A collections-based approach to the species and their distribution based on the bladed Bangiales (Rhodophyta) of Iceland

Abstract An assessment of the 11 species of bladed Bangiales from Iceland in a collection of approximately 1770 specimens collected between 1883 and 2013 was undertaken by combining results from molecular analysis with examination of morphological variation in order to determine their distribution in detail. Seven of the species grow all around Iceland. Of the remaining four species, Porphyra linearis, P. dioica and Pyropia leucosticta have their northern limit of distribution along the southwestern and western part of the country, and Pyropia thulaea, an arctic species, only grows at the eastern coast, which is the coldest part of the coastline. Detailed reliable records of species distribution are important to detect future changes in the flora due to anthropogenic or natural environmental changes and have implications for conservation policy.


Introduction
The bladed Bangiales are a large, cosmopolitan group of red algae that were placed in the genus Porphyra until the revision of Sutherland et al. (2011).The morphological identification of these species has been regarded as highly problematic because of the difficulty of finding reliable morphological characters and the variation within and between species.On the basis of a two-gene phylogeny, Sutherland et al. (2011) split the genus into eight genera: Boreophyllum, Clymene, Fuscifolium, Lysithea, Miuraea, Porphyra, Pyropia and Wildemania.Since then an additional genus, Neothemis, has been discovered (Sánchez et al. 2015a,b).One of the consequences of this revision is that we are now in a position to re-evaluate local and regional Bangiales floras.Although the difficulty of distinguishing species remains, generic circumscriptions enable better placement at the generic level which in turn enables us to focus on species present at the regional and local level.
As a consequence of the difficulty in distinguishing species, names have been misapplied in different parts of the world (e.g.Porphyra umbilicalis, Brodie et al. 2008).This in turn causes a misinterpretation of the distribution of species.Reconstructing a biogeography of a species based on all literature reports can only be achieved if every record listed has been checked against a specimen and the identification verified.Determining species distributions requires confidence that specimens have been identified correctly, that these identifications can be verified, i.e. they can be revisited, and that reliable information exists on where each specimen was collected.A specimen represents an individual record of a particular species from a particular location at a particular point in time and any overall distribution will be inferred in the gaps.Here, we use the example of how collections can be used from a defined area, in this case the island of Iceland, to construct reliable distributions based on a robust understanding of species concepts in that region.We have based our taxonomy on a molecular study of the bladed Bangiales in Iceland undertaken to assess their diversity and based on rbcL and cox1 sequences selected from a collection of c. 750 specimens from 158 stations (Mols-Mortensen et al. 2012).This study revealed that there were 11 species (Table 1), five more than the number previously reported by Gunnarsson and Jónsson (2002): Porphyra amplissima, P. dioica, P. linearis, P. miniata, P. purpurea, P. umbilicalis), and belonging to four of the nine genera of bladed Bangiales: Boreophyllum, Porphyra, Pyropia and Wildemania.
The isolated location of Iceland in the northern North Atlantic makes it suitable for detailed studies of species distribution.The coastal sea around Iceland is characterized by warm temperatures in the southwest part and cooler temperatures in the northeast and eastern part of the country (Figure 1, Astthorsson et al. 2007).The exposed shoreline of the eastern part of the south coast is made of black volcanic sand that is in constant motion and therefore devoid of seaweeds.
In this paper, we have used the results of Mols-Mortensen et al. ( 2012) to re-evaluate morphological identification of all the species based on all the bladed Bangiales specimens that have been collected from Iceland since the first expeditions in the 19th century and used that as a basis to describe those species distributions.
We have also provided a key to the genera of bladed Bangiales found in Iceland.

Materials and methods
A comprehensive study was made of all Icelandic specimens of bladed Bangiales held in the Icelandic Institute of Natural history in Reykjavik (ICEL), the Natural History Museum of Denmark, herbarium in Copenhagen (C), and Natural History Museum in London (BM).A summary of the principal collectors, dates and approximate number of specimens are given in Table 2.The first collections of bladed Bangiales in Iceland were made in the late 19th century and the start of the 20th century (Table 2).Practically no collections were made after that for 60 years until S. Jónsson and Munda began their collections.After that the bulk of the collections were made by Munda between 1963 and1980, and 2012).Most of these collections were made during the summer months.In specific winter collecting trips, Porphyra linearis was collected in south-western and western Iceland.No winter samples exist from other parts of the country.
Morphological identification was reassessed for all the specimens with reference to those for which molecular data were obtained by Mols-Mortensen et al. (2012).Initial identifications were either confirmed or revised.All specimens were databased and the distribution of all those positively identified to species was mapped.Sampling site position was either determined with a GPS device (for all specimens collected after 1999) or by taking positions as latitude/longitude from digital maps (National Land Survey of Iceland) with Lambert conical projection.Maps were created in R (R Core Team 2015).

