Myriam de Haan

Revision of the genus Navicula s.s. (Bacillariophyceae) in inland waters of the Sub-Antarctic and Antarctic with the description of five new species

Van de Vijver B., Zidarova R., Sterken M., Verleyen E., de Haan M., Vyverman W., Hinz F. and Sabbe K. 2011. Revision of the genus Navicula s.s. (Bacillariophyceae) in inland waters of the Sub-Antarctic and Antarctic with the description of five new species. Phycologia 50: 281–297. DOI: 10.2216/10-49.1 A revision of the diatom genus Navicula s.s. in inland water samples from the Sub-Antarctic and Antarctic resulted in the description of five new species, viz. Navicula australoshetlandica Van de Vijver sp. nov., N. dobrinatemniskovae Zidarova & Van de Vijver sp. nov., N. cremeri Van de Vijver & Zidarova sp. nov., N. conveyi Van de Vijver sp. nov. and Navicula bicephaloides Van de Vijver & Zidarova sp. nov. The new species are extensively compared with other similar species. The morphology and taxonomy of three other Navicula taxa present in the same materials are briefly discussed. A critical revision of literature reports of Navicula taxa in the Antarctic and Sub-Antarctic region indicates that despite the large number of records the genus is rather species-poor in the Sub-Antarctic and Antarctic. From a biogeographical point of view, there is a clear separation between the Sub-Antarctic localities in the southern Indian Ocean and the islands in the southern Atlantic Ocean, with several species showing a restricted biogeography.

Four new Luticola taxa (Bacillariophyta) from the South Shetland Islands and James Ross Island (Maritime Antarctic Region)

During a revision of the genus Luticola on the South Shetland Islands and James Ross Island, four unknown Luticola species were observed. Based on detailed light microscopy and scanning electron microscopy observations, the species are described as new to science: Luticola katkae Van de Vijver & Zidarova sp. nov., Luticola vermeulenii Van de Vijver sp. nov., Luticola adelae Van de Vijver & Zidarova sp. nov. and Luticola raynae Zidarova & Van de Vijver sp. nov. Their morphology and taxonomy is discussed comparing each species with similar Luticola taxa. Notes on their ecology are added. Subsequently, the distribution of all Luticola taxa in the subantarctic and Antarctic regions is investigated resulting in a clear separation of the Subantarctic Region, the Maritime Antarctic Region and the Antarctic Continent.

Four new European Achnanthidium species (Bacillariophyceae)

Four new Achnanthidium species belonging to the species complex around A. minutissimum (Kutz.) Czarn. are described from different localities in Europe. Achnanthidium hoffmannii Van de VijVer, eCtor, a. Mertens et jarlMan nov. spec. was found in several oligotrophic, circumneutral rivers in Sweden. The species is characterized by the presence of irregular, slit-like areolae near the valve margin, clearly visible in LM. Achnanthidium acerosum Van de VijVer, lange-Bert. et jarlMan nov. spec., a narrow, linearlanceolate species with protracted, narrowly capitate apices, is likewise described from Sweden, but only found in one oligotrophic river in southern Sweden. Achnanthidium ertzii Van de VijVer et lange-Bert. nov. spec. was observed in a moss vegetation in a Laurisilva forest on the Portuguese island of Madeira. The species has an elongate, linear-elliptical valve outline with clearly capitate apices. The last species, A. tepidaricola Van de VijVer et M. de Haan nov. spec., found in a greenhouse of the National Botanic Garden of Belgium, has almost parallel margins and broadly rounded, protracted, capitate apices. All four species are sufficiently different from similar existing species.

