Biodiversity of green algae covering artificial hard substrate surfaces in a suburban environment: a case study using molecular approaches

In Middle European suburban environments green algae often cover open surfaces of artificial hard substrates. Microscopy reveals the Apatococcus/Desmococcus morphotype predominant over smaller coccoid forms. Adverse conditions such as limited water availability connected with high PAR and UV irradiance may narrow the algal diversity to a few specialists in these subaerial habitats. We used rRNA gene cloning/sequencing from both DNA extracts of the biofilms without culturing as well as cultures, for the unambiguous determination of the algal composition and to assess the algal diversity more comprehensively. The culture independent approach revealed mainly just two genera (Apatococcus, Trebouxia) for all study sites and five molecular operational taxonomic units (OTUs) for a particular study site, which based on microscopic observation was the one with the highest morphological diversity. The culture approach, however, revealed seven additional OTUs from five genera (Chloroidium, Coccomyxa, Coenochloris, Pabia, Klebsormidium) and an unidentified trebouxiophyte lineage for that same site; only two OTUs were shared by both approaches. Two OTUs or species were recovered for which references have been isolated only from Antarctica so far. However, the internal transcribed spacer (ITS) sequence differences among them supported they are representing distinct populations of the same species. Within Apatococcus five clearly distinct groups of ITS sequences, each putatively representing a distinct species, were recovered with three or four such ITS types co-occurring at the same study site. Except for the streptophyte Klebsormidium only members of Trebouxiophyceae were detected suggesting these algae may be particularly well-adapted to subaerial habitats.

Taxonomic revision and species delimitation of coccoid green algae currently assigned to the genus Dictyochloropsis (Trebouxiophyceae, Chlorophyta)

Coccoid green algae traditionally classified in Dictyochloropsis have a complex, reticulate chloroplast, when mature, without a pyrenoid. They occupy remarkably diverse ecological niches as free-living organisms or in association with lichen-forming fungi and were recently shown to form two distinct lineages within Trebouxiophyceae. We used a polyphasic approach to revise the taxonomy of the genus. Based on phylogenetic analysis of the 18S rRNA gene, and detailed morphological investigation using comparative conventional light and confocal microscopy, we have assigned these lineages to two genera, Dictyochloropsis and Symbiochloris gen. nov. We have reconsidered the diagnostic generic features as follows: Dictyochloropsis comprises only free-living algae with a reticulate chloroplast, forming lobes in a parallel arrangement at some ontogenetic stages, and which reproduce only by means of autospores. This agrees with Geitler's original diagnosis of Dictyochloropsis, but not with the later emendation by Tschermak-Woess. Consequently, the species of Dictyochloropsis sensu Tschermak-Woess are assigned to Symbiochloris, with new combinations proposed. Symbiochloris encompasses free-living and/or lichenized algae with lobed chloroplasts and that reproduce by forming zoospores characterized by two subapical isokont flagella that emerge symmetrically near the flattened apex. In addition, using coalescent-based approaches, morphological characters and secondary structure of ITS transcripts, we inferred species boundaries and taxonomic relationships within the newly proposed genera. Two species of Dictyochloropsis and nine species of Symbiochloris are delimited, including the newly described species D. asterochloroides, S. handae, S. tropica, and S. tschermakiae. Our results further support the non-monophyly of autosporine taxa within Trebouxiophyceae.

Widespread green algae Chlorella and Stichococcus exhibit polar-temperate and tropical-temperate biogeography

Chlorella and Stichococcus are morphologically simple airborne microalgae, omnipresent in terrestrial and aquatic habitats. The minute cell size and resistance against environmental stress facilitate their long-distance dispersal. However, the actual distribution of Chlorella- and Stichococcus-like species has so far been inferred only from ambiguous morphology-based evidence. Here we contribute a phylogenetic analysis of an expanded SSU and ITS2 rDNA sequence dataset representing Chlorella- and Stichococcus-like species from terrestrial habitats of polar, temperate and tropical regions. We aim to uncover biogeographical patterns at low taxonomic levels. We found that psychrotolerant strains of Chlorella and Stichococcus are closely related with strains originating from the temperate zone. Species closely related to Chlorella vulgaris and Muriella terrestris, and recovered from extreme terrestrial environments of polar regions and hot deserts, are particularly widespread. Stichococcus strains from the temperate zone, with their closest relatives in the tropics, differ from strains with the closest relatives being from the polar regions. Our data suggest that terrestrial Chlorella and Stichococcus might be capable of intercontinental dispersal; however, their actual distributions exhibit biogeographical patterns.

