Dec 022016
 
Some of the herbarium collections of Marchantia held in the RBGE herbarium

Some of the herbarium collections of Marchantia held in the RBGE herbarium

Many new species are already included in natural history collections around the world, it’s just that nobody has yet got around to examining the material, recognising that it represents something novel, and publishing a name for it. Sometimes these new species are filed under the epithet of a similar named species, sometimes they’re just filed under the genus name with other collections that have not been identified to species, and sometimes they have been annotated to recognise that they’re probably distinct from all the species that have already been described, e.g., as “sp. nov.

David Long has made a huge number of plant collections from around the world in his 40-plus year botanical career, with many of these collections not yet fully examined. Some of this material is being mined for DNA sequencing projects at RBGE, and for some of our key plant groups, as well as sequencing well-identified material, we are also sequencing plants that have not been assigned to species. Molecular lab work is fast compared to close morphological studies of multiple plant specimens; this can therefore speed up the processes of traditional taxonomy, by allowing it to focus on things that are obviously distinct.

One lineage that David Long is particularly involved with, and that remains one of our key plant groups, is the complex thalloid liverworts. Some of our sequencing work has involved Marchantia, which made Xiang et al.‘s recent description of a new species in the genus, Marchantia longii, particularly interesting. In the last few days, the DNA sequences that were included in the paper were made publicly available on the NCBI site, GenBank. One of the regions that was sequenced by Xiang et al., the plastid-encoded RuBisCo Large subunit gene rbcL, was also included in our study, and so I was able to put the two data sets together, and see how the new species fits into our phylogenies.

The results are interesting: When Xiang et al. named M. longii, they did so in part because the area that the plant came from, in northwestern Yunnan, is one in which David has been very active. In fact, at RBGE we had already generated DNA sequence data from nine accessions of Marchantia that David had collected there. I was delighted to find that two of these accessions (collections Long 36155 and Long 34642), which had been filed in our collections without a specific epithet, are an exact genetic match to Marchantia longii. It seems that David really does have an affinity for the plant, having gone out and found some even before it was named for him!

 

Long’s Marchantia

A rapid phylogeny of Marchantia, from the RBGE collections. II. Illuminating our sampling

A rapid phylogeny of Marchantia, from the RBGE collections. I. Sampling

Nov 222016
 
David Long in Gaoligong Shan; photo by Dong Lin

Dr David Long in Gaoligong Shan; photo by Dong Lin

Formerly the head of our Cryptogam section, and currently an extremely active RBGE Research Associate, David Long is well known and respected for his botanical work in the Himalayas, and for his bryological research. He has collected a huge number of taxonomically and phylogenetically interesting bryophytes on numerous plant collecting expeditions, collaborating with researchers around the world. His 2006 monograph on Eurasia Asterella reflects a special interest in the complex thalloid liverworts (Marchantiopsida), which has formed a focal point for subsequent research at RBGE on the systematics of the group (e.g., Villarreal et al. 2015).

Marchantia longii, from Fig. 1, Xiang et al. 2016, The Bryologist

Marchantia longii, from Fig. 1, Xiang et al. 2016, The Bryologist

In October this year, Chinese colleagues You-Liang Xiang, Lei Shu and Rui-Liang Zhu, using morphological and molecular evidence, described a new species of Marchantia from the northwestern region of Yunnan. Their paper, in the American Bryological and Lichenological Society journal The Bryologist, suggests that this is a distinct species, phylogenetically related to Marchantia inflexa, M. papillata and M. emarginata.

Xiang et al. 2016, The Bryologist

Fig. 4, Xiang et al. 2016, The Bryologist

The new species differs morphologically from other Marchantia species in the area by a suite of pore, thallus and receptacle characters, one of the most obvious of which is its very large epidermal pores, which can clearly be seen in the photographs presented by Xiang et al. The authors have named their new plant Marchantia longii R.L.Zhu, Y.L.Xiang et L.Shu, in honour of David, because he is “the specialist of complex thalloid liverworts and made several bryological expeditions in northwestern Yunnan, China”.

