Evolutionary relationships between the varieties of green algae Pediastrum boryanum and P. duplex s.l. (Chlorophyceae, Hydrodictyaceae)

Abstract

The infraspecific relationships of the two most variable species, Pediastrum boryanum and P. duplex s.l. identified on the basis of morphological criteria, have been poorly studied so far. The present study focused on 12 original strains isolated from Polish water bodies and 29 strains from the GenBank database, which represent P. boryanum, P. duplex s.l. varieties and other morphologically similar taxa, against the background of 14 other strains of the family Hydrodictyaceae. In order to estimate the level of congruence between the phylogeny and the classical taxonomic system based on morphological criteria, the strains of P. boryanum and P. duplex s.l., and other morphologically similar taxa were subjected to parallel phylogenetic analyses applying Bayesian and Maximum Likelihood methods to combined molecular data (26S rDNA and rbcL cpDNA) and morphological analyses based on light and scanning electron microscopy, and iconographic documentation of almost all strains published elsewhere. The gene topologies revealed many discrepancies in the morphological features used to delimit the analysed taxa. The polyphyly of both P. boryanum and P. duplex s.l. was confirmed. Pseudopediastrum boryanum var. cornutum (formerly P. boryanum var. cornutum) formed a well supported monophyletic clade, whereas other varieties, including var. boryanum, brevicorne and longicorne, proved to be complex taxa. Previous description of Lacunastrum gracillimum (formerly P. duplex var. gracillimum) was well supported. A clade composed mostly of European strains identified as P. duplex var. rugulosum should be regarded as this taxon, whereas clades containing strains exhibiting P. duplex var. rugulosum-like morphology represent new taxa. Taxonomical changes within both P. boryanum and P. duplex s.l. are required on the basis of a higher number of strains and detailed morphometric data.

Assessing morphological congruence in Dinobryon species and their stomatocysts, including a newly established Dinobryon pediforme–stomatocyst connection

“…www.nature.com/scientificreports www.nature.com/scientificreports/ has previously been found in many microscopic algae [51][52][53] . However, congruence between morphology and molecular phylogeny has been observed in the chrysophyte genus Synura 54 .…”

Integrative Approach Helps Clarify Confusing Taxonomy of the Pseudopediastrum boryanum Species Complex (Chlorophyceae), Including Recognition of five Distinct Species

“…Accession numbers in boldface font indicate new sequences of 26S rDNA and rbcL cpDNA obtained for this study. Other sequences were previously published by a Buchheim et al Lenarczyk and Saługa (2018).…”

“…2005, McManus and Lewis 2005, 2011, Jena et al. 2014, Lenarczyk and McManus 2016, Lenarczyk and Saługa 2018). So far, only a low number of Ps.…”

“…Because of its characteristic star-shaped appearance, Pseudopediastrum boryanum is easy to identify and, thus, well known to many phycologists. A coenobium (a specific type of cell colony) of this species typically lacks perforations and has marginal cells with two projections (lobes ended with hyaline processes), polygonal inner cells, and a reticulate wall ornamentation composed of granules situated regularly in the nodes of a triangular mesh (Lenarczyk and Saługa 2018).…”

“…boryanum morphology. Lenarczyk and Saługa (2018) studied a relatively rich collection of Ps. boryanum strains, but their morphological analysis was based exclusively on qualitative descriptions of morphological features, like the size of coenobia and perforations, the shape of marginal cells, and the type of cell wall surface.…”