Species richness, abundance, distributional pattern and trait composition of butterfly assemblage change along an altitudinal gradient in the Gulmarg region of Jammu & Kashmir, India

Despite enormous diversity, abundance, and role in ecosystem processes, little is known about how butterflies differ across altitudinal gradients. For this, butterfly communities were investigated along an altitudinal gradient of 2700–3200 m a.s.l, along the Gulmarg region of Jammu & Kashmir, India. We aimed to determine how the altitudinal gradient and environmental factors affect the butterfly diversity and abundance. Our findings indicate that species richness and diversity are mainly affected by the synergism between climate and vegetation. Alpha diversity indices showed that butterfly communities were more diverse at lower elevations and declined significantly with increase in elevation. Overall, butterfly abundance and diversity is stronger at lower elevations and gradually keep dropping towards higher elevations because floristic diversity decreased on which butterflies rely for survival and propagation. A total of 2023 individuals of butterflies were recorded belonging to 40 species, represented by 27 genera and 05 families. Six survey sites (S I- S VI) were assessed for butterfly diversity from 2018 to 2020 in the Gulmarg region of Jammu & Kashmir. Across the survey, Nymphalidae was the most dominant family represented by 16 genera and 23 species, while Papilionidae and Hesperiidae were least dominant represented by 01 genera and 01 species each. Among the six collection sites selected, Site I was most dominant, represented by 16 genera and 21 species, while Site VI was least dominant, represented by 04 genera and 04 species.


Introduction
Lepidoptera is the second largest order of Class Insecta. It comprises two sub-orders, i.e., Moths (Heterocera) and Butterflies (Rhaplocera), consisting of about 124 families (Kristensen et al., 2007). According to Van Nieukerken et al. (2011), butterflies count for 1.87% of the global insect fauna. Butterflies are great focal species because they are involved in various environmental processes (Arroyo et al., 1982). Due to their diverse and abundant nature, they are easily identified, collected and sampled round the year. Thus proving to the best models for population and ecology (Pollard, 1991). They are considered valuable indicators of forests due to widespread distribution, different land-use systems (Dar and Jamal, 2021-a;Schulze et al., 2004) and land cover types (Soga et al., 2015). Their pollination efficiency is higher than that of bees at higher elevations. They account for 75% of the floral visitors of the Asteraceae family, one of the most common plant families in Brazilian grasslands (Mota et al., 2016). Lepidopteran species are highly sensitive to climatic factors such as temperature, humidity, rainfall, and wind speed (Bhardwaj et al., 2012), affecting their distribution across environmental gradients seen in both mountainous and low-lying areas. They also have a close https://doi.org/10.1016/j.sjbs.2021.11.066 1319-562X/Ó 2021 The Author(s). Published by Elsevier B.V. on behalf of King Saud University. This is an open access article under the CC BY license (http://creativecommons.org/licenses/by/4.0/). association with the vegetation, that they need for food and protection from predators, especially in the immature stages (Ferrer-Paris et al., 2013). The adults feed on floral nectar, due to this, they are less specialized to their host plant than the larvae. As a result, the distribution of butterfly species is linked to plant structure and community makeup (Carneiro et al., 2014). Availability of plant resources, habitat quality and quality of natural and seminatural habitats are some of the factors that govern the distribution of butterflies. Mountains are ideal for exploring the effects of rising elevation and climate change on species diversity and abundance because they generate a variety of physical conditions in a relatively short distance. Patterns in species richness along altitudinal gradients are well-known ecological phenomena. However, there is a paucity of information about how ecological filtering processes affect the composition and features of butterfly assemblages at high altitudes. Altitudinal species gradients are shaped by longterm speciation processes, dispersal and extinction events (Mittelbach, 2010) and short-term ecological interactions with other organisms and the environment.
Many hypotheses provide a framework for understanding patterns of species richness and abundance along altitudinal gradients. The species energy theory predicts that as the altitude rises, species richness will decline due to increased energy availability and reduced population sizes at the mountain tops (Chown et al., 2012). Another hypothesis explains the decrease of biodiversity along altitude gradients with the species-area relationship (Lomolino, 2000). However, biodiversity does not always follow a linear pattern with increasing altitude and can peak at intermediate altitudes, possibly as a result of reduced biodiversity at low elevations due to human impact, highest productivity at midelevations, and the mid-domain effect, which explains a species richness peak at mid-elevation by stochastic effects of randomly distributed species that overlap more towards the centre of a geographical domain (Colwell et al., 2004). The presence or absence of any species is determined by the traits of the species. Species that live in similar environments and climates have similar traits. Cooladapted species are moving northward and upward to avoid rising temperatures (Parmesan, 2006). Mountain-dwelling species moved their optimal elevation higher than non-mountain species (Lenoir et al., 2008). As a result, examining species traits that are sensitive to climatic and environmental variables, such as those found along altitudinal gradients, could help researchers better understand how species react to climate change (Diamond et al., 2011).
Although Gulmarg is very rich in biodiversity, only a few studies have been carried out to explore the butterfly fauna. Moore, (1874) reported 103 species of butterflies from the Gulmarg region of Jammu & Kashmir. Afterwards, Lang, (1868) explored the butterfly fauna of Gulmarg. Recently, Qureshi et al., (2013) investigated the butterfly fauna of Gulmarg and reported 31 species belonging to 8 families. Sharma & Sharma, (2021) conducted a study in Shiwaliks of the Jammu region and reported 118 species of butterflies represented by 81 genera and 6 families. Moreover, Sheikh et al., (2021) prepared a consolidated checklist of Rhaploceran fauna of Jammu & Kashmir, in which 308 species were reported. In this research paper diversity, abundance, distributional pattern and trait composition of butterflies in Gulmarg region of Jammu & Kashmir, were quantified over a 3-year period along an altitudinal gradient ranging from 2700 m a.s.l to 3200 m a.s.l. Results show that, richness and abundance is stronger at lower elevations and keeps on decreasing as elevation increases. Traits of butterflies were also studied, it showed that most of the traits of butterflies at low elevation kept on changing as elevation increases for e.g., large wing sized butterflies were dominant at higher elevation and small wing sized butterfly species were dominant at lower elevation. Overall, diversity and abundance is not only affected by increasing elevation, but environmental factors in synergism with vegetation change the community structure of butterflies.

