LAUSR

Abstract A new species Temnogametum iztacalense sp. nov. (Zygnemataceae) was described using an integrative taxonomic approach. Material was collected between 2014–2019 from purple mats at the bottom of La Luna Lake, which is a shallow, well-oxygenated, acidic and ultraoligotrophic high mountain lake exposed to high levels of ultraviolet radiation. Morphological analysis revealed that the material belonged to the Zygnemataceae and contained mature zygospores of oblate-sphaeroidal shape; smooth and yellow exospores, finely punctate and brown mesospores, and thin hyaline endospores. Transmission electron microscopy showed vacuolization, wavy thylakoids and a large number of starch granules and plastoglobules. The topology of the concatenated 18S-rbcL tree using the Bayesian method separated T. iztacalense into an independent branch within the Zygnematales. The chromatographic profile of T. iztacalense revealed 20 compounds, the major ones being lutein (596.9 ± 20.9 mg g–1 algae) and β-carotene (171.4 ± 3.3 mg g–1 algae). This is the first reported phylogeny of Temnogametum isolated from this kind of lake based on 18S-rbcL sequences.