Biodiversity of butterflies (Lepidoptera: Rhopalocera) in the protected landscape of Nandhour, Uttarakhand, India

and Sustainable Development, Kosi–Katarmal, Almora, Uttarakhand for their immense support in plant identification. Gracious hospitality received from local people is highly acknowledged. Suggestions and comments made by reviewers and editors in the early draft of this manuscript are acknowledged.


INTRODUCTION
Butterflies (Lepidoptera: Rhopalocera) are a vital component of our natural ecosystems due to their important pollination services, high specificity of habitat utilization and complex interactions in food webs (Rusman et al. 2016). The status of butterfly diversity and richness in a given area reveals information on the ecosystem health and its functioning (Andrew et al. 2011). Butterflies are useful model organisms in predicting the impact of climate change on biodiversity (Warren et al. 2001;Davies 2019), and are an excellent indicator taxon for monitoring changes in ecological parameters such as environmental health, land use, habitat quality, levels of biodiversity, and conservation status (Bonebrake et al. 2010;Sharma et al. 2020;An & Choi 2021). They respond quickly to changes in local vegetation, climatic conditions, land use types, and disturbances (Bergerot et al. 2011;Chettri et al. 2018;Sharma et al. 2020;Verma & Arya 2021). Several anthropogenic drivers of defaunation have resulted in a global decline of about 35% in butterfly abundance over the last 40 years (Dirzo et al. 2014), and due to unscientific management, many species are on the verge of extinction (Wallenius et al. 2010;Wagner 2020). The Indian subcontinent is represented by about 1,501 butterfly species (Kehimkar 2016), and the hilly state of Uttarakhand in the western Himalaya hosts around 508 species of butterflies (Sondhi & Kunte 2018).
The Nandhour landscape located in the eastern part of Uttarakhand, is a representative part of the vast conservation geographic division called Terai Arc Landscape (TAL). The TAL is an eco-fragile Terai-Bhabar region on the outer slopes of the Shiwalik Himalaya to the foothill areas and Gangetic flood plains (Semwal 2005;Chanchani et al. 2014). The entire region of the Nandhour due to its unique topography, geology, and climate is well known for pristine ecological conditions, spatial heterogeneity and rich biodiversity (WII 2019). The central part of the landscape was designated as a Nandhour Wildlife Sanctuary (covering a total geographical area of 269.95 km 2 ) in 2012, and recently an eco-sensitive zone (covering a total geographical area of 540.26 km 2 ) has been established around the periphery of the sanctuary for proper management and propagation of wildlife (Anonymous 2020). However, human activities such as habitat fragmentation, overexploitation, and poaching have posed serious threats to the rich biodiversity of the region (Mehra 2015).
Published data on butterfly fauna is currently lacking from the protected landscape of Nandhour. The landscape has not been surveyed well since the British colonial era. The Nandhour Landscape provides a crucial corridor for wildlife movement across the eastern forests of TAL, such as Brahmadev & Sukhlaphata Wildlife Reserve of Nepal, and the western forests of Corbett & Terai Central Forest Division in India (Verma 2011;WII 2019). In the recent past, few empirical studies have been conducted in protected and unprotected forest ecosystems of Kumaon and Garhwal regions of Uttarakhand (Singh & Bhandari 2003, 2006Joshi 2007;Joshi & Arya 2007;Singh 2009;Bhardwaj & Uniyal 2011;Smetacek 2012;Bhardwaj et al. 2012;Singh & Sondhi 2016;Arya et al. 2020a,b;Samraj & Agnihotri 2021;Verma & Arya 2021). However, the butterfly diversity and richness of Nandhour Landscape received less attention and was not comprehensively reported from the protected sanctuary. Earlier, Arya & Dayakrishna (2017) recorded 35 butterfly species from the Nandhour Wildlife Sanctuary. There are also few reports on recent rediscoveries and new records of butterfly species to Uttarakhand from the Nandhour Wildlife Sanctuary (Sondhi 2017;Kumar et al. 2020).
Studies on butterflies are important from the standpoint of their diversity, conservation, behavioral, and ecological functional roles as well as to assess the impact of land use changes on them (Bonebrake et al. 2010;Chettri et al. 2018). At present, there are no comprehensive studies that understand the systematic composition of butterflies in this region. Hence, this research primarily aims to record butterfly diversity and richness patterns across different habitats in and around the Nandhour Wildlife Sanctuary of biodiversity rich TAL. The study also intends to investigate the anthropogenic factors affecting butterfly diversity, and to provide guidelines for effective and proper butterfly conservation.