On these expeditions to the area, David collected extensively. It remains to be seen, however, whether his own collections include any plants of the newly named Long’s Marchantia!

Nov 162016
 
Telaranea tetradactyla, photographed by David Long (Long 37778)

Telaranea tetradactyla at Benmore, photographed by David Long (Long 37778)

Murphy’s threadwort (Telaranea murphyae) has had a singular position in the British flora. The species was described by renowned bryologist Jean Paton in 1965, from plants collected in the south of England. It’s a tiny leafy liverwort that is found in only four locations, at Tresco and St Mary’s on the Isles of Scilly, Branksome Chine, Poole in Dorset and Alum Chine, Bournemouth. Murphy’s threadwort has always been known to be an alien species in our flora, and yet because it’s never been found elsewhere, the sole responsibility for conserving the species lay with the UK. Being non-native, however, it was not considered a priority for UK Biodiversity Action Plans.

Telaranea tetradactyla from the RBGE fern house, photographed by Lynsey Wilson

Telaranea tetradactyla from the RBGE fern house, growing with Conocephalum conicum; photographed by Lynsey Wilson

Using DNA sequence data from the plant, and comparing it to sequences from other related species, we showed that genetically, the English plants are the same species as a New Zealand plant, Long’s threadwort (Telaranea tetradactyla, synonmy Telaranea longii). Long’s threadwort was already known from several locations in the UK, including inside the fernhouse at RBG Edinburgh, and near the fernery in Benmore. These habitats are not entirely coincidental – the Victorian craze for ferns saw many gardens import living tree ferns from countries such as Australia and New Zealand, with many smaller plants hitching a ride along on their trunks. Today, conscious of plant health issues and the potential transport of pathogens, new plant living collections have to spend time in quarantine before being planted out; past gardeners were less careful, and some of these hitchhikers have subsequently escaped into the local landscape.

Telaranea tetradactyla from the RBGE fern house, photographed by Lynsey Wilson

Telaranea tetradactyla from the RBGE fern house, photographed by Lynsey Wilson

Sinking our UK Murphy’s threadwort plants into the New Zealand species means that any conservation requirements now rest instead with New Zealand, although we can continue to enjoy seeing this diminutive mat-forming liverwort in its select few UK locations.

 

 

Key reference: Porley, R.D., 2013, England’s Rare Mosses and Liverworts. Princeton University Press.

 

 

Villarreal et al. 2014, Journal of Bryology 36(3): 191-199

Villarreal et al. 2014, Journal of Bryology 36(3): 191-199

 

Sep 092016
 
Sphaeropcaros texanus photographed by David Long (Long 33162)

European material of Sphaerocarpos texanus, photographed by David Long (Long 33162)

The Sphaerocarpales (or “Bottle Liverworts”) form a very distinct group in the complex thalloid liverworts, with ca. 30 species in five genera: originally the group just included Geothallus (monospecific), Sphaerocarpos (8-9 species) and Riella (ca. 20 species), with two more monospecific genera, Austroriella and Monocarpus, added within the last few years. All five genera have very unusual, and highly reduced, thallus morphologies. With the exception of Monocarpus, they also all enclose their sex organs (or gametangia – the antheridia and archegonia) in inflated flask-shaped bottles (as can be seen in the accompanying photograph). This feature sets them apart from all other liverworts. All of them are adapted to extreme habitats, including arable fields, hot arid regions, seasonal lakes and pools, and salt pans.

A worldwide revision of the second largest genus of the group, Sphaerocarpos, is over 100 years old (Haynes 1910); other revisional work focuses on individual geographic areas, including South Africa (Proskauer 1955), North America (Haynes & Howe 1923, Frye & Clark 1937, Schuster 1992, Timme 2003), California (Howe 1899), Europe (Reimers 1936, Müller 1954), and France (Douin 1907). No revisions have been made for large areas including Australia, Asia and South America, and most of the work predates any DNA-based concepts of plant identification or species relationships. Bringing the taxonomy of Sphaerocarpos into the 21st century, Dr Daniela Schill spent 18 months (2007-2009) at RBGE on a Sibbald Trust-funded project to compile a world-wide taxonomic revision of the genus. Two field expeditions fed into the project, with Dr David Long collecting European species in Portugal in April 2007, and Daniela collecting North American species in California in March 2008 (funded by the Peter Davis Expedition Fund).

