The phylogeny of 67 populations representing 45 species of Aulacoseira Thwaites was estimated by maximum parsimony methods using a combination of nucleotide sequence data and qualitative and quantitative morphological characteristics of the silica cell wall gathered primarily from original observation by LM and SEM. A new type of character using continuous quantitative variables that describe the ontogenetic-allometric trajectories of cell wall characteristics over the life cycle (size range) of diatoms is introduced. In addition to the 45 Aulacoseira species, the phylogeny also incorporated one Miosira Krammer, Lange-Bertalot, and Schiller species and two outgroup species (Melosira varians Agardh and Stephanopyxis nipponica Gran & Yendo). Fifteen species, represented by 24 populations, also contained molecular data from the nuclear genome (18S rDNA), and 11 of these species (18 populations) contained data from the chloroplast genome (rbcL) as well, which were sequenced or downloaded from GenBank. The phylogeny of Aulacoseira is composed of five major clades: 1) an A. crenulata (Ehrenburg) Thwaites and A. italica (Ehrenburg) Simonsen clade, which is the most basal; 2) an A. granulata (Ehrenburg) Simonsen complex clade; 3) an A. ambigua (Grunow) Simonsen clade; 4) an A. subarctica (O. Müller) Haworth and A. distans (Ehrenburg) Simonsen clade; and 5) an A. islandica (O. Müller) Simonsen clade that also contained endemic species from Lake Baikal, Siberia and many extinct Aulacoseira taxa. Monophyly of Aulacoseira can only be achieved if Miosira is no longer given separate generic status.
Pinnunavis edkuensis is reported as a new diatom species from Egypt from brackish and marine habitats. Its description and diagnoses focus on 12 continuous morphological characters: valve breadth, valve mantle shape and surface area, axial-central area shape and surface area, axial area breadth, distal and proximal interstriae distances, striae slopes, magnitude and position of maximal slope along a semivalve transect, and inter-raphe distance. These characters are considered along their ontogenetic trajectories, using a size vector, by means of regression analyses. Shape was assessed using geometric morphometric methods. Diagnostic comparisons of P. edkuensis were made with P. yarrensis, for which a lectotype was chosen and Grunow’s unpublished description and drawings presented, and P. zalatii, a new name replacing the illegitimate name, Navicula aegyptiaca. P. edkuensis was demonstrated to be a distinct group compared to these two similar species using 11 of the 12 characters. The diagnoses emphasize species recognition by means of anova, regression and randomization analyses and specimen determination primarily by means of regression-based prediction intervals. Additional comments are made on the statistical nature of gaps associated with characters described by discrete or continuous variables, the importance of reporting sample sizes as part of diatom diagnoses and other comparisons, and the role of size in specimen comparability and taxon identification. The generic distinctness of Pinnunavis and Pinnularia is discussed based on a preliminary cladistic analysis of morphological characters.
Are size and arrangement of valve mantle areolae in Aulacoseira Thwaites adapted to light intensity? To test one criterion demonstrating an adaptation, heritability experiments were run on isolates of Aulacoseira subarctica (Müller) Haworth. Several clones of A. subarctica were isolated from Yellowstone Lake (Wyoming, USA), Lewis Lake (Wyoming), and East Rosebud Lake (Montana, USA). Two to four clones from each lake were grown in batch cultures under three irradiance levels: 2, 11.4, and 115 lmol photons . m À 2 . s À 1 . Five randomly chosen valves for each of two replicates of each clone were examined using a scanning electron microscope for a total of 300 valves. Size measurements were taken for each valve examined, and images of mantle areolae were captured on film at a magnification of 20,000 Â . Each image was digitized, and quantitative morphometric areolar characters were measured. A quantitative genetic analysis was performed within each light environment for the mean area of the external opening of mantle areolae, the mean distance between areolae within pervalvar striae, and the mean distance between pervalvar striae. Resulting estimates of heritability from among-lake and within-lake analyses indicate that all three mantle areolar characters could presently respond to selection and thus have potentially done so in the past.
Ochromonas sensu lato is the largest genus in the Chrysophyceae, containing over 100 names. Ochromonas species are biflagellate, naked, plastid‐bearing single cells, distinguished from loricate, scaled, colonial and colorless genera. Most, if not all, species of Ochromonas are mixotrophic, i.e., they photosynthesize but they also engulf bacteria and other small prey. Preliminary evidence from SSU rRNA sequences show that Ochromonas is a polyphyletic genus. Ochromonas tuberculata is the most distinct from all other Ochromonas species. The other Ochromonas species (examined thus far) are scattered in three clades. For example, O. danica and O. sphaerocystis are sister to Poterioochromonas stipitata and P. malhamensis. Four additional species (identified by light microscopy as O. elegans Doflein, O. globosa Skuja, O. ovalis Dolfein, O. sociabilis Pringheim) have SSU rRNA sequences identical to P. malhamensis. Of these, only O. sociabilis has been transferred to Poterioochromonas. Thus, at least some species may be synonymous with others. Two clades of marine species are also known, one containing coastal species and the other containing open ocean species. A number of genera (some also polyphyletic) are interspersed amongst the Ochromonas species (e.g., Chrysolepidomonas, Chrysonephele, Chrysoxys, Cyclonexis, Dinobryon, Epipyxis, Uroglena, Uroglenopsis). The goal of this research (just beginning) is to establish a monophyletic Ochromonas, probably by assigning some species to other genera (existing or new). One major problem is that the type species, O. triangulata Vysotskii, hasn't been observed in over 100 years, and it is unclear which of several clades of Ochromonas contains the type. Results will be discussed.
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