Geophytes of northern Western Ghats (Sahyadri Ranges) of India: a checklist

S.R.T


INTRODUCTION
Geophytes are plants with underground perennial organs (bulbs, corms, tubers or rhizomes) which enable them to survive over unfavorable seasons (Raunkiaer 1934).Although some geophyte species are evergreen, many have adapted to periods of environmental stress such as summer drought or winter cold by dying back to these underground storage organs (Dafni et al. 1981).They then sprout new foliage in the next favorable season.Inflorescences may be produced before, during or at end of the vegetative growing season; a phenology which is constant for most species.Biogeographically, geophytes are widespread around the world in many habitats, but they are most diverse and abundant in the five Mediterranean-climate ecosystems (Doutt 1994;Rundel 1996).The Cape Mediterranean zone of South Africa is generally the most speciose with geophytes comprising up to 40% of some regional floras (Goldblatt 1978;Snijman and Perry 1987).
The remarkable diversity of geophytes in the northern Western Ghats can be seen clearly in the herbaceous flora of lateritic plateaus where geophytes comprise up to 35% of the flora (Lekhak and Yadav 2012).Regional floristic studies have also reported the occurrence of a high number of geophytes in the northern Western Ghats (Cooke 1901(Cooke -1908;;Santapau 1953;Almeida 1990;Lakshminarasimhan and Sharma 1991;Deshpande et al. 1995;Lakshminarasimhan 1996;Pradhan and Singh 1999;Singh et al. 2000;2001;Yadav and Sardesai 2002).It is not only the diversity of geophytes in the northern Western Ghats that is remarkable, but also the diversity of growth-forms.In addition to the typical monocot geophytes with rosettes of basal leaves these geophytes exhibit various growth-forms, such as prostrate leaf geophytes (1 or 2 leaves oriented 180° from each other), single leaf herbs, small cormatous herbs with grass-like leaves, and tuberous herbaceous climbers.Each of these growth-forms has a functional significance.
During the last few decades, many habitats have been affected by mining, windmills, widening of roads, construction of townships and industries in the northern Western Ghats (Watve 2013).Tourism has been growing in some of the scenic areas putting pressure on fragile habitats in the study region.The management of these pressures is often misguided due to poor understanding of the different life forms.In light of this, the present study was carried out to document the diversity of geophytes and to provide a threat assessment of the rare, endangered and endemic geophytic taxa of the northern Western Ghats.The baseline data generated in this study will greatly help in conservation of threatened geophytic taxa.

Study site
The Western Ghats of India is a well-known global hotspot recognized for exceptional biotic diversity and endemism (Padhey and Ghate 2002;Gunawardene et al. 2007;Daniel and Vencatesan 2008), accompanied by an alarming level of habitat loss (Davidar et al. 2007;Panigrahy et al. 2010).Due to its exceptional biota, the Western Ghats has been recognized by UNESCO as a World Heritage Site (United Nations Educational, Scientific and Cultural Organization 2012).The northern half of the Western Ghats of India is locally known as Sahyadri Mountain.It is a chain of flat top mountains of about 750 km in length running parallel to West Coast of the Peninsular India from the river Tapi, South Gujarat (21°03ʹ59.62ʺN, 073°39ʹ08.44ʺE) to Goa (14°56ʹ14.95ʺN, 074°06ʹ49.18ʺE).The confirmed at Botanical Survey of India, Pune (BSI) and Blatter Herbarium, Mumbai (BLAT).Author citation and binomial of collected species verified with international Plant name Index (IPNI).Raunkiaer's system of classification (1934) was used for life form categorization.The IUCN Red List Categories and Criteria version 3.1 (IUCN 2001) was used for assessment of the present status of the geophyte taxa.In the present paper, the families are arranged according to APG III (2009).Important plant species are featured in the Figures 2-9.

RESULTS
The geophytes exhibit remarkable species diversity and comprise approximately 10% plant species of the total flora of northern Western Ghats of India.During the present work, 186 geophyte taxa belong to the 22 different plant families were recorded from northern Western Ghats of India of which 101 are endemic.Habenaria Willd.was found to be the best represented genus with 26 species, followed by Ceropegia L. with 23 taxa.Among the 186 geophyte taxa in the region, 127 are tuberous, 33 bulbous, 19 rhizomatous and 7 are cormatous.The critical field survey has shown that 21 taxa fall into Critically Endangered category of IUCN, 14 into Endangered, 10 into Vulnerable, 14 into Near Threatened, 30 into Least Concern, and 10 into Data Deficient and 87 into Not Evaluated.

