Study on tropical butterfly communities

Relatively few studies have focussed on invertebrates, despite their dominance of the animal community in species richness, abundance and biomass (Wilson 1987; Stork 1988). Insects have been shown to be sensitive to changes in vegetation composition and the physical attributes of the environment (Erhardt 1985; Gardner et al., 1995; Wood & Gillman, 1998) resulting in a decrease in insect diversity (Holloway 1987;

Holloway et al., 1992). Tropical insects are highly diverse (Hamer et al., 2003). Tropical butterfly communities are highly diverse with many endemic species, most of which are to some extent dependant on closed-canopy forest (Collins & Morris, 1985; Sutton & Collins, 1991). Compared with other invertebrate groups, the high visibility of butterflies together with their relatively well studied taxonomy and rapid abundance changes in response to environmental variations and local weather have resulted in them being used regularly as biological indicators of ecosystem health (New 1992; Spitzer et al., 1997; Lawton et al., 1998; Scoble 1992). They have been widely used to assess patterns of tropical insect diversity in forest conservation studies (Brown 1991; De Vries et al., 1997). Inventory and monitoring of butterflies has proven useful in the evaluation of terrestrial landscapes for biological conservation (Samways, 1994). Examples include habitat assessment and classification (New, 1991; Pollard & Yates, 1993; New et al., 1995) as well as evaluation of the effects of land use (Erhardt, 1985; Swengel 1996) and urbanization (Kremen, 1992;

Blair & Launer, 1997). As butterflies are extremely sensitive to changes in vegetation composition and structure, butterfly assemblages may be used to characterize different habitats (Erhardt, 1985). Butterflies in general and swallowtail butterflies (Family Papilionidae) in particular also represent the ‘flagship’ and/or ‘umbrella’ taxa for invertebrate conservation (Collins & Morris, 1985; New et al., 1995). The swallowtail butterflies have become one of the model taxa for understanding the processes involved in evolutionary divergence of host preference, host-specialization and diversification in insects (Wiklund, 1975, 1981; Rausher et al., 1983; Scriber et al., 1991; Tyler et al., 1994;

Thompson, 1994). They have diversified worldwide into more than 475 species and species complexes that differ in the range of plant taxa they attack (Scriber et al., 1995; Tyler et al.,

1995). Most species of the swallowtails are predominantly tropical but a few species are also found in the temperate zones (Slansky, 1972). They are most diverse in the equatorial rainforest zones and Southeast Asia has the highest number of species, while species richness in the eastern Asian region between 20^ο and 40^o N is also high as reflected in the analysis on critical swallowtail fauna where Indonesia, Philippines, China, Brazil and Madagascar are reported to include well over a half of the world’s swallowtails (309 species and 54% of the world total) with highest swallowtail species endemism. Another five countries, India, Mexico, Taiwan, Malaysia and Papua New Guinea bring the total to 68%, which is more than two-thirds (Collins & Morris, 1985). Globally 573 species have been listed out of which nearly 78 species have been listed in the threatened categories. Amongst these, 14 species have been listed as ‘Insufficiently known’ (Scriber, 1973; Collins &

Morris, 1985). In the Indian sub-continent, the family Papilionidae is represented by two sub-families- Parnassiinae (Apollos), which includes 14 species, and Papilioninae (Swallowtails), which include 83 species and sub-species (Evans, 1932; Talbot, 1939).

Swallowtail butterflies are the most spectacular and magnificent of all insects with brilliant colouration and large variations in size ranging from the minute 50 mm wingspan of the Dragontails of India and Malaysia (Lamproptera species) to the giant Birdwings (Troides, Trogonoptera and Ornithoptera species) of India, Indonesia and New Guinea. The female Queen Alexandra’s Birdwing (Ornithoptera alexandrae) is the largest butterfly in the world, attaining a wingspan of over 250 mm. Due to their fabulous colours and aesthetic value, the swallowtails are vulnerable to commercial collection and trading and are the sole insects included in Appendices to CITES. The Birdwings (Troides, Trogonoptera and Ornithoptera species) have been listed by CITES on Appendix II. Butterfly trading based in India and Indo-China is quite extensive and occurs at all levels from personal collectors to substantial business (Collins & Morris, 1985). In the Eastern Himalayas, the trade in the swallowtail butterflies has been most intensive since the early part of the 19^th century and over collection of Teinopalpus imperialis (Kaiser-I-Hind) and Bhutanitis lidderdalii (Bhutan Glory) by private collectors for the international market has been a major threat to not only these specie but the illegal commercial trade in the oriental region has been the primary cause of concern for the continued survival of a number of important localised species. India occupies the 6^th rank in the list of priority countries or ‘critical faunas’ for swallowtail conservation (Collins & Morris, 1985). A total of 77 species have been recorded in the Indian subcontinent out of which 6 species are known to be endemic and only 1 species is threatened (Collins & Morris, 1985). The IUCN has identified the entire Indo-Burma hot

spot that includes the Eastern Himalayas and other Global 200 ecoregions from this hotspot as ‘Swallowtail butterfly-rich zone’ and has also drawn up an action plan for their conservation (‘Swallowtail Conservation Action Plan’, New & Collins, 1991). Many swallowtail butterflies are very restricted in their habitat and geographical range. Some taxa are found only in the montane regions or ‘ecological islands’; others on small geographical islands while many are endemic to microhabitats in tropical forests. As the Papilionids are dependant on forest vegetation, habitat alteration associated with deforestation, agricultural conversion and intensification, alteration of pastures, urbanisation and industrialisation are posing a serious threat to their survival. (Collins & Morris, 1985). Habitat change in densely populated and economically poor tropical regions is of increasing concern (FAO/UNEP, 1981). In tropical South-east Asia in particular, habitat alteration by way of deforestation has posed a serious threat to the survival of the Papilionidae. In the Eastern Himalayas deforestation is occurring throughout the range of an endemic species, Kaiser-I-Hind (Teinopalpus imperialis imperialis Hope, 1843) described as rare by Talbot (1939) and protected by law in India (Wildlife Protection Act, 1972). This species is listed by the IUCN (1996). The present IUCN status of this species is rare and much of its forest habitat is being degraded through shifting cultivation. There has also been commercial overexploitation of this species in the past and the protective legislation enacted in India and Nepal appears not to be very effective. The primary vegetation in extensive areas of Northeast India including Assam has been disturbed by human activities. The quality of the forests is also deteriorating with the dense forests (canopy closure >60%) becoming degraded into open forest or scrub. In Assam the percentage of ‘Very Dense’ forest cover is only 2.1% (1,684 sq.kms), ‘Moderately Dense’ forest cover is 14.5% (11, 358 sq.kms.), ‘Degraded/Open forests’ is 18.9% (14, 784 sq.kms.) and ‘Non-forest’ area is 64.5% of the total area of forest and tree cover (FSI, 2003). This indicates a disturbing trend in the declining primary forest cover. The total estimated area under encroachment is 3,555 sq.kms. and total area under forest fringe villages is approximately 538.35 sq.kms. (0.69% of the Reserved forest area).

A majority of the indigenous inhabitants of Assam are meat eating and almost all communities have expert hunters, trappers and fishermen. Although the traditional practices of trapping and snaring of animals are carried out in very remote areas, shooting wild animals with guns is prevalent. Moreover certain meat is valued as medicinal and such animals are hunted. It has been recommended under the National Forest Policy, 1988 that every state in India shall have atleast 5% of the geographical area under National Parks and

Wildlife sanctuaries, which cover natural ecosystems and greater emphasis needs to be given towards anti-poaching measures in such protected areas.