DNA barcoding reveals cryptic diversity, taxonomic conflicts and novel biogeographical insights in Cystoseira s.l. (Phaeophyceae)

Este artículo contiene 26 páginas, 8 figuras, 2 tablas.Cystoseira sensu lato (s.l.) – encompassing the genera Cystoseira sensu stricto (s.s.), Ericaria and Gongolaria – is a diverse group of forest-forming brown macroalgae endemic to the warm-temperate North-east Atlantic. These algae have immense biogeographic and ecological significance and have been experiencing recent regional declines. Most Cystoseira s.l. display important morphological plasticity and can be confused with similar species. Therefore, species boundaries, geographic ranges and phylogenetic affinities remain imprecise for most. In the face of persistent taxonomic difficulties, several authors underlined the necessity for new molecular-based approaches, but studies so far lacked representativity, resolution and standardization. To fill in these gaps, in this study we sequenced a comprehensive collection of Cystoseira s.l. spanning its entire North-east Atlantic range for a ~1200 bp cox1 barcode, and sequenced selected individuals representing major genetic entities for a few additional plastid markers. Phylogeographic, phylogenetic and species delimitation methods revealed 27 Molecular Operational Taxonomic Units, including unaccounted cryptic diversity, and elucidated with unprecedented resolution species compositions and phylogenetic relationships within each genus. Some entities within the lineages Cystoseira compressa/humilis, Ericaria brachycarpa/crinita, E. selaginoides and tophulose Gongolaria, as well as among free-living algae, conflicted with a priori taxonomic assignments, and required the redefinition, reinstatement and recognition of new taxa. For some, diagnostic mutations and biogeography were more useful for species identifications than morphological characters or conventional barcoding gaps. A few species showed narrow geographic ranges and others were the sole representatives of their respective lineages. Several sister-species showed Atlantic vs Mediterranean complementary ranges. Phylogenetic signal of cox1 was nevertheless insufficient to confidently determine patterns of lineage splitting in several lineages and species complexes and did not improve significantly with additional plastid markers. We discuss novel systematics and biogeography insights considering the advantages and shortcomings of the barcoding approach employed, and how this comprehensive baseline study can be expanded to address multiple questions still left unanswered.This study was funded by the Portuguese Foundation for Science and Technology (FCT) through UIDB/04326/2020, UIDP/04326/2020 and LA/P/0101/2020, EU BiodivRestore253 (FCT: DivRestore/0013/2020), DL 57/2016/CP1361/ CT0010 (to JN), IF/01640/2015 (to PA) and SFRH/BSAB/ 150485/2019 (to EAS). JN has received funding from H2020 (EU) under grant agreement No 730984, Assemble Plus, DMF from Portuguese government grant Fundo Azul under the Seaforest Portugal Project (FA_06_2017_067), and EAS from a Pew Marine Fellowship. Sampling in West Africa was funded by projects MARAFRICA: FCTAGA-KHAN/540316524/2019, ‘Survie des Tortues Marines’ PRCM/STM POOOA4/OA9 by PRCM (Partenariat Régional pour la Conservation de la zone côtière et Marine en Afrique de l’Ouest) and ‘PNBA-site emblématique pour les tortues’ granted to the National Park of the Banc d’Arguin. BS was funded by AFRIMED Project, id EASME/EMFF/2017/1.2.1.12/S4/01/SI2.789059. DS has received funding from University of Catania in the frame of “PiaCeRi-Piano Incentivi per la Ricerca di Ateneo 2020-22, linea di intervento 2.Peer reviewe

Rhodolith occurrences in the Azores (central north Atlantic) between 1998 and 2018. EMODNET Biology dataset:IMAR-Institute of Marine Research, University of the Azores, Portugal; (2021):

Rhodoliths is a general term used to designate non-geniculate coralline red algae (Rhodophyta) that live unattached (Riosmena-Rodríguez, 2017). The term is used here to encompass (i) branched free-living coralline algae devoid of an evident nucleus, but also (ii) nucleated nodules where the biogenic calcium carbonate deposit around the core represents >50%, as well as (iii) “coated grains” where the core is larger than the algal carbonate component

Black coral occurrences on the Azores shelves (central north Atlantic) from 1991 to 2019

Black corals are antipatharian corals that occur from sublittoral to abyssal depths on hard, mixed and soft substrates. Under favourable conditions, some black coral species form dense stands known as black coral gardens which create habitat for a variety of associated specie

DNA barcoding reveals cryptic diversity, taxonomic conflicts and novel biogeographical insights in Cystoseira s.l. (Phaeophyceae)

