John Patrick Kociolek

A PRELIMINARY INVESTIGATION OF THE PHYLOGENETIC RELATIONSHIPS AMONG THE FRESHWATER, APICAL PORE FIELD-BEARING CYMBELLOID AND GOMPHONEMOID DIATOMS (BACILLARIOPHYCEAE) 1

Relationships among the apical pore field‐bearing diatom genera Brebissonia, Cymbella, Gomphonema, Gomphoneis, Didymosphenia, Gomphocymbella, and Reimeria and their close ally Encyonema were evaluated using cladistics. These biraphid genera are a polythetic group defined by chloroplast number and type, mode of sexual reproduction, valve orientation and presence of apical pore fields. Character states of valve as well as non‐siliceous features were described and then polarized using the outgroup method, with the naviculoid genera Anomoeoneis and Placoneis serving as outgroups. The cladistic analysis suggests two groups of terminal taxa, corresponding to to a predominantly cymbelloid lineage and a gomphonemoid lineage. Didymosphenia, previously thought to be closely allied to gomphonemoid diatoms, is shown to be more closely related to Cymbella. Gomphonema appears to be without distinguishing characteristics. Relationships of the other genera are described. The systematic position of small, doubly‐punctate Gomphonema species is discussed.

Freshwater gomphonemoid diatom phylogeny: preliminary results

A cladistic analysis of eleven freshwater gomphonemoid diatom taxa yielded three equally most parsimonious cladograms. The three cladograms suggest Gomphoneis Cleve is non-monophyletic as originally and recently circumscribed. Gomphoneis elegans and G. transsilvanica (Pant.) Krammer are more closely related to Gomphopleura Reichelt ex Tempère than to other members of the genus. Gomphoneis geitleri Kociolek & Stoermer appears to represent a monotypic lineage. Among the taxa with differentiated apical pore fields Gomphonema kaznakowi Mereschkowsky appears to be primitively astigmate.The three cladograms vary with regard to systematic affinities among the Gomphoneis herculeana (Ehrenberg) Cleve group, Miocene gomphonemoid species from Idaho (USA), gomphonemoid taxa from East Africa and Gomphonema sensu stricto. Despite variability in number of puncta rows per stria and presence of an axial plate in the Miocene species from North America, inclusion of these taxa in the analysis provided better resolution of relationships than if they were excluded.

Ultrastructure of Cymbella sinuata and Its Allies (Bacillariophyceae), and Their Transfer to Reimeria, gen. nov.

Light and scanning electron microscopy are employed to describe the ultrastructure of Cymbella sinuata and allied taxa. Observations show the C. sinuata group shares features of valve symmetry and number of apical pore fields with members of the genus Cymbella s. str., while having raphe, striae, and stigmal features similar to Gomphonema species. The features shared between the C. sinuata group and Cymbella appear to be symplesiomorphies, while the group lacks apomorphic features characteristic of Gomphonema. These observations, in addition to a unique construction of the apical pore fields in the C. sinuata group, suggest its placement in a new genus, Reimeria. Features of the new genus are described and its systematic position discussed. A new fossil species, R. lacus-idahoensis is proposed. Cymbella sinuata Gregory and its various infra- specific taxa have been considered to occupy an uncertain taxonomic position. Although origi- nally placed in the genus Cymbella C. A. Ag. by

QUANTITATIVE ANALYSIS OF SILICEOUS MICROFOSSILS IN THE SEDIMENTS OF LAKE ERIE'S CENTRAL BASIN

Quantitative analysis of siliceous microfossils preserved in a radiometrically dated core from the central basin of Lake Erie (North America) shows several distinct periods in the lakes response to anthropogenic effects. Prior to European settlement of the region, microfossil deposition rates were low, and the flora consisted mainly of oligo-stenothermal and benthic species. Deposition rates increased rapidly following settlement and the proportion of summer-blooming species, particularly members of the genus Cyclotetta, increased. During the period ca. 1920–1930 the flora underwent transition from dominance of oligo-mesotrophic species to dominance of species associated with eutrophic conditions. After ca. 1945 the flora became dominated by species tolerant of hypereutrophic conditions. The most recently deposited sediments (post- ca. 1980) contain a qualitatively different flora, probably reflecting reduction of phosphorus loadings to Lake Erie.

