, which can provide near-universal tools to discriminate between species. The barcoding process is iterative, and new information provided by molecular biology contributes to a cycle of discovery, in which traditional morphological concepts can be refined.

RBGE's initial work on lichen barcoding had two components [1]:

  1. The application of barcoding at a floristic scale (for a National Nature Reserve), to test the universality of the approach across a wide range of lichenised-Ascomycetes, especially those associated with aspen (Figure 3),
  2. The targeted study of a difficult genus - Usnea - to test barcoding as a tool to resolve species concepts and aid identification within notoriously difficult genera.

3. Clarification of Species Concepts

Barcoding is currently focussed on taxonomically uncertain and/or conservation priority species. The usefulness of barcoding in this context was demonstrated for the putative Schedule 8 species Calicium corynellum [2] (Figure 4), and is now being extended to taxonomically uncertain species on the Scottish Priority List such as Megalospora tuberculosa, and Pseudocyphellaria species. This improved taxonomy ensures that stretched conservation resources are put to the most effective use. Other focal areas of work include species that are indicators of risk, such as the montane species in the Cladonia coccifera group, or which are dominant community-level indicators, such as the Parmelia saxatilis group.

4. Species Inventory

Taxonomists play an important role in documenting species distributions at local, regional and national scales. These data are fundamentally important in biogeography and conservation biology. Inventory work at RBGE, supported by molecular biology, is now focused on the threatened montane lichen flora of Scotland, with survey effort centred on the Caingorms National Park (Figure 5) and including the taxonomically difficult Stereocaulon species.

5. Photobiont Diversity

Finally, the diversity of lichens is not complete without a consideration of their dual nature, and our work includes the phylogenetics of algae associated with lichens, such as the enigmatic Micarea algae [3]. We are also currently using Next Generation Sequencing to investigate the diversity of cyanobacterial photobionts, and the pattern of lichen selectivity and specificity in structuring species distributions.

Figure 1. The stunning Usnea aurantico-atra, collected by Jospeh Hooker in the 19th Century.
 
Figure 2. Brian Coppins doing survey work in the Cairngorm Mountains (photo - Andy Acton).
 
Figure 3. Lichens on aspen, a dominant habitat for lichens at the Insh Marsh NNR and a focus for floristic scale barcoding.
 
Figure 4. The putative Calicium corynellum, a candidate for Schedule 8 designation which appears identical in Britain to the common Calicium viride.
 
Figure 5. A snow-bed high in the Cairngorm mountains, under-explored and threatened by climate change, these habitats are a focus for taxonomic inventory supported by DNA bar-coding.
 

References

[1] Kelly, L.J., Hollingsworth, P.M., Coppins, B.J., Ellis, C.J., Harrold, P., Tosh, J. & Yahr, R. (2011) DNA barcoding of lichenized fungi demonstrates high identification success in a floristic context. New Phytologist, 191: 288-300.

[2] Yahr, R. (2015) The status of the conservation priority species Calicium corynellum in the British Isles. The Lichenologist, 47: 205-214.

[3] Yahr, R., Florence, A., Škaloud, P. & Voytsekhovich, A. (2015) Molecular and morphological diversity in photobionts associated with Micarea s. str. (Lecanorales, Ascomycota). The Lichenologist, 47: 403-414.