Biodiversity Data Journal :
Taxonomic paper
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Chromosome studies in the aquatic monocots of Myanmar: A brief review with additional records
Corresponding author:
Academic editor: Lorenzo Peruzzi
Received: 11 Feb 2014 | Accepted: 08 May 2014 | Published: 13 May 2014
© 2014 Yu Ito, Nobuyuki Tanaka
This is an open access article distributed under the terms of the Creative Commons Attribution License (CC BY 4.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.
Citation:
Ito Y, Tanaka N (2014) Chromosome studies in the aquatic monocots of Myanmar: A brief review with additional records. Biodiversity Data Journal 2: e1069. https://doi.org/10.3897/BDJ.2.e1069
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Myanmar (Burma) constitutes a significant component of the Indo-Myanmar biodiversity hotspot, with elements of the Indian, the Indochina, and the Sino-Japanese floristic regions, yet thus far only a few reliable sources of the country's flora have been available. As a part of a contribution for the floristic inventory of Myanmar, since it is important in a floristic survey to obtain as much information as possible, in addition to previous two reports, here we present three more chromosome counts in the aquatic monocots of Myanmar: Limnocharis flava with 2n = 20, Sagittaria trifolia with 2n = 22 (Alismataceae), and Potamogeton distinctus × P. nodosus with 2n = 52 (Potamogetonaceae); the third one is new to science. A brief review of cytological researches in the floristic regions' 45 non-hybrid aquatic monocots plus well investigated two inter-specific hybrids that are recorded in Myanmar is given, indicating that the further works with a focus on species in Myanmar that has infra-specific chromosome variation in the floristic regions will address the precise evolutionary history of the aquatic flora of Myanmar.
Aquatic plants, chromosome counts, Limnocharis, Myanmar, Potamogeton, Sagittaria
With its wealth of plant diversity, Myanmar (Burma) constitutes a significant component of the Indo-Myanmar biodiversity hotspot with elements of the India, the Indochina, and the Sino-Japanese floristic regions (ca, 13,500 vascular plants:
The aim of floristic research is not only to count the total number of species but also to evaluate the native flora’s evolutionary origins by comparing with related floristic regions. From this aspect, it is useful to obtain as much information as possible, e.g., chromosome data (
Aquatic plants, which is polyphyletically evolved in fern and fern allies, basal angiosperms, monocots, and eudicots, is known as having numerous chromosomal variation, thus an excellent model for this aim. Here, in addition to the previous contributions of chromosome counts for new or noteworthy aquatic plants from Myanmar (Najas tenuis:
Plant materials of Limnocharis flava (Alismataceae), Sagittaria trifolia (Alismataceae), Najas tenuis (Hydrocharitaceae), Nechamandra alternifolia (Hydrocharitaceae), and Potamogeton distinctus × P. nodosus (Potamogetonaceae) were collected in the expeditions to Myanmar (Bago Division and Shan State) in 2008. The collections were rigorously identified based on morphological characters using the original protologues as well as a previous taxonomic treatment by
Root tips collected in the field were pretreated with 0.002 M 8-hydroxyquinoline at 4 °C in 12 h, and fixed with freshly mixed Carnoy’s fixative (3: 1 ethyl alcohol: acetic acid) for at least 30 min, and then preserved at 4 °C in 12 h. For microscopic observation, root tips were soaked in 1 N HCl for 1 h followed by 10 min at 60 °C. After being immersed in tap water, the materials were stained in a drop of 1.5% orcein acetate solution on a slide glass in 5 min., and then squashed. Then somatic chromosome numbers of the three taxa were obtained by light microscopic examination. For each species, at least two cells were used to confirm the numbers.
Distribution for each species follows
Chromosome researches for aquatic monocots of Myanmar were reviewed with a broad focus on Myanmar and related floristic regions, i.e., the Indian, the Indochina, and the Sino-Japanes floristic regions. The focal species include 45 non-hybrid aquatic monocots listed in
Native to Americas; naturalized to tropical Asia.
Bangladesh, Bhutan, China (nationwide), India (nationwide), Indonesia (Borneo, Java, Sulawesi), Japan, Malaysia (Peninsular), Myanmar, Nepal, Pakistan, Philippines, Thailand; Oceania.
India (Central, Southern), Myanmar, Sri Lanka.
Bangladesh, China (Southern), India (Eastern, Northern, Southern), Myanmar, Nepal, Sri Lanka, Thailand, Vietnam; Yemen, and Sudan.
The chromosome counts given for 45 non-hybrid species of aquatic monocots of Myanmar as well as well-investigated two Potamogeton hybrids among them were reviewed with a focus on infra-specific chromosome variation (Table
The chromosome counts given for 45 non-hybrid species of aquatic monocots of Myanmar as well as well-investigated two Potamogeton hybrids among them. Those recorded from neighboring regions are also provided. The species that have no chromosome counts anywhere in the world are shown with n/a. For some species, mostly cosmopolitan ones, only a few representative literature references are given for each chromosome number. Note that due to incapability of original references, some rare chromosome counts are not included in this table: 2n = 18, 42, 48 for Acorus calamus; 2n = 18, 22 for Acorus gramineus (Acoraceae), 2n = 28 for Pistia stratiotes var. cuneata Engl.; 2n = 28 for Pistia stratiotes var. spathulata (Michx.) Engl.; 2n = 20, 50, 60, 80 for Lemna aequinoctialis; 2n = 44 for Lemna trisulca; 2n = 30, 50 for Spirodela polyrrhiza (Araceae); n = 14 (2n = 28), 2n = 10, 12 for Alisma plantago-aquatica; 2n = 22 for Caldesia parnassifolia; 2n = 26, 39 for Limnocharis flava; 2n = 22 for Sagittaria trifolia var. longiloba (Turr.) Mak.; 2n = 22 for Sagittaria trifolia var. sinensis Sims; 2n = 22 for Sagittaria trifolia var. edulis (Sieb.) Ohwi (Alismataceae); 2n = 24 for Blyxa aubertii; 2n = 60 for Najas marina; 2n = 12+1B for Najas marina var. intermedia (Gorski) A. Braun; 2n = 22, 52, 72, 88, 132 for Ottelia alismoides; 2n = 16, 22, 28, 33 for Vallisneria spiralis (Hydrocharitaceae); 2n = 64 for Eichhornia crassipes; 2n = 26, n = 40 (2n = 80) for Monochoria vaginalis (Pontederiaceae); 2n = 60 for Typha angustifolia (Typhaceae). Also refer to previous cytological reviews (aquatic plants:
Order | Family | Species | Chromo-some number | Floristic region | ||||
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Indian | Myanmar | Indo-china | Sino-Japanese | Others | ||||
Acorales | Acoraceae | Acorus calamus L. | 2n = 24 | |||||
Acorales | Acoraceae | Acorus calamus L. | 2n = 35 | |||||
Acorales | Acoraceae | Acorus calamus L. | 2n = 36 | |||||
Acorales | Acoraceae | Acorus calamus L. | 2n = 44 | |||||
Acorales | Acoraceae | Acorus calamus L. | 2n = 45 | |||||
Acorales | Acoraceae | Acorus calamus L. | 2n = 66 | |||||
Acorales | Acoraceae | Acorus gramineus Sol. ex Aiton | 2n = 24 | |||||
Acorales | Araceae | Cryptocoryne crispatula Engl. | 2n = 36 | |||||
Acorales | Araceae | Cryptocoryne crispatula Engl. | 2n = 54 | |||||
Acorales | Araceae | Cryptocoryne cruddasiana Prain | n/a | |||||
Acorales | Araceae | Pistia stratiotes L. | 2n = 28 | |||||
Acorales | Araceae | Landoltia punctata (G. Mey.) Les & D.J. Crawford | n/a | |||||
Acorales | Araceae | Lemna aequinoctialis Welw. | 2n = 40 | |||||
Acorales | Araceae | Lemna trisulca L. | 2n = 20 | |||||
Acorales | Araceae | Lemna trisulca L. | 2n = 40 | |||||
Acorales | Araceae | Lemna trisulca L. | 2n = 60 | |||||
Acorales | Araceae | Lemna trisulca L. | 2n = 80 | |||||
Acorales | Araceae | Spirodela polyrrhiza (L.) Schleid. | 2n = 40 | |||||
Acorales | Araceae | Spirodela polyrrhiza (L.) Schleid. | 2n = 42 | |||||
Acorales | Araceae | Spirodela polyrrhiza (L.) Schleid. | 2n = 80 | |||||
Acorales | Araceae | Wolffia globosa (Roxb.) Hartog &Plas | n/a | |||||
Alismatales | Alismataceae | Alisma plantago-aquatica L. | 2n = 14 | |||||
Alismatales | Alismataceae | Caldesia parnassifolia (Bassi ex L.) Parl. | n/a | |||||
Alismatales | Alismataceae | Limnocharis flava (L.) Buchenau | 2n = 20 | This study | ||||
Alismatales | Alismataceae | Sagittaria trifolia L. | 2n = 22 | This study | ||||
Alismatales | Hydrocharita | Blyxa aubertii Rich. | 2n = 40 | |||||
Alismatales | Hydrocharita | Blyxa echinosperma (C.B. Clarke) Hook. f. | 2n = 42 | |||||
Alismatales | Hydrocharita | Blyxa echinosperma (C.B. Clarke) Hook. f. | 2n = 74 | |||||
Alismatales | Hydrocharita | Blyxa japonica (Miq.) Maxim. ex Asch. & Gürke | 2n = 42 | |||||
Alismatales | Hydrocharita | Blyxa japonica (Miq.) Maxim. ex Asch. & Gürke | 2n = 72 | |||||
Alismatales | Hydrocharita | Egeria densa (Planch.) Casp. | 2n = 46 | |||||
Alismatales | Hydrocharita | Egeria densa (Planch.) Casp. | 2n = 48 | |||||
Alismatales | Hydrocharita | Elodea nuttallii (Planch.) H. St. John | 2n = 48 | |||||
Alismatales | Hydrocharita | Hydrilla verticillata (L. f.) Royle | 2n = 16 | |||||
Alismatales | Hydrocharita | Hydrilla verticillata (L. f.) Royle | 2n = 24 | |||||
Alismatales | Hydrocharita | Hydrilla verticillata (L. f.) Royle | 2n = 32 | |||||
Alismatales | Hydrocharita | Hydrocharis dubia (Blume) Backer | 2n = 16 | |||||
Alismatales | Hydrocharita | Najas graminea Delile | 2n = 12 | |||||
Alismatales | Hydrocharita | Najas graminea Delile | 2n = 24 | |||||
Alismatales | Hydrocharita | Najas graminea Delile | 2n = 36 | |||||
Alismatales | Hydrocharita | Najas indica (Willd.) Cham. | n/a | |||||
Alismatales | Hydrocharita | Najas marina L. | 2n = 12 | |||||
Alismatales | Hydrocharita | Najas marina L. | 2n = 24 | |||||
Alismatales | Hydrocharita | Najas tenuis Magnus | 2n = 24 | |||||
Alismatales | Hydrocharita | Nechamandra alternifolia (Roxb.) Thwaites | 2n = 16 | |||||
Alismatales | Hydrocharita | Ottelia alismoides (L.) Pers. | 2n = 44 | |||||
Alismatales | Hydrocharita | Ottelia alismoides (L.) Pers. | 2n = 66 | |||||
Alismatales | Hydrocharita | Ottelia alismoides (L.) Pers. | 2n = 68 | |||||
Alismatales | Hydrocharita | Ottelia cordata (Wall.) Dandy | n/a | |||||
Alismatales | Hydrocharita | Vallisneria spiralis L. | 2n = 20 | |||||
Alismatales | Hydrocharita | Vallisneria spiralis L. | 2n = 24 | |||||
Alismatales | Hydrocharita | Vallisneria spiralis L. | 2n = 30 | |||||
Alismatales | Hydrocharita | Vallisneria spiralis L. | 2n = 40 | |||||
Alismatales | Aponogetona | Aponogeton lakhonensis A. Camus | n/a | |||||
Alismatales | Potamogetona | Potamogeton crispus L. | 2n = 52 | |||||
Alismatales | Potamogetona | Potamogeton crispus L. | 2n = 56 | |||||
Alismatales | Potamogetona | Potamogeton distinctus A. Benn. | 2n = 52 | |||||
