Seasonal diversity of butterflies and their larval food plants in the
surroundings of upper Neora Valley National Park, a sub-tropical broad leaved
hill forest in the eastern Himalayan landscape, West Bengal, India
Panchali Sengupta 1, Kamal Kumar Banerjee 2 &
Narayan Ghorai 3
1,3 Department of Zoology, West Bengal State
University, Berunanpukaria, Malikapur, Barasat, District-24 Parganas (North),
Kolkata, West Bengal 700126, India
2 Department
of Zoology, Bidhannagar College, EB Block, Sector-1, Salt Lake City, Kolkata,
West Bengal 700064, India
1 panchali_17sg@yahoo.com, 2 forestkkb@gmail.com, 3 nghorai@gmail.com
(corresponding author)
Abstract: Seasonal butterfly diversity in the
adjacent areas of the upper Neora Valley National Park, a part of the Himalayan
landscape, was studied. The
available larval host plant resources present within, as well as in the
adjoining areas of transect were identified. A total of 4163 butterflies representing
161 species belonging to five families were recorded during this study. One-hundred-and-forty-three species of
plants belonging to 44 families served as the larval food plants of
butterflies. The maximum number of butterfly species and maximum number of
individuals were sampled during the monsoons. The monsoons with least skewed rank
abundance curve of species distribution, was also marked by maximum species
diversity and maximum species evenness. This was probably due to the abundant distribution of luxurious
vegetation that served as food plants for the larval stages of
butterflies. Nymphalidae was the
most dominant family with 43.48% of the total number of species. Autumn followed by the monsoon was associated
with high species richness probably due to the abundance of vegetation that
provides foliage to its larval stages.
Keywords:Autumn, Butterfly diversity, Himalayan
landscape, larval food plant, monsoon, Neora Valley National Park, Nymphalidae,
rank abundance curve, species evenness, species richness.
doi: http://dx.doi.org/10.11609/JoTT.o3446.5327-42| ZooBank: urn:lsid:zoobank.org:pub:748950A3-E4AA-4865-ABC7-DAF294C33BEE
Editor: B.A. Daniel, Zoo Outreach Organization, Coimbatore, India. Date
of publication: 26 January 2014 (online & print)
Manuscript details: Ms # o3446 | Received 19
December 2012 | Final received 09 October 2013 | Finally accepted 03 December
2013
Citation: Sengupta,
P., K.K. Banerjee & N. Ghorai (2014). Seasonal diversity of butterflies and
their larval food plants in the surroundings of upper Neora Valley National
Park, a sub-tropical broad leaved hill forest in the
eastern Himalayan landscape, West Bengal, India. Journal of Threatened Taxa 6(1): 5327–5342; http://dx.doi.org/10.11609/JoTT.o3446.5327-42
Copyright: © Sengupta et al. 2014.Creative Commons Attribution 3.0 Unported License.JoTT allows unrestricted use of this article in any medium, reproduction and
distribution by providing adequate credit to the authors and the source of
publication.
Funding: Self funded.
Competing Interest: The authors declare no
competing interests.
Authors Contribution: PS was involved in the sampling, identification of studied species; statistical analysis of recorded data, manuscript
preparation and site management. KKB was involved in data interpretation,
literature survey and framing up of research questions. NG was engaged in the
sampling, identification of studied species;statistical analysis of recorded data, data interpretation, framing up of
questions and hypothesis along with manuscript preparation.
Author Details: Panchali Sengupta is a PhD
student of the Department of Zoology, WBSU, Barasat, WestBengal. She is currently involved in the study of insect-plant interaction with
special reference to ants and butterflies. Kamal
Kumar Banerjee is Associate Professor, Department of Zoology, Bidhanagar
College, Kolkata. His field of interest involves
wildlife biology and ecology. Narayan
Ghorai is Associate Professor, Department of Zoology, West Bengal State
University, Barasat, West Bengal. His research
interest involves insect-plant interaction, wildlife biology and behavioral
ecology.
Acknowledgements: The
authors are thankful to the Head, Department of Zoology, West Bengal State
University, West Bengal, India for his constant
encouragement and support during the entire study period. Authors would like to
extend their gratitude to Professor Gour Maiti, Department of Botany, Kalyani
University, West Bengal, India for his assistance in the identification of all
the plant based resources. The guidance and efforts of Ram Kumar Chettri,
forest guide, Gorumara National Park is also acknowledged by the authors. The
authors would like to extend their sincere thanks to Siraj-ul-Haq, Dhruba
Manta, Somnath Mandal and all the forest personnel of NVNP for their
cooperation and help.
