Freshwater Molluscs of India: An Insight of into Their Diversity, Distribution and Conservation - Aquatic Ecosystem: Biodiversity, Ecology and Conservation - page 185

evolution (Prashad 1928 ). Some species such as
Sulcospira huegeli show a disjunct distribution,
being found in the central and southern Western
Ghats and in northeastern Indian states (Subba
Rao 1989 ).
Recently, two new species of freshwater mol-
luscs belonging to the genus Paracostoma have
been described from the Western Ghats (Köhler and
Glaubrecht 2007 ). The genus Paracostoma is
monophyletic and is restricted to few streams in the
central Western Ghats and nested within a clade of
Southeast Asian taxa composed of Brotia and
Adamietta . These authors argue that the “origins of
the Indian biota are more complex and diversethan
assumed under the standard Mesozoic vicariance
model . ” Hence, zoogeographically, the Western
Ghats freshwater mollusks offer a great opportunity
for biologists.
A few sporadic studies were carried out in
northern Western Ghats, mainly from Pune by
Tonapi ( 1971 ), and Tonapi and Mulherker ( 1963 ).
Recently, Patil and Talmale ( 2005 ) reviewed land
and freshwater molluscs of Maharashtra State and
listed 72 species and varieties. Most of these
studies were concentrated on distributional aspects
and no indepth study on ecology. In India very
scant attention has been paid to the biology and
ecology of molluscs and in particular of bivalves
(Subba Rao 1989 ), and therefore the ecological
needs of a great majority of the Indian freshwater
molluscs are not known. Apart from Volume IV of
Fauna of British India by Preston ( 1915 ), there are
only two other topics that deal with Indian fresh-
water molluscs; these are Subba Rao ( 1989 ) and
Ramakrishna and Dey ( 2007 ). The topic on Indian
Freshwater Molluscs gave updated information on
the distributions with maps (Ramakrishna and
Dey 2007 ).
Freshwater molluscs of the Western Ghats
region are better known than in other parts of
India or other species-rich areas within South and
Southeast Asia. This assessment is based on the
scattered published work, mostly coming from
the northern Western Ghats and our own fi eld
studies. Still, a large amount of work needs to be
done, examining the ecosystem services these species
provide, the impact of aquatic-invasive plants,
the distribution patterns, population status and

dynamics of molluscs, and their species-specifi c
threats. Most of the data defi cient species identi-
fi ed here have not been collected since their
description (often in nineteenth or early twentieth
century) or have very meagre collection details.
In many cases, the description of the species is
based on either single specimen or very few
specimens, and no natural history or ecology is
detailed. It is important to revisit the type localities
of these species to get adequate information on
ecology and threats, to see if they are still present
or have already become extinct, and in many
cases to confi rm their taxonomic status (Budha
et al. 2011 ). Here we consolidate our study on the
basis of available literature and personal fi ndings
from different surveys in Tables 11.4 and 11.5 .

Endemism

A detailed study on endemism of freshwater mol-
luscs available reveals that 47 species are endemic
from India out of the 202 listed of which 33 are
gastropods and 14 are bivalves (Fig. 11.1a, b ).
Two species are endemic from Andhra Pradesh,
one from Punjab, seven species from Assam,
three from Manipur, one from Meghalaya, two
from Mizoram, 13 from West Bengal, two from
Tamil Nadu, six from Maharashtra, three from
Andaman and Nicobar Islands, fi ve from Kerala
Backwater and three from Jammu and Kashmir
are endemic species.

Endemism from North Himalayan
Region

Mollusca are originated from various invasion of
freshwater fauna into the Himalayas since the
Pliocene period (low-middle mountain fauna).
The transitional zone of Nepal and the Himalayas
has mixed freshwater faunas, from Oriental and
Palaearctic regions with numerous hitherto
neglected endemics, such as Tricula species and
Pisidium spp. They are originated from several
so-called inner valleys of the Himalayas which
were seasonal lakes and wetlands during
Pleistocene glaciations (Nesemann et al. 2007 ).