Cystoseira sensu lato (s.l.) – encompassing the genera Cystoseira sensu stricto (s.s.), Ericaria and Gongolaria – is a diverse group of forest-forming brown macroalgae endemic to the warm-temperate North-east Atlantic. These algae have immense biogeographic and ecological significance and have been experiencing recent regional declines. Most Cystoseira s.l. display important morphological plasticity and can be confused with similar species. Therefore, species boundaries, geographic ranges and phylogenetic affinities remain imprecise for most. In the face of persistent taxonomic difficulties, several authors underlined the necessity for new molecular-based approaches, but studies so far lacked representativity, resolution and standardization. To fill in these gaps, in this study we sequenced a comprehensive collection of Cystoseira s.l. spanning its entire North-east Atlantic range for a ~1200 bp cox1 barcode, and sequenced selected individuals representing major genetic entities for a few additional plastid markers. Phylogeographic, phylogenetic and species delimitation methods revealed 27 Molecular Operational Taxonomic Units, including unaccounted cryptic diversity, and elucidated with unprecedented resolution species compositions and phylogenetic relationships within each genus. Some entities within the lineages Cystoseira compressa/humilis, Ericaria brachycarpa/crinita, E. selaginoides and tophulose Gongolaria, as well as among free-living algae, conflicted with a priori taxonomic assignments, and required the redefinition, reinstatement and recognition of new taxa. For some, diagnostic mutations and biogeography were more useful for species identifications than morphological characters or conventional barcoding gaps. A few species showed narrow geographic ranges and others were the sole representatives of their respective lineages. Several sister-species showed Atlantic vs Mediterranean complementary ranges. Phylogenetic signal of cox1 was nevertheless insufficient to confidently determine patterns of lineage splitting in several lineages and species complexes and did not improve significantly with additional plastid markers. We discuss novel systematics and biogeography insights considering the advantages and shortcomings of the barcoding approach employed, and how this comprehensive baseline study can be expanded to address multiple questions still left unanswered. HIGHLIGHTS Identification of major genetic entities of Cystoseira s.s., Ericaria and Gongolaria.A comprehensive reference cox1 barcode library for Cystoseira s.l.Updated systematics and biogeography of Cystoseira s.l. Identification of major genetic entities of Cystoseira s.s., Ericaria and Gongolaria. A comprehensive reference cox1 barcode library for Cystoseira s.l. Updated systematics and biogeography of Cystoseira s.l

DNA barcoding reveals cryptic diversity, taxonomic conflicts and novel biogeographical insights in Cystoseira s.l. (Phaeophyceae)

Cystoseira sensu lato (s.l.) – encompassing the genera Cystoseira sensu stricto (s.s.), Ericaria and Gongolaria – is a diverse group of forest-forming brown macroalgae endemic to the warm-temperate North-east Atlantic. These algae have immense biogeographic and ecological significance and have been experiencing recent regional declines. Most Cystoseira s.l. display important morphological plasticity and can be confused with similar species. Therefore, species boundaries, geographic ranges and phylogenetic affinities remain imprecise for most. In the face of persistent taxonomic difficulties, several authors underlined the necessity for new molecular-based approaches, but studies so far lacked representativity, resolution and standardization. To fill in these gaps, in this study we sequenced a comprehensive collection of Cystoseira s.l. spanning its entire North-east Atlantic range for a ~1200 bp cox1 barcode, and sequenced selected individuals representing major genetic entities for a few additional plastid markers. Phylogeographic, phylogenetic and species delimitation methods revealed 27 Molecular Operational Taxonomic Units, including unaccounted cryptic diversity, and elucidated with unprecedented resolution species compositions and phylogenetic relationships within each genus. Some entities within the lineages Cystoseira compressa/humilis, Ericaria brachycarpa/crinita, E. selaginoides and tophulose Gongolaria, as well as among free-living algae, conflicted with a priori taxonomic assignments, and required the redefinition, reinstatement and recognition of new taxa. For some, diagnostic mutations and biogeography were more useful for species identifications than morphological characters or conventional barcoding gaps. A few species showed narrow geographic ranges and others were the sole representatives of their respective lineages. Several sister-species showed Atlantic vs Mediterranean complementary ranges. Phylogenetic signal of cox1 was nevertheless insufficient to confidently determine patterns of lineage splitting in several lineages and species complexes and did not improve significantly with additional plastid markers. We discuss novel systematics and biogeography insights considering the advantages and shortcomings of the barcoding approach employed, and how this comprehensive baseline study can be expanded to address multiple questions still left unanswered. HIGHLIGHTS Identification of major genetic entities of Cystoseira s.s., Ericaria and Gongolaria.A comprehensive reference cox1 barcode library for Cystoseira s.l.Updated systematics and biogeography of Cystoseira s.l. Identification of major genetic entities of Cystoseira s.s., Ericaria and Gongolaria. A comprehensive reference cox1 barcode library for Cystoseira s.l. Updated systematics and biogeography of Cystoseira s.l