Butterflies of the myristica swamp forests of Shendurney Wildlife Sanctuary in the southern Western Ghats , Kerala , India

Myristica swamps are unique freshwater swamp forests characterised by predominance of tree species of the Myristicaceae family. There have been few published works on the flora and fauna of myristica swamps but studies on butterflies have been scanty. This work was done in the myristica swamps of Kattilapara in Shendurney Wildlife Sanctuary, Kollam district, Kerala, located in the northern aspect of the Agasthyamalai Hills of the southern Western Ghats. Data on the butterflies were collected over a period of two years supplemented with data from previous visits using Transect method. Butterflies were identified based on field photographs and relevant literature. We recorded 206 species of butterflies belonging to 6 families from the myristica swamps. This included 17 species of Papilionidae, 20 species of Pieridae, 65 species of Nymphalidae, 56 species of Lycaenidae, two species of Riodinidae and 46 species of Hesperiidae.Of the total, 19 species of butterflies were Western Ghat endemics. A checklist of butterflies of the myristica swamp, larval hostplants, status with respect to IUCN criteria, endemicity, and classification as per Indian Wildlife Protection Act (WPA) of 1972 are also provided. Eighty-two species of plants were listed as butterfly larval hosts in the myristica swamp ecosystem, with 27 species being new host records for Western Ghats. None of the butterflies recorded were using plants of Myristicaceae family as larval hosts. A simple index—the percentage occurrence—is proposed to delineate the habitat affinity of species.


INTRODUCTION
Myristica swamps are tropical swamp forests first reported from Kulathupuzha Reserve Forests and adjoining regions of Anchal, Thenmalai and Shendurney Wildlife Sanctuary (WS) in Kollam and Thiruvananthapuram districts of Kerala (Krishnamoorthy 1960).Besides Kerala, they are also known to occur in Karnataka and Goa (Joyce et al. 2014).Myristica swamp forests are floristically lowland (180-200 m) edaphic variants of evergreen forests with canopy at 30-40 m, with pure patches of Myristicaceae trees in a freshwater swamp amidst tropical evergreen patches (Subramanian 1995).These are highly fragmented ecosystems with restricted distribution (Rodgers & Panwar 1988a,b).The dominance of the trees of Myristicaceae family in the swamps gives them their common name (Roby et al. 2014).The myristica swamps are classified as forest type 4c/FS1, under Champion & Seth (1968).
There have been a few studies on the flora and fauna of myristica swamps.Notable works on their basic ecological aspects are by Nair et al. (2007) from Kerala and Ramabhat & Kaveriappa (2009) from Uttara Kannada.Floristic works on this unique ecosystem can be seen in Varghese & Menon (1999), Roby et al. (2007Roby et al. ( , 2014)), Subash et al. (2008), Sreejith et al. (2016) and Joyce et al. (2014).Floristic studies by Roby et al. (2014) had listed 79 species of trees, 93 species of herbs and shrubs, and 49 species of climbers in this ecosystem of which 49 are endemic and 18 are IUCN Red List species.There are only a few studies available on faunal diversity of myristica swamps.The insect diversity in these swamps were studied by Sinu & Sharma (2013); spiders by Joyce et al. (2007a); reptiles by Joyce (2007b,c).The general insect diversity of Shendurney WS was covered by Mathew et al. (2004) and the butterflies list can be seen in Anonymous (2012).
Butterfly fauna of myristica swamps were largely unknown and only a very few studies are available in this regard.Ali et al. (2008) worked on the myristica swamps of Uttara Kannada and recorded 57 species of butterflies in three families Papilionidae, Pieridae, and Nymphalidae.Joyce et al. (2015) identified 72 species in five families and 57 genera during the work in Anchal, Kulathupuzha, and Shendurney over three years.Thus, studies on lepidopteran fauna of myristica swamps have been very scanty.The present study documents of butterflies of myristica swamps of Shendurney WS (8.858 0 N & 77.210 0 E) in the northern aspect of the Agasthyamalai Hills of the southern Western Ghats in Kerala.

