An Updated Survey and Biodiversity Assessment of the

Philippine Journal of Science143 (2): 199-210, December 2014ISSN 0031 - 7683Date Received: ?? ???? 2014

Keywords: Marinduque, opportunistic sampling, biodiversity indices, stylommatophoran, terrestrial prosobranch

An Updated Survey and Biodiversity Assessment of the Terrestrial Snail (Mollusca: Gastropoda)

Species in Marinduque, Philippines

Benjamin O. Sosa III1, Gizelle A. Batomalaque1 and Ian Kendrich C. Fontanilla1,2

1Institute of Biology, University of the Philippines Diliman,Diliman, Quezon City 1101, Philippines

2Natural Sciences Research Institute, University of the Philippines, Diliman, Quezon City 1101, Philippines

Marinduque is an island province of volcanic origin and is found in the southern portion of the Luzon Group of Islands. The island has an uneven topography but has experienced drastic deforestation in recent times. Records on the terrestrial snail species diversity in the Philippines in general and Marinduque in particular are sparse in the zoological literature. Previous literature noted only 13 species in Marinduque, which could be a gross underestimation of the terrestrial malacofaunal diversity of the island because the area was not systematically surveyed. This study aimed to assess the malacofaunal biodiversity of Marinduque and prepare a comprehensive list of snail taxa via opportunistic sampling. Sampling was conducted in 12 pre-determined areas of the island, with emphasis on minimally disturbed areas. This study reported ten (10) new records of stylommatophoran species and six (6) new records of terrestrial prosobranch species in Marinduque, which brings a total of 24 terrestrial snail species known to date (or 26 if two previously recorded species that were not encountered in this study are included).

INTRODUCTIONThe Philippine islands serve as haven for a large number of invertebrate species, including pulmonate stylommatophoran snails, with 88 described species, and terrestrial prosobranch snails, with 14 described species (Springsteen & Leobrera 1986). It is highly likely that these numbers could be gross underestimates of the actual malacofaunal diversity in the Philippines as many more could be undescribed or cryptic species may abound.

Terrestrial snails are divided into two large groups, the informal group Pulmonata and the superorder Caenogastropoda that

includes most species of prosobranchs (Pechenik 2005). The informal group Pulmonata is distinguished by having a lining that can be enclosed by a breathing pore called a pneumostome (Tucker Abbott, 1989) and includes three main suborders that inhabit different habitats: Basommatophora, Stylommatophora and Systellomatophora (Bouchet & Rocroi 2005). On the other hand, superorder Caenogastropoda, which contains almost half of all known gastropod species, includes terrestrial prosobranchs that are grouped into nine families, including the Cyclophoridae. They have gills that are either reduced or are replaced by oxygen-absorbing mantle tissue (Tucker Abbott, 1989).

Springsteen and Leobrera (1986) observed four stylommatophoran families in the Philippines with *Corresponding author: [email protected]

[email protected]

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endemic representatives: Bradybaenidae, Camaenidae, Helicarionidae and Trochomorphidae. Bradybaenidae is the most speciose stylommatophoran family in the Philippines, with 56 species from three genera, 54 of which are from the genus Helicostyla alone. The Camaenidae is comprised of three genera with 16 species, while Helicarionidae has eight species from only two genera, Ryssota and Hemiglypta. The Trochomorphidae is considered the least speciose, with only three species representing a single genus, Trocomorpha.

Springsteen and Leobrera (1986) also noted 14 terrestrial prosobranch species from the Caenogastropoda, all belonging to the Cyclophoridae, and coming from three genera, Cyclophorus, Cyclotus and Leptopoma (Springsteen & Leobrera 1986).

Marinduque Island (Region IV-MIMAROPA) is typical of many islands in the Philippines in terms of exhibiting what Solem (1984) proposed as characteristics for an ideal environment for terrestrial mollusk biodiversity to flourish; these are: (1) isolated environment; (2) dissected topography; (3) rain shadow effects; and (4) uneven litter distribution; these make the island a suitable environment for different adaptations and speciation.

