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The genus Isoetes (Isoetaceae): a provisional checklist of the accepted and unresolved taxa

Authors:
  • Instituto de Pesquisas Ambientais
  • Honam National Institute of Biological Resouces

Abstract and Figures

Isoetes is a widely distributed lycophyte genus of at least 200 species occurring in diverse habitats. The species can be difficult to identify because Isoetes, with its apparent simplicity of form and conserved morphology, provides few diagnostic features to reliably distinguish its species. The last worldwide monograph, published nearly a century ago, listed 77 taxa. The first step in producing a flora or monograph of all known species of a genus is to compile a list of the acceptable species names. The list presented here is a compilation of 192 accepted names representing taxa from regions around the world: chromosome numbers were assigned to 101 of them, with polyploidy settled on 46.7%. Distribution mapping of the accepted species indicates that South America is the center of diversity for Isoetes and species diversity is the highest in temperate regions. Many of the species on this list are rare and have limited ranges. The list of taxa can be used to initiate floristic studies and conservation efforts in keeping with the target goals of the global Strategy for Plant Conservation.
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Phytotaxa 277 (2): 101–145
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Copyright © 2016 Magnolia Press Article PHYTOTAXA
ISSN 1179-3155 (print edition)
ISSN 1179-3163 (online edition)
Accepted by Li-Bing Zhang: 7 Sept. 2016; published: 27 Sept. 2016
http://dx.doi.org/10.11646/phytotaxa.277.2.1
101
The genus Isoetes (Isoetaceae): a provisional checklist of the accepted and unresolved
taxa
ANGELO TROIA1*, JOVANI B. PEREIRA2, CHANGKYUN KIM3 & W. CARL TAYLOR4
1 Dipartimento di Scienze e Tecnologie Biologiche Chimiche e Farmaceutiche (STeBICEF), Sezione di Botanica ed Ecologia Vegetale,
Università degli Studi di Palermo, Via Archirafi 38, I-90123 Palermo, Italy
2 Ruhr-Universität Bochum, Department of Evolution and Biodiversity of Plants, 44780 Bochum, Germany
3 Department of Life Science, Gachon University, Seongnam 13120, South Korea
4 Department of Botany, National Museum of Natural History, Smithsonian Institution, Washington, DC 20560-166, USA
* Author for correspondence: angelo.troia@unipa.it
Abstract
Isoetes is a widely distributed lycophyte genus of at least 200 species occurring in diverse habitats. The species can be dif-
ficult to identify because Isoetes, with its apparent simplicity of form and conserved morphology, provides few diagnostic
features to reliably distinguish its species. The last worldwide monograph, published nearly a century ago, listed 77 taxa.
The first step in producing a flora or monograph of all known species of a genus is to compile a list of the acceptable species
names. The list presented here is a compilation of 192 accepted names representing taxa from regions around the world:
chromosome numbers were assigned to 101 of them, with polyploidy settled on 46.7%. Distribution mapping of the accepted
species indicates that South America is the center of diversity for Isoetes and species diversity is the highest in temperate
regions. Many of the species on this list are rare and have limited ranges. The list of taxa can be used to initiate floristic stud-
ies and conservation efforts in keeping with the target goals of the Global Strategy for Plant Conservation.
Introduction
Isoetes Linnaeus (1753: 1100) is a nearly cosmopolitan genus of heterosporous lycophytes, containing more than 200
species and being the only living genus of the family Isoetaceae (Jermy 1990, Larsén & Rydin 2016). These species
have evolved through an ancient lineage with an extensive fossil record dating from the Devonian Period (Pigg 2001)
and morphology so conserved that members of the genus are recognized in the Triassic Period (Retallack 1997). Today
members of the genus are widely distributed from the tropics to the sub-arctic; they range from submerged, evergreen
aquatics of cold, clear water lakes to upland terrestrial ephemerals of seasonally parched soils over bedrock.
In spite of their long fossil record, widespread distribution, and diverse adaptations, Isoetes species are remarkably
uniform in their morphology. Plants appear simple in form, consisting of a lobed subterranean rootstock producing
a tuft of linear sporophylls above and roots below along the groove between the lobes. This simple, conserved form
provides few characters and character states that can be used to distinguish species. Traditional characters such as
habitat, megaspore size, and megaspore texture are helpful for recognizing species, but they provide few morphological
character states needed to clearly distinguish all the species. More recently, chromosome counts, scanning electron
microscope analysis of spore texture, and DNA sequences have provided critical evidence for diagnosing species, but
these are of little help to botanists in the field.
In addition to the challenge of accurately identifying species with a limited set of morphological characters and
character states, frequent interspecific hybrids produce intermediate character states that further blur distinctions
between species. Isoetes interspecific hybrids are recognized by their production of non-viable, malformed spores of
variable size, shape, and texture (Taylor et al. 1985). DNA cloning and sequencing has revealed that some of these
sterile interspecific hybrids have doubled their chromosome number to reestablish chromosome balance and become
fertile, allopolyploid species (Hoot et al. 2004). Based on chromosome counts it appears that more than half of the
known species of Isoetes are polyploids (Troia 2001).
