Thesica.org, the #1 open access web portal for PhD theses...

Why PhD theses...

PhD thesis is the result of years of hard work.

keyword researchMeasured by download count PhD theses are one of the most popular items world wide on open access repositories. But unless a thesis is published, it is very difficult for other researchers to find out about it and get access to it. Theses are often under-used by other researchers. Thesica.org attempts to address this issue by making it easy to identify and locate copies of many theses in various disciplines.

Floristic study of Wayanad District with special emphasis on conservation of rare and threatened flowering plants

Floristic study of Wayanad District with special emphasis on conservation of rare and threatened flowering plants
M. K. Ratheesh Narayanan

2012

Department of Botany, University of Calicut, Kozhikode 673635, INDIA.

ABSTRACT

The floristic study of Wayanad district envisaged exploration and documentation of the flowering plant diversity of Wayanad district. The thesis is organised into introductory part and systematic part. In the introductory part features of the study area, review of earlier work, methodology, salient findings, floristic analysis and ethnobotany were given. The systematic part taxonomically enumerates the taxa encountered from the study area.

Wayanad is a mid-level plateau, lies in the northwest corner of the Nilgiris. Topographically the district can be divided in two parts, the Southwestern part and the Northeastern part. From the highest altitude of the Western Ghats on the southwest and western border of the district, the plateau of Wayanad gradually slopes down towards northeast and eastward and merging imperceptibly with the Mysore plateau. The forest area in the district is divided into Wayanad Wildlife Sanctuary and Reserve Forests and is endowed with six vegetation types, which support luxuriant growth of diverse plant groups. The ethnic diversity of the district is also very impressive as evidenced by five dominant tribal groups, and these are the communities who still hold knowledge on biodiversity. The mid-level plateau of the district is the most densely populated area and it covers a major part of the land. Most of the natural vegetation of these areas has been replaced by coffee, tea, eucalyptus, banana and rubber plantations.

The thesis is the result of the intensive exploratory studies carried out during the period 2000-2005. Altogether, specimens with 4321 field numbers were collected. The total number of 2034 species belonging to 903 genera and 171 families recorded from an area of 2031 square kilometer form nearly 49% of the flora of the Kerala state (4679 taxa) and more than 10% of the flora of India. Of the 2034 taxa, Dicotyledons are represented by 1521 species belonging to 676 genera under 140 families, and Monocotyledons by 511 species belonging to 225 genera under 29 families. Gymnosperms are represented by 2 taxa. The plants were classified according to Bentham and Hooker’s system with necessary alterations. Keys have been provided for families, genera, species and intraspecific taxa. Illustrations and photographs of selected rare and endemic taxa have been provided. The family Fabaceae with 185 species in 68 genera is the largest family followed by Orchidaceae with 165 species in 68 genera. Poaceae are the third largest family represented in the district with 163 species in 65 genera. Among the 169 families, 43 families are represented by single species each. Of the 901 genera, there are 25 genera with 10 or more than 10 species in each.

Pristine forests in Wayanad are the treasure-house of unique flora and the present floristic exploration in this enigmatic biodiversity region resulted in the discovery of three new taxa, viz. Miliusa wayanadica, Miliusa gokhalae and Oberonia swaminathanii. Two rare and endangered species, considered as ‘possibly extinct’, viz. Eugenia argentea and Hedyotis wynaadensis could be recollected from their type localities after a lapse of 130 years. The study reports a total of 596 endemic taxa in 97 families forming nearly 29% of the total species. Among these Indian endemics, 491 are endemic to Western Ghats. Three hundred and thirty eight taxa of flowering plants collected from the district are endemic to southern Western Ghats (18 %), of which 59 are restricted to Kerala and 15 species exclusive to the study area. Among the 60 endemic genera reported from Western Ghats, 16 were collected from Wayanad during the present study. It includes 3 endemic tree genera, viz. Meteoromyrtus, Otonephelium and Poeciloneuron, out of 6 endemic tree genera of Western Ghats. Jerdonia and Meteoromyrtus are exclusive endemic genera to the study area. It was revealed that 138 taxa are coming under different threat categories and most of them are narrow endemics. It was observed that Wayanad has a peculiarity in having eleven species, and one variety named after the district’s name as wynadensis’/wynaadica’ etc. The interesting fact is that the species like Hedyotis wynaadensis, Oberonia wynadensis, Sonerila wynaadensis, Ischaemum wayanadense, Nothopegia beddomie var. wynadica, Meteoromyrtus wayanaadensis, and finally the recently described new taxon Miliusa wynaadica are reported to be occurring only in Wayanad.

With its unique location, climatic features and diverse habitats, Wayanad harbors a very rich diversity of wild genetic resources of crop plants. There are 434 flowering plants used by the tribal people of Wayanad and the indigenous non-endemic plants in the study area constitute about 65% of the total species.

The present study indicated that Wayanad is not only rich in its habitats and habit-forms but also for the diverse life forms. The life forms include peculiar plants such as saprophytes, insectivorous, parasites and semiparasites. The diverse habitat of the district supports a rich flora and fauna. The evergreen forests and grasslands of Chembra-Vellarimala hill ranges, Vythiri-Sughandhagiri forests, Kurichiarmala and Chanthanathodu harbor more than 80% species of rare and threatened category. Diversity of Rare, Endemic, Endangered and Threatened plants is comparatively low in Wayanad wildlife Sanctuary forests. These areas are under severe threat due various man-made reasons like forest fragmentation, grassland conversion, construction of dams, over-grazing, over-exploitation of forest resources, habitation and cultivation inside the wildlife Sanctuary, forest plantations, conversion of paddy fields, unscientific application of chemicals, invasion of alien species, and forest encroachment. All these facts indicate the immediate need of implementing conservation measures to maintain the species diversity which is our national heritage, and to save the valuable genetic resources for judicious and sustainable utilization for the future generation.