Revision of Ardissoneaceae (Bacillariophyta, Mediophyceae) from Micronesian populations, with descriptions of two new genera, Ardissoneopsis and Grunowago, and new species in Ardissonea, Synedrosphenia and Climacosphenia

Christopher S Lobban; Matt P Ashworth; Terance Camacho; Daryl W Lam; Edward C Theriot

doi:10.3897/phytokeys.208.89913

Revision of Ardissoneaceae (Bacillariophyta, Mediophyceae) from Micronesian populations, with descriptions of two new genera, Ardissoneopsis and Grunowago, and new species in Ardissonea, Synedrosphenia and Climacosphenia

PhytoKeys. 2022 Sep 21:208:103-184. doi: 10.3897/phytokeys.208.89913. eCollection 2022.

Authors

Christopher S Lobban¹, Matt P Ashworth², Terance Camacho¹, Daryl W Lam³, Edward C Theriot²

Affiliations

¹ Division of Natural Sciences, University of Guam, Mangilao, GU 96923, Guam, USA.
² Department of Molecular Biosciences, The University of Texas at Austin, Austin, Texas, USA.
³ LSAMP Program, University of Guam, Mangilao, GU 96923, Guam, USA.

Abstract

Ardissonea was resurrected from Synedra in 1986 and was included as a genus by Round, Crawford and Mann ("The Diatoms") in its own Family and Order. They commented that there might be several genera involved since the type species of the genus possesses a double-walled structure and other taxa placed in Ardissonea have only a single-walled structure. Two other genera of "big sticks," Toxarium and Climacosphenia, were placed in their own Families and Orders but share many characters with Ardissoneaceae, especially growth from a bifacial annulus. Eighteen taxa (11 new species) from Micronesia were compared with the literature and remnant material from Grunow's Honduras Sargassum sample to address the concepts of Ardissonea and Ardissoneaceae. Phylogenetic and morphological analyses showed three clades within Ardissonea sensu lato: Ardissonea emend. for the double-walled taxa, Synedrosphenia emend. and Ardissoneopsis gen. nov. for single-walled taxa. New species include Ardissoneadensistriata sp. nov.; Synedrospheniabikarensis sp. nov., S.licmophoropsis sp. nov., S.parva sp. nov., and S.recta sp. nov.; Ardissoneopsisfulgicans sp. nov., A.appressata sp. nov., and A.gracilis sp. nov. Transfers include Synedrospheniacrystallina comb. nov. and S.fulgens comb. nov. Synedraundosa, seen for the first time in SEM in Grunow's material, is transferred to Ardissoneopsisundosa comb. nov. Three more genera have similar structure: Toxarium, Climacosphenia and Grunowago gen. nov., erected for Synedrabacillaris and a lanceolate species, G.pacifica sp. nov. Morphological characters of Toxarium in our region support separation of Toxariumhennedyanum and T.undulatum and suggest additional species here and elsewhere. Climacospheniamoniligera was not found but we clarify its characters based on the literature and distinguish C.soulonalis sp. nov. from it. Climacospheniaelongata and a very long, slender C.elegantissima sp. nov., previously identified as C.elongata, were present along with C.scimiter. Morphological and molecular phylogenetics strongly suggested that all these genera belong in one family and we propose to include them in the Ardissoneacae and to reinstate the Order Ardissoneales Round.

Keywords: Ardissoneales; Grunow; Mediophyceae; Toxariales; Western Pacific; biodiversity; coral reefs; systematics.

Christopher S. Lobban, Matt P. Ashworth, Terance Camacho, Daryl W. Lam, Edward C. Theriot.

Grants and funding

Terance Camacho was a 2019 intern supported by the NSF-funded U. Guam Louis Stokes Alliances for Minority Participation (LSAMP) Islands of Opportunity grant and worked on the early stages of imaging and analysis. The new SEM and later stages of imaging and write-up of this project were supported by the National Science Foundation award No. OIA-1946352, RII Track-1: Guam Ecosystems Collaboratorium for Corals and Oceans (GECCO). Financial support for SEM and sequencing efforts at the University of Texas at Austin was provided by the Harold C. and Mary D. Bold Regents Professorship of Cryptogamic Botany (Phycology) provided to ECT.