The latest worldwide taxonomic monograph of Isoetes was published almost a century ago (Pfeiffer 1922).
Pfeiffer’s monograph accounted for 77 taxa (65 as species, 8 as varieties, and 4 as forms). More recent estimates have
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102 Phytotaxa 277 (2) © 2016 Magnolia Press
continued to increase the number of species in the genus: ca. 130 species (Jermy 1990), ca. 150 species (Taylor et
al. 1993), ca. 200 (Hoot & Taylor 2001), and ca. 350 species (Hickey et al. 2003). These increases are due to more
botanists interested in the genus, use of new tools to reveal species, and careful searches for Isoetes in the field.
Therefore, it is appropriate to publish a compilation of accepted species names and their known distributions. It is
hoped this information will aid botanists in taxonomic, biogeographic, and phylogenetic studies of the genus and
conservationists with the preservation of the species and their habitats. Understanding plant diversity at the species
level is fundamental as a “basis for both conservation assessments and for management” of species and ecosystems
(Mace 2004).
Target 1 of the Global Strategy for Plant Conservation (GSPC) (Convention on Biological Diversity 2002) is the
production of “An online flora of all known plants.” Before such a flora can be produced, “a widely accessible working
list of known plant species is needed, as a step towards a complete world flora” (Paton et al. 2008). To meet this need,
“The Plant List” was launched online through GSPC at the end of 2010. The Plant List (2013–2016) currently includes
only 93 accepted Isoetes species names out of 230 scientific plant names of species rank. A more complete list of Isoetes
taxa is needed before a flora can be produced. Target 2 of the GSPC states “An assessment of the conservation status
of all known plant species, as far as possible, to guide conservation action”. This cannot be achieved without a more
complete list of the species to be assessed and thus, the achievement of Target 2 is dependent on the accomplishment
of Target 1.
The list presented here is neither a taxonomic revision nor an ultimate checklist, but it addresses a need to have a
more current working checklist available for taxonomic revisions and for the addition of species that will be described
in the future.
Materials & Methods
The list was compiled by regional experts (authors of this paper) on the basis of their experience, i.e. Taylor (North
America), Pereira (Central and South America), Kim (China, Korea, Japan and SE Asia), and Troia (all the remaining
regions). Troia and Taylor served also as general editors, integrating the efforts into one global list.
The nomenclatural data assembled here are based on Index Kewensis and the Gray Herbarium Card Index (both
available at http://www.ipni.org) and Tropicos (http://www.tropicos.org) with later additions of recently described
species. Authors and original publications were checked for each taxon and corrected when necessary, according to
the International Code of Nomenclature (McNeill et al. 2012). Names of authors, dates, and sources were checked
and abbreviated according to The International Plant Names Index (2015), sometimes verified with Stafleu & Cowan
(1976–1988).
The list includes all accepted species with their main (not all) synonyms. Regional syntheses by Croft (1986) and
Roux (2009) together with several global syntheses available on the Internet (Hassler & Swale 2001–2016, Desfayes
2008–2016, Musselman 2012–2016) are important resources. Hybrids are included only if they were previously
described as species or varieties.
The taxonomy of Isoetes in India is unclear, i.e. most of the last described species “appear to represent no more
than infraspecific variation in spore-surface morphology, of uncertain taxonomic significance” (Chandra et al. 2008).
We agree that further study is required into separation of species, and their correct nomenclature and synonymy”
(Chandra et al. 2008), but according to the available literature from Indian and not-Indian researchers, we tried to make
a plausible although preliminary assessment of the species occurring in the country, considering as “good species”
more than the two species estimated by Fraser-Jenkins (2008).
For each accepted taxon, information about its distribution has been added, usually on a national scale and
according to the standards proposed by the International Working Group on Taxonomic Databases for Plant Sciences
(Brummitt 2001).
Finally, we tried to assign to each accepted taxon a chromosome number, on the basis of a critical review of
published data; the reference was made - when possible - to the synthesis published in 2001 (Troia 2001), where the
reader can find details on the reports; only for new species or reports not included in Troia 2001, other references were
cited.
GENUS ISOETES Phytotaxa 277 (2) © 2016 Magnolia Press 139
Results
The resulting checklist (Table 1; Supplemental file) includes 344 names, 192 accepted taxa (183 species, 7
subspecies, 2 varieties), 112 synonyms, 14 hybrids, and 26 unresolved names. Four species, described in 2016
during the processing and revision of this article (I. tamaulipana Mora-Olivo et al., I. vanensis Zare et al., Isoetes
serracarajensis J.B.S. Pereira et al., I. cangae J.B.S. Pereira et al.) have been added as (preliminary) accepted.
Chromosome numbers were assigned to 101 accepted taxa, with a total of 105 counts (because some taxa showed
more than one ploidy level): diploid taxa were 56, whereas polyploid ones were 49 (34 tetraploids, 10 hexaploids, 2
octoploids, 2 decaploids and 1 dodecaploid); note that odd numbers were not reported in this summary because they
usually are typical of hybrid taxa, and also the report of 2n=58 for I. tenuifolia has not been considered. The count
2n=33 reported for I. goebelii (Pereira et al. 2015) has probably to be referred to hybrid specimens, here we confirm
the “accepted” status for that name waiting for the results of additional ongoing research (Pereira in preparation).
