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Monotypic taxa: one of a kind; cause for concern and need for conservation

Plants are the most important biotic component on earth and are at the mercy of the environment they are in. They grow and flourish when the conditions for their sustenance are favourable; these include the right amount of rainfall, temperature, sunshine, soil moisture, and soil nutrients. Each plant species is adapted to the local environmental conditions. Many such species are endemic, while others are found around the globe. The growth conditions are also influenced by local and global environmental changes taking place, either due to natural or anthropogenic causes. Climate change, defined as changes occurring over a longer period of time, could hamper the growth of these plants.

Inventories of plants in a locality provide crucial information that could lead to better management and conservation of our natural resources. Plants are categorised into different types based on characteristic morphological features. One such artificial category that could be useful for better management and conservation is monotypic taxa. Taxa that are represented by a single genus or a single species are called monotypic taxa. A botanical family is said to be monotypic if it is represented by a single genus with a single species. Similarly, a genus is said to be monotypic if represented by the ‘type species’ only. Most of the monotypic genera are endemic, with some of them being rare, endangered, or vulnerable.

Abundance and distribution

India is home to 236 monotypic genera of flowering plants. Out of 236 monotypic genera, 75 % belong to dicots and the rest to monocots. The family Poaceae from monocots is the most dominant, with 32 genera, followed by the Dicot families Leguminosae with 15 genera and Asteraceae with 12 genera; the other families include Rubiaceae, Orchidaceae, Brassicaceae, Cucurbitaceae, Lamiaceae, Menispermaceae, and Cyperaceae. The habit-wise distribution of monotypic genera shows that herbs dominate with 64%, shrubs with 13%, climbers with 8%, and trees with 15%, respectively. Well-known monotypic tree species include Aegle marmelos (Bel/Bilva patre), Limonia acidissima (Wood apple/Belada mara), Pongamia pinnata (Pongam tree/Honge mara), Tamarindus indica (Tamarind tree/Hunase mara), and Kingiodendron pinnatum (Aenne mara); herbs include Cannabis sativa (Indian hemp/Ganja) and Lawsonia inermis (Henna/Gorante); climbers include Hemidesmus indicus (Indian sarsaparilla/Anantha beru), to name a few. In addition, many monotypic genera are rare, endangered, and vulnerable and need to be protected and conserved. The monotypic taxa are distributed unevenly in India and the rest of the world. In India, most of them are found along the Western Ghats, with some occurring in Andhra Pradesh, Arunachal Pradesh, Assam, Meghalaya, Sikkim, Nagaland, Maharashtra, Karnataka, Kerala, and the Himalayas. Some of these genera are also cultivated for their fruits and herbal properties.

Identification and documentation

Identification of plants has always relied on keys, flora, and monographs. Taxonomists not only need to look into these but also possess earlier plant records of the region before embarking on the identification and documentation of new species. Documentation of monotypic taxa is not easy and requires prior knowledge of plant systematics. It is sought with difficulties such as incomplete floristic surveys and records, wrong or misidentification, ‘new species syndrome’, phenotypic plasticity, the presence of synonyms, errors in type specimens, and many more. In addition, errors in herbarium specimens and a lack of upkeep and digitization of herbarium are other barriers to collating and documenting monotypic taxa.

Future course of action

Monotypic taxa are of utmost importance as these could be lost forever, and hence there is a need to take up further studies on documentation. The documentation of monotypic taxa could be complemented by the presence of an inventory of all the plants in the country. In addition, there is a need for digitization of all the specimens in an herbarium and interlinking of all the herbariums in the country for easier accessibility and validation. Field surveys have to be undertaken to overcome the ‘new species syndrome'. Molecular systematics should be applied to resolve taxonomic problems and to look into the phylogeny of monotypic taxa and its geographic distribution. The identification and documentation of a monotypic genera with their economic and medicinal importance could also lead to exploitation and, finally, to losing them. Unless conservation measures and better documentation of monotypic genera are undertaken, these unique genetic wonders could be lost forever.

Content credits:

Balasubramanya Sharma

Research Associate

Department for Climate Change

Environmental Management & Policy Research Institute (EMPRI)

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