Study area
Nandhour Wildlife Sanctuary stretched between 28°56'29.35"─29°16'39.79" N & 79°33'03.82"─80°10'00.03" E, is a sub landscape of the Shiwalik-Bhabar Tract in the central sector of the eastern part of TAL ( Figure 1). This sub landscape of Nandhour (core zone) along with its adjoining buffer area (ecosensitive zone) falls under three protected and managed territorial forest divisions of Uttarakhand i.e. Haldwani Forest Division (HFD in the north-west), Terai East Forest Division (TEFD in the south-east), and Champawat

J TT
Forest Division (CFD in the north-east). Majority of the landscape lies in the HFD of district Nainital (Mehra 2015). The Nandhour Landscape is intersected by the river Nandhour in the north, and bounded by river Gola and river Ladhiya in the west, and by the river Sharda in the east towards Nepal (Verma 2011). Geologically, the landscape consists mostly of alluvial plains (Bhabar), and loose conglomerates & hard sandstones of the Shiwalik Himalaya (Mehra 2015). The topography of Nandhour is represented by steep mountains, high denudational hills, broad & narrow valleys, flat & rugged slopes, and flood plains. Due to the close proximity to the Himalayan mountain range, the region experiences sub-tropical to temperate type of climate, and the maximum average temperature varies from 28°C in January─37°C in May (Mehra 2015). With an annual precipitation of over

J TT
1,400 mm, the region receives most rainfall from the southwest monsoon that breaks in mid June and lasts until the end of September-October (Mehra 2015 (Verma 2011). These natural forest and riverine habitats are home to about 32 mammalian species, including several endangered and flagship species such as the Royal Bengal Tiger Panthera tigris and Asian Elephant Elephas maximus (Mann et al. 2013), 250 species of resident and migratory birds, 15 reptilian species, and 20 fish species (Verma 2011). The landscape is also represented by plantation forests, wetlands, barren lands, human settlements, and cultivated lands.
Appraisal surveys on butterflies were conducted in different forest ranges by covering a variety of habitats in and around the sanctuary. Butterflies were sampled in eight habitat types (sites): human habitation & agricultural land (S1 in Nandhour Range of HFD), Butterfly Conservation Zone (S2 in Nandhour Range of HFD), dense moist riverine forest (S3 in Nandhour Range of HFD), moist Bhabar sal (S. robusta) forest (S4 in Chakata Range of HFD), open dry riverine forest (S5 in Jaulasal Range of HFD), subtropical Chir Pine Pinus roxburgii forest (S6 in Chakata Range of HFD), moist Shiwalik Sal forest (S7 in Dogadi Range of CFD) and moist mixed deciduous forest (S8 in Sharda Range of HFD). Of these S1, S2, S3, S5, S6, and S7 were located in the core zone, while S4 & S8 were located in the buffer area of the sanctuary. For the purpose of the present study, an area of one hectare was selected in each site (Image 1 & Table 1). The sites in the study area were selected on the basis of different land use and forest types to reflect the importance of a mosaic of habitats in sustaining butterfly diversity. Management practices and anthropogenic threats within each site were noted during the study period.

Sampling protocols and data collection
Every month, from March 2018─February 2020, butterflies were sampled for eight consecutive sampling days. Sampling was conducted along three permanent linear transects (each measuring 300 m), spaced about 300-500 m apart from each other, in each of the eight habitat types (sites) selected in the study area. Modified Pollard Walk Method was adopted for the presenceabsence and abundance data of adult butterfly species in each site (Pollard 1977;Pollard & Yates 1993). Diurnal butterflies were counted mostly during optimal conditions of maximum activity, around an imaginary space of 5 m × 5 m × 5 m while walking slowly and uniformly covering each of the three transects of a site between 07.00─13.00 h of a day. A minimum of 1.5 h was spent on butterfly sampling in a permanent transect. The same survey method was employed in each site on consecutive sampling days. The preferred host plants of butterflies available in the sites were also noted through primary observations and secondary information (Wynter-Blyth 1957;Kunte 2000Kunte , 2006Robinson et al. 2010;Sengupta et al. 2014;Nitin et al. 2018;Sondhi & Kunte 2018).
Most of the butterfly species were identified visually with the help of available field guides (Kumar 2008;Kehimkar 2016;Singh 2017;Sondhi & Kunte 2018), photographed by using lens of power 18-15 mm in DSLRs Nikon D3500 and Canon 750D. Species which were difficult to identify superficially were collected by a butterfly net, placed in a clear glass bottle, and identified using morphological keys outlined in the literature (Evans 1932;Wynter-Blyth 1957;Haribal 1992). Each collected individual was released immediately after identification at the site of its capture, and no specimen was harmed or killed during the field visits. Plant species were identified using published information (Verma 2011;Mehra 2015), and by the help of experts and taxonomists at G.B. Pant National Institute of Himalayan Environment and Sustainable Development.

