Platebaikalia - a new monoraphid diatom genus from ancient Lake Baikal with comments on the genus Platessa

Abstract

A new monoraphid diatom genus, Platebaikalia gen. nov., was described based on a detailed morphological investigation using light and scanning electron microscopy. Previously Platessa elegans Kulikovskiy et Lange-Bertalot was described from ancient Lake Baikal, and this species serves as the generitype for the newlydescribed genus. Platebaikalia elegans is a rare taxon found in the deeper parts of Lake Baikal. Platebaikalia elegans is characterized by having multiseriate striae on the raphe valves with biseriate striae on the rapheless valves, though in some specimens a short third row of areolae may be present in some striae. Morphology of striae is helpful to distinguish the genus Platebaikalia from Platessa and other monoraphid genera. Other morphological features that differentiate our new genus from other monoraphid taxa are discussed. We review the morphological data on Platessa species, and based on these data can recognize eight groups of taxa in the genus. Our analysis shows that Platessa as currently circumscribed may contain groups of species that are quite different from one another morphologically, and possibly includes taxa that could be recognized as different at the genus level. A few new combinations are suggested when taxa from the genus Platessa transferred to genera Psammothidium and Planothidium. Some problems of taxonomy of monoraphid taxa are discussed and we believe that taxonomy of this group of diatoms is in need of special attention in future.

Molecular Investigation of the Achnanthidium minutissimum Complex (Bacillariophyceae) from the Transbaikal Region with the Description of Three New Species

“…The diverse and distinctive diatom flora of the lake has been a focus of many studies since the early 20th century [1]. The nonmonophyletic group of monoraphid diatoms has been studied quite extensively in Lake Baikal during the last two decades, with descriptions of many new species and several new genera, such as Trifonovia Kulikovskiy et Lange-Bertalot [2], Gliwiczia Kulikovskiy, Lange-Bertalot et Witkowski [3], Skabitschewskia Kulikovskiy et Lange-Bertalot [4], Platebaikalia Kulikovskiy, Glushchenko, Genkal et Kociolek [5], Gololobovia Kulikovskiy, Glushchenko, Genkal et Kociolek [6] and Platesiberia Kulikovskiy, Glushchenko, Genkal et Kociolek [7]. A comprehensive review and revision of diatoms from Lake Baikal was published in the 2010s [2,4], in which many monoraphid taxa were reported and illustrated, both previously known and new.…”

Achnanthidium tinea sp. nov. – a new monoraphid diatom (Bacillariophyceae) species, described on the basis of molecular and morphological approaches

“…Taxonomy within the genus Achnanthidium is a rather complicated issue. Species boundaries are often not clear enough due to the fact that morphological features alone may not be sufficient to unequivocally identify species, and because values of quantitative features often overlap in similar species, further complicating their separation (Kulikovskiy et al 2016a;2020b;Jahn et al 2017;Tseplik et al 2020). These problems require extensive molecular research, both while describing new species and while studying species already known to science.…”

“…These problems require extensive molecular research, both while describing new species and while studying species already known to science. At present, the Achnanthidium genus includes about two hundred species (Kociolek et al 2020b). Molecular data is available for very few taxa, and correct identification of the representatives of this genus based only on morphological features is often difficult (Kulikovskiy et al 2014(Kulikovskiy et al , 2016aAndreeva et al 2016;Maltsev and Kulikovskiy 2017;Maltsev et al 2018Maltsev et al , 2019.…”