Study area and survey sites
Gulmarg is a famous hill station in the Baramulla district of Jammu & Kashmir, located at 2650 m a.s.l in the Pir Panjal Range of the western Himalayas. In Gulmarg, Six Survey sites, SI-S VI, were selected for accessing butterfly diversity (As shown in Fig. 1). These sites were selected according to the elevation. S I was located by 2700 m a.s.l, while as Site VI was located at 3200 m a.s.l. Glacial deposits, lacustrine deposits, and moraines cover shales, sandstones, schists, and other types of rocks found in it. During the spring and summer, the natural meadows of gulmarg are covered in snow during the winter. Enclosed parks and small lakes are interspersed throughout the fields, which are flanked by verdant pine and forests.

Data collection
The field trips of the study area were undertaken from March 2018 to November 2020 to explore the butterfly diversity. In study area, six survey sites, (SI-S VI) were accessed for butterfly diversity and abundance. In each survey site, GPS coordinates and above sea level length was measured by GPS Garmin Etrex. The butterflies were collected by sweeping net, followed by the photography of them. None of the butterfly species were killed during the collection.

Diversity indices
Shannon diversity index The Shannon index is a metric for determining the diversity and abundance of species. It's calculated using the following formula: Where: H = Shannon index for species diversity, S = Number of species, P i = Proportion of total sample belonging to the i th species, and ln = Natural log Simpson's diversity Index Where: SI = Simpson's Index of species diversity, S = No. of species, and pi = proportion of total sample belonging to the i th species Brillouin index The Index is more sensitive to species abundance It's calculated as N is the total number of individuals in the sample n is the number of individual of species i ln(x) refers to natural logarithm of x Fisher's alpha index It's a tool for determining the diversity of a population. It's calculated by the following formula Where S is equal to number of taxa N is number of individuals And a is fisher's alpha

Results
Altogether we recorded 2023 individuals of butterflies, belonging to 40 species under 27 genera and 5 families. The different species of butterflies are presented in Table 1. Out of 2023 individuals of butterflies, 1121 individuals belong to the family Nymphalidae, followed by 513 individuals belonging to Pieridae, 314 individuals belong to Lycaenidae, 58 individuals belong to Papilionidae, and 17 individuals belong to Hesperiidae (As shown in Fig. 2). The Nymphalidae family had the most species, with 23, followed by Lycaenidae with 8, Pieridae with 7, Papilionidae and Hesperiidae with 1 each (As shown in Fig. 3). The Nymphalidae family had the most genera 16, followed by Lycaenidae with 5 genera, Pieridae with 04 genera, Papilionidae and Hesperiidae with 01 genera each.

Diversity indices along altitudinal gradient
When diversity indices are applied, interpreting species distribution becomes easier. According to Barrantes and Sandoval, (2009), using multiple indices helps eliminate drawbacks of the individual index. Shannon's Index describes species diversity. Maximum species diversity was observed for Site I (2.92), and minimum diversity for Site VI (1.261). When Shannon's index is calculated, a weighted geometric mean of the proportional abundances is employed. Thus, it reflects the logarithm of actual diversity observed and is used frequently. Simpson's index uses the weighted arithmetic mean or proportional abundances and describes species richness and evenness. Thus, a high Simpson's index suggests higher species richness and evenness. The maximum value for Simpson's index was calculated for Site I (0.9413) and the minimum for Site VI (0.6784). This suggests that the species richness at Site I is definitely high and there is an evenness to the species distribution too.
The following index calculated was Brillouin's index. According to Magurran, (1988), this diversity index serves better when there is no surety for the randomness of the sample. Thus, to eliminate any biases raised unknowingly, we employed this index. The maximum value for this index was calculated again for Site I (2.859) and the minimum for Site VI (1.195). Lastly, Fisher's alpha was the fourth alpha diversity index employed. In cases where sample sizes vary a lot, Fisher's alpha has a good discriminating capability. As the sample size for all the sampling stations varied, this index was used. Maximum value for this index was calculated for Site I (3.881) and the minimum for Site VI (0.8299). Thus, all the four alpha diversity indices confirm that maximum alpha diversity was observed at Site I and minimum at Site VI (As shown in Table 2). A Similar type of research was carried out by Dar and Jamal, 2021-b;Naz et al., 2021;Liu et al., 2019;Bokhorst et al., 2018;Qing et al., 2015;Illig et al., 2010;Cutzpool et al., 2010). They also concluded that, diversity indices show a decrease in diversity and abundance decreases along an altitudinal gradient.

Change in abundance of butterfly community along altitudinal gradient
In terms of abundance, Site I, Site II, Site III, Site IV, Site V and Site VI were represented by 865, 403, 366, 148, 139 and 102 individuals (As shown in Table 3). In site I, Hyponephele kashmirica was the most dominant (75) and Kirinia eversmanni cashmirensis was the least abundant (14). In Site II, Pontia daplidice moorei was the most dominant (33), while as Melanitis phedima galkissa and Kaniska canace were least dominant (11 each). In Site III, Vanessa indica was the most abundant represented by 81 individuals, while as Nymphalis vaualbum was the least dominant represented by 06 individuals. In Site IV, Aulocera padma was the most dominat represented by 34 individuals while as Celastrina argiolus kollari was the least dominant represented by 06 individuals. In Site V, Argynius children was the most dominant represented by 37 individuals,   In line with the results that we observed, that total butterfly abundance shows significant decline with an increase in altitude, which, as per the results of some earlier studies carried out by (Afzal et al., 2021;Sharma and Sharma, 2021;Antão et al., 2020;Leingärtner et al., 2014;Diamond et al., 2011).