For figures, images, tables -- click here
Introduction
Studies in India (Kunte 1997; Padhye et al.2006; Bhusal & Khanal 2008) have established a relationship between
butterfly species richness, density and diversity with respect to
seasonality. For instance, tropical
butterflies have been shown to be sensitive to seasonal changes in rainfall
(Barby 1995; Hill et al. 2003). Wynter-Blyth (1957) documented 835 species from the eastern Himalaya in
sharp contrast to only 415 species from the western Himalaya. The lowland forests of Bhutan harbour a
rich and unique diversity of butterflies with maximum number of species
recorded during spring and minimum number during the monsoons (Singh
2012). Saikia et al. (2010), during
their study on 109 species from Rani-Garbhanga Reserve Forests recorded
seasonality of butterflies with differences in the butterfly abundances as well
defined dry and wet season forms due to distinct plant phenological state in
different seasons of the year. Although a list of butterflies from the Darjeeling District of West
Bengal (Maude 1949) is available, studies on the butterflies inhabiting the
rich and diverse Himalayan landscape of Neora Valley National Park (NVNP) are
lacking. NVNP is located at the trijunction of West Bengal, Sikkim (India) and
Bhutan on the north and northeast. Rechila danda, the highest point of this National Park is situated at 3,170m
(Mallick 2010). Therefore, work was
carried out to document diversity of butterflies in different seasons from the
fringe regions of the upper range of NVNP. The diversity and seasonality of butterflies probably reflect the phenophases
of their host plants (Kunte 1997). Therefore an attempt was also made to record the larval food plants of
butterfly species.
Materials and Methods
The present study was conducted in the
adjacent areas of the upper range of the NVNP (26052’–2707’N
& 88045’–88055’E) located in the Kalimpong
sub-division of the Darjeeling District, West Bengal, India (Fig. 1). It was notified as a protected area in
April 1986 and was gazetted in December 1992. The park authorities divided Neora
Valley into two ranges, namely the upper range with its headquarters at Lava,
serving as its western entry point and the lower range with its headquarters
situated at Samsing, the park’s eastern entry point (Mallick 2010).
The phytogeography of NVNP includes
subtropical broad leaved hill forest, montane wet temperate forest along with
subtropical pine forest (Champion & Seth 1968). Rodgers et al. (2002) placed NVNP in the
biogeographic zone 2. The park has
a wide altitudinal range varying from183m in the plains to 3,200m in the hills
(Mallick 2012). The climatic
condition varies between tropical/subtropical in its lower range to temperate
in its upper range (Mallick 2010). The forest structure at the study site was mostly undisturbed. The surrounding terraces had cultivated
fields of forest adjoining dwellers.
Four trail-cum-trekking routes (total
length: 16km) (Table 1) were selected as study sites (i.e., NVNP-1, NVNP-2,
NVNP-3 and NVNP-4) (Table 1). The
survey was conducted between June 2011 and May 2012, following the Pollard-Walk
Method (Pollard 1977) at eight randomly selected line transects (approximately
500m length and 8m breadth) located in each of the study sites. Butterflies were observed twice a day,
(06:00–13:00 hr in the morning and 14:00–17:00 hr in the afternoon)
by walking at a constant pace at each transect. Less time was devoted for sampling in
the afternoon due to reduced butterfly activity at that time of the day. Separate days were devoted to sample
each transect in each study site weekly for a month with the help of two
trained field assistants. The
sampling procedure was repeated at an interval of 30 days. As far as possible, surveys were
conducted on sunny days with less than 30% cloud cover, as butterfly activity
is suppressed on windy or cloudy days (Weiss et al. 1988). The sampling days missed due to
inclement weather conditions were recorded.
The butterflies were observed (using
Bushnell binoculars) and photographed occasionally (using Nikon COOLPIX-P90)
for subsequent identification from literature (Evans 1932; Wynter-Blyth 1957;
Haribal 1992; Kunte 2000; Kehimkar 2008) and reference collection at Zoological
Survey of India. For better
interpretation of collected data the year was divided into five seasons (viz.,
Spring: March; Summer: April–May; Monsoon: June–September; Autumn:
October–November; Winter: December–February). The division of seasons was based on the
variation of rate of precipitation and temperature. Larval host plants were recorded in each
transect and also identified from the adjoining areas of transect. These plants were identified from
published literature (Cowan & Cowan 1979; Polunin & Stainton 2005;
Maity & Maiti 2007; Das et al. 2008) along with assistance from plant
taxonomists. Meteorological data
(i.e., temperature, precipitation) were collected during the study period.