Study Area
The myristica swamps at Mankuthu and Onnam-Mile in Kattilapara region of Shendurney WS were studied (Fig. 1).The Mankuthu myristica swamp lies about 1.5km behind the Kattilapara base camp and is at the edge of the sanctuary, while the Onnam-Mile myristica swamp lies about 2.5km inside the sanctuary on the right of the road leading to Kallar.Anthropogenic factors do not seem to play any significant influence on the swamp ecosystem as both are inside the protected area of the sanctuary.
Two myristica swamps were studied in the Kattilapara region of the Shendurney WS (Image 1).Data on butterflies for POc scores (see below) were collected over a period of two years for every two weeks from May 2016-May 2018 using transect method.Permanent line transects covering 500m over 30 minutes were taken in the morning (8-9 am) and evening (3-4 pm) to study the butterfly diversity of the myristica swamp and the adjoining evergreen forest patch.The transects were such that it covered 500m of swamp and 500m of the adjoining evergreen forests.This intensive two-year work was supplemented with additional data from previous visits to this area using the same 500m/30 min transect method, taken once a month, spanning over the last 10 years (2008)(2009)(2010)(2011)(2012)(2013)(2014)(2015)(2016)(2017)(2018), for butterfly diversity and hostplant records.For delineating species that are myristica swamp dependent, we compared the butterfly occurrences in the myristica transect with another 500m control transect laid in the adjacent evergreen forest.Butterflies that were recorded in more than 50% of transects in myristica swamps in comparison to the adjacent control transect was taken as myristica swamp species (MSS).This included species with 50-75 % occurrence in the swamp, treated as myristica swamp associates (MSA), and those with occurrence of more than or equal to 75% of transects classified as myristica swamp dependents (MSD).MSS = MSA+MSD Those species which were seen <50% were classified as stragglers and were present more outside the swamp than in it.This treatment was supplemented with host plant and early stage data for these butterflies from our observations.Species with their known hostplant distribution restricted to myristica swamps were also considered as myristica swamp dependents (MSD).
To ascertain the habitat affinity and distribution among habitats, we propose here a very simple indexthe percentage of occurrence (POc).The total number of individuals of a species is taken and the proportion of them seen in the particular habitat is calculated.For example, in the case of the swamp, we calculated the POc score as per the following equation: Here n was the absolute number of individuals of a particular species seen in a transect (myristica swamp or evergreen forest) added over the study period.
Butterflies were identified based on field photographs and relevant literature.Oviposition alone was not taken as primary criteria of hostplant confirmation because of the well-known oviposition mistakes.Oviposition on an already known plant species being utilized elsewhere, or presence of more than one instar of the larval stages of a butterfly on the plant on which an egg is laid or successful field observation of the larvae surviving to adulthood on the particular plant was taken into consideration to establish a plant as the larval hostplant.Larval identification follows Bell (1909Bell ( -1927) ) and Kunte et al. (2018).Identification of adult butterflies are based on Evans (1932) and taxonomy follows Kunte et al. (2018).Larval host plants used by butterflies in the myristica swamps were photographed.Floras referred for identification of the larval hostplants are Ramarao (1914), Gamble (1967), Subramanian (1995), Blatter & Millard (1997), Sivarajan & Mathew (1997) , Seethalakshmi & Kumar (1998), Renuka (2000), Ravi & Mohanan (2004) and Nayar et al. (2006).Host plant utilization was checked against Sevastopulo (1973), Kunte (2000Kunte ( , 2006)), Robinson et al. (2001), Kalesh & Prakash (2007, 2015), and Nitin et al. (2018).

Vegetation
The vegetation of the swamps are evergreen species with a majority of the trees being from Myristicaceae.The swamps had a predominance of myristica trees Gymnacranthera farquhariana J.Hk. & Thoms., and Myristica fatua var.magnifica (Bedd.)Sinclair from Myristicaceae family.Other trees observed were Syzygium travancoricum Gamble, Vateria indica L., Hopea parviflora Bedd., Lophopetalum wightianum

Butterfly fauna
In the Myrstica swamp forests, 206 species of butterflies were recorded over a study period of two years (Appendix I).Of these, seven species were MSD with POc value more than or equal to 75, 151 species were MSS with POc >50 and the rest 48 were stragglers (POc <50).