Determination of Interleukin-4, -5, -6, -8 and -13 in Serum of Patients with Breast Cancer Before Treatment and its Correlation to Circulating Tumor Cells

BACKGROUND/AIM

Circulating tumor cells (CTCs) in women with breast cancer are an indication of prognosis before starting systemic treatment. The aim of this study was the evaluation of cytokine profiles as marker for CTC involvement.

MATERIALS AND METHODS

The analysis of CTCs, the time of blood sampling and the methodology were prospectively designed. There were two groups of patients: 100 women with a positive result for presence of CTCs and 100 women negative for CTCs. These groups were matched into pairs by tumor factors and survival/death. A multi-array ELISA was used to screen T-helper cell (Th) 2 cytokines. The results were analyzed by Spearman correlation coefficient and Mann-Whitney U-test.

RESULTS

In patients who were CTC-negative, expression of interleukin-8 (IL-8) and IL-13 was increased (p=0.017 and p=0.045, respectively) if they were negative for progesterone receptor. In patients who died from their tumor, correlation between hormone receptor negativity and an increase in IL-4 was found. IL-5 was increased in patients with lymph node-positive and human epidermal growth factor receptor 2 (HER2)-positive disease (p=0.042). Moreover IL-4 was increased in patients with progesterone receptor-positive and estrogen receptor-negative status (p=0.024). Furthermore, the level of IL-6 was increased in patients with tumor grade G3 without progesterone receptor expression.

CONCLUSION

Th2 cytokines are significantly modified in patients who are CTC-negative and progesterone receptor-positive. We suppose that an increase of IL-4 depends on hormone receptor status. In literature, a correlation between IL-4 and resistance to apoptosis is described. We suspect that IL-4 is responsible for the poor outcome of these cases.

Abstract P1-12-03: Short term quality of life with epirubicin-fluorouracil-cyclophosphamid (FEC) and sequential epirubicin/cyclophosphamid-docetaxel (EC-DOC) chemotherapy in patients with primary breast cancer – Results from the prospective multi-center randomized Adebar trial

Background:

The grade of recommendation for adjuvant dose-dense chemotherapy in patients with high risk primary breast cancer is heterogeneous among international guidelines. Understanding the impact on quality of life (QOL) by adjuvant dose dense chemotherapy in comparison to standard adjuvant chemotherapy is thereby a crucial factor, especially if the benefit is potentially low. This study aims to assess the impact on QOL by adjuvant dose dense chemotherapy in the prospective randomized multi-center ADEBAR trial.

Methods:

QOL was assessed at baseline (t1), before cycle 4 FEC (Epirubicin 60mg/m2 i.v. d 1 + 8, 5-Fluoruracil 500mg/m2 i.v. d 1 + 8, Cyclophosphamide 75mg/m2 p.o. d 1–14, q4w x 6) and cycle 5 EC-DOC (Epirubicin 90mg/m2 plus Cyclophosphamide 600mg/m2 q3w x 4, sequentially followed by Docetaxel 100mg/m2 q3w x 4) (t2), 4 weeks after chemotherapy (t3), 6 weeks after radiation (t4) and 1 year after baseline (t5) using the European Organization for Research and Treatment for Cancer (EORTC) Quality of Life Core Questionnaire (QLQ-C30) and the Breast Cancer-Specific Module (QLQ-BR23). A multivariate mixed model was fitted to test for differences between the two treatment arms. Primary endpoint was global QOL, secondary endpoints physical functioning, nausea&vomiting, fatigue and systemic therapy side effects. A minimum clinically meaningful difference was considered to be 10 points.