Marinduque has a total land area of 960 square kilometers divided politically into six municipalities (Boac, Buenavista, Gasan, Mogpog, Torrijos and Sta. Cruz) (Department of Tourism 2009) and with a population of 227,828 (National Statistics Office 2010). Marinduque’s main river system is Boac-Makulapnit that runs through the center of the province. The island experiences rainy seasons from June to October and a warm, humid climate from December until the third week of May. It is also frequently visited by typhoons from June to November (Department of Tourism 2009). The highest peak in the province is Mt. Malindig (1,157 m) situated in the town of Buenavista (Department of

Tourism 2009). The total forest cover of Marinduque is about 15,132 hectares or roughly just 16% of the total land area (Forest Management Bureau 2010).

Webb (1948), Parkinson et al (1987), and Springsteen and Leobrera (1986) noted only 12 stylommatophoran species and one terrestrial prosobranch species (Cyclophoridae) in Marinduque (see Table 1). These figures could be a gross underestimate of the true malacofaunal diversity in the island, which was not systematically surveyed. This study therefore aimed to (1) obtain an updated list of terrestrial snails found in Marinduque using systematic opportunistic sampling; and (2) determine the degree of richness and diversity of terrestrial snail species in the island.

METHODOLOGY

SamplingSamples of terrestrial snail species were obtained from each of the six municipalities of Marinduque. Sampling sites per municipality were concentrated in the mountainous barangays of each municipality where anthropological impact was minimal and far from any human settlements as compared to most lowland areas, which have been partially cleared due to logging and slash and burn method of farming. These areas have very thick to moderately thick forest cover and are near bodies of water such as rivers, streams or puddles. Table 2 lists the sites where sampling of terrestrial snails was done, while Figure 1 depicts these sampling sites.

The sampling was conducted for a period of six months by a two-person team on multiple sites for each municipality. An approximately 500 square meter quadrat was established using a tape measure for each sampling

Table 1. List of terrestrial snail species found in Marinduque according to Springsteen and Leobrera (1986), Webb (1948) and Parkinson et al (1987).

Group Species

Stylommatophora Helicostyla subcarinatamoellendorfi (Moellendorff, 1897)

Helicostyla bicolorata (Lea, 1840)

Helicostyla rufogaster (Lesson, 1831)

Helicostyla marinduquensis (Hidalgo, 1887)Helicostyla pithogaster (Ferrusac, 1821)Helicostyla mirabilis (Ferrusac, 1821)Helicostyla quadrasi (Hidalgo, 1886)Helicostyla concinna (Sowerby, 1841)Ryssota quadrasi (Hidalgo, 1890)Ryssota otaheitana (Ferrusac, 1821)

Ryssota lamarckiana(Lea, 1852)

Ryssota sagittiferacarinata (Moellendorf, 1894)

Caenogastropoda (prosobranch) Cyclophorus woodianus (Lea, 1862)

Philippine Journal of ScienceVol. 143 No. 2, December 2014

Fontanilla et al.: Biodiversity Assessment of Terrestrial Snail in Marinduque, Philippines

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Table 2. The barangay sampling sites in each of the six municipalities.

Municipality Barangay sampling sites Coordinates

BoacBuenavista

Gasan

MogpogTorrijos

Sta. Cruz

BoiSihi

MalbogDawis

BachaoIlayaTiguion

Gaspar Is., PingganArgaoTigwiTaytayNapo

Tawiran

130 22' 00" N; 1210 56' 00" E130 15' 50" N; 1210 59' 41" E130 16' 25" N; 1210 57' 10" E130 17' 9" N; 1210 53' 22" E130 18' 30" N; 1210 51' 23" E130 19' 58" N; 1210 51' 44"

130 14' 57" N; 1210 51' 31" E130 33' 8" N; 1210 51' 57" E130 16' 26" N; 1210 1' 59" E130 25' 6" N; 1220 5' 2" E

130 25' 35" N; 1220 4' 30" E130 26' 48"N; 1220 4' 27" E

Figure 1. Map of Marinduque showing the Barangays of Marinduque sampled (source: http://www.maphill.com/philippines/region-4/marinduque/simple-maps/blank-map/).

site. Each quadrat was sampled for 1-2 hours for terrestrial snails; both live specimens and empty shells were gathered. Leaf litter sampling was done to ensure even micromollusks would be collected. All samples obtained were placed in plastic container boxes for temporary keeping.

Identification of terrestrial snail speciesSpecies identification based on shell morphology was carried out using Springsteen and Leobrera (1986) and Tucker Abbott (1989) as references.