Change in species richness of butterfly community along elevation gradient
Among the survey sites, Site I with an elevation of 2700 m a.s.l was most dominant with 16 genera and 21 species, followed by Site II with an elevation of 2800 m a.s.l represented by11 genera and 16 species, Site III with an elevation of 2900 m a.s.l represented by 09 genera and 12 species, Site IV with an elevation of 3000 m a. s.l represented by 08 genera and 08 species, Site V with elevation of 3100 m a.s.l represented by 06 genera and 06 species, while as Site VI was least dominant with an elevation of 3200 m a.s.l represented by 04 genera and 04 species (As shown in Table 3 and Fig. 4). In Site I, 11 species belong to family Nymphalidae, 7 species to Pieridae, 2 species to Lycaenidae and 1 species to Hesperiidae. In Site II, 6 species belong to Nymphalidae, 5 species to Pieridae and 5 species to Lycaenidae. In Site III, 6 species belong to Nymphalidae, 2 species to Pieridae and 2 species to Lycaenidae. In Site IV, 5 species belong to Nymphalidae, 2 species to Lycaenidae and 1 species to Papilionidae. In Site V, 5 species belong to Nymphalidae and 1 species to Papilionidae. Lastly, in Site VI, 3 species belong to Nymphalidae and 1 species to Lycaenidae.
Our results are in agreement with the research carried out by (Sharma and Sharma, 2021;Singh and Sondhi, 2016;Sondhi and Kunte, 2016;Chown et al., 2012;Joshi et al., 2008;Joshi and Arya, 2007;Ockinger et al., 2006). They also concluded that that total butterfly species richness significant decline with an increase in altitude.

Impact of environmental gradients on species richness and abundance along an elevation gradient
Biodiversity gradients are the outcome of several temporal and spatial dimensions of evolutionary and ecological processes (Ricklefs and Jenkins, 2011). Abiotic variables, such as climate and topographic gradients, are connected with the majority of these biological processes (Stein et al., 2014). The climate and topography gradients are inextricably linked. Climate change can have an indirect impact on species diversity due to its impacts on vegetation (Stein et al., 2014). While topography has an impact on both climate and vegetation, it also has an impact on species diversity. (Stein et al., 2014;Ruggiero and Hawkins, 2008). We employed four variables to account for climatic factors: (i) average temperature, (ii) average rainfall, (iii) average relative humidity, and (iv) average rainy days are represented from 2018 to 20. All climatic variables were downloaded from Indian Meteorological Department, Govt. of India (''IMD | Home," n.d.).
The average temperature was observed maximum in the month of August and minimum in November. As the monsoon ends in the month of August, this suggests that maximum species richness and abundance are related to the temperature. Another variable is rainfall; the maximum rainfall is observed in the month of monsoon, which falls in the month of July and August. This maximum rainfall is indirectly associated with the growth of floral diversity, on which butterflies and other taxa feed, survive and propagate. The final variable is average relative humidity. It's a well-known fact that the more the relative humidity, the more will be richness and abundance. The maximum value of average relative humidity is seen in July and August, while as minimum average relative humidity is seen in November. Our findings were also in agreement with (Lee et al., 2014;Montero-Munoz et al., 2013;Valtonen et al., 2013;Camero et al., 2007;Clark et al., 2007). They concluded that environmental gradients directly or indirectly influence the butterfly richness and abundance.

Trait composition along an elevational gradient
In this step, we analyzed whether the trait composition of butterflies such as wing-length, abdomen size, body coloration and dispersal of butterfly assemblages change with increasing altitude or not? We observed large winged butterflies were found at higher altitudes than lower altitudes. Along the increasing altitudinal gradient from Site I to Site VI, the percentage of small wing size butterflies shows an increase but started declining after site III. In contrary to medium wing size butterflies, showed a considerable decrease in wing size on altitudinal increase. The percentage of large wing size butterflies increase with increasing elevation. Therefore, we can conclude that wing size decreases as elevation increases. Similarly, abdomen size increases on moving from low elevation to high elevation. At high altitude, most of the catches found were having large abdomen sizes. Lastly, on observing the coloration of the butterflies, we found that altitudinal gradients have no effect on coloration. At lower altitudes, some butterflies were brightly coloured and had a wide variety of coloration, and at high altitude, some were brightly colored and rest were dull coloured. Our findings are in agreement with (Wagner et al., 2011;Gaston et al., 2008); Karl et al., 2008;Berner et al., 2004).