Results
The distribution of the 11 species found in Iceland is shown in Figures 2 and 3. Most of the bladed Bangiales species are found in all coastal regions with suitable substrata.There is a noticeable lack of records from the eastern part of the south coast due to lack of suitable substrata.Porphyra dioica, P. linearis and Pyropia leucosticta are confined to the south-western part of Iceland.Porphyra linearis is almost certainly under-recorded owing to the scarcity of collections in the winter months when this species is present.Pyropia thulaea is only found in eastern Iceland, the coldest part of the coastline.Boreophyllum birdiae and Wildemania abyssicola were only found sporadically and there are large gaps in their corresponding distribution maps.
The growing season for most of the bladed Bangiales species in Iceland is from late May until October with the following exceptions: Porphyra umbilicalis and P. purpurea are found throughout the year.Pyropia thulaea and B. birdiae are autumn species found from August until October, Pyropia njordii has been recorded only in early summer, from late May to the beginning of July, and P. linearis only in January to March.
Porphyra umbilicalis and P. linearis grow in the upper littoral zone of exposed coasts.Wildemania amplissima, W. abyssicola and W. miniata are most frequently found in the sublittoral zone of exposed shores, but occasionally occur in the lowest part of the shore.The other bladed Bangiales species in Iceland are found in the lower littoral of semi-exposed to sheltered coasts.Porphyra purpurea can also be found in extremely sheltered shores growing on small pebbles in muddy estuaries.
All the bladed Bangiales species were found growing on rocks or stones but some can also grow epiphytically.Pyropia leucosticta is epiphytic on Mastocarpus stellatus (Stackhouse) Guiry and occasionally also on other algae (e.g.Fucus spp.), W. abyssicola was found growing on Turnerella pennyi (Harvey) F. Schmitz, and W. miniata and W. amplissima were found growing on diverse algae or on rocks.Even though there is a relatively large collection of bladed Bangiales specimens from the coast of Iceland, evidence of cryptic diversity within the order (Lindstrom 2008) suggests that there are still more species to be discovered in the area.Pyropia thulaea was first described in 1978 (Munda and Petersen 1978) based on specimens from eastern Iceland and Greenland.

Key to genera of bladed Bangiales in Iceland
It was not picked up in the 2007 expedition when the east coast was visited.The species is confined to a few shores on the east coast and has only been reported from August to October which was outside the collecting dates for 2007.It seems to be an arctic species confined to the coldest region in Iceland.
Pyropia njordii is a newly described species from the area (Mols-Mortensen et al. 2012).It is conspicuous, therefore that the lack of specimens prior to 2005 and its abundance during this period suggests that it could be a new arrival in Iceland.Molecular data indicate that it is very closely related to Pyropia brumalis (Mols-Mortensen et al. 2012, fig.12), a species described from the Canadian Pacific.Thus, there is the possibility that Py. njordii is a relatively recent arrival from the Pacific, although the species has been verified in historic collections from Greenland dating back to 1888 (Mols-Mortensen et al. 2014).
Boreophyllum birdiae has disrupted distribution records and is probably under-recorded and/or misidentified owing to confusion with Porphyra purpurea (Neefus et al. 2002).Similarly, distribution records for Wildemania abyssicola are disrupted and, because there are relatively few collections from deep water where it is known to occur, this species is also probably under-recorded.Knowledge of the distribution of both species would benefit from further collecting.
Porphyra dioica is only found in the southwest and probably has its northern distribution limit in Iceland as it has been recorded in the Faroes but not in Greenland (Mols-Mortensen et al. 2012, 2014).The distribution of Pyropia leucosticta coincides with the areas in the southwest, where its principal host species Mastocarpus stellatus forms dense stands on the lower shore.Mastocarpus stellatus is found sporadically along the north and the east coast where Py. leucosticta is not found.Brodie et al. (1998) suggested that Py. leucosticta might be an introduced species in the North Atlantic; in Sutherland et al. (2011), Py. leucosticta is resolved in a clade with taxa from the Pacific, lending weight to this suggestion.A few specimens collected from all sections of the coast, morphologically resembled Pyropia elongata (Kylin) Neefus et J. Brodie (cf. Brodie et al. 2007) but their identity has to await confirmation as no molecular data are available.
Another factor that may affect the biodiversity in the region is the current increase in sea surface temperature.Southern species are likely to extend their distribution into the area (Muller et al. 2009).In addition, we can expect longer seasonal ice-free periods in the Bering Strait and the Northwest Passage, with a potential increase in the number of introduced species from the Pacific (Reid et al. 2007).

Conclusions
Our work demonstrates the value of collections in determining a reliable and verifiable distribution in a defined area and enables a greater understanding of the overall biogeography of a species with implications for diversity, endemism and the presence of non-natives in a region.It also provides a baseline from which temporal change can be assessed and the time of arrival of new species into a geographical area can be determined (cf.Brodie et al. 2007).This work also highlights the problem of the misapplication of names and the importance of applying a robust taxonomy which has enabled us to establish the presence of species in the Icelandic flora which previously had been overlooked.The data are also valuable in relation to conservation policy and have implications for the overall distribution of the species studied.

Figure 1 :
Figure 1: Sea surface temperature around Iceland.Contours show mean monthly temperature (°C) for the years 2000-2010 in (A) March and (B) August.Data from the World Ocean Atlas 2013 (Locarnini et al. 2013).

Table 1 :
Numbers of specimens of each species of bladed Bangiales collected from Iceland during different time periods.

Table 2 :
Collections of bladed Bangiales from Iceland.Four periods can be recognized based on collecting effort.
our sampling from 158 stations in Iceland as part of a general macroalgal survey initiated in 1999 (southwest coast) and continued in 2005 (west/northwest coasts), 2006 (north coast) and 2007 (northeast and east coasts).Additional details can be found in Mols-Mortensen et al. (