Kociolek, Patrick J., Laslandes, Berengere, Benett, Danuta, Thomas, Evan, Brady, Mariska, and Graeff, Carrie.2014. Diatoms of the United States 1: Taxonomy, Ultrastructure and Descriptions of New Species and Other Rarely Reported Taxa from Lake Sediments in the Western U.S.A. Bibliotheca Diatomologica Volume 61. J. Cramer in der Gebrüder Borntraeger Verlagsbuchhandlung, ISBN 978‐3‐443‐57052‐1, 188 pp., PB, 79.00 Euro

Abstract

Diatoms continue to hold a key position in many aquatic studies for several good reasons. For example, diatoms are important (and at times dominant) primary producers, and they are excellent biomonitors of environmental change and superb paleoenvironmental indicators. Their use as biomonitors requires an accurate assessment of the taxonomic composition of assemblages—an area of research that continues to receive considerable attention. This volume is an important contribution to the taxonomic literature on diatoms. The authors describe what they believe to be 50 new diatom species identified from sediments collected from lakes across the western United States. The book includes 80 plates with both high-quality light microscope images and scanning electron micrographs for each described taxon. The book begins with a brief introduction that outlines the history of reporting new diatom species from lakes in the United States, starting with the early collections of European diatomists such as Ehrenberg, Cleve, and others and ending with a listing of some of the more recent contributions from both European and North American researchers, including the National Lakes Assessment (NLA) program that has collected sediments from over 1000 lakes across the United States. The described taxa are from a subset of sediment cores collected from 55 NLA lakes from the western United States (North Dakota to California) including subfossil assemblages from recent (modern) and pre-industrial sedimentary intervals. The authors report a large number of new taxa, previously undescribed or taxa that were never or rarely reported in the literature from the United States, and a few taxa for which the authors propose taxonomic changes. For each taxon, the authors include a morphological description as well as their ecological distribution within their 55-lake survey and, importantly, their systematic similarities and affinities. The authors use a morphological species concept approach where taxa are described by detailed microscopic examination to delineate minor morphological differences (pseudo-cryptic species). Many of the newly described diatom taxa are only distinguishable on the basis of minute ultrastructural features of their frustule and often there appears to be very little difference with previously established taxa. For the researcher whose ultimate goal is the practical use of diatoms to understand environmental change, such fine-grained distinctions between established and new taxa may be somewhat disquieting. It is for this reason that the inclusion of high-quality light microscope and scanning electron images are critical. On this count, the book delivers superbly. Because of the morphological similarity between many new and previously described taxa, it is important that the systematic similarities and affinities are included in the description. Supplying the reader with this information is important from a practical viewpoint, so that diatomists using this book can potentially differentiate these taxa, although this may still prove difficult with light microscopy alone. This information has been provided within a “Discussion” for many of the new taxa in this book, but unfortunately not for all taxa (for example, Aulacoseira spathulata and A. pusilloides). The book will be useful (some may argue essential) for diatomists working not only in the western United States but also in other regions, as it is likely that these taxa are more widespread. The book also reemphasizes that our work on the taxonomic description of diatoms is far from over or, as the authors conclude, the documentation of the inland diatom flora of the western United States is “still in a period of discovery.” Kathleen Rühland, Paleoecological Environmental Assessment and Research Lab (PEARL), Department of Biology, Queen's University, Kingston, Ontario, Canada K7L 3N6; ruhlandk@queensu.ca John P. Smol, Paleoecological Environmental Assessment and Research Lab (PEARL), Department of Biology, Queen's University, Kingston, Ontario, Canada K7L 3N6; smolj@queensu.ca