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Statistical analyses The study employed the statistical software PAST (Hammer et al. 2001) in order to determine the following biodiversity indices for the malacofauna of Marinduque: (1) Shannon’s Index (H), a common biodiversity index sensitive to both the abundance and evenness of the species being measured (Magurran 2004); (2) Simpson’s Index (D), which determines the probability of two randomly sampled individuals to belong to the same species (Siddique et al. 2010); (3) Simpson’s Index of Diversity (1-D), which computes the probability of two randomly sampled species to belong to different species (Siddique et al. 2010); (4) Simpson’s Reciprocal Index (1/D), which measures the number of species that may be found in a community (Magurran 2004); (5) Pielou’s evenness index (J), which determines the degree of equality of species in a certain environment (Mulder et al. 2004); and (6) Simpson’s evenness index (Magurran 2004), which also determines how well distributed are the species found on the island in order to support the results that may be obtained from Pielou’s evenness index.

RESULTS AND DISCUSSION

Sampling results Table 3 summarizes the snail species found in each municipality of Marinduque while Figure 2 shows the snail species obtained. Note that of the six municipalities surveyed, only Buenavista, particularly its municipalities of Sihi and Malbog, did not yield any snail.

Table 4 summarizes the 24 terrestrial snail species collected in Marinduque and their taxonomic families. Of these, 16 are from four families of the Stylommatophora; the Bradybaenidae had the most number of species found (eight), followed by the Helicarionidae (four), then by Trochomorphidae (two), and lastly by the Camaenidae (one) and Achatinidae (one). Interestingly, two of three known trochomorphid species in the Philippines have been found in Marinduque. The remaining eight species are from the prosobranch family Cyclophoridae. One taxon, Leptopoma sp., could only be identified up to the genus level, but it is morphologically distinct from the other Leptopoma species. The total number of species observed in this study (24) contrasts with the 13 species Springsteen and Leobrera (1986), Webb (1948) and Parkinson et al. (1987) recorded (Table 1).

One introduced species, Achatina fulica (Achatinidae), was noted in three barangays (Table 4). Achatina fulica, also known as the Giant African Snail, originated from Africa but were introduced by man to various parts of the world especially in the tropics (Raut & Barker 2002).

Achatina fulica was brought to the Philippines from Taiwan by the Japanese Military during the invasion of the Philippines in 1942 (Pangga 1949).

A total of ten new records of stylommatophorans were noted in Marinduque; four were bradybaenids, two each for the helicaroinids and trochomorphids, and one each for the camaenids and achatinids (Table 4). Helicostyla bicolorata and Ryssota sagittifera carinata, which Springsteen and Leobrera (1986) previously reported, were not encountered in this study. On the other hand, of the eight species of terrestrial prosobranchs found, only one, Cyclophorus woodianus (Figure 2p), was previously reported (Springsteen and Leobrera 1986). In total, there are now 24 species of terrestrial snails in Marinduque (or 26 if H. bicolorata and R. sagittifera are included), and 16 of these are new records (excluding Leptopoma sp.). This study therefore provides the first updated list of terrestrial gastropods in Marinduque.

Biodiversity statistical analyses The richness of species diversity, evenness and over-all biodiversity of the terrestrial malacofauna of Marinduque is summarized in Table 5 based on the indices used in this study.

A total of 137 individuals (excluding the introduced Achatina fulica) were obtained from 23 different species, with a Shannon index score (H’) of 2.726148 out of the highest possible score of 4.523562 if the island had a completely even distribution of species. It also obtained a Simpson’s index score (D) of 0.097774, which is nearer to zero, thus indicating a relatively high species diversity. Based on Marinduque’s Simpson’s Index of Diversity (1-D), there is about 90% probability of obtaining two randomly chosen individuals belonging to two different species in the community, suggesting a high species richness. The Simpson’s Reciprocal Index (1/D) was 10.22771, which is lower compared to the maximum value of 23, the total number of species found in the island. Since Simpson’s reciprocal index is sensitive to both species richness and evenness, the low score can be attributed to the natural patchy distribution of the snail samples on the island (Aravind et al. 2005). Marinduque’s Pielou’s Evenness Index (J’) of 0.857804, which is closer to the maximum value of 1, shows low variation in the community (Mulder et al. 2004). This is supported by Simpson’s Evenness index of 0.426155, which is closer to 0 than 1, denoting lesser species distribution in the community (Hill 1973).