Data analysis
Monsoon affects the diversity and distribution of butterfly community at a temporal scale across India (Wynter-Blyth 1957), and several species are strictly seasonal (Kunte 1997;Harisha & Hosetti 2021). Therefore, an annual survey period was categorized into three main seasons-summer (March-June), rainy (July-October), and winter (November-February) to determine the seasonality pattern of butterflies in the study area. The taxonomic classification of butterflies was adopted from Kehimkar (2016), Sondhi & Kunte (2018). The total number of counted individuals of each species across habitat types was pooled to obtain the relative abundance following Verma & Arya (2021) expressed as a percentage based on total individual counts of butterfly fauna in the study area. A rank abundance curve to depict the distribution pattern of different 22452 J TT species was created by log transforming the individual abundance data following Magurran (2004). Diversity measures were obtained using the Shannon-Weiner diversity index (Shannon & Weaver 1949), Margalef richness index (Margalef 1972), and Pielou evenness index (Pielou 1969). Individual based rarefaction curves were obtained for each habitat types following Gotelli & Colwell (2001). The analyses of diversity measures and rarefaction curves were done using the software PAST (Hammer et al. 2001). In order to compare the species richness and abundance of butterflies across seasons and habitat types, one-way analysis of variance (ANOVA) tests at the 5% level of significance were performed using the software SPSS. The Sorensen's similarity index was calculated to determine the extent of assemblage similarity in different habitat types of the study area (Sorensen 1948).

Overall species composition of butterflies
A total of 10,713 individuals belonging to 89 species and six families were recorded during the study period (2018-20) from eight habitat types selected in the Nandhour Landscape (Appendix 1). The butterfly community was more or less evenly distributed in the study area as depicted by a relatively low steep inclination of the plot in the rank abundance curve ( Figure 2). Detailed account of each family is given below: Family Hesperiidae: This family comprised of eight species and 4.48% of the total recorded individuals (Images 1-8). Species namely, Parnara guttatus (Relative abundance = 1.82) and Borbo bevani (1.29) were the most abundant found across all habitats, while the least abundant species Udaspes folus (0.13) was found in agricultural land, dry riverine, and chir pine forests, & Aeromachus stigmata (0.13) in chir pine forest (Appendix 1).

Seasonality of butterflies
Across the seasons, species richness, and abundance showed significant differences when analyzed through one-way ANOVA (Richness: F = 31.21, df = 2, 21, and P = 0.00; Abundance: F = 21.25, df = 2, 21, and P = 0.00). The highest number of species and individuals were recorded during rainy season (82 species and 50.46% of the total individuals), followed by summer (78 species and 37.56% of the total individuals) ( Table 2). Winter season showed a significantly lower richness and abundance (48 species and 11.97% of the total individuals).
Seasonally, a bi-annual peak in butterfly diversity was observed in the study area (Figure 3). The Shannon diversity (Hs) was at its peak during the dry summers (Mar-May) and the monsoons (Aug-Oct). Diversity was at its minimum during Dec-Jan (winters). Forty-eight species were found across all seasons, 23 species were found during the summer and rainy seasons, 11 species were found during the rainy season, and seven species were found during the summer (Appendix 1).
The calculated diversity measures show high richness patterns in eight habitat types of the study area (Table 3). The maximum species diversity and richness was recorded in the sites represented by riverine forests (S3, S5 with Hs 3.97 & 3.90; Hm 9.21 & 9.15, respectively), while the habitat characterized by human settlements and agricultural land showed the minimum

J TT
diversity, richness, and evenness of the species (S1 with Hs 3.20, Hm 5.11, and J 0.66). Butterfly assemblage in the subtropical Chir Pine forest at S6 was very even in its distribution (J 0.80). The pair-wise comparisons of Sorensen's similarity index for assemblages in different habitat types depicted that riverine forests (S3 & S5) had high similarity (0.87) and a unique species composition (Table 4). Similarly, man managed habitats (S1 & S2) had a high degree of similarity (0.82), and mixed deciduous forest (S8) had high similarity (0.81 & 0.80) with moist riverine forest (S3) and dry riverine forest (S5). 26 species were found across all the habitat types, while nine species were found as habitat specific in the study area (Appendix 1).

