INTRODUCTION

The diatom genus Gomphonema Ehrenberg is large, including over 500 taxa worldwide (Fourtanier & Kociolek 2009). While its members are almost exclusively freshwater in terms of habitats, and many species are associated with impacted trophic levels (e.g. Patrick in Patrick & Reimer 1966), the genus is quite diverse morpho-logically. Variation in valve ultrastructure includes presence or absence of stigmata, areolar structure, structure and position of the apical pore fields, and presence/absence of spines to name a few (Kociolek & Stoermer 1993, but also see Metzeltin & Lange-Bertalot 1998, Reichardt 1999). While some species of Gomphonema appear to be cosmopolitan in their distribution (for example, it appears that G. parvulum (Kützing) Kützing has been reported from all continents on earth), there are many reports of endemic species of Gomphonema from South America (Fricke 1904; Metzeltin & Lange-Bertalot 2007), Africa (Compère 1995, Hustedt 1949, Kociolek & Stoermer 1991), Madagascar (Spaulding & Kociolek 1998), North America (Kociolek & Kingston 1999, Thomas et al. 2009), Europe (Hustedt 1945, Reichardt 1999, 2005), Asia (Lange-Bertalot & Genkal 1999, Li et al. 2006) and Australia and environs (Hustedt 1942, Kociolek et al. 2004).

India is a large, geographically complex country with ten different biogeographic zones covering over 3 million sq. km, about a third the size of all of Europe, but with nearly 50% greater human population (World Population Prospects, 2008). The country shares borders with Bangladesh, Bhutan, Myanmar, China, Nepal and Pakistan. The complexity of India’s freshwater environments includes three major, complex watersheds (Himalayas and the Karakoram ranges; Vindhya, Satpura ranges and the Chota Nagpur Plateau; and the Western Ghats) that cut across the country, related to their sources in the mountains. Freshwater environments range in elevation from sea level at the coast to over 8000 m above sea level.

The diatom genus Gomphonema in India has been documented for over 160 years. First report of the genus in India was by Ehrenberg (1845), who reported G. clavatum, G. gracile and G. turris from "Kolkatta" (then Calcutta) and River Ganges. Since then, 49 separate papers have identified 130 taxa of Gomphonema from India, mostly from lowland habitats. Of these, about 30% have been newly described taxa. In the region around India, gomphonemoid diatoms have been considered by Hustedt (1922), Jüttner et al. (2004) from Nepal, and Mereschkowsky (1906), Kociolek (1992), and Li et al. (2006, in press) from China. Though many species of Gomphonema have been described from India, there are extensive parts of the country that have not been investigated. The Western Ghats mountain range in Southern India, one of the Gondwanaland breakup landmasses, is amongst the most important hotspots of biodiversity. Western Ghats is a chain of mountains that runs parallel with the west coast of India for over 1600 km from 8°15'N to 21°00'N. Due to its distinct physiographic, edaphic and climatic gradients, this region harbors a wide array of habitats with unique geographic position and that support unique sets of flora and fauna. The Western Ghats harbors approximately 5000 species of vascular plants belonging to nearly 2200 genera; about 1700 species (34%) are endemic. There are also 58 endemic plant genera, while nearly three-quarters of the endemic genera have only a single species (Conservation International, 2008). The fauna and flora of this region has attracted attention of systematic and evolutionary biologists because of the mixture of high-level endemism (Inger, 1999; Myers et al. 2000) and various affinities with other biogeographic regions (Bossuyt & Milinkovitch, 2001).

In the present report we have compiled a checklist of the Gomphonema taxa previously reported and described from India (Table 1). We also document and describe with light and scanning electron microscopy three new species of Gomphonema from Central Western Ghats, Karnataka State, India. We also present information about each species' autecology, with particular attention paid to water chemistry and seasonality.

Table 1. Listing of Gomphonema taxa for India and references that have reported each taxon.
(Note: * denotes the species described from Indian administrative boundary; † indicates the studies on fossil material)