The diversity of butterfly species across
seasons was calculated using Shannon index of diversity given by the equation,
H´=Σpi (ln pi), where, pi=ni/N; ni is the number of individuals of ithspecies and N=Σni. The Shannon
index, which combines the number of species within a site with the relative
abundance of each species (Shannon 1948; Magurran 1988) was determined using
vegan package of “R”. Margalef’s
species richness was used to compare the species richness across seasons. This index was calculated using equation
R=(S-1)/ln N, where S is the number of species and N is the number of
individuals (Magurran 1988). Evenness of species reveals how their relative abundance is distributed
in a particular site or sample (Pielou 1969; Magurran 1988). This index is given by the equation,
E=H´/ln S, where H´ is the Shannon index of diversity and S is the number of
species. Rank abundance diagram was
plotted to represent the distribution pattern of species abundances across each
season during the study period (Whittaker 1965). Month-wise variation in the number of
species sampled during the study period was represented graphically.
Results
One-hundred-and-sixty-one species of
butterflies belonging to five families (i.e., Nymphalidae: 43.48%, Lycaenidae:
27.95%, Hesperiidae: 11.18%, Pieridae: 9.32% and Papilionidae: 8.07%) were
observed at different sites during the entire study period (Table 2).
During summer (April–May), the
temperature varied from 3–6 0C (min.) to 20–21 0C
(max.) and a precipitation of 95.2–239 mm was recorded, while the monsoon
months (June-September) had a temperature of 7–8 0C (min.) and
22–23 0C (max.), with a maximum precipitation of 589–620
mm. 1–4 0C (min.)
and 20–22 0C (max.) temperature was recorded during autumn
(October–November), with a precipitation between 16.4–30.0 mm. Winter (December–February)
temperatures ranged from minus 3–1 0C (min.) to 18 0C
(max.), while 4.2–10.9 mm of precipitation was recorded. Spring (March) had a minimum temperature
of 2 0C and maximum temperature of 20 0C with a
precipitation of 20mm (Table 3).
As November to February was marked by a
number of foggy days (Table 4), sampling was carried out mostly on sunny
days. July had the maximum number
of rainy days (Table 4). Thus, a
total of 192 days of sampling was carried out during the entire study period,
each day devoted to two transects studied in the study site (Table 4).
The number of butterfly species and the
total number of individuals recorded is shown in Table 5. The maximum number of butterfly species
(158) and the maximum number of individuals (2480) was recorded during the
monsoons. Shannon index of diversity (H´=4.968) along with the evenness index
of species distribution (E=0.981) also exhibited highest values during this
season (Table 5) as compared to summer (H´=4.819; E=0.974), autumn (H´=4.714;
E=0.961), spring (H´=4.282; E=0.914) and winter (H´=3.872; E=0.811). The season wise species richness values
are recorded in Table 5. Species
richness showed maximum values during autumn (21.78), summer (21.58) followed
by monsoon (20.09) (Table 5). Additionally, the rank abundance curve plotted to represent the
distribution pattern of butterfly species, was least skewed during the
monsoons, as supported by highest values of Shannon diversity and Evenness
index during this season (Fig. 2). In contrast, winter was associated with a most highly skewed species
abundance relationship as evident by lowest values of Shannon diversity and
Evenness index (Fig. 2). However,
rank abundance curve showed intermediate skewness in case of summer, autumn and
spring. The curve representing the
month-wise change in the number of species showed an increasing trend from
March, through April, and reached its peak in June due to increased number of
species with the approaching monsoon. This curve was almost steady throughout this season, and formed a second
shorter peak during September–October followed by a decrease in the
number during late autumn and winter gradually (Fig. 3).