Some minor nomenclatural adjustments regarding spelling and dates of publication have been made. For example,
the terminations of some specific epithets (e.g. dixitei) have been corrected (dixitii) according to Art. 60.12 of the
Code (McNeill et al. 2012). Some dates have been corrected (e.g. in I. luetzelburgii U. Weber, I. organensis U. Weber)
according to Stafleu & Cowan (1976–1988): in other cases (I. storkii T.C. Palmer) dates have been verified on the
original publications.
Although the species list (Table 1) is a provisional checklist, it is useful to generate a synoptic table (Table 2), a
distribution map of these species according to floristic regions “level 2” (Brummit 2001) (Fig. 1), and a synthesis of
the distribution of the different ploidy levels in the genus (Fig. 2).
FIGURE 1. Distribution of Isoetes species richness using the Level 2 regions of Brummitt (2001).
Discussion
The last global monographic treatment of the Isoetaceae (Pfeiffer 1922) accounted for 77 taxa (65 species, 8 varieties,
4 forms). In more recent global compilations Hassler & Swale (2001–2015) listed 143 species and Desfayes (2008–
2015) accounts for ca. 174 taxa. The checklist presented here lists a total of 188 accepted taxa.
Recent estimates of extant Isoetes species range from ca. 150 (Taylor et al. 1993) to about 350 (Hickey et al.
2003). The authors of the present work estimate the number of species to be about 250. This number takes into account
some yet unresolved species groups and other taxa currently being described: Fig. 3 shows the tendency to describe
new taxa in recent years; it shows that an increasing number of taxa have been described during the last 50 years.
Many Isoetes species are rare, sometimes described and known from only the type locality. They are usually
threatened by pollution and destruction of the lakes, rivers, or wetlands and other places where they live (e.g. Bagella &
Caria 2013, Barni et al. 2013). Their habitats are usually inadequately protected. In addition, climate change may alter
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140 Phytotaxa 277 (2) © 2016 Magnolia Press
the hydrological regimes of freshwater inland water bodies (Ruiz 2008). In the online “IUCN Redlist of Threatened
Species” (IUCN 2015), only 28 species of Isoetes have been assessed. Seventeen are listed as threatened or near
threatened, 6 Data Deficient, and 5 Least Concern. Some of those names are synonyms or unresolved taxa, according
to the list presented in Table 1.
TABLE 2. Conspectus showing the number of accepted Isoetes taxa by region, using the Level 2 regions of Brummitt (2001); the number
in front of the region is the code of the region according to Brummitt (2001).
Region Number of taxa
84 Brazil 26
78 Southeastern U.S.A. 21
83 Western South America 19
50 Australia 16
27 Southern Africa 14
12 Southwestern Europe 13
13 Southeastern Europe 12
75 Northeastern U.S.A. 12
85 Southern South America 10
22 West Tropical Africa 9
82 Northern South America 9
34 Western Asia 9
38 Eastern Asia 8
20 Northern Africa 8
79 Mexico 8
71 Western Canada 8
72 Eastern Canada 7
40 Indian Subcontinent 7
76 Southwestern U.S.A. 7
73 Northwestern U.S.A. 7
24 Northeast Tropical Africa 6
25 East Tropical Africa 6
23 West-Central Tropical Africa 5
74 North-Central U.S.A. 5
77 South-Central U.S.A. 5
26 South Tropical Africa 4
36 China 4
43 Papuasia 4
29 Western Indian Ocean 3
31 Russian Far East 3
70 Subarctic America 3
80 Central America 3
81 Caribbean 3
...Continued on next page
GENUS ISOETES Phytotaxa 277 (2) © 2016 Magnolia Press 141
TABLE 2. (Continued)
Region Number of taxa
10 Northern Europe 2
11 Middle Europe 2
14 Eastern Europe 2
30 Siberia 2
41 Indo-China 2
51 New Zealand 2
21 Macaronesia 1
42 Malesia 1
63 North-Central Pacific 1
28 Middle Atlantic Ocean 0
32 Middle Asia 0
33 Caucasus 0
35 Arabian Peninsula 0
37 Mongolia 0
60 Southwestern Pacific 0
61 South-Central Pacific 0
62 Northwestern Pacific 0
90 Subantarctic Islands 0
91 Antarctic Continent 0
FIGURE 2. Distribution of the different ploidy levels in the genus Isoetes. Odd numbers have not been considered.
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142 Phytotaxa 277 (2) © 2016 Magnolia Press
The distribution map of Isoetes species presented in Fig. 1, as well as a synoptic Table 2, illustrate global species
distributions. The number of botanists working in these regions, as well as the accuracy with which individual species
can be mapped affects these distribution patterns. However, the resolution is sufficient to identify several distributional
trends. First, South America appears to be the center of taxonomic diversity for the genus, as suggested by Hickey et
al. (2003), Brazil being the richest region with 26 taxa. Second, diversity in the genus seems to be highest in temperate
regions, with the single main exception of Brazil-Western South America (but here many species occur in temperate/
mountainous areas), where we find 26 + 19 = 44 taxa, one being in common: the other four “biodiversity hotspots”
are in fact Eastern USA (21 in SE + 12 in NE = 26 taxa, 7 being in common), Southern Europe (13 in SW + 12 in SE
= 19 taxa, 6 being in common), Australia (16 taxa), and Southern Africa (14 taxa). Third, several regions appear to
be without Isoetes: in the case of the Asiatic regions (Caucasus, Arabian Peninsula, Middle Asia, Mongolia) possibly
because of insufficient field exploration, more than unsuitability of the climates.
FIGURE 3. Number of accepted Isoetes taxa described in the last 50 years.
As regards to incidence of polyploidy in the genus, according to the data here gathered it results 46.7%; it is a
high value, compared to other groups of vascular plants (cf. Wood et al. 2009), but it is significantly lower compared to
previous estimates (e.g. 61.2% in Troia 2001, which considered 67 taxa vs. 101 taxa here considered), probably thanks
to a better definition of the taxa and to an improved amount of data. It has to be stressed that taxa with more ploidy
levels probably hide different cryptic species: it is the case of I. durieui, I. kirkii, I. muelleri.
The present provisional checklist is the more realistic attempt to assess the species richness and geographic
distribution in Isoetes. It is hoped that this compilation of data will provide a stimulus for further work in improving
our knowledge of diversity and conservation status of these interesting plants, as well as to protect them and the
habitats in which they live.
Acknowledgements
This work has been realized thanks to the decisive stimulus of Richard Lansdown, chair of IUCN-SSC-Freshwater
Plants Specialist Group and through the network of the “Isoetes Research Group” (http://isoetes.myspecies.info/) and
GENUS ISOETES Phytotaxa 277 (2) © 2016 Magnolia Press 143
the “Isoetes group” within the IUCN-SSC-FPSG (http://iucn.org/ssc/fwpsg), both of which all the authors belong to.
We also thank our colleagues Xing-Liu (Wuhan University, China), Deborah Hofstra and Paul Champion (NIWA, New
Zealand’s Institute of Water and Atmospheric research, New Zealand), and Sarvesh Singh (University of Allahabad,
India).
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... Background Merlin's grass, Isoetes of the Lycopsida, are lone survivors of a once much more diverse group of wood-producing lycopsids that also included the Paleozoic tree-lycopods (the rhizomorphic lycopsids sensu DiMichele and Bateman 1996, [1]). The extant genus Isoetes (Isoetaceae) has a nearly worldwide distribution [2][3][4][5] but fairly restricted habitat preferences in that most species live semi-aquatically in habitats that are seasonally inundated. There are purely aquatic and terrestrial species as well [2][3][4][5][6], and repeated transitions between aquatic/semi-aquatic and terrestrial habitats have been inferred for the genus [7,8]. ...
... The extant genus Isoetes (Isoetaceae) has a nearly worldwide distribution [2][3][4][5] but fairly restricted habitat preferences in that most species live semi-aquatically in habitats that are seasonally inundated. There are purely aquatic and terrestrial species as well [2][3][4][5][6], and repeated transitions between aquatic/semi-aquatic and terrestrial habitats have been inferred for the genus [7,8]. Isoetes plants are generally quite small but some species may reach a height over 50 cm or more [4,5]. ...
... Isoetes plants are generally quite small but some species may reach a height over 50 cm or more [4,5]. The stem takes the form of a lobed corm [3][4][5][6], to which the leaves are helically attached forming a basal rosette [4,5]. The leaves usually have four air channels [4,6] (although exceptions have been reported, [9]) and may have megaor microsporangia sunken into the base of the leaf. ...
Article
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Background Merlin’s grass ( Isoetes , Isoetaceae, Lycopsida), is the extant remnant of the isoetalean wood-producing lycopsids that originated during the Paleozoic, possibly in aquatic or boggy habitats. Modern day species are aquatic, semi-aquatic or terrestrial and occur almost worldwide. They display little morphological variation; the lobed corm has helically arranged leaves with internal air channels and basal sporangia. Genetic variation has also proven limited, which has hampered phylogenetic inference. We investigate evolutionary relationships in Isoetes , using molecular data and an extended sample of species compared to previous work, adding species that have never before been included in a phylogenetic study. Results Our results reveal an unexpected discovery of an “ Amborella syndrome” in Isoetaceae: a single poorly known species is sister to the remaining family. The species, Isoetes wormaldii , is a rare endemic to the Eastern Cape of South Africa. Its leaves are flattened with a rounded point, which sharply contrasts with the awl-shaped leaves of most other species of Isoetes . The remaining species of Isoetes are resolved in five major clades, also indicated in previous work. While the phylogeny shows geographic structure, the patterns are complex. For example, tropical-southern African species occur in at least five clades, and Indian, Australian and Mediterranean species in at least three clades each. Conclusion The evolutionary and biogeographical history of Isoetes is not easily explained, and may conceivably include ample extinction and a mixture of ancient and more recent processes. Previously shown difficulties with node age estimation increase the problem. The here demonstrated sister-relationship between the phylogenetically, morphologically and genetically distinct Isoetes wormaldii and the remaining family appears to bridge the morphological gap between Isoetes and its extinct relatives, although further studies are needed. Moreover, it shortens the branch length to its living sister genus Selaginella , and may enhance node age estimation in future studies. Isoetes wormaldii is critically endangered, known only from one (to a few) minor populations. Immediate actions need to be taken if we want to prevent this unique species from going extinct.