Spore SEMs of Sphaerocarpus drewiae, taken by Daniela Schill

Spore tetrads of Sphaerocarpos drewiae, SEMs taken by, and plate prepared by, Daniela Schill

Daniela’s work is based on morphological and anatomical characters, including spore characters that she observed using Scanning Electron Microscopy (SEM). Her aim has been to produce identification keys to the species, species descriptions, species lists, synonyms, botanical drawings, distribution maps, and ecological, nomenclatural and taxonomical notes. Although the study is not yet published, much of it, including SEM plates for spores from the ca. 9 different species (as seen on the right), is complete.

In parallel, RBGE staff have also been sequencing multiple accessions of all available Sphaerocarpos species, producing data that has helped inform some of Daniela’s taxonomic decisions, and that also allow us to generate a stand-alone phylogeny for the genus.

This research will lead to some taxonomic changes. For example, European Sphaerocarpos texanus plants differ from American S. texanus, both in their DNA sequences and in their spore characters, and so they are likely to be considered a separate species. Furthermore, European Sphaerocarpos michelii material includes three different forms based on spore characters; these are also confirmed by molecular research, and may be recognised at or below the rank of species.

 

References:

Cargill, D.C. & J. Milne. 2013. A new terrestrial genus and species within the aquatic liverwort family Riellaceae (Sphaerocarpales) from Australia. Polish Botanical Journal 58(1): 71-80.

Douin R. 1907. Les Sphaerocarpus français. Revue Bryologique 34(6): 105-112.

Frye T.C. & L. Clark. 1937. Hepaticae of North America. University of Washington Publications in Biology 6: 105-113.

Haynes C.C. 1910. Sphaerocarpos hians sp. nov., with a revision of the genus and illustrations of the species. Bulletin of the Torrey Botanical Club 37(5): 215-230.

Haynes C.C. & M.A. Howe. 1923. Sphaerocarpales. North American Flora 14: 1-8.

Howe  M.A. 1899. The hepaticae and anthocerotes of California. Memoirs of the Torrey Botanical Club 7: 64-70.

Müller K. 1954. Die Lebermoose Europas. In: Rabenhorst’s Kryptogamenflora von Deutschland, Österreich und der Schweiz. 3. Auflage. Volume VI. Part 1. Leipzig, Akademische Verlagsgesellschaft Geest & Portig K.-G., Johnson Reprint Corporation (1971), New York, London.

Proskauer J. 1955. The Sphaerocarpales of South Africa. The Journal of South African Botany 21: 63-75.

Reimers H. 1936. Revision des europäischen Sphaerocarpus-Materials im Berliner Herbar. Hedwigia 76: 153-164.

Schill D.B., L. Miserere & D.G.Long. 2009. Typification of Sphaerocarpos michelii Bellardi, S. terrestris Sm. and Targionia sphaerocarpos Dicks. (Marchantiophyta, Sphaerocarpaceae). Taxon 58(2): 638-640.

Schuster R.M. 1992. Sphaerocarpales. In: The hepaticae and anthocerotae of North America V. Field Museum of Natural History, Chicago: 799-827.

Timme S.L. 2003. Sphaerocarpaceae. In: Bryophyte Flora of North America, Provisional Publication.

 

Sep 082016
 

One of the main problems with sampling largely from herbarium specimens, rather than from material that has been specifically collected for DNA work (rapidly dried in silica gel then maintained at low humidity), is that the quality of the DNA is unpredictable and usually rather poor. Therefore, despite starting out with 169 accessions and about 20 species of Marchantia, the actual successes, where we were able to get good quality DNA sequence data, were substantially lower. What we currently have is a slightly unbalanced data matrix, with 82 Marchantia accessions for rbcL, and 78 Marchantia accessions for psbA-trnH.

