Butterfly species richness and diversity in rural and urban areas of Sirajganj , Bangladesh

An appraisal of butterfly species diversity study was conducted in four selected parts of Sirajganj District, Bangladesh, as a part of an ecological research. The study was conducted from March 2015 to April 2016. A total of 19,343 butterflies belonging to five families and 12 subfamilies was recorded. A random sampling of forest, riverside rural, and urban areas in Sirajganj District revealed the presence of 65 butterfly species, dominated by Lycaenidae (37%) over Nymphalidae (33%) followed by Pieridae (19%), Hesperiidae (7%), and Papilionidae (4%). Butterfly fauna in Bangabandhu Sheikh Mujib Jamuna Ecopark (BJEP), compared with the percentage of other study sites, was very high (Hs= 4.03) and the percentage of hedge species was relatively higher (45%) than that of improved grassland and forest interior species. The relative abundance of the butterflies varied with the site, month, and family significantly. Considering the landscape of Sirajganj, steps to enhance riverside natural gardening should be adopted to maintain butterfly diversity and sustain the ecosystem services derived from them.


INTRODUCTION
Butterflies are known to be the indicator species for their interaction with the environment. Butterflies occupy a vital position in ecosystems, and their occurrence and diversity are considered to be good indicators of the health of terrestrial biota (Kunte 2000). They trigger some signal in response to the physical and chemical changes in the environment; they play a significant role in pollination and in community ecology. Evolutionary mechanism of pollination has largely depended on the scaly jewels (Pollard 1991). The compilation of species lists and identification of habitat preferences and abundances are the first steps in effectively conserving biodiversity through the establishment of species baselines and basic ecological requirements (Chowdhury et al. 2017). The butterfly fauna in the northeastern and southeastern parts of Bangladesh is relatively rich and diverse in contrast to favourable habitat, elevational gradients, and microclimatic regimes. Most of the studies on this group are primarily conducted on the evergreen and mixed evergreen forest areas of Bangladesh; however, other parts of Bangladesh lack baseline studies. Torban (2004) mentioned some locations in the northwestern and northern part of Bangladesh as potential territory for butterflies. Sirajganj is one of the 64 districts of Bangladesh situated in the northern part of this country, and this is an initial baseline for butterfly diversity in a mixed habitat setting where the urbanization process is prevalent.

Study Area
Sirajganj District, situated in northern Bangladesh, has an area of about 2,497.92km². It is a part of Rajshahi Division, the gateway to northern Bengal. It is bordered on the north by Natore District and Bogura District by the Jamuna River on the east. In this current study, we chose four distinct study areas based on their floral diversity and distribution: Bangabandhu Sheikh Mujib Jamuna Ecopark (BJEP)this park was partially developed during the construction of the Jamuna Bangabandhu Sheikh Mujib Bridge on the Jamuna River. BJEP covers approximately 50.02ha and is situated in the western part of the Jamuna River. Natural vegetation, including small natural forests, is mainly covered with deciduous and semi-deciduous vegetation. This area has a rich diversity of weeds and bushes.
Belkuchi-this study site aligns with the catchment area of the Jamuna River. Embankments and some human settlements made the site stable. This area, with low disturbance from human interference, is composed of mixed vegetation lands cultivated for seasonal crops, grasses, flowers, and vegetables. The area consists of a variety of butterfly associate plants for nectaring, viz., Pisum sativum, Brassica juncea, Ixora rosea, Catharanthus roseus, Clerodendrum viscosum, Atrocarpus lacucha, Citrus spp., and Tridax spp.
Haidarpur-this study site is an urban area. It is a highly human-disturbed area. Urbanization process is prevalent in this study site. Most people run hand looms and power looms in their dwelling areas. Vegetation, mainly seedlings of fruit and flowering plants, are of mixed types.
Kodomtoli-Kodomtali is situated in the low-lying catchment area of the Brahmaputra-Jamuna river basin. Large low-lying paddy fields were found at this site. Vegetation mostly consists of Brassica sp. in addition to some areas for cultivating shrubs and vegetables. The soil is mostly muddy in texture. The present study was conducted during March 2015 to April 2016.

Data collection and identification of butterflies
The study has been conducted by line transect method. The authors covered one permanent transect at every study site each month. Observations were taken between 08.00h and 16.00h. Butterflies were primarily identified directly by watching and taking photographs using Canon-600D camera. Sometimes specimens were caught for identification and then released after photographing, viz., Parnara sp., Pelopidus sp., Mycalesis sp., and Telicota sp. In a few cases, specimens were collected with sweep nets and carried to the laboratory for further identification processes. Climatic conditions such as temperature, humidity were measured by Thermo Hygrometer (model 288 -ATH). Butterflies were identified based on physical features with the help of reference books viz., Evans (1932), Kehimkar (2013). The scientific name and common name of butterflies were followed by Larsen (2004).

