The genetic and morphological diversity of the photobionts in foliicolous species of Porina (Porinaceae)

Baloch, E. & Grube, M.
Institute for Plant Science, Karl-Franzens-University Graz, Holteigasse 6, A-8010 Graz, Austria

Species of the lichen family Porinaceae are frequently found on leaves in the understorey of tropical rainforests. They are well adapted to microhabitats with low light and humid climate and associated with trentepohloid algae of the genus Phycopeltis.
The diversity of the photobionts in species of the Porina epiphylla and P. rufula group is investigated. The dataset also comprises sequences of photobionts of related Porina species, Cephaleuros (photobiont of the lichen genus Strigula, Strigulaceae), and the free living Trentepohlia iolithus.
The algae were studied morphologically with fluorescence microscopy. Direct PCR was applied to small fragments of the algal colony for amplification of the plastidal rbcL gene. A phylogenetic analysis was implemented using a Baysian MCMCMC approach.
The phylogenetic analysis shows that species of foliicolous Porina prefer certain morphological growth forms of their algal partner. However these morphological growth forms of vegetative colonies of symbiotic Phycopeltis do not represent monophyletic lineages. Growth as closed radiate plates is found in several lineages that emerge at basal positions in one major group, also including samples that grow in irregular plates with somehow spaced cells. In agreement with other studies, we have no indication that the growth form of the algae is modified after lichenization by the Porina mycobiont. Algal switching seems to be common but restricted to algae of the same growth type.


Genetic diversity of lichen photobionts of a specified locality

Guzow-Krzeminska, B.
University of Gdansk, Department of Molecular Biology, ul. Kladki 24, 80–822 Gdansk, Poland, e-mail: beatagk@biotech.univ.gda.pl

The following lichen species collected from the same stand were studied: Caloplaca decipiens, Caloplaca saxicola, Lecanora albescens, Physcia caesia, Physconia grisea, Protoparmeliopsis muralis, Xanthoria parietina. The following photobionts were found based on the ITS rDNA sequence analysis (BLAST and phylogenetic analysis): Trebouxia arboricola, T. gigantea, T. impressa, T. incrustata. Trebouxia arboricola was the most common photobiont at the site studied. It was found in Caloplaca decipiens, C. saxicola, Lecanora albescens and Xanthoria parietina. This suggests that T. arboricola can form a lichen thallus with a wide range of mycobionts. The sequences obtained from Caloplaca saxicola and Lecanora albescens were found to be identical in the ITS rDNA region. It is possible that free-living cells of Trebouxia arboricola were a photobiont source for newly arriving spores of mycobionts C. saxicola and L. albescens.
It was also found that photobionts of Physconia grisea were identical in their ITS rDNA region. This lichen produces ascomata very rarely. The results may indicate that this lichen disperses by thallus fragmentation or by soredia propagation.
The following photobiont species were identified from specimens of Protoparmeliopsis muralis collected from the same locality, they were: T. gigantea, T. impressa, T. incrustata. It is possible that this species is very successful in colonizing new habitats because of the low selectivity level.


Ecological versus evolutionary dependence in associations of Physciaceae and Trebouxia

Helms, G.
Experimentelle Phykologie und Sammlung für Algenkulturen, Albrecht-von-Haller-Institut, Universität Göttingen, Untere Karspüle 2, 37073 Göttingen, Germany

The ecological and evolutionary dependence of Physciacean mycobionts on their photobionts was investigated. Most species of which multiple specimens were analyzed were found to associate with photobionts of one Trebouxia subclade only. Sexual and asexual reproductive modes were not found to correlate with a low or high degree of selectivity respectively. Notably, crustose species often had low degrees of selectivity and foliose species were usually highly selective. Further, sexual species often were associated with ITS-variants that were different from those found in closely related asexual species. This suggests that alga sharing is not a common mode of photobiont acquisition in apotheciate species. The high degree of selectivity which was found in most Physciaceae species contrasted to the apparent lack of selectivity in the photobionts. Therefore, in analogy to parasitic systems, photobionts were denoted as host organisms and mycobionts as associates. According to an apparent dependence of most mycobionts on particular photobionts, correlated phylogenies could be suspected in the associated taxa (Fahrenholz´ Rule). However, the analyses showed that associated taxa do not share a common evolutionary history. It is suggested that competition among mycobionts for photobionts might represent the evolutionary force that promotes higher selectivity in little selective mycobionts (resource partitioning) and at the same time destabilizes highly specific associations resulting in host switches as a possible strategy to avoid competitive pressure.