A total of 143 species of plants belonging
to 44 families were recorded as the larval host plants of the butterflies
(Table 6). An overwhelming number
of butterfly larvae fed on dicotyledons rather than on monocots. The only two groups associated with the
monocotyledons were Satyrinae subfamily of Nymphalidae and Hesperiinae
subfamily of Hesperiidae butterflies. Nymphalidae utilized 25 plant families and thereby exhibited highest
host plant diversity (number of plant families used per butterfly family) in
this study site (Table 6). Larvae
of Satyrinae mostly preferred plants of Poaceae. Plants of Urticaceae supported a large
population of Acraea sp. (Heliconiinae subfamily), Araschnia sp, Symbrenthiasp., Vanessa sp. and Aglais sp. (Nymphalinae subfamily), while Euploealarvae predominantly depended on Moraceae plants. Lycaenidae showed the second highest
host plant diversity and utilized 20 plant families as their larval resource
(Table 6). Fabaceae, Ericaceae,
Myricaceae and Loranthaceae were the major food plants of larval
lycaenids. A total of six families
encompassing 20 species were recorded as the host plants of Pieridae
butterflies. While Coliadinae fed predominantly on plants of Fabales, Pierinae
butterflies chose Brassicales and mistletoes as their larval resource (Table
6). 28 species of plants belonging
to 13 families served as food plants for larvae of Hesperiinae, Pyrignae and
Coeliadinae. Although Hesperiinae
larvae fed on Poaceae and Pyrignae utilized Acanthaceae, Coeliadinae
butterflies used plants of families Combretaceae, Moraceae, Euphorbiaceae,
Sabiaceae (Table 6). Four plant
families were used by the Papilionidae butterflies as their larval resources.
Lauraceae and Rutaceae were their predominant larval food plants (Table 6).
Discussion
Among the butterflies of the Himalayan
region, 80% are recorded as forest species of which 60% occur below 3000m
elevation (Uniyal & Mathur 1998). The upper range of the NVNP is recognised as the last virgin wilderness
in West Bengal (UNESCO World Heritage Centre 2009; Mallick 2010). Such a pristine habitat of tropical to
temperate broad leaved forest along with dense undergrowth provides suitable
resources for the butterflies. The
tropical monsoon climate of this region with little temperature fluctuation between
seasons but with huge differences in rainfall, support the abundance of herbs
and shrubs as predominant larval host plants of Hesperidae, Pieridae,
Nymphalidae and Lycaenidae butterflies as observed in this study. Nymphalidae,
the dominant family as in any other tropical region, had well built butterflies
with large wingspan that helped them to obtain resource from all habitats
(Majumdar et al. 2012).
Wynter-Blyth (1957) identified two periods
(March-April and October) as peak season of butterfly abundance in India. Kunte (1997) threw light on the
abundance and species diversity of butterflies based on seasonality in four
tropical habitats in Northern Western Ghats. Butterfly diversity at local or regional
scales is closely related to their host plant density (Gutierrez & Mendez
1995; Cowley et al. 2001). A
Rank-Abundance curve with steep gradient indicated low evenness (Magurran 2004)
and low species diversity (Kunte 2008), in contrast to a curve with shallow
gradient which represented high evenness (Magurran 2004) along with high
species diversity (Kunte 2008). A
similar trend is evident in the present study (Fig. 2). Maximum species diversity along with
highest species evenness as observed during the monsoons could be correlated
with the abundant distribution of luxurious vegetation which was said to be in
suitable phenophase to support the growth of the larval stages of these
butterflies. The monsoons were also
associated with a greater abundance of species that had occurred in low
frequency during summer (Atluri et al. 2011). Pöyry et al. (2009), stressed the
importance of local habitat quality to explain species richness. Higher values of species richness as
observed during autumn, summer and monsoon could be indicative of the presence
of specific butterfly larval host plants during this season. This pattern is consistent with that of
Wynter-Blyth (1957), Kunte (1997) and Padhye et al. (2006). Month wise
fluctuation in the sampling size of butterflies could be attributed to the
distinct changes from the wet season (May–October) to the dry season
(November–April) forms (Emmel & Leck 1970; Saikia et al. 2010) in
butterflies. Along with a distinct
surge in butterfly distribution as observed during the monsoons (Atluri et al.
2011), butterflies are said to form peaks at transition periods between the wet
season and the dry season (Emmel & Leck 1970).
