Pyropia plicata sp. nov. (Bangiales, Rhodophyta): naming a common intertidal alga from New Zealand

Abstract A commonly found red alga of the upper intertidal zone of New Zealand rocky coasts is described for the first time as Pyropia plicata sp. nov. This species has been incorrectly known as Porphyra columbina Mont. (now Pyropia columbina (Mont.) W.A.Nelson) for many years. Pyropia plicata is widespread and common, and it is readily distinguished from other species of bladed Bangiales in New Zealand by its distinctive morphology, with pleated blades attached by a central rhizoidal holdfast.


Introduction
For many years the most commonly found and widespread species of bladed Bangiales in New Zealand has been incorrectly known as Porphyra columbina Mont. Based on material collected from the New Zealand subantarctic Auckland Islands (Montagne 1842(Montagne , 1845, Porphyra columbina was the fi rst species in the order described from the New Zealand region. Th e name P. columbina has been applied to specimens with widely ranging growth forms and colour states found in diverse habitats from subantarctic to warm temperate areas of New Zealand, Australia, and South America (e.g.
pretations of the species concept in New Zealand (e.g. Laing 1928, Levring 1955, Chapman 1969, the name P. columbina in New Zealand has been generally applied to a common species with a very distinctive rosette-like morphology and deeply folded or pleated blades, found in the upper intertidal zone of mainland shores, as treated and illustrated in Nelson and Conroy (1989) and Adams (1994: p. 143). Th is species was assigned the code "ROS54" by Broom et al. (1999) and has been referred to by this code in a number of subsequent publications (e.g. Hemmingson and Nelson 2002, Jones et al. 2004, Nelson et al. 2006, Sutherland et al. 2011. Th e combination of targeted collections of members of the Bangiales from throughout the New Zealand region, and analyses of sequence data coupled with morphological and anatomical investigations, has revealed many undescribed species around the archipelago (e.g. Broom et al. 1999, Nelson et al. 2001, Nelson and Broom 2005, Nelson et al. 2006. Recent collections of bladed Bangiales from subantarctic regions revealed at least four distinct species present on the Auckland Islands. With these data and specimens, Nelson and Broom (2010) were able to reexamine the original concept of P. columbina and the subsequent interpretations and applications of this name. Th ey concluded that P. columbina is not conspecifi c with the mainland rosette-forming species referred to as ROS54, but rather it is primarily distributed in cold temperate areas of the southern hemisphere. Th ey confi rmed its presence on Auckland, Campbell, Antipodes, Chatham and Falkland Islands, and established that it is rarely present on mainland New Zealand (i.e. only one collection from the southern coast of the South Island from more than 700 samples of bladed Bangiales sequenced from the New Zealand region).
Although the monophyly of the Bangiales had been shown to be well supported by a number of studies (e.g. Oliveira and Bhattacharya 2000, Müller et al. 2001, Saunders and Hommersand 2004, Oliveira et al. (1995) demonstrated that neither of the two genera traditionally recognised in the order on the basis of gametophyte morphology ( Bangia for fi laments, Porphyra for foliose species) were monophyletic. A series of subsequent studies (e.g. Müller et al. 1998, Broom et al.1999, Oliveira and Bhattacharya 2000, Lindstrom and Fredericq 2003, Nelson et al. 2006, Lindstrom 2008 provided further evidence of the diversity within the order and the need for segregate genera. Sutherland et al. (2011) revised the order Bangiales, recognising 15 genera of which eight are foliose. Porphyra columbina is now placed in the genus Pyropia ( Py. columbina (Mont.) W.A. Nelson).
Th e rosette-forming species of Pyropia , previously referred to as ROS54, is formally described here.