DISCUSSION
The present study is an outcome of intensive and extensive field collections and herbarium studies carried between the years 2008-2012.During the present work, 186 geophyte taxa have recorded from northern Western Ghats of India (Table 1).They are belonging to the 22 families.Habenaria Willd.was found to be the largest genus with 26 geophyte taxa in the study region, followed by Ceropegia L. with 23 taxa.Among the 186 geophyte taxa in the region, 127 are tuberous, 33 bulbous, 19 rhizomatous and 7 cormatous.About 62 taxa are restricted to the northern Western Ghats (Ahmedullah and Nayar 1986;Nayar and 1996;Mishra and Singh 2001;Gaikwad and Yadav 2004;Gaikwad et al. 2014a).The genus Ceropegia shows the highest incidence of endemism with 20 endemic taxa (85.95%), followed by genus Habenaria with 14 (53.84%)endemic taxa.Most of the endemic taxa are restricted to small biogeographical areas and are rare in occurrence.Their populations have been declining rapidly due to habitat modification and anthropogenic pressures.
Apart from species richness, geophytes exhibit several interesting growth forms in the study region (Table 1).Each of these growth forms has functional significance.In case of prostrate leaf geophytes, flat leaves reduce the rate of water loss around the roots.Lovegrove (1993) has stated that prostrate leaves act as water-trapping umbrellas, reducing the rate of water loss, and creating favorable microclimates for growth.According to Karen et al. (1999), prostrate leaves create a CO2 enriched environment below.A moist environment under leaves could encourage activity of microorganism, which in turn produce CO2.A CO2 enriched environment might increase photosynthetic CO2 uptake.Geophytes possess grass like leaves that provide camouflage amongst grasses, and are therefore more difficult for herbivores to recognize; thus protecting plants against herbivory.
In the northern Western Ghats, the annual life cycle of biogeographical province of Sahyadri Mountain covers about 6,500 km 2 of mountainous terrain.It straddles the states of South Gujarat, Maharashtra and Goa (Figure 1).The climate is characterized by monsoon rain and can be divided into three seasons, a rainy season (June-October), a winter season (November-February) and a summer season (March-May).Thus, the monsoon season (rainy season) is followed by a considerable stretch of dry period between November and May.
During the monsoon, the study region receives high rainfall (600-700 cm) that results in a relative humidity of up to 94%.Nevertheless, it is just 14% during hot and dry summer on open rocky plateaus and exposed hill slopes, when temperature reach up to 42°C in summer.

Data collection
Field visits undertaken to various localities of the northern Western Ghats of India, which included Ambolighat, Ambaghat, Chandoli National Park, Harishchandragad, Kalsubai Hills, Kas Plateau, Mahabaleshwar, Marleshwar, Radhanagri Wildlife Sanctuary and Wasotafort (Figure 1).During field visits, information on habitat, distribution, endemism, growth form, vegetative growing season and period of flowering and fruiting was gathered.Collected plant species were identified by consulting relevant literature and regional floras (Cooke 1901(Cooke -1908;;Santapau 1953;Almeida 1990;Lakshminarasimhan and Sharma 1991;Lakshminarasimhan 1996;Pradhan and Singh 1999;Singh et al. 2000;2001;Yadav and Sardesai 2002).The identity of the geophytic species was geophytes involves flowering in the monsoon season, from June to October.They produce seeds rapidly and aerial parts die back to underground perennial organs so that the plants remain dormant in long dry season.New leaves are usually produced in response to the monsoon rain in the month of June, and vegetative growth continued until October.Inflorescences are usually produced during or to the end of the vegetative growing season.However, several genera, mostly among monocotyledons (e.g., Amorphophallus, Chlorophytum, Crinum, Curcuma and Drimia) and a few of dicotyledonous (e.g., Brachystelma and Euphorbia) have changed this pattern of flowering.They flower in the summer (April-May), often without leaves.The monsoon flowering species are generally synanthous, i.e., with flowers and leaves developing simultaneously, whereas the summer flowering ones are often hysteranthus, i.e., with flowers and leaves developing in different seasons.Beside the above-mentioned two patterns of flowering, some geophytes like Euphorbia fusiformis, E. fusiformis var.khandalensis, Habenaria viridiflora, Zeuxine gracilis and Z. longilabris flower in the winter season (Soumen 2010;Binojkumar and Balakrishnan 2010).In fact, a flowering period is constant for most of the geophytes species.
Two types of seeds are observed in geophytes-one with a hard seed coat that makes the seeds highly buoyant, and the other is chlorophyllus, which is probably lacking a cork layer, as seeds are non-buoyant.The first seed type is recorded in the genera Chlorophytum, Dipcadi, Drimia, Iphigenia and Pancratium, while the second type is known for Aponogeton bruggenii, A. satarensis, Crinum solapurense and Crinum viviparum var.viviparum (Koshimizu 1930;Hannibal 1966;Manasse 1990;Yadav and Gaikwad 2003;Bjora et al. 2006;Gaikwad et al. 2014b).In fact, the latter species have adapted to an aquatic habitat.

Figure 1 .
Figure 1.Map of northern Western Ghats (Sahyadri ranges) of India, including collection localities (see text).