Two new pliocene species of Cyclostephanos (Bacillariophyceae) with comments on the classification of the freshwater Thalassiosiraceae

Two new species of the diatom genus Cyclostephanos Round are described from Pliocene fossil deposits in western North America. Cyclostephanos undatus is distinguished from other Cyclostephanos species by its tangentially undulate valve face; Cyclostephanos fenestratus is distinguished by its extremely shallow alveoli. This paper records previously unreported morphological detail of Cyclostephanos and speculates that structure of the punctum, labiate process and strutted process may enhance diagnosis of the freshwater genera of the Thalassiosiraceae Lebour emend. Hasle. Cyclostephanos undatus is similar to several Cyclotella species, but its external costae are raised and its alveolar morphology is similar to that of Cyclostephanos dubius (Fricke) Round. Cyclostephanos fenestratus is similar in external view to Stephanodiscus Ehrenb. However, the two species described here have flat cribra covering the mantle puncta and the labiate processes appear to lack external tubes, whereas Stephanodiscus species have domed mantle cribra and external tubes.

CHROMOSOME NUMBERS IN DIATOMS: A REVIEW

Previously published observations on chromosome numbers for 43 diatom taxa are reviewed. Members of five centric families, as well as araphid, monoraphid and biraphid pennate species are included in the list. Greatest range in diploid complement is found in the biraphid group, where the smallest (8) and largest (130) numbers have been reported. Chromosome numbers are compared with alternative hypotheses of diatom phylogeny and appear to support the scenario of an initial dichotomy between centries and pennates. The occurrence of polyploidy in diatoms is also discussed.

OBSERVATIONS ON NORTH AMERICAN GOMPHONEIS (BACILLARIOPHYCEAE). I. VALVE ULTRASTRUCTURE OF G. MAMMILLA WITH COMMENT ON THE TAXONOMIC STATUS OF THE GENUS1,2

Recent questions concerning the taxonomic status of the diatom genus Gomphoneis Cleve have prompted critical examination of the valvar morphology of a species originally included in the genus. Light and electron microscopic observations on G. mammilla (Ehr.) Cl. show that the characteristics put forth by Cleve to delineate the genus are present in this taxon. Striae composed of two rows of simple areolae located in depressions on the valve and longitudinal lines formed by a broad internal axial plate were observed in G. mammilla. The presence of two apical spines on the headpole and the structure of a bilobed apical pore field located at the footpole are described, in addition to other valve features. Valve morphology of G. mammilla is compared with that of doubly‐punctate Gomphonema species with the result that we recommend the two genera remain separate.

TAXONOMY AND ECOLOGY: A MARRIAGE OF NECESSITY

Rather than a marriage of convenience, which implies a relationship that is non-rigorous and has a substantial degree of independence, we argue that as we move forward through the 21st Century, studies on the taxonomy and ecology of freshwater diatoms will, and by necessity must, be linked. This linkage will be forged by integrated research programs and facilitated by tools that support both taxonomy and ecology. We examine the history of taxonomic and ecological research with freshwater diatoms, and suggest the potential interplay and mutual support offered by these two disciplines. Future research programs, including conservation of freshwater ecosystems, will require a formal commitment of conceptual and practical issues for each of these areas of science.

Taxonomy and systematic position of the Gomphoneis quadripunctata species complex

Contribution Number 000 of the Great Lakes Research Division Light microscopical observations were made on material from Lake Baikal containing Gomphoneis quadripunctata (Ostr.) Dawson ex Ross & Sims. The material had originally been used by Skvortzow to describe many subspecific taxa of this species. The many forms present all have multiple stigmoids positioned around the central area, septa at both poles, and undifferentiated apical pore fields. From the large number of taxa identified by Skvortzow, three species are recognized: G. hastata (Wisl.) Kociolek & Stoermer, comb, nov., G. tumida (Skv. in Skv. & Meyer) Kociolek & Stoermer, comb, nov., and G. quadripunctata. Species were segregated by differences in initial valve length and corresponding variation in valve shape and morphology. Of the three species recognized, G. hastata and G. tumida possess longitudinal lines in girdle view, while in G. quadripunctata such lines are absent. Relationships of these three species to G. olivaceoides (Hust.) Carte...

UNICELL ONTOGENY and PHYLOGENY: EXAMPLES FROM THE DIATOMS

Systematists have recently taken a renewed interest in ontogenetic data and its value as an estimator of phylogeny. At least two main areas of interest have become apparent in this regard. The first concerns overall correspondence between ontogenetic sequences and phylogeny, as exemplified by the work of Lfivtrup (1978, 1984, 1986). The second concerns the use of ontogenetic transformations in determining polarity of particular character states. Nelson (1978, see also Nelson and Platnick 1981) has restated Haeckel’s biogenetic law in Von Baerian terms. The ontogeny criterion suggests that: