HOME

TheInfoList



OR:

''Takakia'' is a
genus Genus (; : genera ) is a taxonomic rank above species and below family (taxonomy), family as used in the biological classification of extant taxon, living and fossil organisms as well as Virus classification#ICTV classification, viruses. In bino ...
of two species of
moss Mosses are small, non-vascular plant, non-vascular flowerless plants in the taxonomic phylum, division Bryophyta (, ) ''sensu stricto''. Bryophyta (''sensu lato'', Wilhelm Philippe Schimper, Schimp. 1879) may also refer to the parent group bryo ...
es known from western North America and central and eastern Asia. The genus is placed as a separate
family Family (from ) is a Social group, group of people related either by consanguinity (by recognized birth) or Affinity (law), affinity (by marriage or other relationship). It forms the basis for social order. Ideally, families offer predictabili ...
, order and
class Class, Classes, or The Class may refer to: Common uses not otherwise categorized * Class (biology), a taxonomic rank * Class (knowledge representation), a collection of individuals or objects * Class (philosophy), an analytical concept used d ...
among the mosses.


Discovery

''Takakia'' was discovered in the
Himalayas The Himalayas, or Himalaya ( ), is a mountain range in Asia, separating the plains of the Indian subcontinent from the Tibetan Plateau. The range has some of the Earth's highest peaks, including the highest, Mount Everest. More than list of h ...
and described by William Mitten in 1861. It was originally described simply as a new
liverwort Liverworts are a group of non-vascular land plants forming the division Marchantiophyta (). They may also be referred to as hepatics. Like mosses and hornworts, they have a gametophyte-dominant life cycle, in which cells of the plant carry ...
species ('' Lepidozia ceratophylla'') within an existing genus, and it was thus long overlooked. The discovery of similar odd plants in the mid-20th century by Dr. Noriwo Takaki (1915–2006) in
Japan Japan is an island country in East Asia. Located in the Pacific Ocean off the northeast coast of the Asia, Asian mainland, it is bordered on the west by the Sea of Japan and extends from the Sea of Okhotsk in the north to the East China Sea ...
sparked more interest. The many unusual features of these plants led to the establishment in 1958 of the species ''Takakia lepidozioides'', in a new genus ''Takakia'', named to honor the man who rediscovered it and recognized its unique characteristics. The species originally described by Mitten was subsequently recognized by Grolle as belonging to this new genus, and accordingly renamed ''Takakia ceratophylla''. All of the plants originally collected lacked any reproductive structures; they were sterile
gametophyte A gametophyte () is one of the two alternating multicellular phases in the life cycles of plants and algae. It is a haploid multicellular organism that develops from a haploid spore that has one set of chromosomes. The gametophyte is the se ...
plants. Eventually, plants with archegonia were found, which resembled the archegonia found in mosses. Fertile plants bearing antheridia and
sporophyte A sporophyte () is one of the two alternation of generations, alternating multicellular organism, multicellular phases in the biological life cycle, life cycles of plants and algae. It is a diploid multicellular organism which produces asexual Spo ...
s were first reported in 1993 from the
Aleutian Islands The Aleutian Islands ( ; ; , "land of the Aleuts"; possibly from the Chukchi language, Chukchi ''aliat'', or "island")—also called the Aleut Islands, Aleutic Islands, or, before Alaska Purchase, 1867, the Catherine Archipelago—are a chain ...
, and both structures were clearly of the form found in primitive mosses. This discovery established ''Takakia'' as a genus of moss, albeit an unusual one. In
Asia Asia ( , ) is the largest continent in the world by both land area and population. It covers an area of more than 44 million square kilometres, about 30% of Earth's total land area and 8% of Earth's total surface area. The continent, which ...
, ''Takakia'' has since been found in
Sikkim Sikkim ( ; ) is a States and union territories of India, state in northeastern India. It borders the Tibet Autonomous Region of China in the north and northeast, Bhutan in the east, Koshi Province of Nepal in the west, and West Bengal in the ...
(in the
Himalayas The Himalayas, or Himalaya ( ), is a mountain range in Asia, separating the plains of the Indian subcontinent from the Tibetan Plateau. The range has some of the Earth's highest peaks, including the highest, Mount Everest. More than list of h ...
), North Borneo,
Taiwan Taiwan, officially the Republic of China (ROC), is a country in East Asia. The main geography of Taiwan, island of Taiwan, also known as ''Formosa'', lies between the East China Sea, East and South China Seas in the northwestern Pacific Ocea ...
, and
Japan Japan is an island country in East Asia. Located in the Pacific Ocean off the northeast coast of the Asia, Asian mainland, it is bordered on the west by the Sea of Japan and extends from the Sea of Okhotsk in the north to the East China Sea ...
. In
North America North America is a continent in the Northern Hemisphere, Northern and Western Hemisphere, Western hemispheres. North America is bordered to the north by the Arctic Ocean, to the east by the Atlantic Ocean, to the southeast by South Ameri ...
, the genus is found in the
Aleutian Islands The Aleutian Islands ( ; ; , "land of the Aleuts"; possibly from the Chukchi language, Chukchi ''aliat'', or "island")—also called the Aleut Islands, Aleutic Islands, or, before Alaska Purchase, 1867, the Catherine Archipelago—are a chain ...
and
British Columbia British Columbia is the westernmost Provinces and territories of Canada, province of Canada. Situated in the Pacific Northwest between the Pacific Ocean and the Rocky Mountains, the province has a diverse geography, with rugged landscapes that ...
. It occurs in a variety of local habitats, from bare rock, to moist humus, and grows at elevations ranging from
sea level Mean sea level (MSL, often shortened to sea level) is an mean, average surface level of one or more among Earth's coastal Body of water, bodies of water from which heights such as elevation may be measured. The global MSL is a type of vertical ...
to the subalpine.