RESULTS AND DISCUSSION
Over the study period, 65 species belonging to 50 genera and five families were recorded. Among those four areas, BJEP represented all the species (65 species) because of its high floral diversity and deep vegetation, followed by Haiderpur with 58 species, Belkuchi with 37 J TT species, and Kodomtoli with 33 species. All observed species and counted numbers are given in Table 1.
In this current study, we gave precedence to richness of butterfly species as our primary response variable. Changes in habitat quality caused by urbanization might alter insect richness, resulting in either a decrease or more rarely in increases, in the richness of specific insect groups (McKinney 2008). Among the four sites, BJEP and Haiderpur showed significant differences in species composition. Butterflies are found in both rural and urban habitats; diversity and richness are much lower in urban areas than in natural ones (Raupp et al. 2010). Overall, recorded species richness of this study showed how butterfly abundance and diversity remained low in the urban areas compared to the forest lands.
Among the five families of the observed species from Sirajganj District, the most dominant family was Lycaenidae having covered 37% of the total species (24, out of 65). Papilionidae was the least abundant family, with four species. The diversity profile of butterflies showed variations in the four sampling sites ( Figure 3). In general, the four sampling sites showed richness in high species and high evenness of distribution (Table 2). Specifically, BJEP showed maximum diversity (Hs= 4.03) of butterflies, whereas Haiderpur showed minimum diversity (Hs = 3.74). Evenness of distribution in all the study sites was found to be high (e H/S̑ = 0.7198 to 0.8653). Greater flowering resources increases species richness as well as survivability in an ecosystem (Wix et al. 2019). Floral diversity of BJEP has different flowering understory vegetation during the dry season (November-March) resulting in the most significant number of Lycaenidae accounted from this semi-natural forest (24 species out of 65, 37%), and hence, Zesius chrysomallus Hübner, 1819 was sighted as a new distributional record for Bangladesh from BJEP (Rahman et al. 2016).  The Whittaker plot according to the abundance of different butterfly species is shown in Figure 4. Melanitis leda and Eurema blanda show relative abundances of 4.02% and 3.91% respectively. Both these species account for 8.03% of total individuals encountered in this current study from the four areas. Species accumulation/ rarefaction curves as a function of the number of samples shown in Figure 5 represent that most common species are found in the sampling area, where curves generally grow rapidly at first. The red solid curve represents samples in the BJEP followed by Kadamtoli with light blue, Belkuchi with blue, and Haiderpur with green. Correspondence analysis has greatly simplified the story in the data ( Figure 6); formed with family-wise species abundance consisting of 65 species, representing four different habitat/sampled sites. Each curve represents a different butterfly species richness level in four different locations.

Butterfly species richness and diversity in rural and urban areas of Sirajganj
Imam et al.   Early successional forests have some valuable ecosystem services for insect population growth. It can support biodiversity at large (Chazdon 2008). BJEP covers some natural forests in the western part of the river Yamuna which support a good number of butterfly species throughout the seasons. The presence of their host plant may have resulted in the high species diversity. Butterflies show a strong response to the vegetation of their habitat (Oostermeijer & van Sway 1998). Besides, the use of chemicals causes damage to the natural environment (Sharma & Singhvi 2017). In urban areas, modification of landscape, establishment of factories, random cleanup of bushes reduces the potential habitat for butterflies. Thus, the chance of natural pollination decreases.

J TT
Butterflies in four habitats showed a highly seasonal trend in pre-monsoon (March-May) and winter season (October-November). Some species, viz., Rapala manea,

CONCLUSION
The present study address several unreported aspects of butterfly and their diversity in the study area as well as northern part which was not well explored previously. More detailed study is required to evaluate the habitat condition through butterfly diversity in the northern part of Bangladesh. The vegetation of the riverside area allows a functional variety of flora that are sources of host plants and nectar plants for butterflies, even home to different wild animals viz., birds, reptiles, and so on. The conservation of habitat and wild fauna remains a daunting task in Bangladesh due to overpopulation and a lack of knowledge about habitat conservation. It is suggested that greater emphasis be given on sustainable forest management and integrated conservation approaches in riverside rural as well as urban habitats to maintain the natural balance. www.threatenedtaxa.org The Journal of Threatened Taxa (JoTT) is dedicated to building evidence for conservation globally by publishing peer-reviewed articles online every month at a reasonably rapid rate at www.threatenedtaxa.org. All articles published in JoTT are registered under Creative Commons Attribution 4.0 International License unless otherwise mentioned. JoTT allows allows unrestricted use, reproduction, and distribution of articles in any medium by providing adequate credit to the author(s) and the source of publication.