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Land snail from limestone karst in Java: an update with notes on their distribution

Limestone karst in Java is rich of land snail fauna. Unfortunately, the ecosystem is now threatened by mining or tourism activities. However, the impact of that activities on land snail diversity is not well studied. The objective of this study was to inventory the diversity of land snail in limestone karst with focus on their ecological and distribution in Java. Purposive sampling methods using plots (10 x 10 m) were used in 12 different stations in Western Java, Central Java, and Yogyakarta during 2017-2018. Thirty-five species from eleven families of land snail were identified. The highest species richness and population of land snails were found in Watu Blencong (16 species and 158 individuals). Landouria rotatoria distributed in eight locations, while Japonia ciliocinctum (85 individuals) distributed in six locations. Results showed that extended distribution records of ten land snail species were reported. Currently, 63 species of land snails species have been identified in karst ecosystem in Java.


Introduction
Karst is unique landscape formed by slow erosion of limestone, which consist of calcium carbonate (CaCo 3 ) [1]. Most karsts were formed millions of years ago by calcium-secreting marine organisms (e.g., corals and brachiopods) before tectonic movements lifted them above sea level [1]. The biodiversity in karst ecosistem is also unique, consisting of species that survive in highly alkaline environment, permanent dry conditions, and low oxygen, i.e. endemic species of land snail [2].
Land snails (Gastropoda) are the second most successful and diverse animal groups on land with an estimated 24.000 living species [3]. Most of land snails have a shell with various shape and color to protect from predator or unsuitable climate [4]. Limestone, a rich mineral soil, is abundant in karst area [1]. Some studies showed that land snail is dominant group (diversity and population) in karst ecosystem [5]. Compared to other natural ecosystem, land snail diversity and population in karst ecosystem was higher [4,5].
In Java, karst ecosystem spread from west (Banten) to east (Banyuwangi), including its satellite island (Madura) [6]. Two important karst areas in Java are Gombong Selatan and Gunung Sewu. Karst is a source of ground water and also as tourism destination [6]. Human activities, such as mining, logging, road construction, and tourism are threatened of karts ecosystem [1,2,6].
Previous studies of fauna diversity in karst ecosystem in Java have been reported [7,8,9,10]. In Menoreh karst area was reported 30 species of arthropods, 6 species of chiropteras [7], 9 species of

Sampling techniques
Land snails found in each plot were observed carefully for two hours. Both life and dead (shells) land snails were collected. Life specimens then were relaxed by drowning in water overnight and then preserved in 70% ethanol. The shells was washed in running water, cleaned using a brush, and dried under the sun during the day. The locality of each stations were recorded. All specimens were brought to Museum Zoology Bogor and were identified based on references [25,26,27]. The species found was classified into Prosobranchia (mantle cavity widely open and possess an operculum to seal the aperture) and Pulmonata (mantle cavity with closable narrow pneumostome and no operculum). The land snail specimens then was classified based on their habitat and note of distributions.

Analysis
Characteristic species (species only was found in a one or group stations) was chosen to explain the uniqueness of each or a group stations [28]. Unique species, such as singleton (species represented by only one specimen) and doubleton (species represented by two specimens) were identified [29]. The relative abundance was determined based on the ratio of individuals found to the total number of individuals recorded. Frequency of distribution of species was calculated by the number of stations where the species found divided by the total number of sampled stations. Four groups species were classified based on their frequency: very accidental species (vac, frequency less than 10%), accidental species (acc, frequency varied 10-24%), common species (cmt, frequency varied 25-49%), and constant species (cst, frequency more than 50%) [30]. Biological rarity was determined by the number of specimens per species, while ecological rarity was determined by the number of station that species found [31,32]. Land snails diversity was analysed by Shannon's diversity index [H'=-Σ(ni/n) ln (ni/n)]. Degree of equality of species in a certain environment was analysed by Pielou's evenness index (J=H'/ln S). Probability of two randomly sampled individuals belong to the same species was analysed using Simpson's dominance index [D = Σi(ni/n) 2 ]. Note: S (number of species), ni (number of individual of species i), n (number of individual) [33]. Jaccard similarity was used to analyse similarity of species in between stations [29]. The cophenetic correlation coefficient (r) was used to measure the pairwise distances between the original data [34]. The categories are: very good fit (r >0.9), good fit (0.8 < r < 0.9), poor fit (0.7 < r < 0.8), and very poor fit (r < 0.7) [35]. All statistical analysis were performed using PAST 2.17c [36].

Biodiversity indices
The total number of land snails individual ranged 6-158 individuals, while number of species ranged 3-16 species. In average, the number of individual ranged 2-11.75 individuals. Shannon's diversity index ranged 1.01-2.25. ST9 was classified as medium, while 11 stations were classified as low diversity. Simpson's dominance index ranged 0.18-0.39 and all stations were classified as low. Pielou's evenness index ranged 0.49-0.94 and 3 stations (ST3, ST4, and ST9) were classified as medium, while 9 stations were classified as high.

Discussion
Pulmonata is a group of land snail which breath using primitive lung, while Prosobranchia breath using advanced gills [13]. The ratio species of Pulmonata and Prosobranchia is 22:13. In average, results showed that the number of individual of Pulmonata (18.4 individuals) was higher than Prosobranchia (17.8 individuals). Previous study in Grobogan karst area were found the ratio of species Pulmonata and Prosobranchia was 10:23 and the ratio of individual was 1:11 [22]. The species distribution between Pulmonata and Prosobranchia was almost similar (2.68:2.38). This result is similar to previous studies in Sabah, Malaysian-Borneo which found that Pulmonata species tend more dominant and more evenly distributed than Prosobranchia [4,5]. Based on the individual rarefaction (figure 1), increasing the individual number is not always followed by increasing the species number, such as in ST6 (55 individials, 5 species), ST1 (81 individuals, 10 species), ST3 (94 individuals, 8 species). The highest was found in ST9 (158 individuals, 16 species). The number of individual in ST9 is almost twice in ST1. Meanwhile, new finding species (figure 2) also showed the same trends. The main peak were found in ST4 and ST5 (5 species), i.e., P. pupillaris, B. similaris, A. gracile, P. acutissimum, and S. octona. Both stations located in Bogor regency with distance between locations is about 28 km. The local condition may difference (ST4 is near the settlement and ST5 is near the limestone mining area). The second peak new species finding were observed in ST1-ST2, ST2-ST3, and ST8-ST9. It is interesting that after doing 9 sampling, we still found new finding (Chloritis fruhstorferi, Chloritis transversalis). It showed that the composition of land snail species in each station highly varied.
We summarized the results of this study together with previous studies of land snails in karst area in Java (table 1). Based on table 1, Pulmonata is dominant in all studies. Thirteen species (8 Pulmonata, 5 Prosobranchia) were similar with previous syudy in Sukolilo [22]. Four pulmonate species were similar with previous study in Gunung Sewu [20], while 9 Pulmonata genera and 4 Prosobranchia genera were similar with the later study in Gunung Sewu [21]. The later in Selo, Gunung Merbabu National Park, Boyolali regency, Central Java province is not karst area [23], but the location was close to this study. Previous study in Maros, Central Sulawesi [37] were identified 7 families, 17 genera, and 28 species and Pulmonata was dominated (5 families and 12 genera)