All these values would make more sense if there is another island to compare it with, but since this study is the first of its kind in the country, no Philippine data are available for comparison. Outside the Philippines, however,



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Table 3. Terrestrial snail samples found in each site.

Municipality Barangay Species

Boac Boi Helicostylarufogaster (Lesson, 1831)

Buenavista Sihi -

Malbog -

Gasan BachaoIlaya Ryssota lamarckiana (Lea, 1852)Cyclophorus woodianus (Lea, 1862)Cyclophorus daraganicus (Hidalgo, 1888)Trochomorpha schmakerii (Moellendorf, 1894)Helicostyla rufogaster (Lesson, 1831)

Dawis Ryssota lamarckiana (Lea, 1852)Helicostyla sphaerica (Sowerby, 1841)Helicostyla pithogaster (Ferrusac, 1821)Achatina fulica (Ferrusac, 1821)

Gaspar Island, Pinggan

Cyclophorus fernandezi (Hidalgo, 1888)Obbalisteri (Gray, 1825)Helicostyla simplex (Jonas, 1834)Leptopoma sericinum (Kobelt, 1886)Nipponochlamys semisericata (Pilsbry, 19020Achatina fulica (Ferrusac, 1821)

Tiguion Helicostyla fischeri (Hidalgo, 1889)Cyclophorus fulguratus (Pfeiffer, 1852)Hemiglyptosis fouillioyi (Hidalgo, 1888)Leptopoma pileus (Sowerby, 1843)Cyclophorus woodianus (Lea, 1862)Helicostyla marinduquensis (Hidalgo, 1887)Ryssota otaheitana (Ferrusac, 1821)Leptopoma sp.(Pfeiffer, 1847)

Mogpog Argao Helicostyla pithogaster (Ferrusac, 1821)

Sta. Cruz Napo Ryssotala marckiana (Lea, 1852)Helicostyla pithogaster (Ferrusac, 1821)Helicostyla rufogaster (Lesson, 1831)

Taytay Chloraea fibula (Reeve, 1842)

Tawiran Ryssota otaheitana (Ferrusac, 1821)Cyclophorus daraganicus (Hidalgo, 1888)Helicostyla fischeri (Hidalgo, 1889)Helicostyla subcarinatamoellendorfi (Moellendorf, 1897)Cyclophorus fernandezi (Hidalgo, 1888)Trochomorpha metcalfei (Pfeiffer, 1845)Cyclophorus woodianus (Lea, 1862)Chloraea fibula (Reeve, 1842)Leptopoma woodfordi (Sowerby, 1889)Achatina fulica (Ferrusac, 1821)

Torrijos Tigwi Helicostyla rufogaster (Lesson, 1831)Helicostyla pithogaster (Ferrusac, 1821)

Marinduque’s species count of 29 could be compared with Bioko Island, of volcanic origin, off the coast of Equatorial Guinea, which is more than twice the area of Marinduque and with a species count of 68 (Wronski et al. 2014). Closer to home is Hahajima Island (land area=20.8 km2) of the Ogasawara Archipelago in the Northwestern Pacific, with a total of 53 known species of land snails; in the Higashizaki Peninsula alone (land area=0.3 km2), 12 species were found (Chiba et al. 2007).

Based from these biodiversity indices, it can be concluded that Marinduque has a very high species richness and diversity but has low species distribution and evenness across the island, which could possibly be attributed to two factors: habitat loss and varying degrees of disturbance of the area sampled. In fact, around three quarters of Marinduque’s land area has been classified as alienable or disposable, and the Department of Environment and Natural Resources (DENR) ranked the island province as third in terms of the most denuded forest cover amongst



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Figure 2h. Chloraea fibula.Figure 2g. Helicostyla sphaerica.

Figure 2f. Helicostyla simplexFigure 2e. Helicostyla subcarinata moellendorfi.

Figure 2d. Helicostyla fischeri.Figure 2c. Helicostyla marinduquensis.

Figure 2b. Helicostyla pithogaster.Figure 2a. Helicostyla rufogaster.

StylommatophoraBradybaenidae



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Figure 2o. Trochomorpha schmakerii.Figure 2n. Trochomorpha metcalfei.

Trochomorphidae

Figure 2m. Nipponochlamys semisericata.Figure 2l. Hemiglyptosis fuoilloyi.

