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Type specimens of the Rhizocarpon geographicum group. Thallus habits are shown in the left hand panels (i) and ascospores are shown in the right hand panels (ii). Ai & ii, R. drepanodes (M-0024019); Bi & ii, R. ferax (UPS L-108361); Ci & ii, R. tinei subsp. arcticum (UPS L-582559); Di & ii, R. diabasicum (H-9502464); Ei & ii, R. frigidum (S L-587); Fi & ii, R. prospectans (H-9502588); Gi & ii, R. lecanorinum (L-0399782); Hi & ii, R. macrosporum (UPS L-069173); Ii & ii, R. lindsayanum (H-9502545); Ji & ii, R. riparium (H-9502857); Ki & ii, R. saanaënse (H-9502520); Li & ii, R. sphaerosporum (S L-571); Mi & ii, R. sublucidum (H-9502642); Ni & ii, R. tavaresii (H-9502640). Scales: i = 1mm; ii = 10 µm.
Source publication
As part of a comprehensive revision of the
Rhizocarpon geographicum
species group using molecular and morphological approaches, we examined the name-bearing types of 15 species. We report ambiguities and inconsistencies with the reported features of some type specimens, original descriptions, and circumscriptions employed in keys for the identifica...
Contexts in source publication
Context 1
... Fig. 1Ai & ii) Rhizocarpon ferax H. Magn. ( Fig. 1Ci & ( Fig. 2) As there is no material eligible as a possible lectotype for Linnaeus's name in his herbarium (LINN), and Linnaeus (1753) cited the illus- tration of Dillenius (1742), the illustration serves as original material and has to be designated as a lectotype under Art. 9.12 of the current ...
Context 2
... Fig. 1Ai & ii) Rhizocarpon ferax H. Magn. ( Fig. 1Ci & ( Fig. 2) As there is no material eligible as a possible lectotype for Linnaeus's name in his herbarium (LINN), and Linnaeus (1753) cited the illus- tration of Dillenius (1742), the illustration serves as original material and has to be designated as a lectotype under Art. 9.12 of the current Code ( McNeill et al. 2012). Jørgensen et ...
Context 3
... Leicester Lit. Phil. Soc. 63: 58 (1969 ( Fig. 1Gi & ii) The nomenclature of this taxon is confus- ing because of the use of several very similar epithets: lecanora, lecanoricum, lecanorinum, and lecanorum. Flörke (1819: 4) described his variety "lecanora" from sandstone rocks around "Quedlingburg nach Westerhausen bei Blankenburg"; there can be little doubt that material distributed in the ...
Context 4
... Fig. 1Hi & ii) Rhizocarpon riparium ssp. lindsayanum (Räsänen) Thomson Nova Hedwigia 14: 456 (1967). Basionym: Rhizocarpon lindsayanum Räsänen, Revista Sudamer. Bot. 7: 87 (1942); type: Great Britain, Perthshire, Dunkeld, Birnam Hill, April 1856, W. L. Lindsay (H-9502545-as "Lecidea ...
Context 7
... Fig. 1Ki & ii) Rhizocarpon sphaerosporum Räsänen Ann. Bot. Soc. Zool.-Bot. Fenn. "Vanamo" 19 (not.): 6 (1944); type: Sweden, Uppsala, Gottsunda, 1893, E. Pärsson (S L-571-isotype, as "Rhizocarpon lecanorinum var. cyclica, Rhizocarpon ...
Context 8
... Fig. 1Li & ii) Rhizocarpon sublucidum Räsänen Ann. Bot. Soc. Zool.-Bot. Fenn. "Vanamo" 21 (not. 16): 3 (1947); type: Switzerland, Les Mosses, 1882, E. A. Vainio ...
Context 9
... Fig. 1Mi & ii) Rhizocarpon tavaresii Räsänen Arch. Bot. Soc. Zool.-Bot. Fenn. "Vanamo" 3: 85 (1949); type: Portugal, Minho, Serra do Gerez-Outeiro Moço, 19 June 1947, C. N. Tavares (H-9502641- ...
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Revisions of British and Irish Lichens vol 41: 1–30
Free download available at:
https://britishlichensociety.org.uk/identification/lgbi3
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DNA barcoding is a powerful method for the identification of lichenized fungi groups for which the diversity is already well-represented in nucleotide databases, and an accurate, robust taxonomy has been established. However, the effectiveness of DNA barcoding for identification is expected to be limited for understudied taxa or regions. One such region is Antarctica, where, despite the importance of lichens and lichenized fungi identification, their genetic diversity is far from characterized. The aim of this exploratory study was to survey the lichenized fungi diversity of King George Island using a fungal barcode marker as an initial identification tool. Samples were collected unrestricted to specific taxa in coastal areas near Admiralty Bay. Most samples were identified using the barcode marker and verified up to the species or genus level with a high degree of similarity. A posterior morphological evaluation focused on samples with novel barcodes allowed for the identification of unknown Austrolecia, Buellia, and Lecidea s.l. species. These results contribute to better represent the lichenized fungi diversity in understudied regions such as Antarctica by increasing the richness of the nucleotide databases. Furthermore, the approach used in this study is valuable for exploratory surveys in understudied regions to guide taxonomic efforts towards species recognition and discovery.