Alismatales | Potamogetona | Potamogeton distinctus A. Benn. × P. nodosus Poir. | 2n = 52 | This study | ||||
Alismatales | Potamogetona | Potamogeton maackianus A Benn. | 2n = 52 | |||||
Alismatales | Potamogetona | Potamogeton maackianus A Benn. | 2n = 56 | |||||
Alismatales | Potamogetona | Potamogeton × malainoides Miki | 2n = 52 | |||||
Alismatales | Potamogetona | Potamogeton lucens L. | 2n = 52 | |||||
Alismatales | Potamogetona | Potamogeton nodosus Poir. | 2n = 52 | |||||
Alismatales | Potamogetona | Potamogeton octandrus Poir. | 2n = 28 | |||||
Alismatales | Potamogetona | Potamogeton wrightii Morong | 2n = 52 | |||||
Alismatales | Potamogetona | Stuckenia pectinata (L.) Börner | 2n = 78 | |||||
Alismatales | Potamogetona | Stuckenia pectinata (L.) Börner | 2n = 84 | |||||
Alismatales | Ruppiaceae | Ruppia maritima L. | 2n = 20 | |||||
Ruppia maritima L. | 2n = 40 | |||||||
Asparagales | Amaryllidaceae | Crinum thaianum J. Schul. | n/a | |||||
Commelinales | Pontederiaceae | Eichhornia crassipes (Mart.) Solms | 2n = 32 | |||||
Commelinales | Pontederiaceae | Monochoria hastata (L.) Solms | 2n = 28 | |||||
Commelinales | Pontederiaceae | Monochoria hastata (L.) Solms | 2n = 80 | |||||
Commelinales | Pontederiaceae | Monochoria vaginalis (Burm.f.) C. Presl ex Kunth | 2n = 24 | |||||
Commelinales | Pontederiaceae | Monochoria vaginalis (Burm.f.) C. Presl ex Kunth | 2n = 48 | |||||
Commelinales | Pontederiaceae | Monochoria vaginalis (Burm.f.) C. Presl ex Kunth | 2n = 52 | |||||
Commelinales | Typhaceae | Typha angustifolia L. | 2n = 30 | |||||
Poales | Eriocaulaceae | Eriocaulon setaceum L. | n/a |
Of 45 non-hybrid aquatic monocots and two interspecific hybrids among them, more than two thirds have no chromosome variation. Meanwhile, the following nine species have infra-specific chromosome variation, i.e., Acorus calamus, Cryptocoryne crispatula, Blyxa echinosperma, Hydrilla verticillata, Najas graminea, Ottelia alismoides, Vallisneria spiralis, Monochoria hastata, and M. vaginalis (Table
Potamogeton is known as having numerous inter-specific hybrids, and each parental combination is varied from intra-ploidy crosses to inter-ploidy ones (
Thanks are due to the following personnel in Myanmar for their help in arranging our field work: U. Htun Paw Oo, Ex-director of Nature and Wildlife Conservation Division; U. Soe Win Hlaing, Ex-director General, Forest Department, Ministry of Environmental Conservation and Forestry. We also thank Prof. T. Koyama, director of the Kochi Prefectural Makino Botanical Garden (Japan), who initiated the Myanmar-Japanese cooperative program to inventory the plants of Myanmar, and gave us the opportunities to study the Myanmar plants, Prof. J. Murata, curator of the University of Tokyo (Japan), who principally organizes the Myanmar-Japanese inventory project, and Dr. T. Ohi-Toma, assistant professor of the University of Tokyo (Japan), who helps the first author to use the facilities of the botanical gardens, the university of Tokyo.
Conceived and designed the study: YI NT. Collected the samples in the field: YI NT. Performed the chromosome observation: YI. Analyzed the data: YI. Wrote the paper: YI. Corrected and revised manuscript: NT.