Results:

1306 patients were recruited between 3/2002 and 5/2005 675 were assigned to the FEC and 688 to the EC-DOC arm. Compliance to QOL assessment was 74% at baseline and 58% four weeks after therapy, but dropped to 11% after one year follow up. After the beginning of treatment global QOL dropped in both arm by 3 to 4 points. In the EC-DOC arm QOL dropped further at t3 by 7 points and stayed stable in the FEC arm. 6 weeks after radiation QOL exceeded baseline in both arms by 6 to 8 points. The differences between treatment arms were strongest at t3 (54.1 vs. 49.7) but did not reach clinical relevance at any point in time. Physical functioning, nausea vomiting, fatigue and systemic therapy side effects followed with some minor exceptions similar patterns, but showed higher amplitudes.

Conclusion:

In conclusion we could not detect a statistically significant difference between the two treatment arms in QOL parameters, indicating that dose dense adjuvant chemotherapy did not impact QOL at a clinically relevant level compared to standard adjuvant chemotherapy.

Citation Format: Schwentner L, Harbeck N, Singer S, Eichler M, Rack B, Forstbauer H, Wischnik A, Scholz C, Fink V, Huober J, Friedl T, Weissenbacher T, Härtl K, Kiechle M, Janni W. Short term quality of life with epirubicin-fluorouracil-cyclophosphamid (FEC) and sequential epirubicin/cyclophosphamid-docetaxel (EC-DOC) chemotherapy in patients with primary breast cancer – Results from the prospective multi-center randomized Adebar trial. [abstract]. In: Proceedings of the Thirty-Eighth Annual CTRC-AACR San Antonio Breast Cancer Symposium: 2015 Dec 8-12; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2016;76(4 Suppl):Abstract nr P1-12-03.

Abstract P4-01-03: Prognostic relevance of circulating tumor cells across different molecular subgroups in the adjuvant SUCCESS-A study

Aim: The prognostic value of circulating tumor cells (CTCs) in the adjuvant setting has recently been demonstrated in the SUCCESS A Study (Rack et al. JNCI 2014). As breast carcinomas depend on partly different pathways for progression, the relevance of CTCs could differ between molecular intrinsic subtypes of breast cancer. Aim of this study was therefore to analyze the prognostic impact of CTCs in molecular subtypes of a large patient cohort.

Methods: Within the adjuvant SUCCESS A Study, patients were treated either with 5-Flourouracil, Epirubicin and Cyclophosphamid (FEC) followed by Docetaxel (D) or with FEC followed by D and Gemcitabine (DG). There was no restriction with regard to molecular subtype, however a high recurrence risk was required for study entry. In addition patients were assessed prospectively for the presence of CTCs before chemotherapy. Molecular subtypes were defined as: triple negative (TN), hormone receptor positive and grading 1/2 (LUM A like), hormone receptor positive and grading 3 (LUM B like), HER2 positive (HER2 like). We studied whether the addition of CTC status (0 CTC vs > 0 CTCs) to well-known predictors such as age, BMI, tumor size, lymph node status improved the prediction of overall survival (OS) and disease free survival (DFS) across all patients and especially within molecular subtypes using likelihood ratio tests, which compared multivariable Cox regression models with and without CTC and the interaction between CTC and molecular subtype.

Results: Information about molecular subtype and CTCs was available in a total of 1994 patients. At least one CTC was seen in 422 (21.2%) of patients. 383 (19.2%) were TN, 798 were LUM A like (40.0%), 328 (16.4%) were LUM B like (16.4%) and 485 (24.3%) were HER2 like. The effect of CTC on overall survival had a HR of 2.50 (95%: 1.75 to 3.58) for the entire cohort. However as the effect was different across subtypes (p=0.04, likelihood ratio test), subtype specific HR were calculated. The effects on OS were most prominent in LUM B like patients (HR=3.96; 95%CI: 1.93 to 8.14) and LUM A like patients (HR=3.57; 95%CI: 1.81 to 7.03), less strong in HER2 like (HR=2.35; 95%CI: 1.04 to 5.32) and not present in TN patients (HR=1.18; 95%CI: 0.62 to 2.24). CTC status had a clear effect on DFS as well (HR=1.93, 95%CI: 1.48 to 2.52). It could not be shown that this effect was different across subtypes (p=0.07, likelihood ratio test). However, the effect size was similarly distributed like the ones for OS.