Myristica swamp Dependents (MSD)
Idea malabarica (Moore, 1877) is a typical MSD species with a POc value of 87.5 (Table 1).The regionally preferred host plant is Parsonisia spiralis Wall.ex G.Don (Apocynaceae), and this plant is mostly restricted to the myristica swamps of the region, which explains its high POc value 87.5.For Papilio dravidarum Wood-Mason, 1880, Clausena heptaphylla (Roxb.)Wight & Arn. and Glycosmis pentaphylla (Retz.)DC. (Rutaceae) are the known larval hostplants seen in the swamp.The species was found to have a POc value of 81.81.For Neopithecops zalmora dharma (Moore, [1881]), Glycosmis mauritiana (Lam.)Tanaka, and Glycosmis pentaphylla (Retz.)DC. (Rutaceae) are the known larval hosts seen in the undergrowth of the swamp edges.This small lycaenid had a POc of 80.95.Arhopala alea (Hewitson, 1862) had three known host species Terminalia paniculata Roth, Hopea sp.(Dipterocarpaceae) and Syzygium salicifolium (Wight) J.Graham (Myrtaceae).This is a rare butterfly in the region with POc value of 76.92.Males were seen mudpuddling on the sandy edges of swamps in drier winter months.Pachliopta pandiyana (Moore, 1881) is a monophagus species endemic to Western Ghats that feeds on Thottea siliquosa (Lam.)Ding Hou (Aristolochiaceae).This host plant was an ecotone species seen at the edges of the swamps.The

Myristica swamp associates (MSA)
There were 151 species that were MSA.They had a POc value between 50 and 75.This implies that they spend much of their time in and around the myristica swamps than outside it.These included 37 Hesperiid species, 40 Lycaenids, 45 Nymphalids, 13 Papilionids, 14 Pierids and two Riodinids (Appendix I).Eighteen taxa listed in the MSA category were found to be endemic species of which 11 species were strictly Western Ghat endemics (Table 2).Two species were Red-Listed by IUCN and 29 species were listed in the various Schedules of the Indian Wildlife (Protection) Act, 1972(WPA 1972) (Appendix I).

Stragglers
Forty-eight species were found to be stragglers; of them, three were endemics, three were in IUCN Red List and six species were listed in the WPA 1972.Three species were endemics in the straggler category: Prioneris sita (Felder & Felder, 1865) is endemic to southern India and Sri Lanka, Eurema nilgiriensis (Yata, 1990) is endemic to the Western Ghats, and Rapala lankana (Moore, 1879)

Host plant utilization
The complete list of plants of myristica swamps of the study area was obtained from Nair et al. (2007).Eighty-one plant species recorded during the study were butterfly larval hosts in the myristica swamp.Of these, 54 species of plants that we observed as larval hosts were already known larval host plants being used elsewhere for butterflies in the Western Ghats (Table 3).We also found 27 species of new hostplant records being used by 43 species of butterflies (Table 4).

CONCLUSIONS
In our study, we found 206 species of butterflies from Papilionidae, Pieridae, Lycaenidae, Riodinidae, Nymphalidae, and Hesperiidae from myristica swamps of Shendurney.Of these only seven species were MSD, which are restricted to the swamps of the region, and 23 species of butterflies were endemic to peninsular India of the Western Ghats complex.With respect to WPA 1972, 32 species seen in the swamps are protected and seven species are in the Red List of IUCN.It was noted that most of the butterflies were shared species with the nearby evergreen patches and only seven species were specifically partial to it.We confirmed the presence of the rare Eurema nilgiriensis (Yata, 1990) Nilgiri Grass Yellow butterfly from Shendurney, extended its range into Agasthyamalais and have recorded Ventilago bombaiensis Dals., as its site-specific larval hostplant.Eighty-one species of plants were recorded as butterfly larval hosts in the myristica swamp ecosystem, with 27 species being new host plant records for Western Ghats.Interestingly, none of the butterflies recorded were using plants of myristicaceae family as larval hosts as far as it is known.The POc is a simple index that can be easily applied to assess habitat association of any taxa.