Figure 2k. Ryssota otaheitana.Figure 2j. Ryssota lamarckiana.

Helicarionidae

Figure 2i.Obba listeri.

Camaenidae



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Figure 2w. Leptopoma sp.Figure 2v. Leptopoma sericinum.

Figure 2u. Leptopoma pileusFigure 2t. Leptopoma woodfordi.

Figure 2s. Cyclophorus fulguratus.Figure 2r. Cyclophorus fernandezi.

Figure 2q. Cyclophorus daraganicus.Figure 2p. Cyclophorus woodianus.

Terrestrial ProsobranchsCyclophoridae

Figure 2. Snail species obtained in Marinduque Figure 2: Snail species obtained in Marinduque.



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Table 4. Summary of the snail species found in the province of Marinduque. Those with (*) are new records for the island.Achatinafulica was not counted, being an introduced species, although its presence was noted in the areas it was found.

Group SpeciesNo. of individuals Family

Stylommatophora Helicostyla rufogaster (Lesson, 1831) 7 Bradybaenidae

(pulmonate) Helicostyla pithogaster (Ferrusac, 1821) 8 Bradybaenidae

Helicostyla marinduquensis (Hidalgo, 1887) 9 Bradybaenidae

Helicostyla fischeri (Hidalgo, 1889)* 3 Bradybaenidae

Helicostyla subcarinatamoellendorfi (Mollendorff, 1897) 1 Bradybaenidae

Helicostyla simplex (Jonas, 1834)* 8 Bradybaenidae

Helicostyla sphaerica (Sowerby, 1841)* 2 Bradybaenidae

Chloraea fibula (Reeve, 1842)* 10 Bradybaenidae

Obba listeri (Gray, 1825)* 10 Camaenidae

Trochomorpha metcalfei (Pfeiffer, 1845)* 1 Trochomorphidae

Trochomorpha schmakerii (Moellendorf, 1894)* 1 Trochomorphidae

Ryssota lamarckiana(Lea, 1852) 8 Helicarionidae

Ryssota otaheitana (Ferrusac, 1821) 6 Helicarionidae

Hemiglyptosis fouillioyi (Mollendorf, 1893)* 2 Helicarionidae

Nipponochlamys semisericata (Pilsbry, 1902)*Achati nafulica (Ferrusac, 1821)*

1-

HelicarionidaeAchatinidae

Caenogastropoda Cyclophorus woodianus (Lea, 1862) 8 Cyclophoridae

(prosobranch) Cyclophorus fernandezi (Hidalgo, 1888)* 3 Cyclophoridae

Cyclophorusdaraganicus (Hidalgo, 1888)* 4 Cyclophoridae

Cyclophorus fulguratus (Pfeiffer, 1852)* 2 Cyclophoridae

Leptopoma woodfordi(Sowerby, 1889)* 2 Cyclophoridae

Leptopoma pileus(Sowerby, 1843)* 5 Cyclophoridae

Leptopoma sericinum (Kobelt, 1886)* 34 Cyclophoridae

Leptopomasp. (Pfeiffer, 1847) 2 Cyclophoridae

Table 5. Values obtained for each index used to characterize Marinduque’s malacofaunal biodiversity.

Biodiversity index Values obtained

Shannon (H') 2.726148

Simpson (D) 0.097774

Simpson (1-D) 0.902226

Simpson (1/D) 10.22771

Pielou's evenness (J') 0.857804

Simpson evenness (E1/D) 0.426155

the provinces of the Philippines (Cunanan 2012). In contrast, Hahajima’s Higashizaki Peninsula, with only a fraction of the total land area of Marinduque, has a significantly greater number of snail species, and this is most likely due to the lack of human disturbances as a result of its relative inaccessibility (Chiba et al. 2007).

Why Marinduque has high terrestrial snail species diversityThis richness in terrestrial snail species can be attributed to three major factors. First is Marinduque’s relative isolation from mainland Luzon. The island was formerly submerged in water during the Cretaceous period around 66 million years ago (MYA) based on dating of its oldest rock formation, the Cretaceous Marinduque Serpentinite (Mines and Geosciences Bureau 2010); it most likely surfaced alongside the rest of the Luzon island complex during the massive rotation of the Philippine Sea Plate around the Middle Eocene (45 MYA) (Hall 1997). Marinduque was probably connected to Luzon during the last ice age roughly 10,000 years ago when water levels were 120 m lower (Heaney 1985). Solem (1984) suggested that the isolation of a certain island from other larger islands drives organisms to adapt to the limited resources found in its environment. Since snails have clumped distributions, these snail species adapt to the specific kinds of food, predators and climate present in their location.



