Original paper
Achnanthales from Teahupo’o fringing reef (Tai’arapū, Society Archipelago, South Pacific): specificities and biogeography
Riaux-Gobin, Catherine; Witkowski, Andrzej; Coste, Michel; Jordan, Richard W.; Galzin, René
Nova Hedwigia Band 120 Heft 1-4 (2025), p. 419 - 454
66 references
published: Apr 30, 2025
published online: Jan 29, 2025
manuscript accepted: Sep 4, 2024
final revised version received: Aug 27, 2024
manuscript revision requested: Aug 27, 2024
manuscript received: Nov 10, 2023
DOI: 10.1127/nova_hedwigia/2025/0935
ArtNo. ESP050012031018, Price: 29.00 €
Abstract
Samples from Teahupo’o fringing reef, Tai‘arapū peninsula, Tahiti-iti (Society Archipelago, South Pacific), have a high species richness of benthic marine Achnanthales. Cocconeis adamantina sp. nov., a small-celled and abundant taxon, pertaining to the Loculatae section, has an SV similar to that of Cocconeis sp. 1 previously observed in Madagascar, but with RV uniseriate striae up to the margin and a constant morphology. A less abundant and larger member of the Loculatae, first observed in the South Pacific, is provisionally named herein as C. olympica. It is characterized by having an elliptic to discoid valve shape and areolae in the median sector of the SV with only one apical bar (as in C. scutellum f. decussata), whereas at the valve periphery, it shows secondary bars. The RV of the former taxon is different from that in C. scutellum f. decussata. A wide phenotypic plasticity may be associated with the Loculatae or a local endemism (small-scaled endemism), hypotheses that will only be disentangled via genetics. Campyloneis grevillei is common in Teahupo’o, while apparently absent in previous South Pacific collections. Campyloneis is a genus with morphological characters difficult to fix. Cocconeis testudo Giffen 1963, is here transferred to Campyloneis as C. testudo comb. nov. Among several rare and insufficiently documented taxa, a small Cocconeis may pertain to group 2B, previously defined as part of a complex comprising C. peltoides. The Achnanthales assemblage from Teahupo’o is particularly diverse, with several taxa ranked as morphs (or formae), pointing to the possible influence of local geology on the establishment and diversification of benthic diatoms, allowing for the differentiation of highly silicic environments (volcanic high islands with a more or less restricted coral reef), versus old and more calcic environments (such as atoll lagoons with low connection to the open ocean).
Keywords
morphs • endemism • diversity • geology • coral reef extension