Reboulia hemisphaerica thallus, photographed by David Long (Long 34254)

Reboulia hemisphaerica thallus, photographed by David Long (Long 34254)

We also sequenced both rbcL and psbA-trnH from material of two accessions that we thought were Marchantia but where the sequences turned out to be Reboulia (from Texas) and Wiesnerella (from Bhutan). A quick check of the herbarium voucher specimens for both of these showed that they represented mixed collections of more than one complex thalloid species, for which the “wrong” plant parts had ended up in our silica dried tissue collection. Taking fortune from misfortune, both Reboulia and Wiesnerella form quite adequate outgroups for the phylogeny!

Wiesnerella denuda, photographed by David Long

Wiesnerella denuda thallus, photographed by David Long (Long 36267)

Out of the 20 species that we HAD hoped to sample, we ended up with only 12 named Marchantia species for rbcL (Marchantia polymorpha, M. paleacea, M. linearis, M. papillata, M. inflexa, M. emarginata, M. pinna, M. chenopoda, M. debilis, M. hartlessiana, M. quadrata and M. romanica), and 15 for psbA-trnH (Marchantia polymorpha, M. paleacea, M. linearis, M. papillata, M. inflexa, M. emarginata, M. pinna, M. chenopoda, M. debilis, M. globosa, M. pappeana, M. hartlessiana, M. subintegra, M. quadrata and M. romanica); we also had three Marchantia polymorpha subspecies (polymorpha, ruderalis and montivagans) and two Marchantia paleacea subspecies (paleacea and diptera).

That’s a little disappointing, representing, as it does, fewer than half of the 38 currently recognised species in the genus. However, we did also sequence a number of Marchantia accessions that had not been determined to species, and although many of them were good DNA matches to species that we had sampled, several are clearly different to everything else that we have included: one distinct lineage in Yunnan, China, another that occurs in Yunnan and Nepal, and a third in Indonesia and Malaysia. That’s balanced again by taxa that may not have been identified correctly; the psbA-trnH sequences from African material of M. debilis, M. globosa, M. pappeana and M. polymorpha, for example, are identical.

Intriguingly, in the “Preissia” clade, as well as M. romanica, there appear to be two lineages of Marchantia quadrata, one consisting of accessions from Denmark, Sweden and Sichuan, China, and the other with accessions from Svalbard, Norway and Utah, USA. These may tie in with subspecies quadrata (for the first lineage) and subspecies hyperborea (for the material from Svalbard and Utah), but the degree of genetic divergence is far higher than that found between many of the recognised species in Marchantia. It is a bit disconcerting, however, to notice that we have managed to overlook any Marchantia quadrata material from Scotland in our sampling!

The next step in the project, before it’s time to reveal any of the phylogenetic trees I’ve alluded to, is a phase of reciprocal illumination where we reconcile morphological information from the herbarium specimens with the information derived from the molecular sequence data. In other words, it’s time to double check our plant identifications, a part of the project that’s now in the capable hands of Dr David Long; the pile of Marchantia specimens is already on his desk!

 

 

Relevant posts

A rapid phylogeny of Marchantia, from the RBGE collections. I. Sampling

A rapid phylogeny of Marchantia, from the RBGE collections. II. Illuminating our sampling

Sep 062016
 

University of Edinburgh/RBGE student David Bell, studying for the Masters degree in the Biodiversity and Taxonomy of Plants; thesis submitted August 2009.

Supervisors: Dr David Long and Dr Michelle Hart.

 

David used plastid DNA barcode markers rbcL (from 34 accessions) and psbA-trnH (from 36 accessions) to look at the four species of Herbertus in Europe, H. aduncus subsp hutchinsiae (British Isles, Norway and Faroes), H. stramineus (British Isles, Norway and Faroes), H. borealis (Scotland and Norway) and H. sendtneri (European Alps).

In addition to the four recognised taxa, David’s study identified a fifth species, later named as H. norenus, that occurs in Norway and the Shetland Isles.

A paper based on David’s MSc thesis work was published in Molecular Ecology Resources in 2012.

