Molecular systematics of Jania species (Corallinales, Rhodophyta) from south-eastern Australia based on cox 1 and psbA DNA sequence analyses Author Macagnan, Leonardo B. Universidade Federal de Santa Catarina, Centro de Cie ̂ ncias Biolo ́ gicas, Departamento de Bota ̂ nica, Floriano ́ polis, SC 88040 - 900, Brazil Author Venturin, Claudia S. Universidade Federal de Santa Catarina, Centro de Cie ̂ ncias Biolo ́ gicas, Departamento de Bota ̂ nica, Floriano ́ polis, SC 88040 - 900, Brazil Author Azevedo, Marina L. Universidade Federal de Santa Catarina, Centro de Cie ̂ ncias Biolo ́ gicas, Departamento de Bota ̂ nica, Floriano ́ polis, SC 88040 - 900, Brazil Author Harvey, Adela La Trobe University, Department of Environment and Genetics, Plenty Road, Bundoora, Vic. 3083, Australia Author Gurgel, C. Frederico D. Universidade Federal do Rio de Janeiro, Instituto de Biodiversidade e Sustentabilidade - NUPEM, Macaé, RJ 27965 - 045, Brazil & Former address: The University of Adelaide, School of Biological Sciences, Adelaide SA 5000, Australia; State Herbarium of South Australia, Department for Environment and Water, SA Government, PO Box 2732, Kent Town, SA 5071, Australia; & SARDI Aquatic Sciences, Department of Primary Industries & Regions, SA Government, PO Box 120, Henley Beach SA 5022, Australia. Corresponding author: fredgurgel @ nupem. ufrj. br text Phytotaxa 2023 2023-07-28 606 2 87 103 http://dx.doi.org/10.11646/phytotaxa.606.2.1 journal article 10.11646/phytotaxa.606.2.1 1179-3163 8202610 Jania crassa J.V.Lamouroux —Woelkerling et al. (2015a) reported J. verrucosa as a heterotypic synonym of J. crassa . Jania crassa has been traditionally reported from subtropical and tropical coasts around the world, including Australia (Womersley and Johansen 1994 , Woelkerling et al. 2015a), New Zealand ( Woelkerling and Nelson 2004 ), Brazil ( Wallace et al. 2003 ), and China ( Xia et al. 2013 ). Our psb A results confirmed that all Australian, Spain and New Zealand J. crassa specimens form a monophyletic group with maximum phylogenetic support. The results here corroborate the current biogeographic hypothesis that J. crassa is widely distributed across the world. Due to the fact that different researchers have been using different markers to study Jania systematics, we were unable to determine whether one of the two South African J. crassa cox 1 clades from Kogame et al. (2017) belong to or are phylogenetically related to the Australian, New Zealand and Spain J. crassa psb A clade. A psb A singleton from New Zealand ( MK 413379), morphologically identified as J. crassa by Twist et al. (2019) , is phylogenetically unrelated to the main J. crassa clade ( Fig. 3 ). If not a case of simple mix-up or misidentification, MK 413379 may represent a rare new endemic species from New Zealand ( Fig. 4 ). Future examination of herbarium specimens from the same locality as the MK 413379 specimen may clarify this issue (outside the scope of this study). Psb A and cox 1 were not able to determine the phylogenetic position of J. crassa singletons MK 413379 and LC071784, respectively, due to the lack of phylogenetic support, with the exception of the psb A Bayesian tree (Figs 1,2) which showed high phylogenetic support for MK 413379 as a sister species to Jania cf. rosea also from New Zealand . Lugilde et al. (2019) reported Jania longifurca Zanardini from specimens collected in northern Spain , Galicia , using morpho-anatomical and psb A phylogenetic analyses. We included their psb A sequences in our analyses. Our phylogenetic and SDM results showed that the population identified as J. longifurca from Atlantic Spain corresponds to the same entity as J. crassa from Australia and New Zealand identified by Harvey et al. (2020) and Twist et al. (2019) , respectively (Figs 3,4). It is likely that J. longifurca should be synonymized with J. crassa , however further analysis of topotype material of J. longifurca or the lectotype specimen of this species is required to support this systematic conclusion. The Lugilde et al. (2019) study convincingly showed how phenotypically plastic specimens of J. crassa can show high morphological variation related to the environment, e.g., deeper maërl or stable rocks substrate. Changes in J. crassa habit in Galicia was attributed to changes in substrate type, including associated microhabitat conditions that the specimens grew on. The atypical prostate morphology grows on mäerl beds and is characterized by thin intergenicula, irregular dichotomous branching, and the presence of secondary attachment discs. The typical longer, erect, robust form grows on intertidal and subtidal rock substrate. The great capacity of J. crassa to adapt its morphology to inhabit distinct local micro-habitats might be one reason why this species has been able to successfully colonize a wide geographic range and multiple oceans. The main and first morphological character used to start the morpho-anatomical identification key to species of Jania confirmed to occur in south-eastern Australia from Harvey et al. (2020) is whether the branching pattern is either (predominantly) dichotomous or pinnate. As documented by Lugilde et al. (2019) , J. crassa , as well as J. rosea from southern Australia (Gurgel, pers. observ.), can express both morphotypes, often on the same specimen. Such drastic phenotypic plasticity in a widely distributed species contributes to widespread species misidentifications in the literature. Future species identification, phylogenetic and taxonomic studies, classification proposals, and descriptions of new Jania species will ultimately rely on a mix of molecular data, supported and reinforced by detailed anatomical/morphological data.