A study of epiphyte algae of some lichen species

Mikhailyuk, T. I. & Kondratyuk, S. Ya.
Department of Lichenology and Bryology, M.H. Kholodny Institute of Botany NASU, Kyiv, Ukraine

Lichen thallus may serve as substrate for a number of aerophyte algae. Epiphytic algae (EA) growing on lichen thalli was hitherto not object of special investigations. Data on EA from lichen thalli are rather scarce and incidental.
36 samples of lichen thalli of 3 model species (Aspicilia cinerea, A. contorta var. hoffmannii, Candelariella vitellina), the most common epilithic lichens on granite outcrops of Steppe zone of Ukraine, were the main material of this study. Samples were provided from 12 model plots, 6 of which are situated in dry conditions of the upper portions of slope, another 6 in wet conditions of slope along river. Totally 43 algal species (Cyanoprocaryota – 15 species, Chlorophyta – 27, and Eustigmatophyta – 1) were found with the use of cultural methods (Bold Basal medium). Fottea stichococcoides, Geminella terricola, Desmococcus olivaceus, Elliptochloris bilobata, E. subsphaerica, Chlorella minutissima, Klebsormidium flaccidum found to be the most widely distributed among EA.
The highest species diversity of EA is recorded for C. vitellina (36 species), less on A. contorta (26) and A. cinerea (22). Furthermore, abundant development and sometimes macroscopic growth of EA was found on C. vitellina and A. contorta, while EA on A. cinerea are recorded only singly.
On one side, species content of EA found to be rather close to content of lithophilic algae of granite outcrops of the same plots. Distribution of EA and lithophilic algae along the river bank slope is rather similar (only green algae are present in the upper portions of the slope, and cyanobacteria [Gloecapsa dermochroa, Chlorogloea microcystoides, Symploca willei, Tolypothrix byssoidea] found at the lower part of the slope). On another side, there is a number of EA, which are absent among lithophilic algal group. Furthermore, among latter Elliptochloris bilobata, Symploca willei, Tolypothrix byssoidea found to be rather abundant on lichen thalli.


Photobiont diversity in the genus Xanthoria

Nyati, S., Scherrer, S. & Honegger, R.
Institute of Plant Biology, Zollikerstrasse 107, University of Zürich, CH 8008, Zürich, Switzerland

In only a small number of lichens has the photobiont ever been studied at species level, and very little is known about photobiont diversity within populations. In an ongoing project we investigated the genetic diversity within Trebouxia photobionts of >11 Xanthoria species from worldwide locations and photobiont diversity within 4 populations of X. parietina from coastal, rural and urban sites in Europe. The genetic diversity of the fungal partners was studied in parallel experiments (see contributions of C. Eichenberger et al. and R. Honegger et al.). Trebouxia photobionts of all except 2 Xanthoria spp. were brought into sterile culture, altogether more than 300 isolates. rDNA (ITS 1 and 2, 5.8S) sequences were used as a molecular marker at species level. In comparative sequence analyses X. flava and the majority (28/37) of X. parietina samples from Caucasus to SW Europe harboured T. arboricola, but 5 out of 37 isolates were far away from known sequences. A clearly separated, more diverse cluster not containing any known sequence data comprised Trebouxia isolates from X. capensis (ZA), X. parietina (IS, CH, I), X. calcicola (CH, TN), X. ligulata (NZ), X. polycarpa (USA, ARM), and two unnamed Xanthoria sp. (ZA, AUS). Another small cluster comprised the Trebouxia isolates from 4 unnamed Xanthoria sp. from the Eastern Mediterranean. X. candelaria had T. gelatinosa, X. borealis fragments from the same collecting site contained either T. arboricola or an unknown Trebouxia sp. An astonishing photobiont diversity was noted in populations of X. parietina. We used RAPD markers and RFLP of PCR-amplified rDNA and sequenced representatives of emerging groups. Between 20 and 60 thalli growing side by side per population were examined. RAPD-PCR of the sterile cultured X. parietina partners, a presumably homothallic ascomycete (see contributions of R. Honegger et al. and S. Scherrer et al.), also refer to high genetic diversity within populations, the reasons being a matter of debate.


