Asterionellopsis tropicalis (Bacillariophyceae): a new tropical species found in diatom accumulations

Abstract

The diatomAsterionellopsis glacialissensu latoforms high-density patches in the surf zone of somesandy beaches worldwide and was until recentlyconsidered a cosmopolitan species. With the recentdescription of four cryptic species, the identity ofspecimens found in these accumulations remainsuncertain. In this study, diatom patches weresampled from two sandy beaches of the Braziliancoast: one tropical (Futuro Beach, 3°S; 38°W) andone subtropical (Cassino Beach, 32°S; 52°W). Finestructure of frustules and the sequencing of threephylogenetic markers revealed the subtropicalstrains to beA. guyunusaeand the tropical strains tobe a new species, here described asAsterionellopsistropicalissp. nov.A. tropicaliswas differentiatedmorphologically by the number of striae in 10lmatthe foot pole and head (39–44; 38–45, respectively),fromA. lenisilicea(46–55; 46–64),A.maritima (46–51; 46–60), andA. thurstonii(42–58; 55–70). Thenumber of striae at the head region of thevalvocopula (10lm) helped to distinguishA. tropicalis(56–62) fromA. guyunusae(61–64), butA. tropicaliswas morphologically undistinguishablefromA. glacialis. The sequence divergence fromother identifiedAsterionellopsisspecies was 13%–16%(Cox1), 11%–12% (5.8S+ITS2) and 2%–6% (RbcL),andA. tropicalisformed a distinct monophyleticclade with high support in all analyzed phylogenetictrees (single or multi-locus). This work will aid inthe understanding of the ecological andphysiological diversity of diatom patches that arekey to the trophic webs of sandy beaches