The genus Surirella (Bacillariophyta) in the sub-Antarctic and maritime Antarctic region

A revision of taxa from the genus Surirella from the Antarctic region resulted in the description of three new taxa: S. subantarctica Van de Vijver & Cocquyt sp. nov., S. heardensis Van de Vijver & Cocquyt sp. nov. and S. australovisurgis Van de Vijver, Cocquyt, Zidarova & Kopalová sp. nov. Detailed light (LM) and scanning electron microscope (SEM) observations are used to characterize these three new taxa. Comparisons with similar taxa and the ecological preferences of each species are added. The morphological characteristics of a fourth Antarctic Surirella taxon, S. kerguelensis Grunow are illustrated as this taxon was only known from a few hand drawings and LM pictures. Finally, a fifth taxon, S. lapponica A. Cleve was found on South Georgia and likewise illustrated. The revision of these species made clear that the genus Surirella showed similar biogeographical trends as other, previously revised genera indicating that a distinct Antarctic diatom flora exists.

Nitzschia epiphytica, N. epiphyticoides and N. pseudepiphytica (Bacillariophyta), three small diatoms from East and Central Africa

Cocquyt C., de Haan M., Jahn R. and Hinz F. 2012. Nitzschia epiphytica, N. epiphyticoides and N. pseudepiphytica (Bacillariophyta), three small diatoms from East and Central Africa. Phycologia 51: 126–134. DOI: 10.2216/10-61.1 Nitzschia epiphytica and N. epiphyticoides are two small diatoms from Central and East Africa described by Müller in 1905 and by Hustedt in 1949, respectively. To reduce the confusion that exists between the two species, the type of N. epiphyticoides and the original material of N. epiphytica were reexamined by light and scanning electron microscopy. Because N. epiphytica was described from several samples by Müller, a lectotype is designated. The variability of these two Nitzschia species was studied using both historic material and more recent material from Lake Tanganyika. A third taxon, Nitzschia pseudepiphytica, which corresponds rather well with the emended species description of N. epiphytica given by Hustedt in 1949, is described. The distribution of these three small Nitzschia species is probably restricted to tropical Africa and reported occurrences elsewhere in the world need to be re-investigated.

The Ultrastructure of Gomphonema augur and Gomphonema gautieri (Bacillariophyta)

Abstract The ultrastructure of Gomphonema gautieri (Van Heurck) Lange-Bert, et Metzeltin was studied based on a small population from a small Swedish, slightly acid, eutrophic river. The observations were compared with the holotype slide of G. augur var. gautieri Van Heurck, as the species was originally described in 1885. The valves are characterized in having a typical clavate outline with the largest width near the broadly rounded headpole. The species can be separated from G. augur Ehrenb. by its larger valve dimensions, the presence of broad shoulders on the headpole and the lower number of areolae per stria. Based on these differences, a separation of both taxa is justified.

Reconciling biodiversity and carbon stock conservation in an Afrotropical forest landscape

Positive relationships between carbon storage and taxonomic diversity are not predominant at the local scale. Protecting aboveground carbon stocks in tropical forests is essential for mitigating global climate change and is assumed to simultaneously conserve biodiversity. Although the relationship between tree diversity and carbon stocks is generally positive, the relationship remains unclear for consumers or decomposers. We assessed this relationship for multiple trophic levels across the tree of life (10 organismal groups, 3 kingdoms) in lowland rainforests of the Congo Basin. Comparisons across regrowth and old-growth forests evinced the expected positive relationship for trees, but not for other organismal groups. Moreover, differences in species composition between forests increased with difference in carbon stock. These variable associations across the tree of life contradict the implicit assumption that maximum co-benefits to biodiversity are associated with conservation of forests with the highest carbon storage. Initiatives targeting climate change mitigation and biodiversity conservation should include both old-growth and regenerating forests to optimally benefit biodiversity and carbon storage.