Description

''Takakia'' is the oldest known extant genus of land plants, estimated to have branched off the other mosses around 390 million years ago. The genus also has the highest number of fast-evolving genes of any moss. They secrete a microbe-harboring mucilage to establish a diverse
microbiome A microbiome () is the community of microorganisms that can usually be found living together in any given habitat. It was defined more precisely in 1988 by Whipps ''et al.'' as "a characteristic microbial community occupying a reasonably wel ...
containing microbes associated with
nitrogen fixation Nitrogen fixation is a chemical process by which molecular dinitrogen () is converted into ammonia (). It occurs both biologically and abiological nitrogen fixation, abiologically in chemical industry, chemical industries. Biological nitrogen ...
and
mycorrhiza A mycorrhiza (; , mycorrhiza, or mycorrhizas) is a symbiotic association between a fungus and a plant. The term mycorrhiza refers to the role of the fungus in the plant's rhizosphere, the plant root system and its surroundings. Mycorrhizae play ...
. The plant's Japanese name (''nanjamonja-goke'') "impossible moss" reflects this.Schofield, W. B. 1985. ''Introduction to Bryology'', pages 143–154. (New York: Macmillan). . It was believed to have the lowest known
chromosome A chromosome is a package of DNA containing part or all of the genetic material of an organism. In most chromosomes, the very long thin DNA fibers are coated with nucleosome-forming packaging proteins; in eukaryotic cells, the most import ...
count (''n''=4) per cell of any
land plant The embryophytes () are a clade of plants, also known as Embryophyta (Plantae ''sensu strictissimo'') () or land plants. They are the most familiar group of photoautotrophs that make up the vegetation on Earth's dry lands and wetlands. Embryophyt ...
,Schuster, Rudolf M. 1966. ''The Hepaticae and Anthocerotae of North America'', volume I, pages 262–263. (New York: Columbia University Press). but some plants of the small Australian daisy '' Brachyscome dichromosomatica'' are now known to have a count of ''n''=2. From a distance, ''Takakia'' looks like a typical layer of moss or
green alga The green algae (: green alga) are a group of chlorophyll-containing autotrophic eukaryotes consisting of the phylum Prasinodermophyta and its unnamed sister group that contains the Chlorophyta and Charophyta/ Streptophyta. The land plants ( ...
e on the rock where it grows. On closer inspection, tiny shoots of ''Takakia'' grow from a turf of slender, creeping
rhizome In botany and dendrology, a rhizome ( ) is a modified subterranean plant stem that sends out roots and Shoot (botany), shoots from its Node (botany), nodes. Rhizomes are also called creeping rootstalks or just rootstalks. Rhizomes develop from ...
s. The green shoots which grow up from the turf are seldom taller than 1 cm, and bear an irregular arrangement of short, finger-like leaves (1 mm long). These leaves are deeply divided into two or more filaments, a characteristic not found in any other moss.Buck, William R. & Bernard Goffinet. 2000. "Morphology and classification of mosses", pages 71–123 ''in'' A. Jonathan Shaw & Bernard Goffinet (Eds.), ''Bryophyte Biology''. (Cambridge: Cambridge University Press). . Both the green shoots and their leaves are very brittle. Unlike in other
