Integrative approach reveals four new cryptic species in the genus Gayliella (Ceramiaceae, Rhodophyta)¹

Abstract

The filamentous red algal genus Gayliella, typified by G. flaccida, was segregated from Ceramium for a group of epiphytic species on the basis of morphological data and molecular phylogenetic analyses. However, while the genus was well investigated in some geographical areas, the treatment of the Brazilian taxa “Ceramium flaccidum” and “C. dawsonii” was incomplete and they were not transferred to Gayliella due to the problematic status of the specific epithets. Brazilian “C. flaccidum” did not fit within the circumscription of Gayliella flaccida; Brazilian “C. dawsonii” was positioned in three distinct lineages, none of which corresponded to known Gayliella species. Since the establishment of Gayliella, there has been no re‐evaluation of Brazilian species, so this study revises the genus in Brazil using molecular and morphological data. Brazilian “C. flaccidum”, “C. dawsonii”, and other Brazilian collections were investigated by an integrative approach using phylogenetic analysis, genetic divergence, two species delimitation methods using three molecular markers (rbcL, cox1, and partial LSU), and comparative morphological and quantitative analyses. This molecular‐assisted alpha taxonomy (MAAT) analysis placed Brazilian samples in five distinct well‐supported lineages. For these, we propose a new combination, Gayliella dawsonii comb. nov. (lineage 2), based on analysis of type specimens and molecular data obtained from specimens collected near the type locality, and four new species: Gayliella ardissonei sp. nov. (“Ceramium flaccidum” from Brazil), G. iemanja sp. nov. (“C. dawsonii” lineage 3), G. tamoiensis sp. nov., and G. jolyana sp. nov. (“C. dawsonii” lineage 1).

Phylogenetic Analysis of the Red Algal Tribe Ceramieae Reveals Multiple Morphological Homoplasies but Defines New Genera

“…Gayliella is strongly supported in all analyses (Figs 2; 3; S2-S4) and it is well-circumscribed (Cho et al . 2008a; Gomes et al . 2020; Huaqiang et al .…”

“…2006) showed 9% and 23% genetic divergence in rbc L and COI-5P, respectively. Combinations of characters can nevertheless define clades and genera, such as Gayliella (Gomes et al . 2020).…”

“…— Ceramium nitens (Ceramiaceae, Rhodophyta), an uncommon species from Brazil. Revista Brasileira de Botânica 24: 359-63. Gomes F. P., Maggs C. A. & Barros-Barreto M. B.…”

On the track of unknown algae

“…An operational definition of cryptic species is “two or more distinct species that are erroneously classified (and hidden) under one species name” (Bickford et al., 2007, p. 148). In algal research over the last two decades, the widespread use of molecular systematics, DNA barcoding, and automated barcode gap recognition has identified cryptic species in many groups of seaweeds (e.g., Gomes et al., 2020; Jesús et al., 2019). Often building on results from the early phases of molecular systematics (see Maggs et al., 2008), approaches range from long‐term global studies of particular taxa to geographically circumscribed sampling campaigns.…”

“…Gomes et al. 's (2020) study of six tiny cryptic Gayliella species from Brazil resulted in the proposal of four new species and a new combination that required epitypification. Determining correct names for all 12 cryptic species previously attributed to Polysiphonia scopulorum worldwide (Díaz‐Tapia & Verbruggen, 2024) is therefore a major achievement given the complexity of the phylogenetic and taxonomic information.…”