Materials and methods
Th is study is based on specimens of foliose Bangiales collected from throughout the New Zealand region, particularly from the North, South and Chatham Islands from 1987 to 2012, as part of diversity surveys. Voucher material is deposited in the her-barium of the National Museum of New Zealand Te Papa Tongarewa (WELT, Th iers 2012). Selected examples have been used for molecular sequence analyses (e.g. Broom et al. 1999, Nelson et al. 2006, Sutherland et al. 2011) as well as cell wall polysaccharide investigations (Hemmingson and Nelson 2002). Terminology for packets of reproductive cells follows Nelson et al. (1999). Distribution. New Zealand -North I., South I., Chatham Is. Sequence data. GenBank -nSSU -AF136426, rbc L -GU046410, voucher specimen = WELT A024408.
Etymology. plicata -folded or pleated. Description. Th e blades of Pyropia plicata are deeply folded and when fully extended are seen to have a circular to oval shape. Th e blades are very variable in size, generally in the range of 4-12 cm in diameter although reproductively mature thalli have been found to range from 1.5 cm through to 42 cm in diameter. Th e thalli are attached to rock substrata by a centrally located holdfast, made up of rhizoids extending from cells in the lower (central) area of the blade. Th e thalli are robust and very strongly attached to rock substrata in the upper intertidal zone of rocky open coasts ( Figure 2). Th alli are primarily purple to grey in colour, but they become bleached particularly in summer and autumn and become khaki to yellow-green particularly on the upper edges.
Th alli are monostromatic and monoecious. Sterile regions of the blades are ca. 50-55 μm thick and the margin of the blade has a ragged or irregular appearance bordered by several layers of small pale cells (Figure 3). Fertile regions of the blade develop around the margins with sterile cells intermixed with patches of spermatangia and presumed zygotosporangia (Figure 4).
In the early stages of development spindle-shaped carpogonia form trichogynes on both sides of the blade, in marked contrast to the box-like shape of the neighbouring sterile cells ( Figure 5). Blades increase in thickness to ca. 85-110 μm in zygotosporangial regions ( Figure 6) and ca. 60-70 μm in mature spermatangial regions ( Figure 7). Th e zygotosporangia when mature are deep red and the packets vary in size, becoming lozenge shaped at maturity with divisions up to a/8, b/8, c/8 ( Figure  6). Th e spermatangial patches become golden as they develop and when mature are divided into packets ca. a/2, b/2, c/8 (Figure 7). Spermatia and zygotospores are usually released before reaching the maximum division formulae.
Typically Pyropia plicata is found on the upper intertidal shores of open coasts on rocky substrata. It has not been found growing epiphytically and is uncommon in sheltered areas. Th e deep pleats and central attachment of P. plicata enable the retention of moisture between the folds in the blade. Th is morphology would appear to be advantageous in the upper intertidal habitats where it is found, as this species can be out of water for periods of up to eight hours between tidal cycles. Th e outer part of a clump of P. plicata may be dried with a cellophane-like appearance yet within the folds, parts of the blade remain wet.
Pyropia plicata shows no particular seasonal trends in its distribution, with reproductively mature specimens collected throughout the year. Collections of this species have been made from the northern tip of the North Island, through to areas on the south western and south eastern South Island, as well as on the Chatham Islands. It has not been found on the Th ree Kings Islands, Stewart Island, or any of the New Zealand subantarctic islands.
Distinctive features: Pyropia plicata can be distinguished from other New Zealand species of bladed Bangiales by a number of distinctive features. It is the only species of Pyropia present on mainland shores with a marked rosette-like growth form. Although the ribbon-like blades of P. cinnamomea may become eroded with age, the basal position of the holdfast in this species diff ers from P. plicata . In addition, these two species can be distinguished by colour, and also by the division formulae of zygotosporangia. On intertidal shores P. plicata is characteristically found in the high intertidal but below the position occupied by Clymene coleana (W.A.Nelson) W.A.Nelson from which it can be easily distinguished. Clymene coleana has fi nely divided fi nger-like lobes rather than the continuous circular to oval deeply pleated blade of P. plicata . Although both of these species have a predominantly grey colour in winter months, they bleach to diff erent colours in bright light, with C. coleana becoming golden compared with the khaki colour of P. plicata . In addition the zygotosporangia and spermatangia are arranged in separate areas of the blade in C. coleana rather than being intermixed in P. plicata .

Discussion
A major problem in Bangiales taxonomy has been the incorrect application of names, making studies of the ecology and comparative physiology of species exceedingly diffi cult. Th e need for molecular sequence data in Bangiales taxonomic studies has been emphasised by many authors over the past decade in order to clarify species concepts as well as the phylogenetic relationships amongst taxa (e.g. Lindstrom andFredericq 2003, Nelson et al. 2006). Such data have led to the discovery of cryptic taxa amongst species with very similar morphologies (e.g. Brodie and Irvine 1997, Broom et al. 2002, Neefus et al. 2002, Lindstrom and Fredericq 2003, Brodie et al. 2007, Lindstrom 2008. Descriptions of foliose members of the Bangiales have traditionally emphasised features such as blade shape and size, colour, and texture, in addition to division formulae for spermatangia and phyllosporangia, number of cell layers, number of plastids (e.g. summarised in Lindstrom and Cole 1993). In addition to external morphology (including marginal structure) and reproductive features, Miyata and Kikuchi (1997) also found seasonality and habitat (whether species are epiphytic or epilithic) to be have value taxonomically when distinguishing species of bladed Bangiales in Japan.
As circumscribed by Sutherland et al. (2011), the genus Pyropia encompasses species displaying a wide range of morphological forms, a wide colour spectrum and at least four diff erent types of arrangements of reproductive regions on sexual thalli. Th is genus is the most speciose of the Bangiales, and it also has the widest geographic distribution, with species occurring from tropical to cold temperate waters. Pyropia plicata has been recognised in the fl ora of mainland New Zealand for a long time, but has remained without a formal name as a result of confusion over the application of the name P. columbina . Th is situation was able to be clarifi ed only after material collected in the subantarctic islands became available for study . Although mature thalli of Pyropia plicata range widely in size and also in colour, the fundamental shape of the blade, and the arrangement of reproductive regions are consistent, and enable this species to be readily distinguished. Within the genus Pyropia , P. plicata is grouped within a clade of at least 15 southern hemisphere species. Th e majority of these species are currently undescribed but the clade includes P. virididentata , P. cinnomomea and P. columbina , Sutherland et al. 2011.