Herbertus norenus, photographed by David Long

Mixed sward including Herbertus norenus, photographed in Shetland by David Long

 

Bell et al. 2012, MER

 

 

Other student projects at the Gardens:

Student projects at RBGE: DNA barcoding British liverworts: Lophocolea

Student projects at RBGE: Barcoding British Liverworts: Plagiochila (Dumort.) Dumort.

Student projects at RBGE: Barcoding British Liverworts: Metzgeria

Aug 122016
 

University of Edinburgh/RBGE student Kimberley Fackler, studying for the Masters degree in the Biodiversity and Taxonomy of Plants; thesis submitted August 2013.

Supervisors: David Bell, Dr David Long and Dr Laura Forrest.

 

Kim sampled from the six species of Metzgeria generally recognised to occur in the UK. She used standard DNA barcode markers rbcL, matK, psbA-trnH and ITS2.

Metzgeria furcata, vice county 49, Long 8069; photographed by David Long

Metzgeria furcata, vice county 49, Long 8069; photographed by David Long

Metzgeria furcata (L.) Dumort.

M. violaceae (Ach.) Dumort.

M. conjugata Lindb.

M. consanguinea Schiffn.

M. pubescens (Schrank)

M. leptoneura Spruce

Phylogram generated from accessions of Metzgeria species found in the UK

Phylogram generated from accessions of Metzgeria species found in the UK

 

DNA barcoding for all regions but rbcL delimited seven genetic lineages of Metzgeria within the UK. There was a lower amount of sequence variation in rbcL, suggesting that it is suitable for use at a higher taxonomic level than this genus.

Six of the genetic entities correspond to the current species concepts in Metzgeria. Metzgeria furcata was split into two sister groups, in line with the findings of Fuselier et al. 2009; these two groups may correspond to variety ulvula and variety furcata.

Conservation implications: If lineages do not have names, they have no legal recognition, no protection, and we cannot gather information about their rarity or distributions.

 

 

Related Posts

Student projects at RBGE: DNA barcoding British liverworts: Lophocolea

Student projects at RBGE: Barcoding British Liverworts: Plagiochila (Dumort.) Dumort.

Student projects at RBGE: Barcoding British Liverworts: Metzgeria

Student projects at RBGE: DNA barcoding of the leafy liverwort genus Herbertus Gray in Europe and a review of the taxonomic status of Herbertus borealis Crundw.

Aug 122016
 

University of Edinburgh/RBGE student Lucy Reed, studying for the Masters degree in the Biodiversity and Taxonomy of Plants; thesis submitted August 2011.

Supervisors: Dr David Long, Dr Michelle Hart and David Bell.

The leafy liverwort genus Plagiochila is known for high levels of infraspecific morphological variation and blurred species boundaries. To address this, Lucy sequenced the plastid rbcL and matK plant barcode loci, along with the plastid psbA-trnH spacer, and the nuclear ITS region, assessing the genetic distinctiveness of four British taxa of Plagiochila sect. Plagiochila (Plagiochilaceae), as part of our wider project to DNA barcode the British bryophyte flora. The molecular matrix consisted of sequences from 14 accessions of P. asplenioides, 15 accessions of P. britannica, 3 accessions of P. norvegica, 7 accessions of P. porelloides, and two accessions that were not confidently identified to any species. Most of the samples came from across the UK, although plants from Ireland, Italy, Norway, Sweden and Switzerland were also included. Several outgroups were also available – 5 accessions of P. carringtonii, 3 accessions of P. heterophylla, 3 accessions of P. bifaria, 4 accessions of P. punctata, 5 accessions of P. spinulosa, and 2 accessions of P. exigua.

Lucy also undertook a herbarium study, to revise morphological characters for the taxa and correlate them with the molecular results. She scored a range of non-reproductive characters, using 13 of these for Principal Component Analysis (PCA). Because the plants are dioicous, using reproductive characters would have required male and female plants; furthermore, sporophytes are rarely collected, and not known at all for P. norvegica.

Using the three plastid markers rbcL, matK and psbA-trnH, Lucy resolved two species groups – a P. asplenioides-P. brittanica group, and a P. porelloides-P. norvegica group. The branch lengths for tree produced from the regions that she sequenced were, however, short and statistical support was absent, so the markers could not reliably be used to distinguish P. asplenioides from P. britannica, or P. porelloides from P. norvegica. On the other hand, only one of the 7 P. britannica accessions that was successfully sequenced for ITS resolved with P. asplenioides; the rest resolved with P. porelloides. Again, branch lengths within clades were too short to confidently distinguish species.

