MOLECULAR PHYLOGENY OF ANTARCTIC PRASIOLA (PRASIOLALES, TREBOUXIOPHYCEAE) REVEALS EXTENSIVE CRYPTIC DIVERSITY¹

Abstract

Trebouxiophytes of the genus Prasiola are well known in Antarctica, where they are among the most important primary producers. Although many aspects of their biology have been thoroughly investigated, the scarcity of molecular data has so far prevented an accurate assessment of their taxonomy and phylogenetic position. Using sequences of the chloroplast genes rbcL and psaB, we demonstrate the existence of three cryptic species that were previously confused under Prasiola crispa (Lightfoot) Kützing. Genuine P. crispa occurs in Antarctica; its presence was confirmed by comparison with the rbcL sequence of the type specimen (from the Isle of Skye, Scotland). Prasiola antarctica Kützing is resurrected as an independent species to designate algae with gross morphology identical to P. crispa but robustly placed in a separate lineage. The third species is represented by specimens identified as P. calophylla (Carmichael ex Greville) Kützing in previous studies, but clearly separated from European P. calophylla (type locality: Argyll, Scotland); this alga is described as P. glacialis sp. nov. The molecular data demonstrated the presence of P. crispa in Maritime and Continental Antarctica. P. antarctica was recorded from the Antarctic Peninsula and Shetland Islands, and P. glacialis from the Southern Ocean islands and coast. Such unexpected cryptic diversity highlights the need for a taxonomic reassessment of many published Antarctic records of P. crispa. The results also indicate that marine species of Prasiola form a well-supported monophyletic group, whereas the phylogenetic diversity of freshwater species is higher than previously suspected (at least three separate lineages within the genus include species living in this type of environments).

Molecular and morphological diversity of Zygnema and Zygnemopsis (Zygnematophyceae, Streptophyta) from Svalbard (High Arctic)

“…In general, application of molecular methods in morphologically uniform protists usually reveals hidden diversity on various levels, depending on the selected marker(s) (e.g. Nemjová et al ., 2011; Moniz et al ., 2012; Heesch et al ., 2016). …”

“…For example, Antarctic and Arctic endemites are common within diatom species complexes (Souffreau et al ., 2013; Kociolek et al ., 2017; Pinseel et al ., 2017). Antarctic microchlorophytes (De Wever et al ., 2009) or Prasiola (Moniz et al ., 2012) also possess endemic lineages. Typically, different species within a single protist genus may exhibit contrasting distribution patterns (Heesch et al ., 2016; Ryšánek et al ., 2016).…”

“…Prasiola crispa (Lightfoot) Kützing (Trebouxiophyceae, Chlorophyta) is very common in both the Arctic and Antarctic. Recent molecular investigations showed that the Antarctic morphospecies Prasiola crispa, in fact, comprises three cryptic species (Moniz et al ., 2012). Moreover, a similar study in the Arctic even revealed cryptic genera among Prasiolales (Heesch et al ., 2016).…”

Morphology and phylogenetic position of a freshwater Prasiola species (Prasiolales, Chlorophyta) in Korea

“…A total of 36 species have been reported in this genus, at least 14 of which are freshwater organisms (Moniz et al 2012b, Guiry andGuiry 2015).…”

“…The genus of leafy green algae, Prasiola Meneghini includes marine, terrestrial (mostly supralittoral), and freshwater species characterized by monostromatic blades generally expanding above and narrowing to a short stipitate region at the base (Rindi et al 2004, Moniz et al 2012a, 2012b, Guiry and Guiry 2015. A total of 36 species have been reported in this genus, at least 14 of which are freshwater organisms (Moniz et al 2012b, Guiry andGuiry 2015).…”