Corallina (Corallinales, Rhodophyta) from Tristan da Cunha and the Falkland Islands: implications for South Atlantic biogeography

Abstract

A molecular and morphological taxonomic study of Corallina (Corallinales, Rhodophyta) from Tristan da Cunha and the Falkland Islands revealed Corallina chamberlainiae J.Brodie & R.Mrowicki sp. nov. from both South Atlantic archipelagos, and Corallina cf. caespitosa only in the Falkland Islands. Analysis of mitochondrial COI-5P and plastid psbA resolved C. chamberlainiae as a distinct clade composed of specimens from Tristan and the Falkland Islands (COI-5P), in addition to two matching New Zealand samples (psbA). In psbA analyses, C. cf. caespitosa was close to two species from Japan (as C. pilulifera and C. melobesioides) but was separate from C. caespitosa sensu stricto from Britain and C. ferreyrae (isotype) from Peru. In COI-5P analyses, C. cf. caespitosa was in a clade with C. caespitosa (holotype) and close to, but distinct from, C. ferreyrae and an unidentified South African Corallina species. Application of the Automatic Barcode Gap Discovery (ABGD) and Poisson tree processes (bPTP) for COI-5P lumped C. chamberlainiae into one clade, whereas the Generalized Mixed Yule Coalescent (GMYC) model split it into two well-supported groups, one of which only contained Falkland Island specimens. All three models lumped C. cf. caespitosa with C. caespitosa. C. chamberlainiae closely resembles C. officinalis, the generitype, but is distinguished by smaller size and a more compressed thallus towards the apex. Corallina cf. caespitosa resembles C. caespitosa but is smaller and has fused, palm-like upper fronds. Neither of these taxa is conspecific with C. ferreyrae although C. caespitosa was recently synonymized with C. ferreyrae. C. chamberlainiae and C. cf. caespitosa occupy similar intertidal habitats to their respective, closely related counterparts C. officinalis and C. caespitosa. The results indicate cryptic diversity and suggest that there are many misidentified Corallina species. The paucity of South Atlantic studies of the Corallinales points to the need for a much greater taxonomic effort in this biogeographic region.

Type specimen sequencing, multilocus analyses, and species delimitation methods recognize the cosmopolitan Corallina berteroi and establish the northern Japanese C. yendoi sp. nov. (Corallinaceae, Rhodophyta)

“…We expand the distribution of this species recently described by Brodie et al. (2020) from the southern Atlantic (Falkland and Tristan da Cunha Islands) and New Zealand, to include central and southern Chile. Additionally, sequencing of the syntype material of Corallina officinalis var.…”

“…1), flabellate in specimens from the Falkland Islands (Brodie et al. 2020, figs. 12–16), and flagelliform (slender and whip‐like branches) in those from Peru (Dawson et al.…”

“…2009) versus 1–5 mm from Falkland Islands and Peru (Brodie et al. 2020), thalli with short fronds from the Falkland Islands with longer intergenicula and more numerous and compressed terminal intergenicula than populations from the UK (Brodie et al 2020), and thalli with a distinct midrib from California, USA (Dawson 1953). Our collections from Chile also showed a range of thallus variation (Fig.…”

Resolving some of the earliest names for Corallina species (Corallinales, Rhodophyta) in the North Pacific by sequencing type specimens and describing the cryptic C. hakodatensis sp. nov. and C. parva sp. nov.

“…2018), and more recently from southern hemisphere waters (Brodie et al. 2021, Calderon et al. 2021).…”

“…Molecular taxonomic reassessments have been published for Corallina species from the NE Atlantic Ocean and Mediterranean Sea (Robba et al 2006, Walker et al 2009, Brodie et al 2013, Williamson et al 2015, Pardo et al 2017, Yesson et al 2018, and more recently from southern hemisphere waters (Brodie et al 2021, Calderon et al 2021. Revisions have also occurred in the NE and NW Pacific, where four formerly recognized genera, Pachyarthron, Serraticardia, Marginisporum, and Yamadaia were placed in synonymy under Corallina by Hind et al (2014), Hind and Saunders (2013), and Martone et al (2012), respectively.…”