Conclusion: With regard to OS the prognostic effect of CTCs in this study cohort seems most prominent in patients with hormone receptor positive disease. It is still significant in HER2 positive, but not in TN breast cancer patients. Results with regard to DFS trended into the same direction, differences within subgroups could however not be shown, possibly due to power reasons.

Citation Format: Wolfgang Janni, Andreas Schneeweiss, Lothar Häberle, Peter A Fasching, Lukas Schwentner, Mahdi Rezai, Jörn Hilfrich, Hans Tesch, Georg Heinrich, Helmut Forstbauer, Thomas Friedl, Fabienne Schochter, Susanne Albrecht, Bernadette Jäger, Julia Jückstöck, Tanja Fehm, Volkmar Müller, Klaus Friese, Werner Lichtenegger, Matthias B Beckmann, Brigitte Rack. Prognostic relevance of circulating tumor cells across different molecular subgroups in the adjuvant SUCCESS-A study [abstract]. In: Proceedings of the Thirty-Seventh Annual CTRC-AACR San Antonio Breast Cancer Symposium: 2014 Dec 9-13; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2015;75(9 Suppl):Abstract nr P4-01-03.

Biodiversity of soil cyanobacteria in the hyper-arid Atacama Desert, Chile

The cyanobacterial diversity of soils of the Atacama Desert (Chile) was investigated using 16S rRNA gene cloning/sequencing directly from soil samples and 16S rRNA gene sequencing from unialgal cultures. Within the hyper-arid Atacama Desert, one of the driest parts of the world, 10 sites with differing altitude and distance to the shore were sampled along a total air-line distance (from south to north) of ~1,100 km. Filamentous cyanobacteria belonging to Nostocophycideae and Synechococcophycideae were present. Oscillatoriophycideae exhibited the highest species richness among the subclasses of cyanobacteria, and included mostly filamentous species along with some coccoids (e.g., Chroococcidiopsis). Thirty species-level phylotypes could be recognized using a cut-off of 99% 16S rRNA sequence similarity within the 22 genera defined at 97% 16S rRNA sequence similarity. Eight of the 30 taxa could be detected by both clonal and culture sequences. Five taxa were observed only in cultures, whereas the cloning approach revealed 17 additional taxa, which might be in the collection but unsequenced, hard-to-cultivate, or entirely unculturable species using standard cultivation media. The Atacama Desert soils have a high diversity of phylotypes, among which are likely both new genera and new species awaiting characterization and description.

Biotechnological screening of microalgal and cyanobacterial strains for biogas production and antibacterial and antifungal effects

Microalgae and cyanobacteria represent a valuable natural resource for the generation of a large variety of chemical substances that are of interest for medical research, can be used as additives in cosmetics and food production, or as an energy source in biogas plants. The variety of potential agents and the use of microalgae and cyanobacteria biomass for the production of these substances are little investigated and not exploited for the market. Due to the enormous biodiversity of microalgae and cyanobacteria, they hold great promise for novel products. In this study, we investigated a large number of microalgal and cyanobacterial strains from the Culture Collection of Algae at Göttingen University (SAG) with regard to their biomass and biogas production, as well antibacterial and antifungal effects. Our results demonstrated that microalgae and cyanobacteria are able to generate a large number of economically-interesting substances in different quantities dependent on strain type. The distribution and quantity of some of these components were found to reflect phylogenetic relationships at the level of classes. In addition, between closely related species and even among multiple isolates of the same species, the productivity may be rather variable.