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Second, Marinduque, like many islands in the Philippines, is a heterogenous island with varying elevation patterns as well as dry and wet regions that are suitable for snail speciation. In fact, moist areas like rain forests that receive regular precipitation can serve as refugia for many snails even at a microscale (Hylander et al. 2004). In addition, elevation could also affect diversity. For instance, de Chavez and de Lara (2011) observed in Mt. Makiling in Laguna, Luzon a positive correlation between elevation or altitude, among others, with diversity and abundance of land snails, particularly in the undisturbed and intact rain forests. In our study, however, some areas at higher altitudes were not included. For example, the highest elevation surveyed was at 125 m at Sitio Tiguion in Gasan. Mt. Malindig, the highest mountain in Marinduque (1,157 m), was not surveyed admittedly because of the lack of knowledge about the terrain of these areas and the lack of available guides, which prevented us from sampling in those areas. Including them in subsequent surveys could shed more light on the true malacofaunal diversity of Marinduque.

Third is a dissected topography, which, according to Solem (1984), is suitable for snail species to thrive. The dissected topography of an area acts as an important key in determining the climate, amount of heat received by a certain area, and the types of plants that can inhabit in it. In this study, it was observed that bradybaenids in Marinduque are frequently found in areas with high trees such as coconut (Cocos nucifera), mango (Mangifera indica), and papaya (Carica papaya), to name a few. Bradybaenids, especially Helicostyla rufogaster (Figure 2a) and H. pithogaster (Figure 2b), were also found in highly situated portions of the ‘nito’ (Lygodium circinnatum) vines. These snail species prefer high altitude habitats in order to escape the monitor lizards or ‘bayawak’ (Varanus sp.) preying on them as observed by the locals in the area. Camaenids, helicarionids and trocomorphids found in Marinduque prefer low lying habitats with high forest litter where they are camouflaged to evade predators such as monitor lizards, birds and frogs. The preference of these snails in low lying habitats could be attributed to the absence of monitor lizards in the sampling sites they were found. Interestingly, the helicarionids Ryssota lamarckiana (Figure 2j) and R. otaheitana (Figure 2k) are found in highly disturbed areas such as coconut husk piles from copra and dried coconut kernels where oil is extracted. Subsequent surveys in the island will therefore benefit with the inclusion of abiotic (temperature and humidity) and biotic (vegetation) parameters to correlate these with the distribution patterns of the snails.

Conservation status of Marinduque snailsWith roughly only 16% of the total land area of Marinduque with rain forest, much of the original habitat

of terrestrial snails has already been lost to give way to land use, primarily agriculture. It is highly likely that some species may have already become extinct due to habitat loss. In fact, two previously recorded species, H. bicolorata and R. sagittifera, were not detected in this survey. The presence of the invasive species such as A. fulica also raises some concern as they may compete with the native fauna. Furthermore, some snails are actually consumed by the locals of the island, particularly R. otaheitana and R. lamarckiana, whereas others, such as H. marinduquensis, H. rufogaster, H. pithogaster and H. sphaerica, are sold for their shells. There is therefore an urgent need to assess the conservation status of these snails before their habitats disappear.

RECOMMENDATIONSFor future studies, we recommend that sampling be done at night as snails are nocturnal. Furthermore, more time should be allocated for leaf litter sampling due to the limited number of microsnails observed. We also recommend areas at higher elevations, particularly Mt. Malindig, to be surveyed, and physic-chemical parameters such as temperature and humidity and biotic factors such as vegetation, particularly native flora, be included. Furthermore, highly disturbed and urban areas should also be surveyed to identify the presence of other introduced terrestrial malacofauna.

ACKNOWLEDGEMENTSWe thank Dr. Carmela Espanola for her valuable input on the statistical analyses and the Commission on Higher Education (CHED) for the funding. We also acknowledge Rufo Labay, Arnold Sosa, Averel Sosa, and Carlo Sosa for their assistance in obtaining snail samples.

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An Updated Survey and Biodiversity Assessment of the