DISCUSSION
The present study revealed that the protected Nandhour landscape of TAL, with 89 species belonging to six families hosts good diversity (Hs 3.927) and richness (Hm 9.484) of butterflies (Appendix 1, Table  3). The recorded butterfly richness constituted about 17.50% of the total known species from Uttarakhand (Sondhi & Kunte 2018). Previous to this study, there are known records of 20 species in Nandhour Village (S1), 34 species in Butterfly Zone (S2), 32 species in Machhli Van (S3), 26 species in Suryadevi Temple (S4), and 28 species in Jaulasal (S5), which altogether constituted 53 species of butterflies from the protected area of Nandhour (Arya & Dayakrishna 2017). Of them, 42 species were also recorded in the present study, while the rest 47 species (out of 89 species) represent new records for the Nandhour Landscape (Appendix 1). The unreported butterfly species included Spialia galba (Hesperiidae), Pachliopta aristolochiae, Graphium doson (Papilionidae), Ixias marianne, Colotis sp., Belenois aurota (Pieridae), Neopithecops zalmora, Freyeria trochylus (Lycaenidae), Hypolimnas misippus, Cupha erymanthis, Neptis sankara, and Ypthima huebneri (Nymphalidae). Most of these species are either common or uncommon in Uttarakhand (Sondhi & Kunte 2018). Such results substantiate the importance of natural forest habitats in sustaining and maintaining the rich butterfly diversity. More intensive and consistent monitoring protocols could result in the addition of new butterfly species to the protected landscape of Nandhour.
In comparison to modern empirical studies conducted previously in different forest ecosystems of Uttarakhand, Samraj & Agnihotri (2021) (2007) reported 54 species in the Pindari area of Nanda Devi Biosphere Reserve, Joshi (2007) reported 40 species in the Motichur Sanctuary of Rajaji National Park, Singh & Bhandari (2003, 2006 recorded 183 species in the Dehradun Valley of Garhwal region. Furthermore, annual rainfall patterns have a significant impact on tropical butterflies (Wolda 1988;Valtonen et al. 2013), and the occurrence of dry-wet seasonal cycles generate bi-annual rhythms in species diversity and similarity of butterfly communities by bringing changes in the host plant dynamics of the region (Grøtan et al. 2012(Grøtan et al. , 2014. The reported high diversity and richness during dry summers (Mar-May) and wet monsoons (Aug-Oct) is in concordance with previous findings from the study area (Arya & Dayakrishna 2017), as well as from the regions experiencing tropical to sub-tropical type of climate in India (Gupta et al. 2019;Arya et al. 2020a).
Amongst the sampled habitats, butterfly richness was significantly low in the site (S1) characterized by human habitation and agricultural land (Figure 4). Local transportation, increased cultivation with use of chemical fertilizers & pesticides, and other human activities might have resulted in the least diversity and richness in S1 (Table 3). Generalist species like P. brassicae, P. demoleus, P. polytes, C. pomona, E. hecabe and P. guttatus dominated this habitat (Appendix 1). It is known that declines in soil properties caused by pollution from anthropogenic toxins and habitat simplification through agriculture could result in reduced diversity and local extinctions of butterflies (Öckinger et al. 2006;Gilburn et al. 2015;Braak et al. 2018). On the other hand, the relatively less disturbed sites characterized by dense moist and open dry riverine habitats (S3 & S5), had the highest number of species and ample diversity ( Figure 4, Table 3). Natural forests, especially associated with the riverine ecosystems usually have greater environmental heterogeneity, provide unique vegetation & large quantities of diverse resources, better mating & ovipositioning sites, safety from predation, and low disturbance, hence are highly preferred by several butterflies, including specialist species (Cabette et al. 2017;An & Choi, 2021). Species namely, A. selenophora (in S3), C. agrarius, L. confusa, Y. asterope (in S5), Pseudocoladenia fatih, T. nara, Charaxes bharata, Hestinalis nama, Kallima inachus, and Vagrans egista (in both S3 & S5) were found as habitat specific butterflies in the riverine forests (Appendix 1). Similarly, A. amantes, F. asoka were unique to the moist Shiwalik Sal forest (S7), A. stigmata, Ypthima nareda to the subtropical Chir Pine forest (S6), and Zizula hylax to the butterfly zone (S2). These findings suggest that since the Nandhour landscape comprises of a variety of forest habitats types, it provides a congenial living environment and a diverse food supply for many species. Also, these results corroborate with a few earlier findings from nearby regions that revealed a high butterfly diversity and richness in natural habitats, but a low diversity and richness in habitats disturbed or managed by the human activities (Arya et al. 2020a; Samraj & Agnihotri 2021; Verma & Arya 2021).