Phytoplankton diversity and community composition along the estuarine gradient of a temperate macrotidal ecosystem: combined morphological and molecular approaches

Microscopical and molecular analyses were used to investigate the diversity and spatial community structure of spring phytoplankton all along the estuarine gradient in a macrotidal ecosystem, the Baie des Veys (eastern English Channel). Taxa distribution at high tide in the water column appeared to be mainly driven by the tidal force which superimposed on the natural salinity gradient, resulting in a two-layer flow within the channel. Lowest taxa richness and abundance were found in the bay where Teleaulax-like cryptophytes dominated. A shift in species composition occurred towards the mouth of the river, with the diatom Asterionellopsis glacialis dramatically accumulating in the bottom waters of the upstream brackish reach. Small thalassiosiroid diatoms dominated the upper layer river community, where taxa richness was higher. Through the construction of partial 18S rDNA clone libraries, the microeukaryotic diversity was further explored for three samples selected along the surface salinity gradient (freshwater - brackish - marine). Clone libraries revealed a high diversity among heterotrophic and/or small-sized protists which were undetected by microscopy. Among them, a rich variety of Chrysophyceae and other lineages (e.g. novel marine stramenopiles) are reported here for the first time in this transition area. However, conventional microscopy remains more efficient in revealing the high diversity of phototrophic taxa, low in abundances but morphologically distinct, that is overlooked by the molecular approach. The differences between microscopical and molecular analyses and their limitations are discussed here, pointing out the complementarities of both approaches, for a thorough phytoplankton community description.

Abstract P1-04-06: Discordance of the ER- and HER2-status on disseminated tumor cells compared to the primary tumor in patients with early breast cancer

Background: Differences in ER- and HER2-expression on metastases compared to the primary tumor (PT) are a known phenomenon and may have clinical implications in respect of targeted systemic treatment approaches. The aim of this study was to evaluate both ER- and HER2-status on disseminated tumor cells (DTCs) in the bone marrow (BM) of patients (pts) with early breast cancer (EBC) and to compare these with the corresponding PT.

Methods: BM aspirates were obtained at the time of first surgery. After Ficoll enrichment for mononuclear cells two cytospins with 106 BM cells were evaluated for ER-, HER2- and cytokeratin (CK) -expressions simultaneously by immunocytochemistry using a triple fluorescence staining method with antibodies directed against human ER (secondly labeled with Cy3, red), HER2 (Coumarin-AMCA, blue) and CK (DyLight488, green). The manual analysis was conducted using a computerized fluorescence microscope (Axioskop, Zeiss, Germany). Criteria for CK- and HER2-positivity were the ring-like appearance of the respective membrane stainings and for ER-expression a nuclear staining. Only pts with the detection of CK positive cells (DTC+) and known ER- and HER2-status of the PT (n = 54) were selected for this analysis.

Results: The median number of DTCs was 13 (range 1-95; total number of DTCs detected: 1082). 40 (74%) of the pts had at least one ER-positive (pos) DTC, 24 (44%) at least one HER2-pos DTC, 14 (26%) at least one ER-pos/HER2-pos DTC, and 50 (93%) at least one ER-negative/HER2-negative (neg) DTC, while 10 (19%) pts had only ER-neg/HER2-neg DTCs.

The concordance rate between ER-status on DTCs and PT was 74%. Pts with an ER-pos PT were significantly more likely to have at least one ER-pos DTC (34 out of 42) than pts with an ER-neg PT (6 out of 12; Chi-square test, χ2 = 4.66, p = 0.031). 39 (93%) of the 42 pts with ER-pos PT had at least 1 ER-neg DTC.

The concordance rate between HER2-status on DTCs and PT was 52%. The probability of having at least one HER2-pos DTC was not related to the HER2-status of the PT (Chi-square test, χ2 = 0.34, p = 0.56). 22 (46%) of the 48 pts with a HER2-neg PT had at least one HER2-pos DTC. All of the 6 pts with a HER2-pos PT had at least one HER2-neg DTC.

7 out of 10 pts with a triple-neg PT had at least one DTC pos for ER, HER2 or both. Further the heterogeneity of the ER- and HER2-expression on DTCs compared to the PT for different DTC counts was evaluated. We detected all possible combinations of ER- and HER2-experssion on DTCs regardless of the respective status of the PT.