Species summaries:

  1. Plagiochila asplenioides: Lucy considered this species to be relatively easy to distinguish, because of its larger and more robust habit and larger leaves. There was, however, potential for confusion when dealing with smaller plants. However, in combination with DNA sequence data from the four loci, most individuals could be identified.
  2. Plagiochila porelloides: Lucy found that molecular sequence data could clearly separate this species from P. asplenioides and P. britannica. However, P. norvegica, which is separated from P. porelloides mainly by leaf apex shape and leaf margin tooth size, was not distinguishable using molecular data, and may be better either sunk, or reduced to a variety of P. porelloides, which already contains a lot of morphological variability.
  3. Plagiochila britannica: Lucy proposed that discrepancies between the plastid and nuclear gene topologies could be down to a hybrid origin for this species, fitting the diploid (n=18) status of the plant, as opposed to the haploid (n=9) status of both P. asplenioides and P. porelloides (key references: Paton, 1979; Newton, 1986).
  4. Plagiochila norvegica: originally described from Norway, this species has subsequently been found in Sweden and in England. Lucy included samples from England and Norway, but found no molecular evidence that they were distinct from P. porelloides, while the morphological differences that separate the taxa could be related to environmental conditions (Paton 1999).
Plagiochila asplenioides vice county 79 Long 8476

Plagiochila asplenioides vice county 79, Long 8476; photographed by David Long

Plagiochila britannica vice county 50, Long 37707

Plagiochila britannica vice county 50, Long 37707; photographed by David Long

 

Related Posts

Student projects at RBGE: DNA barcoding British liverworts: Lophocolea

Student projects at RBGE: Barcoding British Liverworts: Plagiochila (Dumort.) Dumort.

Student projects at RBGE: Barcoding British Liverworts: Metzgeria

Student projects at RBGE: DNA barcoding of the leafy liverwort genus Herbertus Gray in Europe and a review of the taxonomic status of Herbertus borealis Crundw.

Aug 122016
 

University of Edinburgh Biotechnology student Kenneth McKinlay’s 4th year honours project, 2013. Supervisors: Dr David Long, Dr Laura Forrest

David Long and Kenneth checking out the Lophocolea on a decaying log in the Scottish Borders

David Long and Kenneth check out Lophocolea on a decaying log in the Scottish Borders

Kenneth barcoded all six species of British Lophocolea, L. bidentata, L. bispinosa, L. brookwoodiana, L. fragrans, L. heterophylla and L. semiteres, attempting to get data from three plastid regions (rbcL, matK, psbA-trnH) and one nuclear region (ITS2). The data generated from the rbcL and psbA-trnH regions was effective in discriminating between all the species sampled; however useful data were not obtained from matK or ITS2.

Genetic markers:

1. rbcL: bidirectional sequence data was generated for 38 accessions.

2. matK: amplification was not successful with the primer sets used (LivF1A, LivR1A).

3. psbA-trnH: bidirectional sequence data was generated for 40 accessions.

4. ITS2: although PCR amplification was successful for 35 accessions, the low quality of many of the sequences generated, and the presence of clear heterozygous positions in sequence data from some accessions, made this data set problematic to analyse, so it was excluded from the study.

Lophocolea bispinosa vice county 98 Long 4725

Lophocolea bispinosa vice county 98, Long 4725; photographed by David Long

Lophocolea semiteres vice county 98, Long 0578

Lophocolea semiteres vice county 98, Long 0578; photographed by David Long

 

 

 

 

 

 

 

 

Species and trees:

Distance tree generated using rbcL barcode sequence data for UK Lophocolea accessions

Distance tree generated using rbcL barcode sequence data for Lophocolea accessions, rooted on Chiloscyphus

L. fragrans – all accessions were genetically uniform, forming a monophyletic group.

L. heterophylla – although there was a little genetic variation, again, accessions of this species formed a distinct clade for both rbcL and psbA-trnH.