Global population structure of the lichen photobiont Nostoc

O’Brien, H., Miadlikowska, J. & Lutzoni, F.
Department of Biology, Duke University, Durham NC 27708 USA

While species delimitations within the genus Nostoc are poorly understood, members of a monophyletic lineage within the genus are abundantly distributed in free-living and symbiotic terrestrial habitats throughout the world, covering such climatic extremes as tropical, desert, and arctic regions. We used multi-locus sequence data (rbcLX, nifV1, rpoC2) to determine if geography, habitat or mycobiont association best explained the population structure found within this lineage. Soil samples and cyanolichens were collected from northern boreal forests in Canada, Western Europe, and China, as well as the Canadian arctic, Costa Rican rainforest, western North American bunchgrass steppe, and eastern North American temperate mixed forest. Nostoc DNA was amplified directly from samples using cyanobacteria-specific primers for three protein coding loci and small subunit rDNA. Phylogenetic analyses and Analysis of Molecular Variance indicate that geography is a strong determinant of photobiont population structure for some lichen species, but not for others. Direct effects of habitat on photobiont communities are confounded by indirect effects due to the effect of habitat on mycobiont community composition, but we are beginning to separate these factors by examining photobionts from lichens with partially overlapping habitat ranges and by estimating rates of gene flow and recombination for the mycobionts. In combination, these data will give us new insight into the evolutionary and demographic forces that shape lichen community structure.


Photobiont in selected lichens from different habitats in South Brazil

Reis, R. A. (1), Cordeiro, L. M. C. (1), Blaha, J. (2), Iacomini. M. (1) & Grube, M. (2)
(1) Departamento de Bioquímica e Biologia Molecular, Universidade Federal do Paraná, CP 19046, 81530-990 Curitiba, Brazil; (2) Institute for Plant Science, Karl-Franzens-University Graz, Holteigasse 6, A-8010 Graz, Austria

Recently much progress was achieved with regard to phylogenetic hypotheses of lichen photobiont. Most studies so far concentrated on photobiont selectivity in temperate regions. In this study we investigate the photobionts of several species of the families Physciaceae, Ramalinaceae, Parmeliaceae and Teloschistaceae from ecologically different habitats in South Brazil: Atlantic rain forest, mangrove, mixed rain forest, restinga and a managed, open site. Tropical representatives of the investigated families contain different photobiont lineages than found in environments of temperate to cold regions. The detected lineages likely represent a large number of yet undescribed algal species, which are exclusively found in tropical habitats. In addition to the molecular data, observations of cultured photobionts will be presented and discussed. Supported by CAPES (BR).


A study of carbohydrates of some lichen algae

Shnyukova, E. I., Mikhailyuk, T. I. & Kondratyuk, S. Ya.
Department of Lichenology and Bryology, M.H. Kholodny Institute of Botany NASU, Kyiv, Ukraine

Investigations of separate components (photo- and mycobionts) of unique lichen associations, i.e. which are able to survive in conditions of dramatic exchanges of temperature and humidity will allow to understand defense mechanisms using by lichens.
Carbohydrates (CH), as components of cell walls, mucilage covers, as well as products of assimilation in green algae, play important role in defense of photobiont cells in extremal conditions and help to survive them.
CH of 2 model algal species Desmococcus olivaceus and Trentepohlia umbrina (Chlorophyta), the most widely distributed photobionts of lichens (Ettl & Gaertner 1995) are investigated. Data on content of various groups of CH in cells of algae mentioned (% of dry mass) were compared with the same data from phylogenetically close species growing mainly in water environment. Data on CH of D. olivaceus were compared with data from Chlorella vulgaris (both are representatives of the Trebouxiophyceae); data from T. umbrina – with data from Enteromorpha linsa (Ulvophyceae).
It is found that amount of mono-, di- and oligosaccharides in terrestrial green algae studied (3.51 in D. olivaceus and 2.23 in T. umbrina) is much lower in contrast to algae of water ecosystems (5.38 in C. vulgaris and 10.1 in E. linsa). On another side, much higher amount of structural and reserve polysaccharides is found in terrestrial algae (D. olivaceus – 8.98 and 3.23 consequently, T. umbrina – 11.57 and 5.04) in contrast to water algae (C. vulgaris – 2.25 and 0.78 consequently, E. linsa – 7.80 and 1.80). This phenomena shows that in terrestrial algae structural polysaccharides seem to be used for development of much dense cell walls as well as peculiarities of life of terrestrial algae (alternation of periods of active vegetation in wet conditions and anabiosis in dry periods) stimulate putting by higher concentration of reserve nutrient substances in cells.
Financial support of the STCU NN18R is deeply acknowledged.


