Genus Peltigera Research Articles

ASSESSING REPRODUCTIVE ISOLATION IN HIGHLY DIVERSE COMMUNITIES OF THE LICHEN-FORMING FUNGAL GENUSPELTIGERA

The lichen-forming fungal genus Peltigera includes a number of species that are extremely widespread, both geographically and ecologically. However, morphological variability has lead to doubts about the distinctness of some species, and it has been suggested that hybridization is common in nature. We examined species boundaries by looking for evidence of hybridization and gene flow among seven described species collected at five sites in British Columbia, Canada. We found no evidence of gene flow or hybridization between described species, with fixed differences between species for two or more of the three loci examined. Reproductive isolation did not reflect a solely clonal mode of reproduction as there was evidence of ongoing gene flow within species. In addition, we found five undescribed species that were reproductively isolated, although there was evidence of ongoing or historical gene flow between two of the new species. These results indicate that the genus Peltigera is more diverse in western North America than originally perceived, and that morphological variability is due largely to the presence of undescribed species rather than hybridization or intraspecific variation.

Increased soil nitrogen associated with dinitrogen‐fixing, terricolous lichens of the genus Peltigera in northern Minnesota

Dinitrogen (N2)‐fixing lichens (cyanolichens) have long been recognized as a source of exogenous N in various ecosystems, yet the effects of nitrogen inputs from these lichens have been little studied. Cyanolichens of the genus Peltigera Willd. are often the dominant members of the earth‐dwelling (terricolous) cyanolichen community. They occur in diverse habitats around the globe, but no studies of their influence on soil N have been reported.We conducted field and laboratory investigations with the primary objective of determining whether soil N availability is increased near healthy thalli of terricolous dinitrogen‐fixing lichens. We measured available soil N in situ with ion‐exchange resin bags, potentially mineralizable N with laboratory incubations, total soil N, and soil temperature. Measurements were taken along transects that extended away from thalli of Peltigera, perpendicular to and parallel to topographic contours. Studies were conducted in ten types of forest across northern Minnesota, including two contrasting sites that represent extremes of habitat for Peltigera.Soil N availability, potentially mineralizable N, and soil %N increased significantly with proximity to healthy thalli of Peltigera (P‐values<0.05). Moreover, potential N mineralization was highly correlated with soil %N (R2=0.765). Our results suggest a potential zone of influence that extends 1.5 m from thalli of Peltigera. The data indicate that soil temperature is not a primary factor in these associations.

New approach to an old problem: Incorporating signal from gap-rich regions of ITS and rDNA large subunit into phylogenetic analyses to resolve the Peltigera canina species complex

The Peltigera canina species complex consists of foliose lichenized bitunicate ascohymenial discomycetes forming section Peltigera within the genus Peltigera (Lecanoromycetes, lichen-forming Ascomycetes). To test the circumscription of highly polymorphic species and to resolve relationships among putative members of the P. canina complex, part of the nuclear ribosomal DNA large subunit (LSU rDNA) and the entire internal-transcribed spacer (ITS rDNA) were sequenced for 84 individuals representing 33 putative Peltigera taxa. Seventeen of the 25 taxa from the P. canina complex are well established and widely accepted. The remaining eight taxa have been proposed recently but are undescribed. A hypervariable region in ITS1 (ITS1-HR, sites 111–237 in our alignment) showed remarkable variation in length, especially in the P. canina complex, ranging from 8 to 126 bp, and contained several microsatellites. We describe here an alignment-free method to code such large gap-rich hypervariable regions for phylogenetic analyses. Variation among ITS1-HR sequences greatly contributed to species delimitation and species identification and can be a major asset to future population studies for specific species within section Peltigera. Sequences of ITS1-HR alone were sufficient to identify all existing species of Peltigera from the P. canina species complex and related sections Retifoveatae and Horizontales included in this study. However, only when INAASE (for short ambiguously aligned regions) and ITS1-HR coded characters were added to the combined analysis of nonambiguous LSU and ITS sites was it possible to reach the level of phylogenetic resolution and support necessary to disentangle the P. canina complex. We report here complete concordance between phylogenetically based and morphologically based species delimitation for 15 of the 17 species from the P. canina complex (P. canina, P. cinnamomea, P. degenii, P. evansiana, P. frigida, P. kristinssonii, P. laciniata, P. lambinonii, P. lepidophora, P. membranacea, P. monticola, P. ponojensis, P. praetextata, P. rufescens and P. ulcerata). Four of the eight newly proposed but undescribed taxa most likely represent new species (P. “fuscopraetextata”, P. “neocanina”, P. “neorufescens” and P. “scotteri”) within the P. canina complex. We found that morphologically and chemically distinct P. didactyla s. str. and P. didactyla var. extenuata form two non-sister monophyletic entities, therefore the latter taxon should be recognized at the species level (P. extenuata). The North American and European populations of the morphologically uniform P. degenii might represent two sibling species because they were found to be genetically distinct and monophyletic. Two major monophyletic groups within the P. canina complex (CICADE = CInnamomea + CAnina + DEgenii group and PORUDI = POnojensis + RUfescens + DIdactyla group) seem to be correlated with different humidity preferences. Although some authors previously have suggested interspecies recombination within the P. canina complex, we did not find statistically significant evidence for this phenomenon based on LSU and ITS sequences.