Conclusions: Our study confirms that the ER- and/or HER2-status on DTCs may differ compared to the PT. This discordance could be especially important for pts with a triple-neg PT and ER-pos or HER2-pos DTCs, since they might respond favorably to an endocrine or HER2-targeted therapy. On the other hand, the presence of ER-neg or HER2-neg DTCs in pts with ER-pos or HER2-pos PT might explain some of the failures of adjuvant endocrine or HER2 targeted therapy.

Citation Information: Cancer Res 2013;73(24 Suppl): Abstract nr P1-04-06.

Congruence of chloroplast- and nuclear-encoded DNA sequence variations used to assess species boundaries in the soil microalga Heterococcus (Stramenopiles, Xanthophyceae)

Background

Heterococcus is a microalgal genus of Xanthophyceae (Stramenopiles) that is common and widespread in soils, especially from cold regions. Species are characterized by extensively branched filaments produced when grown on agarized culture medium. Despite the large number of species described exclusively using light microscopic morphology, the assessment of species diversity is hampered by extensive morphological plasticity.

Results

Two independent types of molecular data, the chloroplast-encoded psbA/rbcL spacer complemented by rbcL gene and the internal transcribed spacer 2 of the nuclear rDNA cistron (ITS2), congruently recovered a robust phylogenetic structure. With ITS2 considerable sequence and secondary structure divergence existed among the eight species, but a combined sequence and secondary structure phylogenetic analysis confined to helix II of ITS2 corroborated relationships as inferred from the rbcL gene phylogeny. Intra-genomic divergence of ITS2 sequences was revealed in many strains. The ‘monophyletic species concept’, appropriate for microalgae without known sexual reproduction, revealed eight different species. Species boundaries established using the molecular-based monophyletic species concept were more conservative than the traditional morphological species concept. Within a species, almost identical chloroplast marker sequences (genotypes) were repeatedly recovered from strains of different origins. At least two species had widespread geographical distributions; however, within a given species, genotypes recovered from Antarctic strains were distinct from those in temperate habitats. Furthermore, the sequence diversity may correspond to adaptation to different types of habitats or climates.

Conclusions

We established a method and a reference data base for the unambiguous identification of species of the common soil microalgal genus Heterococcus which uses DNA sequence variation in markers from plastid and nuclear genomes. The molecular data were more reliable and more conservative than morphological data.

Molecular diversity of phototrophic biofilms on building stone

Composition and diversity of aeroterrestrial phototrophic microbial communities are up to now poorly understood. Here, we present a comparative study addressing the composition of algal communities on sandstone substrata based upon the analysis of rRNA gene clone libraries from environmental samples and crude cultures. From a west-facing, shaded wall area of the mediaeval castle ruin Gleichen (Thuringia, Germany), sequences mainly related to the green algae Prasiococcus and Trebouxia (Trebouxiophyceae) were retrieved. A south-west-facing, sun-exposed wall area was mainly colonized by Apatococcus and a Phyllosiphon-related alga. Just a few species, in particular Stichococcus-related strains, were ubiquitous in both areas. Samples from a basement vault exposed to low irradiance exhibited Chlorophyceae like Chromochloris and Bracteacoccus. Thus, most green algae on the daylight-exposed walls were affiliated to Trebouxiophyceae, whereas Chlorophyceae were dominant in samples taken from the site kept under low irradiance. Accordingly, cyanobacterial communities were different: the sun-exposed area was dominated by Synechococcus-related organisms, while on the shaded wall area, cyanobacteria were almost absent. The filamentous Leptolyngbya dominated samples from the basement vault. Scanning electron microscopy revealed endolithic algal morphotypes (coccoid algae and diatoms) dominant in open pores between mineral particles. Here, the organisms may be also involved in biogenic weathering of stone.