... The lycophyte genus Iso€ etes is a heterosporous plant group, which is globally distributed with approximately 250 species (PPG 2016;Troia et al. 2016). The genus occurs fully submerged in rivers, streams, lakes, or ponds, or terrestrial in seasonally inundated areas from climatic arctic to tropical warm regions (Pereira 2020;Taylor et al. 2016). ...
... The genus is notorious for its morphological simplicity and likely convergence of inhabiting aquatic and terrestrial habitats, which lead to taxonomic difficulties (Taylor and Hickey 1992). Among the lycophytes, Iso€ etes also possesses the highest proportion of polyploids (about 47% of species; Troia et al. 2016) with allopolyploidization playing a fundamental role in the diversification of the genus (see Hoot et al. 2004;Kim et al. 2010;Pereira et al. 2019c). Allopolyploidy leads to a combination of morphological characteristics that hamper efforts to identify species in Iso€ etes (Hoot et al. 2004;Pereira et al. 2019c). ...
Article
Isoëtes cipoensis and I. longifolia , two new endemic tetraploids from the Cerrado (Brazilian savanna), are described, illustrated, and compared to their similar species. Isoëtes cipoensis can be distinguished by a set of characters such as flaccid, straight, and erect leaves, deltate labia, presence of conspicuous sclerified phyllopodia, baculate megaspores with frequent long spine-like macroelements, and distally echinate microspores. Isoëtes longifolia is characterized by having a fully submerged habitat in the river, flaccid, long leaves (70‐100 cm long), oblong labia, uniformly baculate megaspores, and densely echinate microspores. Importantly, chloroplast genomes already published for the species further support their phylogenetic distinctness in comparison to other species from the tropical region in Brazil. This study provides a key and distribution map for the species from the Brazilian savanna and scanning electron microscopy images of the mega- and microspores for the new species. These species are only known from their type location. We suggest I. cipoensis and I. longifolia should be classified as Data Deficient (DD) and Endangered (EN) species, respectively, based on the IUCN criteria.
... Problems arise not only on global scale, where one has to recognize dozens of species, as aquatic genera usually are subcosmopolitan and speciose (e.g. Callitriche L.: Ito et al., 2017; Isoëtes L.: Troia et al., 2016; Potamogeton L.: Kaplan et al., 2013; Ranunculus L. section Batrachium DC.: Wiegleb et al., 2017; Utricularia L.: Silva et al., 2018), but also on regional level, where the number of the genus representatives is modest. ...
... e. U. vulgaris and U. macrorhiza), are sympartric. Such difficulty with hybrid discrimination is rather a rule in aquatic plants (Kaplan et al., 2013;Troia et al., 2016;Wiegleb et al., 2017), highlighted here for the first time for Utricularia. ...
Article
Most of Utricularia taxa in temperate Eurasia are poorly distinguished by vegetative characters, while flowering is rare in some of them. Thus, we aimed to clarify the taxonomy and distribution of temperate Eurasian Utricularia. We supplemented the existing results of intensive morphological and genetic studies of Utricularia mainly from West and Central Europe with our data from East Europe and North Asia. We combined molecular barcoding (nuclear ITS and plastid rps16 regions) and fingerprinting (ISSR) techniques (74 collection localities) with morphological analysis of herbarium collections (more than 1800 specimens from 16 herbaria) and numerous natural populations with a special focus on hardly accessible Siberian and Far Eastern regions of Russia. We demonstrated that temperate Eurasian Utricularia taxa could be easily discriminated with barcoding approach if the hybridization is taken into account. Genetic and morphological variation of U. macrorhiza in comparison with U. vulgaris supported the treatment of the former as a separate species. We have revealed U. tenuicaulis previously treated as fertile lineage of U. australis and its sterile hybrid with U. macrorhiza (U. × japonica) in the Russian Far East and the latter additionally in southwestern East Siberia, outside their known distribution. For the first time we evidenced hybridization between U. tenuicaulis and U. vulgaris. The sterile hybrid (U. × neglecta) is widely distributed in Europe and West Siberia. In the Northern Hemisphere, plants initially referred to as sterile U. australis represent in fact U. × japonica and U. × neglecta, and the name U. australis should not be applied to any of them. Utricularia ochroleuca and U. stygia represent a complex of sterile forms with continuous morphological variation (U. × ochroleuca) originated from hybridization between U. intermedia and U. minor. Almost forgotten Japanese species U. multispinosa appeared to be sister to all temperate Eurasian species, and it was revealed for the first time in the southern Russian Far East.We have refined the distributions of Utricularia species in East Europe and North Asia and have shown that extant areas of U. macrorhiza and U. vulgaris are explained by the temperature regime – an important insight in context of global climate change. Full-text available on request.