Differential land snail damage to selected species of the lichen genus Peltigera

The intensity of grazing of two land snails, Cantareus aspersa and Limax sp., on three epigaeic species of Peltigera with ( P. horizontalis, P. neckeri) and without ( P. praetextata) secondary compounds, were studied in the field in three transects of 2×50 m along an altitudinal gradient in the surroundings of Pistoia (Tuscany, Italy). The results were confirmed by laboratory experiments and were carried also out on a further species lacking lichen compounds ( P. degenii), showing that land snails definitely prefer thalli lacking lichen secondary compounds. Damage intensity is correlated to the thallus size of the lichens.

Long-term impacts of simulated climatic change on secondary metabolism, thallus structure and nitrogen fixation activity in two cyanolichens from the Arctic.

• Although the most pronounced effects of stratospheric ozone depletion and climate warming probably will occur in polar regions, arctic lichens have not been much studied in relation to climate change. • Samples of two arctic cyanolichens of the genus Peltigera, exposed in situ to ambient and enhanced UV-B radiation and ambient and increased temperatures, were collected in 2001, 5yr after the establishment of the experimental set-up. Thallus dimensions and size, coverage of soralia, nitrogen fixation activity and levels of UV-C-absorbing substances were measured. • Warming had pronounced positive effects on the tridepsides methyl gyrophorate and gyrophoric acid, and unidentified trace substances. However, the combination of enhanced UV-B and increased temperatures did not lead to higher than control levels. Warming reduced coverage of soralia. There were no significant treatment effects on thallus size, dimensions and nitrogen fixation activity. • UV-B radiation did not to have any adverse effects. The accumulation of tridepsides with warming may be related to increased activity of pathogenic microorganisms or insect herbivores.

Phylogenetic Revision of the GenusPeltigera(Lichen‐Forming Ascomycota) Based on Morphological, Chemical, and Large Subunit Nuclear Ribosomal DNA Data

Peltigera (Peltigerineae, lichenized Ascomycota) is one of the most widespread lichen genera incorporating bi‐ and trimembered associations involving fungi, green algae (cf. Coccomyxa), and cyanobacteria (cf. Nostoc). A wide range of morphological and chemical (secondary compounds) variation at both the intra‐ and interspecific levels is present in this genus. Compared to many other genera of macrolichens, its taxonomy, including chemotaxonomy, still remains poorly understood. Existing infrageneric classifications of Peltigera are almost exclusively based on photobiont composition of the thallus. These classifications assumed that bi‐ and trimembered taxa were distinct monophyletic entities. The genus Peltigera has never been the focus of a comprehensive phylogenetic study. The most recent and widely accepted subdivision of the genus into seven groups is based mainly on morphological and chemical characters. Relationships among species of Peltigera are investigated here using chemical, morphological, and large subunit nuclear ribosomal DNA (LSU nrDNA) data. We test the monophyly of these seven morpho‐chemical Peltigera groups and propose a classification based on a phylogenetic approach. Data sets of 42 chemical characters (terpenoids), 31 morphological characters, and 1135 LSU nrDNA characters for 96 samples representing 38 Peltigera species, eight undescribed putative Peltigera species, and nine species from seven potentially closely related genera from Peltigerineae were subjected to maximum parsimony analyses. Morphological, chemical, and molecular analyses were carried out independently and on a combined data set. Monophyly of Peltigera, including Hydrothyria, was confirmed. The genus Hydrothyria is transferred to Peltigera and a new combination Peltigera hydrothyria Miadlikowska & Lutzoni is proposed. Eight monophyletic sections within the genus Peltigera, with high bootstrap support, are circumscribed: sections Peltigera, Polydactylon Miadlikowska & Lutzoni, Chloropeltigera Gyeln., Peltidea (Ach.) Vain., Horizontales Miadlikowska & Lutzoni, Retifoveatae Miadlikowska & Lutzoni, Phlebia Wallr., and Hydrothyriae Miadlikowska & Lutzoni. Unequivocal morphological and chemical synapomorphies for all sections except section Peltidea are recognized and presented. A key for identification of the sections is provided. In addition, a key based on four main terpenoids for determination of the chemotypes and species within section Polydactylon is included. Five terpenoids (50–54) identified on thin‐layer chromatography plates for P. elisabethae and P. horizontalis chemotype I are added to the list of substances found in Peltigera. Five chemotypes, mainly from Poland and Norway, are reported from Peltigera thalli for the first time: P. malacea chemotype V, P. leucophlebia chemotype II, P. hymenina chemotypes II and III, and P. collina chemotype IV. Three main types of vein structure in Peltigera were recognized based on SEM studies.

