Asynchronous multitrophic level regime shifts show resilience to lake browning.

Lake browning is widespread due to increased supply of dissolved organic carbon under climate warming and nitrogen deposition. However, multitrophic level responses to lake browning are poorly understood. Our study aims to explore such responses across multitrophic levels based on sedimentary records of diatoms, chrysophyte stomatocysts and chironomids in a remote headwater lake in the Three Gorges Reservoir region, central China. Although all biotic proxies were analysed in the same core, the timing of shifts in chironomids (1886 ± 18 CE) preceded that in chrysophyte stomatocysts (∼1914 ± 10 CE) and diatoms (∼1941 ± 6 CE). Shifts in biotic communities were closely linked to rising temperature, δ15N depletion (a proxy for nitrogen deposition), δ13C enrichment (a proxy for littoral moss expansion), as well as biotic interactions, whereas the relative importance of the driving forces varied among the three biotic groups. Our results suggest that the zoobenthos grazing effect might be more important than bottom-up pathways in humic environments. Additionally, the coexistence of benthic, littoral and pelagic algae after the 1950s suggested that mixotrophic chrysophytes could reduce lake browning through heterotrophic processes and sustain the ecological equilibrium between littoral, pelagic and benthic productivity. Therefore, lake browning ecosystem regime shifts require analyses of multiple trophic levels. Our results suggest that heterotrophy may become more important in lake ecosystem carbon cycling with water brownification in Mulong Lake, as well as similar montane lakes.

Integrative Approach Helps Clarify Confusing Taxonomy of the Pseudopediastrum boryanum Species Complex (Chlorophyceae), Including Recognition of five Distinct Species.

Sixteen monoclonal strains classified into six morphotypes typical of, or close to, intraspecific taxa of Pseudopediastum boryanum, including P. alternans (ALT), P. boryanum var. boryanum (BOR), P. boryanum var. cornutum (COR), P. boryanum var. forcipatum (FOR), P. boryanum var. longicorne (LON), and P. boryanum var. perforatum (PER), were simultaneously subjected to phylogenetic (26S rDNA and rbcL cpDNA) and morphometric analyses. Marginal cell shape, coenobium and cell size, and granule density on the cell surface were analyzed statistically. The shapes of some morphotypes (BOR, COR, FOR, and PER) were also compared to the shapes of corresponding type illustrations. Pseudopediastrum boryanum var. boryanum, without any reliable morphological and phylogenetic data, appeared to be a questionable taxon that needs a neotype. The variety longicorne proved to be a complex taxon that should be split after morphometric data of more strains and of the corresponding lectotype are included in the statistical analysis. A new species, Pseudopediastrum oblongum, was described, and four varieties were elevated to the species level, which resulted in establishing new combinations, P. cornutum, P. forcipatum, P. perforatum, and P. subgranulatum. Reference sequences for the new species and combinations were obtained. The paleoecological value of P. boryanum sensu lato appeared to be limited by the relatively low percentage of marginal cells typical of particular varieties and a high risk of their misidentification in the light microscope. The shape of marginal cells seemed to be the best diagnostic feature. Granule density could be helpful to discriminate between certain taxa.

Assessing morphological congruence in Dinobryon species and their stomatocysts, including a newly established Dinobryon pediforme-stomatocyst connection.

The chrysophyte genus Dinobryon Ehrenberg consists of 44 taxa, which occur in freshwaters, rarely marine waters, mostly in temperate regions of the world. The taxa of Dinobryon produce characteristic solitary or dendroid colonies and resting stages called stomatocysts. Only 20 Dinobryon taxa have information on produced stomatocysts and only four stomatocysts are reliably linked with vegetative stages using modern identification standards employing scanning electron microscopy (SEM) analyses. In this study, an encysted material of Dinobryon pediforme (Lemmermann) Steinecke was collected in two lakes in contrasting regions of Poland. Light microscopy (LM) and scanning electron microscopy (SEM) analyses revealed that Dinobryon pediforme produces stomatocyst #61, Piatek J. that is described here as new morphotype following the International Statospore Working Group (ISWG) guidelines. This raises to five the number of reliable links between vegetative stages of Dinobryon species and corresponding stomatocysts. Phenotypic similarities between Dinobryon species and their stomatocysts, analysed for five reliably established links, showed no relationships in size and shape between loricas and stomatocysts belonging to the same species. The morphological characters of loricas and stomatocysts mapped onto the phylogenetic tree of the five Dinobryon species revealed only little congruence between their morphology and phylogenetic relationships.

Dismantling a complex of anther smuts (Microbotryum) on carnivorous plants in the genus Pinguicula.

The anther smuts of the genus Microbotryum are known from host plant species belonging to the Caryophyllaceae, Dipsacaceae, Lamiaceae, Lentibulariaceae, Montiaceae, and Primulaceae. Of these, the anther smuts on Caryophyllaceae, in particular on Silene spp., are best known because they include model organisms studied in many disciplines of fungal biology. For Microbotryum species parasitic on Caryophyllaceae, a high degree of host specificity was revealed and several cryptic species were described. In contrast, the host specificity within Microbotryum pinguiculae occurring in anthers of different Pinguicula species (Lentibulariaceae) has not been investigated in detail until now. The anther smuts on Pinguicula alpina, P. villosa, and P. vulgaris, on which M. pinguiculae was described, were analyzed using nuc rDNA ITS1-5.8S-ITS2 and nuc rDNA 28S D1-D2 sequences and morphology to determine if they belong to one polyphagous species or rather represent three host-specific species. The results of the morphological investigations revealed no decisive differences between the anther smuts on different Pinguicula species. However, genetic divergence and molecular phylogenetic analyses, which split the specimens according to host plant species, supported host specificity of the anther smuts on different Pinguicula species. Accordingly, in addition to Microbotryum pinguiculae s. str. on Pinguicula vulgaris, M. alpinum sp. nov. on P. alpina from Europe and M. liroi sp. nov. on P. villosa from Asia are described and illustrated.

Doassansiopsis caldesiae sp. nov. and Doassansiopsis tomasii: two remarkable smut fungi from Cameroon.

Three recent collections of Doassansiopsis from western Cameroon are assessed taxonomically. Doassansiopsis caldesiae M. Piatek & Vánky is described as a new species from infected leaves of Caldesia reniformis (D. Don) Makino. Its diagnostic characters are flat, nonthickened sori with spore balls as blackish, slightly elevated dots, more or less globoid spores, conspicuous cortical sterile cells and parasitism on Caldesia reniformis of family Alismataceae. The species is compared to another Doassansiopsis species on host plants belonging to family Alismataceae. Doassansiopsis tomasii Vánky is described from two localities on Nymphaea nouchali Burm.f. var. caerulea (Savigny) Verdc. (Nymphaeaceae), which represents the first report of this smut from Cameroon and western Africa. Similarities between this species and Doassansiopsis nymphaeae (Syd. & P. Syd.) Thirum. and D. ticonis M. Piepenbr. are outlined and the global distribution of the three taxa is mapped. The species concept in the genus Doassansiopsis is discussed, and a key to all known species of the genus is provided.