... The lycophyte family Isoetaceae consists of a single extant genus, Isoetes L., which comprises approximately 250 living species worldwide (Troia et al. 2016;Brunton and Troia 2018). The Isoetes species occur in a variety of seasonally or permanently inundated habitats -such as ponds, small ditches, streams, lakes, wetlands, and terrestrial habitats in the tropical to subarctic biomes (Merrill and Perry 1940;Hoot et al. 2006;Singh et al. 2021). ...
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Isoetes philippinensis, a critically endangered site-endemic lycophyte, was rediscovered after the last collection in 1969. The present study elucidates the morphology and ecology of the species-which have not been fully investigated-by describing the detailed morpho-anatomical characters, collecting water samples for physico-chemical analysis, and providing an in situ description of its habitat. The diagnostic characteristics of the species included long microphylls (up to 63 cm long), cobwebby megaspores and microspores, and the presence of velum. The morphology of I. philippinensis exhibits the features of other aquatic, amphibious and terrestrial species of Isoetes-such as the presence of lacuna in the roots, air chambers in the leaves, reduced stele, and abundance of parenchyma cells throughout the organs. Water-quality values are within the minimum acceptable limit. Threats to the population of I. philippinensis are discussed and characterized as Critically Endangered (CR A1c, B2a). The information presented here is vital for both in situ and ex situ conservation of the species.
... Isoëtes is a heterosporous genus globally distributed with an estimated 250 species (PPG, 2016;Troia et al., 2016), 29 of which are recorded in Brazil to date (Pereira, 2020). The genus can be readily identified by having narrow linear leaves, which form a rosette and contain transversely four air chambers, a single sunken sporangium at the base of each leaf, and usually a globose stem with normally 2-4 lobes (Jermy, 1990). ...
Article
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Revealing the unrecognized diversity within cryptic species has profound implications in the taxonomy, systematics, evolutionary studies, and species protections throughout plant groups. Isotes is prone to a high rate of cryptic speciation because of its morphological simplicity, stasis, and convergence. Phylogenetic studies revealed cryptic species in the genus from the Brazilian semi-arid region (the Caatinga), which comprises the least studied and most endangered flora in Brazil. Here we conducted morphological analyses and chromosome counts, and took advantage of phylogenetic analyses already published for the genus to provide a taxonomic revision of Isotes from the Caatinga. Isotes anamariae and I. harleyi are two new species, which were revealed by molecular data and subtle morphological characters. This study provides descriptions, chromosome counts, illustrations of the most important morpho-taxonomic characters of species from the Caatinga, and a key to identify them. All species from this region are diploid and we show the importance of diploids in detangling the origin of polyploids in Brazil.
... Currently, there are ~200 named taxa (species, subspecies, hybrids) of Isoetes worldwide (Troia et al. 2016), with perhaps 100 more expected to be recognizable based on morphology (Brunton and Troia 2018). Molecular studies suggest that, in addition, there may be 50 or more morphologically cryptic taxa in North America alone (Schafran 2019). ...
Article
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In Canada, the globally rare lycophyte, Columbia Quillwort (Isoetes minima), is currently known from four subpopulations, all within a 25-km radius of Castlegar in the Selkirk and Monashee Mountain ranges of southern British Columbia. These constitute just over a quarter of all known subpopulations in Canada and the United States. The species is found in Canada in sloping pocket meadows that are naturally fragmented within a larger forested matrix. The plants grow in spring seepage areas in thin soils that discourage the establishment of larger, more vigorous vascular plant competitors. Long combined within Isoetes howellii (sensu lato), I. minima has only recently been confirmed to be a distinct species, and, in 2019, it was assessed as Endangered by the Committee on the Status of Endangered Wildlife in Canada (COSEWIC). We build on information in the COSEWIC status report by describing the species’ morphology and ecology in greater detail and provide a comparison of critical identification features of closely related species as well as a dichotomous key for Isoetes species in British Columbia.
... cytology Cytological studies in 1998 by D.M. Britton determined that populations from four different lakes in Pirin National Park were decaploid (2n=10×=110) (Figure 3). Aquatic Isoetes lacustris (s.s.) and terrestrial I. durieui Bory are the only other known European decaploids (Troia, 2001;Troia et al., 2016). Pyrenean endemic I. creussensis is considered to be dodecaploid (2n=12×=132) (lazare & Riba, 2010;Brunton et al., 2020). ...
Article
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Isoetes pirinica sp. nov. is an endemic lycophyte of the eastern Balkan Region, found only in the Pirin Mountains of southwestern Bulgaria. It is the fourth decaploid (10×) species of the genus to be recognized globally. It has uniquely small spores for an Isoetes of such a ploidy level and commonly exhibits an exceptionally echinate-like megaspore ornamentation for a member of the I. lacustris complex. The species is one of many endemic vascular plants of the Pirin Mountains and is believed to be of recent (<12,000 years BP) origin. While geographically restricted, I. pirinica
... The genus Isoetes Linnaeus (1753: 1100) in India is represented by 28 taxa (Patil & Rajput 2017) but a number of them have been synonymised (Fraser-Jenkins et al. 2016, Troia et al. 2016, Singh et al. 2021. While exploring the Western Ghats for the revision of Isoetes, individuals collected from Panchgani tableland (Satara, Maharashtra) were identified as Isoetes dixitii Shende (1945: 50). ...