Discussion
Biodiversity is changing dramatically and quickly all over the world. The significance of this transition, however, is unclear, as community-level alterations may obscure differences in individual population trajectories. For decades, ecologists and biogeographers have been fascinated by the richness, abundance, and distribution of species along elevational gradients (Rohde, 1999). In a range of habitats and taxa, multiple studies have observed species distribution along elevational and latitudinal gradients, and many mechanisms have been proposed to explain spatial variation in species richness (Szewczyk and McCain, 2016). The factors that underpin species distribution over elevational gradients, on the other hand, remain poorly understood. It is widely accepted that species diversity decreases as elevation rises, such declines are rarely clear. Several quantitative studies of diverse taxa have discovered evidence for four main species diversity patterns along elevational gradients: monotonic decrease, low plateau, low plateau with a midelevational peak, and unimodal mid-elevational peak, with the last being the most common (Grytnes and McCain, 2007  Environmental variables such as climate and vegetation properties have been used to explain animal species richness and abundance distribution patterns (Mittelbach, 2010). Environmental gradients (EG) such as temperature, humidity, rainfall and vegetation cover are the potential drivers of broad-scale patterns of species richness and abundance. From 2700 to 3200 m a.s.l, we looked into the influence of environmental gradients and vegetation on butterfly distribution. We assessed the strength of the association among butterflies, vegetation, and climate. Among the environmental conditions that shift strongly with elevation is temperature, which gradually decreased with elevation and proved detrimental for the butterfly community. Butterflies survival and reproduction are highly dependent on temperature variations. Any deviation from the optimal temperature causes substantial inhibition and propagation. As evident, temperature decreases as altitude increases, which decreases the species richness and abundance. Similar results are also shown by rainfall. As the elevation increases, humidity decreases, which hinders the growth of vegetation, on which butterflies rely for survival and propagation. Therefore, species richness and abundance decrease.
Furthermore, altitudinal climatic circumstances substantially constrain the availability and turnover of basal resources, vegetation cover is discovered to have a considerable impact on the butterfly community and can be seen as nature's own field trials. While studying the environmental gradients, a linear decrease of species richness and abundance was observed along the altitudinal gradient. This linear decrease may be due to the non-favorable environmental conditions, which doesn't support the propagation of butterfly species. Results depict that, Site I was having the highest species richness (21 species), followed by Site II (16 species), Site III (12 species), Site IV (8 species), Site V (6 species) and Site VI (4 species). This linear decrease of butterfly species is due to the direct influence of environmental gradients, which doesn't support species richness at higher altitudes. As already described, Shannon's diversity index reflects diversity. Among the sites, Site I was showing maximum species diversity and Site VI was least diversity. Similarly, Simpson's Index, Brillouin's index and Fisher's alpha showed maximum values in Site I and the least value in Site VI.
Studies involving the conservation of butterfly diversity are vital as Lepidoptera are an integral part of the food chain connecting autotrophs and heterotrophs. They are also well-known ecological indicators, sensitive to climatic and ecological changes and respond quickly to the stratification of the vegetation in terms of temperature, wind, light and humidity . Moreover, studying the diversity of butterflies provide us with insight information about changes in abundance, evenness and richness affected by vegetation and species interactions and land-scapes. The information about the species diversity, richness and abundance help in constructing conservation measures and management practices.

Conclusion
Our findings showed that in the Gulmarg region of Jammu & Kashmir, butterflies species richness and abundance are decreasing linearly as the elevation increases. This linear decrease is the resultant of decrease in vegetation assemblages along with other environmental factors which act along the altitudinal gradient. Thus we can conclude that, butterfly species are abundant at the lower elevation and keeps on decreasing as the elevation decreases. Alpha diversity indices are also in agreement with our results. Moreover, this linear decrease is not only due to the elevation, but environmental factors such as temperature, rainfall, humidity are also acting along with vegetation.

Declaration of Competing Interest
The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.