bryophyte Bryophytes () are a group of embryophyte, land plants (embryophytes), sometimes treated as a taxonomic Division (taxonomy), division referred to as Bryophyta ''Sensu#Common qualifiers, sensu lato'', that contains three groups of non-vascular pla ...
s, the egg-producing archegonia and sperm-producing antheridia are not surrounded by perichaetial leaves or other protective tissues. Instead, the gametangia are naked in the angle formed between the stem and the vegetative leaves. The
sporophyte A sporophyte () is one of the two alternation of generations, alternating multicellular organism, multicellular phases in the biological life cycle, life cycles of plants and algae. It is a diploid multicellular organism which produces asexual Spo ...
develops a long stalk ending in an elongated
spore In biology, a spore is a unit of sexual reproduction, sexual (in fungi) or asexual reproduction that may be adapted for biological dispersal, dispersal and for survival, often for extended periods of time, in unfavourable conditions. Spores fo ...
capsule. The capsule contains a central columella over and around which the spores are produced. When the sporophyte is mature, the capsule ruptures along a single spiral slit to release the spores. In the year 2023 the complete
genome A genome is all the genetic information of an organism. It consists of nucleotide sequences of DNA (or RNA in RNA viruses). The nuclear genome includes protein-coding genes and non-coding genes, other functional regions of the genome such as ...
sequence of '' Takakia lepidozioides'' from
Tibet Tibet (; ''Böd''; ), or Greater Tibet, is a region in the western part of East Asia, covering much of the Tibetan Plateau and spanning about . It is the homeland of the Tibetan people. Also resident on the plateau are other ethnic groups s ...
was deciphered. It faces
extinction Extinction is the termination of an organism by the death of its Endling, last member. A taxon may become Functional extinction, functionally extinct before the death of its last member if it loses the capacity to Reproduction, reproduce and ...
due to
climate change Present-day climate change includes both global warming—the ongoing increase in Global surface temperature, global average temperature—and its wider effects on Earth's climate system. Climate variability and change, Climate change in ...
.Ruoyang Hu, Xuedong Li, Yong Hu, Runjie Zhang, Qiang Lv, Min Zhang, Xianyong Sheng, Feng Zhao, Zhijia Chen, Yuhan Ding, Huan Yuan, Xiaofeng Wu, Shuang Xing, Xiaoyu Yan, Fang Bao, Ping Wan, Lihong Xiao, Xiaoqin Wang, Wei Xiao, Eva L. Decker, Nico van Gessel, Hugues Renault, Gertrud Wiedemann, Nelly A. Horst, Fabian B. Haas, Per K.I. Wilhelmsson, Kristian K. Ullrich, Eva Neumann, Bin Lv, Chengzhi Liang, Huilong Du, Hongwei Lu, Qiang Gao, Zhukuan Cheng, Hanli You, Peiyong Xin, Jinfang Chu, Chien-Hsun Huang, Yang Liu, Shanshan Dong, Liangsheng Zhang, Fei Chen, Lei Deng, Fuzhou Duan, Wenji Zhao, Kai Li, Zhongfeng Li, Xingru Li, Hengjian Cui, Yong E. Zhang, Chuan Ma, Ruiliang Zhu, Yu Jia, Meizhi Wang, Mitsuyasu Hasebe, Jinzhong Fu, Bernard Goffinet, Hong Ma, Stefan A. Rensing, Ralf Reski, Yikun He: ''Adaptive evolution of the enigmatic ''Takakia'' now facing climate change in Tibet''


Classification


References


External links

* J. R. Spence & W. B. Schofield. 2005. ''Bryophyte Flora of North America''
Takakiaceae
{{Taxonbar, from=Q80293 Moss genera Takakiopsida