Article
The genus Isoetes Linnaeus (1753: 1100) in India is represented by 28 taxa (Patil & Rajput 2017) but a number of them have been synonymised (Fraser-Jenkins et al. 2016, Troia et al. 2016, Singh et al. 2021). While exploring the Western Ghats for the revision of Isoetes, individuals collected from Panchgani tableland (Satara, Maharashtra) were identified as Isoetes dixitii Shende (1945: 50). The species can be distinguished by its rudimentary velum, elongated sporangia, megaspores tuberculate with uneven tubercles (Shende 1945; Patil & Rajput 2017).
Article
A sterile hybrid between diploids Isoetes gymnocarpa and I. longissima (s.s.) (Isoetaceae) is described from Anguillara, Trapani Province, Sicily, Italy. Although closest in morphology to I. gymnocarpa with which it was growing, the small group of hybrid plants also exhibited features of I. longissima which occurred abundantly within 50 m of the site. In addition to such classic hybrid characteristics as larger plant size (hybrid vigour) and polymorphic, aborted megaspores with ornamentation intermediate between that of the putative parents, the microspores of the hybrid exhibit both the arachnoid ornamentation features of I. gymnocarpa and the echinate features of I. longissima (s.s.). Isoetes ×angeloi, hyb. nov., is the first non-aquatic Isoetes hybrid to be formally described. It is also the first hybrid quillwort to be confirmed from the Mediterranean Basin.
Article
Isoëtes cangae is a critically endangered submerged quillwort endemic from Amazon ferruginous outcrops fields in north Brazil. The species inhabit a single oligotrophic lake with specific light irradiance quality and quantity. We analyzed light irradiance in field conditions to study the relationship between irradiance and species morphological and physiological traits. Specifically, we compared the I. cangae growth and photosynthesis in ex situ cultivation under control (CI - 20 µmol.m⁻².s⁻¹) and high irradiance (HI – 400 µmol.m⁻².s⁻¹). Light spectra in natural habitat suggest that I. cangae is a shade-tolerant species and the results in artificial light confirmed the growth impairment under long-term HI. Plants showed photosynthesis inhibition and the loss of older leaves, which were gradually replaced by new leaves. Our results highlight that the proper management of light irradiance is fundamental in ex situ and in situ cultivation for I. cangae conservation.
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Target 1 of the Global Strategy for Plant Conservation (GSPC) is, "a widely accessible working list of all known plant species, as a step towards a complete world Flora". This paper discusses the importance of the Target to the GSPC itself, to many sectors of science and society, and to decision makers. It then examines the progress made to date and prospects for the Target's completion. Good progress has been made in bryophytes, ferns and gymnosperms with widely accessible working lists either complete or almost so for these groups. Online working lists are available for around 50% of flowering plants. In all, Target 1 is around 53% complete. It is estimated that there are around 352,000 flowering plants and that the current gap in online coverage is around 177,000 species. The major families constituting the gap are identified, the four largest being Apocynaceae, Malvaceae, Ericaceae and Apiaceae. The large majority of families for which there is no working list available are either cosmopolitan or pantropical in distribution. However, progress to date suggests that neither broad distribution nor large numbers of species in a family are insurmountable problems in compiling working lists. The major barrier to completion of Target 1 remains the availability of taxonomists to contribute to the target. Completion of Target 1 by 2010 is possible if botanical institutions recognise the importance of the Target and collaborate, lever funding and prioritise activities appropriately.
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This is the twenty-three of a series of reports of chromosomes numbers from Mediterranean area, peri-Alpine communities and the Atlantic Islands, in English or French language. It comprises contributions on 56 taxa: Anthriscus, Bupleurum, Dichoropetalum, Eryngium, Ferula, Ferulago, Lagoecia, Oenanthe, Prangos, Scaligeria, Seseli and Torilis from Turkey by Ju. V. Shner, T. V. Alexeeva, M. G. Pimenov & E. V. Kljuykov (Nos 1768-1783); Astrantia, Bupleurum, Daucus, Dichoropetalum, Eryngium, Heracleum, Laserpitium, Melanoselinum, Oreoselinum, Pimpinella, Pteroselinum and Ridolfia from Former Jugoslavia (Slovenia), Morocco and Portugal by J. Shner & M. Pimenov (1784-1798); Arum, Biarum and Eminium from Turkey by E. Akalin, S. Demirci & E. Kaya (1799-1804); Colchicum from Turkey by G. E. Genç, N. Özhatay & E. Kaya (1805-1808); Crocus and Galanthus from Turkey by S. Yüzbaşioǧlu, S. Demirci & E. Kaya (1809-1812); Pilosella from Italy by E. Di Gristina, G. Domina & A. Geraci (1813-1814); Narcissus from Sicily by A. Troia, A. M. Orlando & R. M. Baldini (1815-1816); Allium, Cerastium, Cochicum, Fritillaria, Narcissus and Thymus from Greece, Kepfallinia by S. Samaropoulou, P. Bareka & G. Kamari (1817-1823).