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The Tröllaskagi Peninsula in northern Iceland hosts more than a hundred small glaciers that have left a rich terrestrial record of Holocene climatic fluctuations in their forelands. Traditionally, it has been assumed that most of the Tröllaskagi glaciers reached their Late Holocene maximum extent during the Little Ice Age (LIA). However, there is evidence of slightly more advanced pre-LIA positions. LIA moraines from Iceland have been primary dated mostly through lichenometric dating, but the limitations of this technique do not allow dating of glacial advances prior to the 18th or 19th centuries. The application of ³⁶Cl Cosmic-Ray Exposure (CRE) dating to Tungnahryggsjökull moraine sequences in Vesturdalur and Austurdalur (central Tröllaskagi) has revealed a number of pre-LIA glacial advances at ~400 and ~700 CE, and a number of LIA advances in the 15th and 17th centuries, the earliest LIA advances dated so far in Tröllaskagi. This technique hence shows that the LIA chronology in Tröllaskagi agrees with that of other European areas such as the Alps or the Mediterranean mountains. The combined use of lichenometric dating, aerial photographs, satellite images and fieldwork shows that the regional colonization lag of the commonly used lichen species Rhizocarpon geographicum is longer than previously assumed. For exploratory purposes, an alternative lichen species (Porpidia soredizodes) has been tested for lichenometric dating, estimating a tentative growth rate of 0.737 mm yr⁻¹.
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Lichenometric dating: Science or pseudo-science?—Response to comments by Michael A. O’Neal, pp. 244—245 - Volume 86 Issue 2 - Gerald Osborn, Daniel McCarthy, Aline Walintschek, Randall Burke
Lichenometry, a method for dating rock surface exposure mainly in high latitudes and mountain environments, is based on estimates of lichen growth rates, but over the last 70 years it has been severely criticised. Its chief limitation is its questionable reliability due to three main problems: the species belonging to the Rhizocarpon subgenus, most often used by lichenometrists, are hard to identify; growth studies have highlighted the intrinsic variability of growth both seasonally and annually, with species sensitively responding to a wide range of environmental factors; and the same sensitive dependence also applies to the time taken for colonization on fresh rock surfaces. These problems cast doubt on many absolute dating studies and critics have suggested that, at best, the technique should only be used for relative dating. This paper provides guidance on identification procedures and suggests alternative dating methods based on lichen size-frequency distributions and cross-dating with other lichen species, thus avoiding reliance on a single species or support from other methods. With appropriate development, it is hoped that these approaches can provide a way forward that allows the technique to contribute more reliably to the dating of rock surfaces in regions where there are few other dating options.
Flood frequency analyses relay on different source of data, including botanical records. Among these, the potential of dendrogeomorphology for flash flood reconstruction in torrential river systems has already been demonstrated in the specialized literature; however, studies combining other approximation techniques such as lichenometry are comparatively less abundant; and very few studies have questioned the advantages and disadvantages of applying these techniques in these particular fluvial environments. Here, we discuss the advantages and limitations of the use of Dendrogeomorphology and Lichenometry in the analysis of flash floods. We provide examples of application in different river systems that show how to overcome the disadvantages and provide complementary and even alternative information to classical sources. The methodological basis of the botanical data sources is based on the periodic environmental changes that condition the growth rate of living trees, manifested in sequence of tree-rings (i.e. studied by Dendrochronology) as well as the growth of several crustaceous lichens’ species, manifested in the accumulated centripetal growth of the stems (studied by Lichenometry). These growth sequences can be used for relative and absolute dating of flood events by identifying growth disturbances related to this process. The results obtained are event dating and measurements of palaeo-stage, flooded area, residence time, depths, velocities and generating flows that can be used for the study of flash floods, allowing to improve the analysis of frequencies and the magnitudes of past floods. Yet, several challenges remain when using these approaches. The interannual variations of these environmental changes (sequences of dry or wet, cold or warm years, variations in insolation, plagues and epidemics, anthropic interference...) could limit the use of these sources for analysing flash floods, given that they require prior filtering processes of the climatic and environmental signal for the identification of disturbances, through the establishment of reference or pattern series, or the development of lichenometric growth curves. However, the advantages and contributions of these data sources and techniques far outweigh the methodological limitations, making them a promising field for the study of environmental changes in river systems.