Scientific user requirements for a herbarium data portal

Abstract The digitization of herbaria and their online access will greatly facilitate access to plant collections around the world. This will improve the efficiency of taxonomy and help reduce inequalities between scientists. The Botanic Garden Meise, Belgium, is currently digitizing 1.2 million specimens including label data. In this paper we describe the user requirements analysis conducted for a new herbarium web portal. The aim was to identify the required functionality, but also to assist in the prioritization of software development and data acquisition. The Garden conducted the analysis in cooperation with Clockwork, the digital engagement agency of Ordina. Using a series of interactive interviews, potential users were consulted from universities, research institutions, science-policy initiatives and the Botanic Garden Meise. Although digital herbarium data have many potential stakeholders, we focused on the needs of taxonomists, ecologists and historians, who are currently the primary users of the Meise herbarium data portal. The three categories of user have similar needs, all wanted as much specimen data as possible, and for those data, to be interlinked with other digital resources within and outside the Garden. Many users wanted an interactive system that they could comment on, or correct online, particularly if such corrections and annotations could be used to rank the reliability of data. Many requirements depend on the quality of the digitized data associated with each specimen. The essential data fields are the taxonomic name; geographic location; country; collection date; collector name and collection number. Also all researchers valued linkage between biodiversity literature and specimens. Nevertheless, to verify digitized data the researchers still want access to high quality images, even if fully transcribed label information is provided. The only major point of disagreement is the level of access users should have and what they should be allowed to do with the data and images. Not all of the user requirements are feasible given the current technical and regulatory landscape, however, the potential of these suggestions is discussed. Currently, there is no off-the-shelf solution to satisfy all these user requirements, but the intention of this paper is to guide other herbaria who are prioritising their investment in digitization and online web functionality.

An evaluation of selected Neidium species from the Antarctic region

The presentation of three distinct Neidium taxa from the sub-Antarctic and Maritime Antarctic region after examining more than 1500 samples from a broad variety of aquatic and terrestrial (micro-)habitats suggests that taxa representing the genus Neidium Pfitzer are not only quite rare in these regions, but that the three species also represent well-defined biogeographical distributions. N. nyvltii sp. nov., N. antarcticum sp. nov. and N. aubertii Manguin are characterized by linear to linear–lanceolate valves with rostrate to capitate apices, a single prominent longitudinal canal along the valve margins and lacinia covering the distal raphe endings. Neidium nyvltii is a benthic alkalophile growing in the Maritime Antarctic region under high total phosphorus (TP) and moderately high chloride concentrations, while the closest taxa for comparison (N. kozlowii Mereschkowsky and its varieties) are also alkalophilic, growing under lower TP concentrations in northern temperate–Arctic regions. Neidium aubertii is an acidophile with a sub-Antarctic distribution, whereas the most comparable taxa are N. bisulcatum (Lagestedt) Cleve, and N. bergii (A. Cleve-Euler) Krammer & Lange-Bertalot both are alkalophiles with northern hemisphere distribution and commonly occurring in the Arctic. There is some evidence of parallel similarities in valve forms between the polar northern and southern hemispheres. The significance of this parallelism is yet to be determined.

THE GENUS MICROCOSTATUS IN THE ANTARCTIC REGION

The genus Microcostatus was erected in 1998 by Johansen & Sray to accommodate a small number of tiny naviculoid species belonging to the former section Naviculae minusculae, characterized by the presence of the typical microcostae, a series of external transapical costae near the axial area, the possession of a simple raphe system and the lack of a conopeum, typical for the genus Fallacia. During a survey of the Antarctic non-marine diatom flora, two Microcostatus species were found in several localities in the southern Atlantic and Indian Ocean. Comparison with type material and with the sparse literature that exists on the genus Microcostatus, the Antarctic species were identified as Microcostatus naumannii (Hustedt) Lange-Bertalot and M. maceria (Schimanski) Lange-Bertalot. The species showed the typical northern distribution although some older records of M. naumannii were known from the Antarctic Region. The purpose of this study was the morphological characterization of both species using detailed light and scanning electron microscopy observations. Their ecology and worldwide biogeographical distribution was discussed in the view of the debate on the global distribution of microorganisms.