New species of lichenicolous fungi occurring on Peltigera in Ecuador and Europe

A study of the lichenicolous fungi occurring on species of the lichenized genus Peltigera has resulted in six new species: Libertiella curvispora, L. didymospora, L. fennica Alstrup, Polycoccum superficiale, Roselliniella peltigericola, and Zwackhiomyces kiszkianus. A key to the five known species of Libertiella is included. This paper brings the number of fungi known on this host to 87, of which 61 are not known from any other host genus, providing additional evidence for the richness of Peltigera thalli as a host for novel fungi. The possible hypotheses to explain the richness of this host genus for lichenicolous fungi are enumerated; these are not mutually exclusive.

The Lichen Genus Peltigera, Exclusive of the P. canina Group, in Norway

The Lichen Genus Peltigera, Exclusive of the P. canina Group, in Norway

Effect of simulated acid rain on nitrogenase activity in the lichen genus peltigera under field and laboratory conditions

Lichens of the genus Peltigera were exposed to simulated acid rain in the laboratory and at a field site in Southwestern Alaska. Exposure to simulated rainfall of pH 4.4 had no effect upon acetylene reduction in P. rufescens after experiments of 28 and 60 days duration, although in the former experiment there was some evidence of a transient effect after 14 days. Simulated acid rain of pH 3.4 or 4.4 also had no effect upon nitrogenase activity in P. aphthosa during a 21-day field study, indicating that nitrogenase activity in Peltigera is not sensitive to precipitation in this range of acidity.

The Control of Cadmium Uptake in the Lichen Genus Peltigera

Intra- and extracellular Cd uptake in the lichen genus Peltigera were investigated, and intracellular uptake found to display Michaelis-Menten kinetics. Compared with values reported for Zn uptake in free-living algae and fungi, Peltigera had low affinities for Cd and low maximum uptake rates. Intra-, and to a lesser extent extracellular uptake rates were temperature dependent. When lichens were incubated concurrently with Cd and equimolar concentrations of a range of other cations, most were found to reduce both extra- and intracellular Cd uptake, implying that the Cd uptake systems had low specificities. Mg, though not a strong competitor for extracellular Cd uptake, inhibited intracellular Cd uptake to a similar extent to borderline elements, and it is postulated that intracellular Cd uptake occurs by a system which normally transports Mg. Although concurrently-supplied cations reduced Cd-induced inhibitions of photosynthesis, the reductions were not proportional to the effect of the cations on intracellular Cd uptake. This indicated that other cations affected the toxicity of Cd to photosynthesis by some means in addition to reducing Cd uptake. Intracellular Cd uptake was light-stimulated, suggesting that a close relationship existed between metal uptake and metabolism. The rate of intracellular Cd uptake in the dark was probably not directly linked to the supply of respirable reserves, as it was unaffected by prolonged storage in the dark, and was not increased by adding glucose. It is hypothesized that light-stimulated Cd uptake represents active entry into algal cells, but with uptake in the dark it is not clear which symbiont is involved, and whether energy is required.

Natural and Experimentally-induced Zinc and Copper Resistance in the Lichen Genus Peltigera

Using a tolerance index based on metal-induced reductions in photosynthesis, members of the lichen genus Peltigera, sampled from a range of sites with contrasting metal status, were demonstrated to possess Zn tolerance directly proportional to the Zn content of the thallus. Tolerance was not related to the concentration of other cations present in the thallus or weight of thallus per unit surface area. Although differences in Cu tolerance were found, these were not related to the Cu content of the thallus but rather to the Zn content. In the laboratory, pretreatment of P. membranacea with low concentrations of Zn significantly decreased the inhibition of photosynthesis caused when subsequently supplied with high levels of Zn compared to water pretreated plants. Increased resistance to Cd but not Cu was also found, although it was not possible to increase either Cu or Zn resistance by pretreatment with Cu.

Chimeroid Associations in the Genus Peltigera

Chimeroid Associations in the Genus <i>Peltigera</i>

Modifications of nitrogen-fixing algae in lichen symbioses

THE factors responsible for the establishment of lichen symbioses involving nitrogen-fixing blue-green algae are poorly understood1,2 and it has not been clear how the algae are modified to remain in association, virtually ceasing to grow and yet fixing N2 at high rates. We report here that in the lichen genus Peltigera morphological, physiological and biochemical modifications of the algae may all be involved in this process.

Seasonal and Spatial Variation of Nitrogen Fixation in the Barrow, Alaska, Tundra

A seasonal study of nitrogen fixation was carried out on the arctic tundra in the vicinity of Barrow, Alaska. Nitrogen fixation rates were measured on tundra cores at selected sites at 10-day intervals throughout the summer. The acetylene reduction technique was the principal tool. Significant nitrogen fixation was found throughout the mid-summer months. Indirect evidence suggests that blue green algae of the genus Nostoc were the principal agents along with lichens of the genus Peltigera since isolated specimens of these reduced acetylene with high efficiency. A survey of nitrogen fixation was also carried out on subarctic alpine tundra in the