'Y'Scenedesmus (Chlorophyta, Chlorophyceae): the internal transcribed spacer 2 rRNA secondary structure re-revisited

Including RNA secondary structures improves accuracy and robustness in reconstruction of phylogenetic trees. It is possible to simultaneously infer alignments and phylogenies on the primary sequence and the secondary structure information. For the internal transcribed spacer 2 (ITS2), a phylogenetic RNA transcript marker, two different structure conformations (I or Y shape for helix I) were published for Scenedesmaceae, and a third appeared in the ITS2 database. We contrast the effects on phylogenetic tree reconstruction of different structure sets for a small scenedesmacean subset, using neighbour-joining, maximum parsimony and, for the first time, maximum likelihood, on sequence-structure alignments. Generally our study supports inclusion of secondary structure information. However, we found that any of the three structure conformations is equally fit for phylogenetic studies, but prefer the I shape for helix I. Moreover, our results enable us to give general recommendations on how to build a phylogenetic tree using ITS2 sequence-structure alignments, including different methods to obtain the secondary structures. Thus, we hope to provide a valuable contribution not only for scenedesmacean ITS2 phylogeny, but also for other approaches using RNA transcript markers.

Phylogenetic relationships of the Physciaceae inferred from rDNA sequence data and selected phenotypic characters

The monophyletic origin of the ascomycete family Physciaceae, its position within the Lecanorales and the phylogenetic structure within the family were investigated using nuclear rDNA sequence analyses. The common origin of the Caliciaceae and Physciaceae as previously shown (Wedin et al 2000) was confirmed. Further it could be shown that the Caliciaceae are nested within the Physciaceae. A unique region in loop 37 of the SSU rRNA secondary structure model was identified, which characterizes the Physciaceae/Caliciaceae. The SSU rDNA sequence data did not support a particular relationship with any other Lecanoralean family. Analyses of ITS rDNA sequences revealed a bifurcation of the Physciaceae/Caliciaceae clade, which was found to be congruent with the distribution of certain morphological characters. The congruence with the ITS phylogeny demonstrated the phylogenetic significance of ascus type, hypothecium pigmentation, ascospore characters and excipulum type. Fine-structure details of ascospores and the structure of excipula were found to be important in the recognition of convergences in these traits. Other previously used characters, i.e., growth habit, certain ascospore types or structure of the upper cortex, were found to be of multiple origins within the Physciaceae. All monophyletic lineages of noncrustose growth habit exhibit uniform ascospore types, indicating a higher evolutionary age of ascospore types than foliose growth habit. The taxonomic segregation of the Physciaceae into the Physciaceae and Caliciaceae is proposed here.

Molecular Evidence for the Wide Distribution of Two Lineages of Terrestrial Green Algae (Chlorophyta) over Tropics to Temperate Zone

Phylogenetic analyses of 18S rDNA sequences from environmental clones and culture strains revealed a widespread distribution of two subaerial green algal lineages, Jenufa and Xylochloris, recently described from rainforests in southeast Asia. A new lineage of Jenufa (Chlorophyceae), most closely related to or even conspecific with J. minuta, was formed by sequences of European origin. Two more lineages of Jenufa were formed by three additional sequences from Ecuador and Panama. The other lineage was a close relative of Xylochloris irregularis (Trebouxiophyceae), probably representing a new species of the genus and distinct from the only so far described species, X. irregularis. It comprised two distinct clades each containing almost identical sequences from Germany and Ecuador. Analyses of the new sequences for both genera allowed to presume a preference of J. minuta to subaerial growth on rock or artificial hard substrates combined with a remarkable adaptation to extended periods of darkness, whereas Xylochloris may preferably occur on tree bark or in the soil.

Biodiversity effects on ecosystem functioning change along environmental stress gradients

Positive relationship between biodiversity and ecosystem functioning has been observed in many studies, but how this relationship is affected by environmental stress is largely unknown. To explore this influence, we measured the biomass of microalgae grown in microcosms along two stress gradients, heat and salinity, and compared our results with 13 published case studies that measured biodiversity-ecosystem functioning relationships under varying environmental conditions. We found that positive effects of biodiversity on ecosystem functioning decreased with increasing stress intensity in absolute terms. However, in relative terms, increasing stress had a stronger negative effect on low-diversity communities. This shows that more diverse biotic communities are functionally less susceptible to environmental stress, emphasises the need to maintain high levels of biodiversity as an insurance against impacts of changing environmental conditions and sets the stage for exploring the mechanisms underlying biodiversity effects in stressed ecosystems.