Do different photobiont species and strains affect the morphological and chemical characters of a lichen and invitro-resynthesis products?

Stocker-Wörgötter, E.
Institute of Plant Physiology; University of Salzburg, Hellbrunner Str. 34, A-5020 Salzburg Austria

In numerous test series, the production of lichen metabolites in cultured mycobionts and in vitro resynthesis stages was found to be strongly affected by the composition of the nutrient media and dominant environmental parameters in the habitat.
In the present study, the role of the photobiont (algal populations) on morphogenesis and cell differentiation processes of the mycelia was studied. A tight connection was found between a given developmental step in cell differentiation, e.g. formation of a layered structure, formation of podetia, fruiting bodies etc. by the mycelia and the production of secondary lichen metabolites.
The influence of the algae/cyanobacteria and algal transfer products (polyols, glucose) on morphogenetic processes was investigated by testing lichens that exhibit highly differentiated and unusual growth forms; e.g. the Australasian lichen Cladia corallaizon, a lichen forming netlike structures (fenestrations), Thysanothecium scutellatum, colonizing rotten wood and termite moulds after bushfires, the tropical lichen Stereocaulon ramulosum representing a tripartite symbiosis and the lichenised basidomycete Dictyonema glabratum.
In all investigated cases, the different photobionts and also their transfer carbohydrates contributed to considerable and macroscopically visible morphogenetic effects; moreover influenced the production of typical secondary lichen metabolites.


Variation of trebouxioid photobionts in selected lichens

Wornik, S. (1), Blaha, J. (1), Opanowicz, M. (2) & Grube, M. (1)
(1) Institute for Plant Science, Karl-Franzens-University Graz, Holteigasse 6, A-8010 Graz, Austria; (2) Department of Systematics and Phytosociology, Institute of Plant Biology, University of Wroclaw, ul. Kanonia 6/8, 50-328 Wroclaw, Poland

Trebouxioid algae are the most common photobionts in the large order Lecanorales. Much progress has been made lately on the phylogeny of these photobionts and an increased sampling of lichen species provides new insights in their symbiont selectivity. These data show that there are significant differences in the photobiont selectivity in different lichen species. Generally, widespread crustose lichens appear to be less selective for photobiont species than foliose or fruticose lichens (with Umbilicaria as an exception). For example, Lecanora rupicola is associated with diverse species of Trebouxia, whereas Xanthoria parietina, Flavocetraria nivalis and species of Letharia, Physcia and Physconia, are associated only with particular lineages of single Trebouxia species. Based on these results we will propose selectivity indices. Haplotype networks will be presented for individual species of photobionts. These show the extremely wide geographic distribution of certain common algal genotypes, while others seem to be rarer or limited to certain environmental conditions.


Culture and DNA analyses of the photobionts of selected species of the genus Xanthoparmelia from Australia

Zocher, B. & Stocker-Wörgötter, E.
Institute of Plant Physiology, University of Salzburg, Hellbrunnerstr. 34, 5020 Salzburg, Austria

Lichens of the genus Xanthoparmelia (Vain.) Hale, a segregate of Parmelia Ach. are distributed mainly in southern Africa, Australia and New Zealand. In comparison, only few species are known from Europe. Xanthoparmelia is one of the most dominant groups of saxicolous lichens in hot, semi-arid climates frequently growing in open and exposed habitats. Their thalli are foliose to subcrustose, loosely adnate to very tightly adnate and their upper surface is pale yellow-green to grey-green.
For the present study, we investigated X. antleriformis, X. cheelii, X. filarszkyana, X. flavescentireagens, X. lineola, X. metaclystoides, X. substrigosa and X. tasmanica.
The Yamamoto-method was used for isolation of the algal cells; for subculturing different nutrient media were tested, relatively high growth rates were obtained on malt yeast medium. DNA analyses of the cultured photobionts were performed to determine the identity of the photobionts and if there is genetic variation among the tested algal populations in Australian species of Xanthoparmelia. A further goal is to elucidate the relationships between the isolated algal strains.

top