L. semiteres & L. brookwoodiana – these formed a single clade. All the accessions of L. semiteres (including material from the UK and Belgium) were genetically uniform, while two different genotypes were observed for L. brookwoodiana. While L. semiteres is known to be an introduced species in the UK, it’s possible that the three different genotypes in this clade represent separate introductions.

L. bispinosa – species formed a single genetically uniform group; this nests within a L. bidentata grade.

L. bidentata – accessions of this widespread and common species formed a grade, with three genetically distinct groups. One of these groups may represent L. cuspidata, a species that was sunk into L. bidentata by Bates and Walby in 1991, due to a lack of consistently distinguishing morphological characters. The results of this study suggest that a recircumscription of L. bidentata, “probably the commonest leafy liverwort in the British Isles” (Hodgetts, 2010), is required.

 

Related Posts

Student projects at RBGE: DNA barcoding British liverworts: Lophocolea

Student projects at RBGE: Barcoding British Liverworts: Plagiochila (Dumort.) Dumort.

Student projects at RBGE: Barcoding British Liverworts: Metzgeria

Student projects at RBGE: DNA barcoding of the leafy liverwort genus Herbertus Gray in Europe and a review of the taxonomic status of Herbertus borealis Crundw.

 

 

Jun 302016
 

The genus Aitchisoniella contains a single species, A. himalayensis, which was described by Pakistani botanist Professor Shiv Ram Kashyap from plants that he collected in Mussoorie, Uttarakhand, India (1914). Subsequently (1929) he also found the species in Shimla and Kullu in Himachal Pradesh. Although reports of new locations followed (Kanwal, 1977, Pant et al., 1992, Bischler et al., 1994), near Nainital in Uttarakhand, the species was only known from the north-west Himalayas of India until 2010, when its range was extended by RBGE bryologist Dr David Long, on the ‘Kunming/Edinburgh Expedition to Sichuan’. David found Aitchisoniella at two localities in China, in Litang and Daocheng counties of south-west Sichuan Province.

Athalamia pinguis, Sichuan, photographed by David Long (Long # 40305)

Fig. 1. Athalamia pinguis in Sichuan, showing stalked sexual branches (carpocephala), photographed by David Long (Long # 40305)

Aitchisoniella looks quite different to other complex thalloid liverworts: it doesn’t have the stalked sexual branches (carpocephala) that are present in most complex thalloid species like Marchantia, or Athalamia (as can be seen in the photograph, Fig. 1). Instead, the female sex organs (archegonia), and therefore the sporophytes, grow on the lower (ventral) side of a short receptacle (as can be seen in the photograph, Fig. 2). The receptacle is part of the main thallus, with air chambers and air pores, and a groove on the underside of the thallus from which characteristicly complex-thalloid pegged rhizoids grow.

 Aitchisoniella himalayensis in Sichuan showing terminal sporophyte-bearing receptacles, from Long 39886

Fig. 2. Aitchisoniella himalayensis in Sichuan, showing terminal sporophyte-bearing receptacles, photographed by David Long (Long # 39886)

Originally, Aitchisoniella was thought to belong to the Exormothecaceae family of complex thalloid liverworts, along with Exormotheca and Stephensoniella. Earlier this year, we transferred all the plants in Exormothecaeae into another family, Corsiniaceae, where they joined Corsinia and Cronisia (Long et al. 2016a).

Complex thalloid phylogeny reconstructed by Villarreal, J.C., B.J. Crandall-Stotler, M.L. Hart, D.G. Long, L.L. Forrest. 2015. Divergence times and the evolution of morphological complexity in an early land plant lineage (Marchantiopsida) with a slow molecular rate. New Phytologist. DOI: 10.1111/nph.13716

Fig. 3. The phylogenetic position of Aitchisoniella, from the complex thalloid phylogeny reconstructed by Villarreal et al. (2015)

However, having fresh material of the plant meant that we were able to extract DNA from it, and add it into our molecular phylogeny for the group (Villarreal et al. 2015). The results were unexpected, with Aitchisoniella grouping with species from a different complex thalloid family, Cleveaceae (Fig. 3). The growth forms are quite different, as all the species in Cleveaceae have got stalked carpocephala. However, once we started to think more about the evolution of these plants, and look more objectively at differences and similarities, one thing struck us: the spores of Aitchisoniella (see Fig. 4) look more like the spores of plants in Cleveaceae (e.g. Athalamia, Fig. 5) than they do like spores of plants in Exormothecaceae (e.g. Fig. 6).

