Pandit Govind Ballabh Pant Memorial Lecture: II

commonly known as the pitcher plant, is endimic to Khasi Hills. The genus
Nepanthes has 67 species out of which one species each is 64 species are found in
South east Asia, Malaysia, North Queensland and New Calendonia. The foregoing
examples are pointers to the Gondwanaland influence.
The Brahmaputra valley contains extensive areas with natural vegetationswamps
and grassland- with large herbivours fauna typical of alluvial grasslands.
Examples are rhinoceros, buffalo, swamp deer, hog deer, pygmy hog and hespid
hare (Rodgers and Panwar, 1988). Being tropical/subtropical evergreen forest there
is high degree of species richness and high degree evolutionary activity resulting in
pockets of high degree of endemism. Added to it is the fact that with the rise of
Himalaya, there were many micro-climates due to altitudinal and latitudinal factors
leading to large number of small, rather isolated, pockets. Such a situation not only
isolated geographically many widespread species but also presented newer sites for
colonization.
That this has been and still is a region of high evolutionary activity is clear from
the cytogeographic studies on genera like Rhododendron, Camelia, Magnolia,
Buddleia etc. of Janaki Ammal (1950, 1952 a-b, 1953, 1954, Janaki Ammal and
Saunders 1952). The north Eastern Himalaya and North Eastern States together
with South Eastern Provinces of China (like Yunnan and Szechwan) are very active
centres. There are ecologically and phytogeographically highly diversified and
floristically among the richest in the world. Here diploids (2x) geographic ranges of
tetraploids (4x), hexaploids, (6x) octoploids, (8x) and do-decaploids (12x). Thus the
higher the level of ploidy, narrower is the geograpic range. The higher ploids are
essentially endemics confined to narrow region. These are some very meaningful
data from chromosome geography. During colonization of the new habitats new
polypoid races and species of the foregoing genera were produced which seem to
have had a high survival value (Fig. 5 and 6). The highest level of polyploidy in these
genera is seen in the species growing in this region.
Fig. 5- Distribution of polyploides of Rhododenderons in North Eastern India Source:
Janaki Ammal 1954
Fig. 6- Distribution of polyploids of Buddleia in North Eastern India Source: Janaki
Ammal 1954.
There are few temperate species of the Assam Himalaya found in the Nilgiris,
which is another floristrically rich area. The species are: Ternstroemia japonica,
Rhododedron arboreum, Hypericum hookerianum, Thalictrum javantium,
Cotoneaster buxifolia, Parnassia wightiana, Lonicera ligustrina, Gaultheria
fragrantissima, Symplocos laurinana etc. (Nayar, 1977). Some botanists believe that
the presence of such floristic element in Nilgiris is an indication of their being
Pleistocene relicts. According to this view, during Pleistocene glaciation, temperate
flora and fauna moved south. On retreat of the glaciation, temperate relicts were left
at higher altitudes of southern mountains, and continuous distribution between
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