As per the Indian Wildlife (Protection) Act 1972, five species identified in the present study are legally protected under different schedules (Appendix 1). Butterflies namely, L. boeticus (Lycaenidae), Libythea lepita, Neptis soma (Nymphalidae) are listed under Schedule II, and E. core, Euploea mulciber (Nymphalidae) are listed under Schedule IV (Anonymous 2006). Endemic butterflies of the Indian Himalayan Region included Potanthus dara (Hesperiidae), D. durga (Riodinidae), H. sena (Lycaenidae), Acraea issoria, Aglais caschmirensis, Athyma cama, Neptis hylas, and Ypthima nikaea (Nymphalidae) (Appendix 1). Such faunal records along with the reported rich diversity of butterflies signify a high conservation value of the study area. This means, the region must be conserved more intensely, especially by focusing on scientific management of riverine forest habitats located in and around the sanctuary. Butterflies are an excellent ecological indicator group for scaling and quantifying riverine characteristics because of their strong relationship with larval food plants, and riverine zones are thus conservation priority sites (Cabette et al. 2017;An & Choi 2021). Stream sides or muddy bogs in riverine forests are important microhabitats for those adult butterflies seeking rich puddling grounds to intake water and nutrients lacking in their larval diet (Nelson 2007;Verma & Arya 2021).
Human induced pressures in forest habitats from activities such as increased cultivation, forest fires, cattle grazing, illicit felling & logging, and collecting fuelwood, fodder & forest products could threaten the existence of several butterfly species in the protected landscape of Nandhour. These disturbances could have adverse impacts on their host plants in natural habitats, while the use of pesticides and fertilizers in cultivated areas adjacent to the sanctuary could be detrimental to rich biodiversity of the region (Braak et al. 2018;An & Choi 2021;Verma & Arya 2021). Being phytophagous, butterflies play vital role in the 'green' food webs of tropical ecosystems (Kitching et al. 2020), and form a critical food base for organisms at higher trophic levels (Bonebrake et al. 2010). Agricultural chemicals cause butterfly declines and may disrupt their complex ecological interactions, potentially harming insectivorous species such as birds and bats (Gilburn et al. 2015;Forister et al. 2016). Thus, it is extremely important that the soil properties in the cultivated lands of the protected Nandhour Landscape should not be deteriorated by the use of any sort of biocide, and the practice of organic farming must be encouraged by the concerned authorities for better socio-economic development of local inhabitants as well as for regional biodiversity conservation and natural balance.

CONCLUSION
The present study indicates the high conservation value of ecologically fragile natural habitats in sustaining rich diversity including several habitat specific, legally protected, and endemic butterflies of the Himalayas. However, overexploitation, illegal utilizations, excessive grazing, unauthorized access, and non-forestry related developments could cause declines in diversity by directly limiting important food choices and resources. Such activities should be regulated and strictly monitored in the protected Nandhour landscape. Special emphasis should be placed on the preservation and restoration of J TT interconnected natural forests supporting rich diversity, as well as providing better gene flow between butterfly populations. The establishment of several biodiversity offsets in different habitats will aid in the proliferation of butterflies. Government authorities and local bodies associated with management of the sanctuary should focus on activities related to plantation of more host plants and continuous monitoring programs to ensure their effective long-term conservation in the landscape. S-summer | R-rainy | W-winter | *-represents new records for the Nandhour Landscape | #-represents legally protected species under the Indian Wildlife (Protection) Act 1972 | E-represents endemic butterflies of the Indian Himalayan Region (Evans 1932;Wynter-Blyth 1957;Smetacek 2012;Kehimkar 2016) | arepresents species also reported by Arya & Dayakrishna (2017).