Article
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Premise of research. The heterosporous lycopsids of Isoetes show limited morphological and genetic variation despite a worldwide distribution and the ancient origin of the lineage. Here major relationships within the genus are clarified, using a substantially larger sampling of species than in previous studies. A first assessment of divergence times of clades is made, and the implications for dispersal mechanisms and biogeographic distribution patterns are discussed. Methodology. On the basis of sequences from three gene regions and 109 specimens representing 74 species of Isoetes, phylogeny and node ages were estimated using parsimony and Bayesian inference. Pivotal results. Three rooting approaches (outgroup analysis, midpoint rooting, and clock rooting) coherently resolved a diverse clade containing species from South Africa, India, Australia, and South America (clade A) as sister to remaining Isoetes. Analysis of divergence times of clades yielded a median age of the crown group of 147 million years ago (mya) using a birth-death tree prior and 165 mya using a Yule tree prior. Clade A was dated to 111 or 125 mya, respectively. While the earliest divergences in Isoetes appear readily explained by ancient vicariance, patterns in younger clades are consistent with dispersal processes, sometimes over long distances. Isoetes andicola (Amstutz) L.D. Gómez, once hypothesized to represent a separate lineage and assigned to the genus Stylites, is here included in a phylogenetic study for the first time. It is closely related to some other South American species, despite its peculiar morphology with a dichotomizing stem. Conclusions. Despite limited intrageneric variation at the molecular and morphological levels, node ages as well as species composition (phylogeny) indicate a Mesozoic origin of the extant clade. Biogeographic patterns appear complicated and intriguing but need more research. Tuberculate megaspore ornamentation (sensu Pfeiffer) is ancestral in the genus, as indicated by current knowledge. Other megaspore patterns appear restricted to two subclades.
Article
Quillworts or Çim Eǧreltisi, species of the genus Isoetes L. in Turkey and the Levant, are poorly studied despite extensive floristic studies in the region. The Flora of Turkey lists 4 taxa: Isoetes olympica A.Braun (2n = 22), I. histrix Bory var. histrix (2n = 20), I. subinermis (Bory) Cesca & Peruzzi [=I. histrix Bory var. subinermis Durieu (2n = 22)] and I. duriei Bory (2n = ca. 121). An additional species, I. anatolica Prada & Rolleri, was described in 2005 from Bolu province, and we report the first count for this species, 2n = 22. In Syria and Lebanon 2 species are known: I. olympica from a site in Syria and a known but undescribed plant from Akkar province (Lebanon) and adjacent Syria (2n = 22, first count). A preliminary molecular phylogeny for these species is presented; their distribution and cytology are discussed. The taxonomy and nomenclature of the I. histrix and I. duriei groups need considerable further study. The first hybrids for the region are documented.
Article
The Isoëtes karstenii complex includes those species characterized by laevigate megaspores, acute to free ala apices, a highly reduced labium, and distributions in the high altitude páramos of Venezuela, Colombia, and Ecuador. These species have been variously treated in the literature. Many early authors placed all Andean laevigate-spored specimens in Isoëtes lechleri, a central Andean species, while one later author recognized up to eight northern Andean species distinct from I. lechleri. This research represents a revisionary study to determine the number and identity of the taxa in this complex. Multivariate and descriptive analyses of morphological data and chromosome counts were performed. Five species are recognized including the previously described I. karstenii and I. palmeri. One variety is transferred from I. lechleri to I. karstenii (I. karstenii var. anomala). Three of the recognized species are newly described: I. fuliginosa, I. hemivelata and I. precocia. Chromosome counts revealed that I. karstenii and I. precocia are diploids (2n = 22) and that I. palmeri is tetraploid (2n = 44). Estimates of chromosome number based on spore size for I. fuliginosa and I. hemivelata indicate that they are polyploid (2n ≥ 44).
Article
Despite its ancient origins, its worldwide distribution, and adaptation to diverse habitats, Isoëtes has a highly conserved morphology. This feature has made it difficult to resolve species and species relationships using morphological characters. In this paper, we report the utility of nucleotide sequences from the nuclear internal transcribed spacer (ITS) regions, chloroplast atpB/rbcL intergenic spacer region, and second intron of a LEAFY (LFY) homolog for identifying species relationships, delimiting basic diploid species, and determining hybrid origins. Variation in the ITS regions and atpB/rbcL spacer is most useful at the family level in Isoëtes and the LFY second intron is appropriate at the species and population level. The tree resulting from an analysis of the combined nuclear ITS and chloroplast atpB/rbcL spacer contains three major well supported clades (bootstrap ≥ 99%): an Old-World/California clade (I. abyssinica, I. longissima, I. velata, I. nuttallii, and I. orcuttii), an Asian/Australian clade (I. taiwanensis, I. japonica, I. kirkii, and I. drummondii), and a poorly resolved clade consisting of nine North American species. To further resolve and delimit the North American species, a combination of the LEAFY second intron and ITS data was used. The resulting consensus tree has limited resolution, supporting the hypothesis that the North American species complex radiated rapidly. The combination of LFY and ITS data provided numerous characters, both substitutions and indels, that are useful in species delimitation and identification of cryptic species. ITS sequence data, through additive banding and sequence misalignment, is also useful in confirming interspecific hybrids and determining their parental origins.