Dual influence of terrestrial and marine historical processes on the phylogeography of the Brazilian intertidal red alga Gracilaria caudata

Abstract

In this study, we explored how past terrestrial and marine climate changes have interacted to shape the phylogeographic patterns of the intertidal red seaweed Gracilaria caudata, an economically important species exploited for agar production in the Brazilian north‐east. Seven sites were sampled along the north‐east tropical and south‐east sub‐tropical Brazilian coast. The genetic diversity and structure of G. caudata was inferred using a combination of mitochondrial (COI and cox2‐3), chloroplast (rbcL) and 15 nuclear microsatellite markers. A remarkable congruence between nuclear, mitochondrial and chloroplast data revealed clear separation between the north‐east (from 03° S to 08° S) and the south‐east (from 20° S to 23° S) coast of Brazil. These two clades differ in their demographic histories, with signatures of recent demographic expansions in the north‐east and divergent populations in the south‐east, suggesting the maintenance of several refugia during the last glacial maximum due to sea‐level rise and fall. The Bahia region (around 12° S) occupies an intermediate position between both clades. Microsatellites and mtDNA markers showed additional levels of genetic structure within each sampled site located south of Bahia. The separation between the two main groups in G. caudata is likely recent, probably occurring during the Quaternary glacial cycles. The genetic breaks are concordant with (i) those separating terrestrial refugia, (ii) major river outflows and (iii) frontiers between tropical and subtropical regions. Taken together with previously published eco‐physiological studies that showed differences in the physiological performance of the strains from distinct locations, these results suggest that the divergent clades in G. caudata correspond to distinct ecotypes in the process of incipient speciation and thus should be considered for the management policy of this commercially important species.

Phylogeography of Colpomenia sinuosa (Ectocarpales, Phaeophyceae) along the Brazilian coast

“…(2019) for Hypnea pseudomusciformis and Ayres‐Ostrock et al. (2019) for Crassiphycus caudatus . Marine phylogeographic studies in Brazil, using macroalgae as model organisms or otherwise, hypothesize the influence of distinct processes acting as barriers to gene flow along the Brazilian coast, such as (1) estuaries or the mouth of major rivers namely the Doce river, the São Francisco river, and the Amazon river (Floeter et al.…”

“…2019); (4) southern Bahia state as a climate refuge during glaciation maxima (Ayres‐Ostrock et al. 2019, Menezes et al. 2020); (5) the Cape Frio coastal upwelling (Cortinhas et al.…”

Barriers to gene flow along the Brazilian coast: a synthesis and data analysis

“…The first allozyme study was published in 1991 (Aron & Solé-Cava, 1991;Russo & Solé-Cava, 1991) and the last in 2018 (Pazoto, Ventura, Duarte, & Silva, 2018). Only four articles (6%) targeted autotrophic organisms, two terrestrial vascular plants (mangroves) and two red macroalgae, and two of them used chloroplast-encoded markers (Ayres-Ostrock et al, 2019;Mori, Zucchi, Sampaio, & Souza, 2015). Only one more recent article used the SNP technique (Siccha-Ramirez et al, 2018).…”

“…Populations in this area tend to retain new mutations and low genetic diversity, which is a signature of sudden population expansion (Grant & Bowen, 1998). Several studies reports this particular genetic pattern in the region such as fish species (da Silva et al, 2016;Machado et al, 2017;Santos et al, 2006), macroalgae species (Crassiphycus caudatus: Ayres-Ostrock et al, 2019;Hypnea pseudomusciformis : Nauer et al, 2019), marine vascular plants (Rhizophora spp. : Francisco et al, 2018), a cnidarian (Mussismilia hispida : Peluso et al, 2018), nemerteans (Ototyphlonemertes spp.…”

“…: Lazoski et al, 2011), crustaceans (Excirolana braziliensis : Hurtado et al, 2016, polychaetes (Perinereis spp. : Paiva et al, 2019), and red macroalgae (Crassiphycus caudatus : Ayres-Ostrock et al, 2019;Hypnea pseudomusciformis : Nauer et al, 2019).…”