Spores of Aitchisoniella himalayensis. (A) Distal view; (B) proximal view; (C) lateral view; (D) detail of distal view. (A and C) from Long 39886. (B and D) from Long 40020. Scale bars: (A–C) = 5 μm, (D) = 2 μm.

Fig. 4. Spores of Aitchisoniella himalayensis from Long et al. 2016: (A) Distal view; (B) proximal view; (C) lateral view; (D) detail of distal view. (A & C) from Long 39886. (B & D) from Long 40020. Scale bars: (A–C) = 5 μm, (D) = 2 μm.

Athalamia hyalina spore images from M. P. Steinkamp and W. T. Doyle American Journal of Botany Vol. 68, No. 3 (Mar., 1981), pp. 395-401

Fig. 5. Spores of Athalamia hyalina (Cleveaceae) from Steinkamp & Doyle (1981): 1. distal view (x 1,100); 2. proximal view (x 1,100); 3. equatorial view (x 1,100); 4. close-up of pore (x 6,000); 5. distal face (x 3,000).

 

Exormotheca spores: E. bulbigena - A, distal view, B, proximal view. E. holstii - C, distal view, D, proximal view, E, distal view, F, proximal view. From Bornefeld et al., 1996.

Fig. 6. Spores of Exormotheca from Bornefeld et al. (1996): E. bulbigena – A, distal view, B, proximal view. E. holstii – C, distal view, D, proximal view, E, distal view, F, proximal view.

Characters like spore shape used to be considered to be quite neutral in bryophyte evolution, features that were not really acted on by natural selection. Following this theory, spore characters were thought to be indicative of true and ancient relationships, changing very little across huge amounts of time. We have since moved away from this view, with, for example, small changes in the shape and size of spores known to have drastic effects on their aerodynamics. However, within the complex thalloids, it does seem that characters like the presence or absence of carpocephalum branches are quite variable within families, while spore morphology can be indicative of deeper relationships.

As a result of this work, based on both molecular and morphological evidence, we have transferred the genus Aitchisoniella to the family Cleveaceae (Long et al. 2016b), where it joins the four genera accepted by Rubasinghe et al. (2011): Athalamia, Clevea, Peltolepis and Sauteria.

 

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Borenfeld, T., O.H. Volk & R. Wolf. 1996. Exormotheca bulbigena sp. nov. (Hepaticae, Marchantiales) and its relation to E. holstii in southern Africa. Bothalia 26,2: 159–165.

Kanwal, H.S. 1977. Marchantiales of district Naini Tal (Kumaun Hills) U.P., India. Revue Bryologique et Lichénologique, 43: 327–38.

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Pant, G., S.D. Tewari & S. Joshi. 1992. An assessment of vanishing rare bryophytes in Kumaun Himalaya – thalloid liverworts. Bryological Times, 68/69: 8–10.

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Steinkamp, M.P. & W.J. Doyle. 1981. Spore wall ultrastucture in the liverwort Athalamia hyalina. American Journal of Botany 68: 395-401.

 

Villarreal, J.C., B.J. Crandall-Stotler, M.L. Hart, D.G. Long & L.L. Forrest. 2015. Divergence times and the evolution of morphological complexity in an early land plant lineage (Marchantiopsida) with a slow molecular rate. New Phytologist. 209: 1734–46, doi: 10.1111/nph.13716.

 

Long, D.G., L.L. Forrest, J.C. Villarreal, B.J. Crandall-Stotler. 2016. The genus Aitchisoniella Kashyap (Marchantiopsida, Cleveaceae) new to China, and its taxonomic placement. Journal of Bryology.