**Abstract**

Intensive botanical survey was done more than two decades on Tropical Dry Evergreen Forest from four coastal districts *viz*. Cuddalore, Kancheepurm, Nagai and Villupuram of Tamil Nadu and Union Territory of Pondicherry. A total of 87 protected (hillocks, reserve forest) and unprotected (sacred groves, unclassified vegetation) sites were regularly studied from five districts. From this study 82 endemic taxa were enumerated. In addition 25 endemic species were added for the analysis through literature screening and herbarium consultation from 10 Coromandel coastal districts of Tamil Nadu. In all 107 species were recorded, among them 19 are trees, 18 shrubs, 9 climbers and 61 herbs. Distribution of these endemic species were analysed and categorised into endemic to the country, peninsular India, southern India, Eastern and Western Ghats, state and district level. Interestingly the study found that some endemic species were disjunctly distributed in between districts, states, ghats, climatic regimes and bioregions. The disturbance, threat status and conservation measures of few endemic and IUCN red listed species were also studied and discussed.

**Keywords:** conservation, Coromandel Coast, disjunction, endemism, Pondicherry, Tamil Nadu, IUCN status, tropical dry Evergreen Forest

#### **1. Introduction**

India is one of the 18 extremely diverse and top 10 species-rich countries of the world, in which a total of 4381 taxa belonging to 1007 genera and 176 families, including 4303 angiosperms, 12 gymnosperms and 66 pteridophytes, out of 18,043 species have been confirmed as endemic to India [1]. Recently, in angiosperms a total of 58 genera have been identified as endemic to India, of which 49 are confined to Peninsular India [2]. Though the term 'endemism' coined during eighteenth century Chatterjee [3, 4] was the first who studied the endemism of the Indian flora. He was considered 6850 species that are unique to this region (61% of flowering plants), of which 3169 species are restricted to Himalayas and 2045 to Peninsular India (PI). Blasco [5] was estimated about 1268 endemic dicotyledons to south India; however Nayar [6] recorded 2100 flowering plants endemic to PI. Later, Nayar [7] reported 141 genera endemic to India; while Ahmedullah & Nayar

[7] found 55 genera endemic to PI of which 45 are monotypic [7]. Recently, Irwin & Narasimhan [9] enumerated only 49 genera which are endemics to India, excluding several genera based on nomenclatural changes and extended distribution. Nayar [10] categorised the endemic genera of India into 3 patterns based on the distribution *viz*. Himalayan Endemic Genera, Peninsular Indian Endemic genera and Andaman & Nicobar Islands Endemic genera. Meanwhile there are no families which are endemic to India [8].

In India, Western Ghats has much more endemic (2116 species) taxa than rest of India. State-wise analysis Tamil Nadu ranking first with 410 species, followed by Kerala (357), Maharashtra (278) and Andaman and Nicobar Islands together contributes with 278 taxa [2]. In Eastern Ghats (EG), a total of 166 endemic taxa, under 117 genera and 43 families are known to occur, of which 129 dicots and 46 are monocots. Sudhakar Reddy & Raju [11] recorded 400 endemic spermatophytes from the EGs of Andhra Pradesh and their adjacent coastal plains.

The Flora of Tamil Nadu published during 1983, 1987 and 1989 in 3 volumes, and the report after Betty & Ramachandran [12] was added 192 taxa belonging to 130 genera and 61 families between the period 1989 and 2013. These additions were compiled from research articles, unpublished thesis and research reports by several botanists [13–19]. Among them 87 taxa are new to the science as well as endemic to the state of Tamil Nadu. The high concentration of endemic plants once again proves that the southern India is one of the top ten mega biodiversity hotspot area. It directly reflects the habitat stability, environmental quality, and rich biodiversity and conservation values in a specific area. However the Coromandel Coast is another unique bioregion, as flood plain and a buffer zone between the hill range of Eastern Ghats and Bay of Bengal; and this was not studied or updated since Roxburgh [20]. The main aim of this work is to explore the wealth and threat status of endemic plants diversity from the Coromandel Coast and especially from the fragile ecosystem of Tropical Dry Evergreen Forests (TDEF), was classified by Champion and Seth [21].

#### **2. Materials and methods**

The geographical area of Tamil Nadu is 130,058 km2 and has roughly rhomboidal shape in appearance. It lies between 8° 5<sup>0</sup> -13° 35' N latitude and 76° 15<sup>0</sup> -80° 20<sup>0</sup> E longitude. The state occupies 4.08% of the total area of the country. It has the coast line of 990 km at east and land boundary of 1200 km towards west. The state is divided into 38 districts of which 13 districts lies on the east coast. The natural land mass of the state was divided into the Eastern Ghats, Coastal Plains, Central plateau and Western Ghats. Most part of the 13 coastal districts considered as the Coromandel Coast of Tamil Nadu (**Figure 1**). The entire coast of Tamil Nadu, is chiefly sandy with outcrops of rocky headlands at Kancheepuram, Kanyakumari, Tirunelveli and Villupuram districts. The coastal vegetation had further subdivided into Strand, Estuarine and Coastal Tropical Dry Evergreen Forest types (Nair and Henry [22]).

#### **2.1 Study area**

The present study has included 13 coastal districts of Tamil Nadu; Karaikal and Puducherry regions from Union Territory (UT) of Pondicherry along the Coromandel Coast of south India. However, regular intensive survey was done since 1996 to till date on four coastal districts (Cuddalore, Kancheepuram, Nagai and Villupuram) and two regions (Puducherry and Karaikal) from the UT of Pondicherry. Forest cover of Cuddalore is 444 km<sup>2</sup> (11.98%) out of 3706 km<sup>2</sup> , Kancheepuram 372 km<sup>2</sup> (8.31%) out of 4474 km<sup>2</sup> and Villupuram 1011 km<sup>2</sup>

*Endemic Vascular Plants from the Coromandel Coast of Tamil Nadu, Southern India DOI: http://dx.doi.org/10.5772/intechopen.94333*

**Figure 1.** *Study area - Coromandel Coast and detailed study at district level.*

(14.06%) out of 7190 km<sup>2</sup> geographical area [23]. The forest cover at Union Territory of Pondicherry is 50.06 km<sup>2</sup> (10.43%) out of 480 km<sup>2</sup> area [24].

Geologically, part of Cuddalore and Villupuram districts belonged to the formation of Cuddalore sandstone during Miocene period [25]. The soil along the coast is sandy loam or red ferralitic and in certain places covered with alluvial deposits and becoming clayey at interior [26, 27]. The coastal plains are extending up to 40– 60 km [28] and are overlained by a thin soil layer supporting agriculture. The substratum erupted into hillocks and mounds at Kancheepuram and Villupuram districts and into undulating terrain in Cuddalore districts. The scattered hillocks rise up to 450 m with interrupted vegetation among the charkonite or gneiss rocks. The natural vegetation is mostly found on less fertile and red ferralitic soil, whereas black clay and alluvial soils were brought under cultivation [29].

A typical maritime tropical climate with dissymmetric rainfall regime occurs in the study area. The mean annual rainfall recorded during 2007–2016 period was 1256 mm with mean rainy days of 56 per year. The minimum temperature 17.7°C is in January, maximum temperature 40.5°C in May and the mean is 28.5°C. The average relative humidity is 76% and the weather is generally cool during December to January with the late nights dewy. Dry weather prevails during April to June. Wind speed ranges from 5 to 9 km/h during July to September but extremely higher during the cyclonic days, during October to December [30].

#### **2.2 Field survey**

Four types of vegetation covers including micro and macro habitats *viz*., Hillocks (HL), Reserve Forest (RF), Sacred Groves (SG) and Unclassified Vegetation (UC) were identified using Geological Survey of India (GSI) map, Google map and interview with people. The areas of HL vegetation are ranging from 680 to 2200, RFs from 100 to 350, SGs from one to 40 and UCs from 0.5 to 35 hectares (ha). The elevation of HL was found between 150 and 450, RFs 100 to 350, SGs sea level to 80 and UC sea level to 40 m a.s.l.

Botanical surveys were made extensively once in a week on 87 sites from five districts with a team of four members, visiting each and every site with an interval of 4–6 months and monitored pre-monsoon and post-monsoon changes from 1996 to 2019. These sites were geo-referenced with Garmin Global Positioning System (GPS), followed by intensive species enumerations including herbs, shrubs, trees and climbers; collection of voucher samples and photographed the key characters of the plants. A total of 15,316 herbarium sheets were prepared from the sample collections and deposited at AURO! Herbarium, Auroville, India. The nomenclature of all plant species recorded in this study was verified in www.plantsoftheworld online.org. In addition, Endemic plants of Indian Region (Ahmedullah & Nayar [10]), The Flora of the Gulf of Mannar, Southern India [31], Endemic Vascular Plants of India [2], Plant Discoveries [32], research articles between 2013 and 2019 period and different herbarium such as Saint Joseph College (SJC) Tiruchirapalli, Madras Herbarium (MH!) Coimbatore, Foundation of Revitalization of Local HealthTraditions (FRLH) Bangalore, French Institute of Pondicherry (HIFP) Puducherry, and Sri ParamaKalyani Center for Ecological Studies (SPKCESH) Tirunelveli was referred and enriched the endemic species list to the study area.

#### **2.3 Analyses**

Based on phytogeographical distribution six groups of endemic regions were categorised, such as 1. the state Tamil Nadu, 2. Eastern Ghats (EG), 3. EG & Western Ghats (WG), 4. Southern India (SI), 5. Peninsular India (PI) and 6. Entire India except Himalayas. In addition, disjunct nature of distribution of these endemic species between or among the regions was also studied. Site disturbances such as browsing, cutting, lopping, and clear felling, encroachment for cultivation purposes, construction of big modern temple, construction and widening the metal road, digging irrigation channels and cementing the thrashing floor were studied and categorised into low, medium and high by following Venkateswaran & Parthasarathy [33]. High ranks signify high levels of anthropogenic disturbance in the forests. The disturbance codes were co-related with four life forms and threat status of all species was verified with www.iucnredlist.org (version 2020–2). Threat assessment and possible conservation measures were undertaken on few endemic and endangered species through Auroville greening and Botanical Garden Projects.

#### **3. Results**

Through our regular field study on 87 sites, 25 (SG) sites are from Cuddalore, 22 (8 HL, 6 RF, 4 SG, 4 UC) from Kancheepuram, one site (1RF) from Nagai, 28 (3 HL, 4 RF, 13 SG, 8 UC) from Villupuram districts of Tamil Nadu, 10 (8 SG, 2 UC) from Puducherry region and entire Karaikal region, Union Territory of Pondicherry. Altogether, 1197 species were listed from 127 families and 584 genera, of which 196 species are trees, 113 shrubs, 172 climbers and 716 herbs. Through literature screening and referring the herbarium 25 endemics were added. Finally a total of 107 endemic species were compiled for the Coromandel Coast of Peninsular India and analysed. Of which 19 species are trees, 18 shrubs, 9 climbers and 61 herbs (**Figure 2**). These endemic species were represented by 74 genera and 33 families, of which Leguminosae (17 species from 10 genera) is the dominant family followed by Acanthaceae (13 species from 5 genera), Euphorbiaceae (10 species from 5 genera) and Poaceae (9 from 9 genera). The other dominant families are Apocynaceae and Rubiaceae, had 4 species each (**Figure 3**).

*Endemic Vascular Plants from the Coromandel Coast of Tamil Nadu, Southern India DOI: http://dx.doi.org/10.5772/intechopen.94333*

**Figure 2.**

*Endemic plants of CC and their habits representation.*

**Figure 3.** *Detail of endemic plant families, genera and species.*

#### **3.1 Disturbance**

Qualitatively, classified disturbances were noted from four vegetation types (**Table 1**; **Figure 4**). These disturbance codes were correlated with life form, threat status and ethno-botanical values of endemic species. In general, from 50 to 65% of species were represented in disturbed category. Maximum numbers of species are encountered at medium level of disturbance, followed by undisturbed, low and high level of disturbance. Reasons for the threat are: root of *Decalepis hamiltonii* and fruit of *Phyllanthus indo-fischeri* were extensively collected for their medicinal properties; *Justicia beddome*i, *Leucas wightiana* and *Lindernia minima* are endangered due to narrow and disjunct distribution; *Derris ovalifolia*, *Drypetes porteri*, and *Koilodepas calycinum* are facing habitat loss; *Pterocarpus santalinus* was threatened due to illegal logging; *Sterculia populifolia* living with rocky outskirts; and the herbs are generally facing pressure by grazing.