The higher host plant diversity seen
amongst the Nymphalid and Lycaenid butterflies in this zone of the National
Park are probably due to the greater host plant diversity as previously
reported from amongst the South East Asian Nymphalidae and Lycaenidae (Fiedler
1998). The preference for Poaceae
hosts observed among Satyrinae larvae in this and other studies (Wynter-Blyth
1957; Haribal 1992; Munguira et al. 1997; Peñal & Wahlberg 2008) are
significant. Himalayan distribution
of the Heliconiinae subfamily of butterflies (Uniyal 2007; Borang et al. 2008;
Singh 2009) also supported their presence in this study site. Occurrence of Glochidion sp., a
common tree of the middle to upper Himalayan region along with Lonicerasp. (Cowan & Cowan 1979), a shrubby climber, probably sustained the larval
population of Athyma sp. and Parasarpa sp respectively. The relationship between Euthalia
lubentina- Moraceae, E.aconthea- Moraceae and Anarcardiaceae and E.sahadeva with Fagaceae threw light on the difference in the food plant
preference by Euthalia butterflies (Wynter-Blyth 1957; Kehimkar
2008). Ulmus sp. and Celtissp. (Ulmaceae) which constitute the essential part of the broad leaved forest
of higher elevations (Maity & Maiti 2007) supported the larval population
of Apatura sp and Hestina sp of butterflies. Wide scale distribution of Urticasp., Debreagesia sp., Girardiana sp., Boehmeria sp. and Elatostemmasp. (Urticaceae) (Cowan & Cowan 1979; Maity & Maiti 2007) sustained the
larval population of Symbrenthia hypselis, S. hippoclus, S. niphanda,Vanessa indica, V. cardui, Araschnia prorsoides and Aglais cashmiriensis (Nymphalinae subfamily) (Wynter-Blyth 1957; Haribal 1992;
Kehimkar 2008). The association between Grewia sp. Libythea lepita,
Celtis tetrandra, L. narina and C. cinnamomea with
both L. myrrha and L. narina also stressed the importance of
specific food plants for the butterflies (Haribal 1992; Kehimkar 2008). Daninae butterflies fed on Apocyanaceae,
Asclepiadaceae and Moraceae, all plants possessing a milky fluid (Erhlick &
Raven 1964).
According to the Singh & Pandey (2004)
model, Lycaenidae, should represent 29.5% of the total number of species
sampled in northeastern India. Although being the second most (27.95%) abundant family in this study
site, Lycaenidae still appears to be slightly under represented in this study,
which points towards the need for further investigation. The larvae of Heliophorus sp. andLycaena phlaeas fed largely on the Polygonum sp. and Rumex
nepalensis, respectively, throughout its range in the Himalayan region
(Uniyal 2007; Borang et al. 2008; Singh 2009). Myrisinae (Ardisinia solanacea)
served as larval resource of Nacaduba kurava (Polyommatinae
subfamily). Besides this, legume
feeding was prevalent amongst other Polyommatinae larvae (Wynter-Bylth 1957;
Haribal 1992; Kehimkar 2008). Among
Riodininae, Dodona adonira, D. eugenes and Zemeros flegyaswere the butterfly species of northeastern India (Borang et al. 2008). Other Himalayan species, Abisara
fylla D.egeon and D.ouida (Uniyal & Mathur 1998) were
also associated with Maesa chisia plants. D. dipoea was reported due
to the distribution of its host plant, Arundinaria maling which formed
an important part of this forest habitat. Overhanging parasitic flora along with Rhododendron sp served as
the food plants of a majority of Theclinae subfamily of lycaenid larvae
(Wynter-Blyth 1957; Kehimkar 2008).
Besides association of Gonepteryx
rhamni with Vaccinium sp., Fabales were decidedly the most important
food plant of other Coliadinae butterflies (Ehrlich & Raven 1964). The extensive cultivation of Brassica
juncea in the adjoining areas of the National Park may be the supportive
larval host plant of Pieris butterflies. Pieris larvae are known to
detoxify and eliminate, rather than sequester, the degradation products of
glucosinolates (present in Brassicales) (Müller et al. 2003).
The marked reduction in the abundance of
Hesperiidae in this study in accordance to that previously stated by the Singh
& Pandey (2004) model for northeastern Indian hesperids, probably generates
an urgent need for their further study in similar areas.
The association between black-bodied
papilionids with Rutaceae and red-bodied papilionids with Aristolochiaceae were
similar to observations made on Assam papilionidae (Barua et al. 2004). While Lauraceae - Magnoliaceae served as
the food resource for Graphium eurous and Chilasa slateri larvae,Meandrusa payeni, Chilasa agestor and Graphium sarpedon depended
solely on Lauraceae to sustain their larval population (Wynter-Blyth 1957;
Haribal 1992). A report on the
occurrence of Kaiser-I-Hind Teinopalpus imperialis, from Darjeeling
District (Kehimkar 2008) also confirms their record in this study. Species such as Bhutanitis
lidderdalei and Teinopalpus imperialis were strictly seasonal
and found on wing between April–November. Such a seasonal trend could be
attributed to synchrony with phenology of their food plants (Spitzer 1983).
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