Diversity of Land Snails in the Karst Areas of Sta. Teresita, Cagayan Province, Luzon Island with Notes on New Distribution Records
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Philippine Journal of Science 150 (S1): 525-537, Special Issue on Biodiversity ISSN 0031 - 7683 Date Received: 04 Oct 2020 Diversity of Land Snails in the Karst Areas of Sta. Teresita, Cagayan Province, Luzon Island with Notes on New Distribution Records Julius A. Parcon1*, Ireneo L. Lit Jr.1,2, Ma. Vivian C. Camacho1,2, and Emmanuel Ryan C. de Chavez1,2 1Museum of Natural History 2Institute of Biological Sciences, College of Arts and Sciences University of the Philippines Los Baños, College 4031 Laguna, Philippines Malacofaunal research in a karst ecosystem is very limited not only in the northern region of Luzon Island but in the entire Philippines amidst extensive habitat disturbance and destruction. To address this, the diversity and abundance of land snails in the karst areas of Santa Teresita, Cagayan Province were determined. A total of 25 5 x 5 m2 quadrats were randomly set in five stations in the karst landscape. A total of 1206 land snails comprising 45 species under 36 genera representing 17 families were sampled. Camaenidae was the most represented family with 10 species. Luzonocoptis antennae constituted 25.1% of the total number of samples (303 individuals) and was the most abundant species in all stations. Of the 36 genera, five are new records in the Philippines. Several karst endemics and introduced species were recorded. Diversity indices showed diverse land snail fauna with Shannon-Weiner diversity index (H’) of 2.80, with evenness (J’) of 0.36 and dominance index of (D’) of 0.11. Species accumulation curve (SAC) showed late asymptote with a completeness ratio of 0.92. The study demonstrated that land snails in Sta. Teresita, Cagayan Province are rich and diverse. It is very important to recognize Sta. Teresita as priority sites for malacofaunal conservation, and consider the further evaluation of these sites to be designated as a protected area. Keywords: biodiversity, Cagayan, karst, land snails, limestone INTRODUCTION 2004), hunting of bats for food (Scheffers et al. 2012), and uncontrolled tourism (Alcala et al. 2007). Furthermore, The Philippines has tropical karsts that cover about 10% biodiversity documentation in these habitats is among 2 (approximately 35,000 km ) of the country’s land area the most neglected, where only 10% of the total karsts (Piccini and Rossi 1994). The 29% (approximately 10,150 have been surveyed (NRCP 2016). Most available 2 km ) of these karst landscapes have been declared as studies were conducted on the diversity and ecology of either a national park, national monument, or a protected cave-dwelling bats from different islands (Quibod et al. landscape (Restificar et al. 2006). However, many karsts 2019). The scarcity of biological information on karsts in remote areas still lack institutionalized protection. could eventually weaken the justification in the long run These ecosystems are adversely affected by anthropogenic for the conservation of various karst-associated species activities such as limestone mining, phosphate and guano despite the increasing number of threats, which could lead extraction, harvesting of edible swiftlet nests (Hobbs to localized extinctions. *Corresponding Author: [email protected] 525 Philippine Journal of Science Parcon et al.: Diversity and Distribution of Land Vol. 150 No. S1, Special Issue on Biodiversity Snails in Sta. Teresita, Cagayan, Philippines Tropical karsts are known as biodiversity arks due to of which 171,362 ha are classified as secondary and their high species diversity arising from a multitude old-growth forests, while 3,081 ha are mossy forests. of ecological niches afforded by variable climatic The biodiversity in NECKBA is not well studied; conditions, fissured cliffs, and extensive caves (Clements however, it is considered as among important sites et al. 2006). These are unique ecosystems characterized harboring various threatened endemic species of flora by high calcium carbonate deposits considered as and fauna such as the Rafflesia leonardii, Philippine eagle evolutionary hotspots for speciation and function as (Pithecophaga jefferyi), and the Northern Luzon Giant habitat islands for many calcium-dependent animals, Cloud Rat (Phloeomys pallidus). The baseline data on including land snails (Schilthuizen et al. 2003; Clements the malacofauna of its karst areas is still lacking. If there et al. 2006). On the other hand, non-karst habitats such are existing records, these are probably unpublished as tropical rainforest make unfavorable habitats for land or remain as gray literature. Thus, in this preliminary snails due to lack of available nutrients, negligible litter, study, we determined and analyzed the land snail diversity and abundance of predators (Solem 1984; Schilthuizen patterns on the limestone hills of Sta. Teresita. and Rutjes 2001). The Philippines harbors 31% (22,000 out of 70,000 species) of all mollusks described worldwide (Ong et MATERIALS AND METHODS al. 2002) with approximately 90–95% endemism, but most of the recorded are marine species. There are very few terrestrial malacological studies (Bartsch 1909; Study Site Clench and Archer 1931; Faustino 1930; Valdez et al. Sta. Teresita (18°15'0" N, 121°53'0" E) in Cagayan 2021) that particularly focus on karsts. However, many Province is a fourth-class municipality that is 588 km researchers in the country are less interested to study land away from Manila (Figure 1). Its altitude ranges from snails. Some of the reasons could be the inaccessibility 26–72 m above sea level. The area has a Type III climate of literature on Philippines mollusks, particularly on where rainfall is evenly distributed throughout the year taxonomy. According to Springsteen and Leobrera mainly due to the northeast trade winds. From November– (1986), the taxonomy of these animals is likewise in a January, the northwest monsoon from East Asia brings dry state of flux due to many species are morphologically and cool winds to this valley floor. Because of the open very similar and it is difficult to identify the specimen coastline, it experiences cold mornings and evenings, even at a family level. Moreover, juveniles are sometimes with average temperatures ranging from 18–21 °C. hardly distinguishable from their adult forms. It also The soil pH is neutral ranging from 7.6–7.8, relative requires skill to find land snails in their natural habitat, and humidity from 86.77–99%, soil moisture from 4.84–8.12 3 –3 perhaps being a non-charismatic animal few students and m ∙ m , calcium content from 22.86–30 (me/100 g). researcher are not attracted to study them. Interestingly, Karst ecosystem of Sta. Teresita is composed of conical many new species are still being discovered; for instance, hills fragmented by non-calcareous agricultural land in there were new genera, eight new species, and two new several hundreds of meters. It has an altitude ranging subspecies described between 2017–2020 alone (Páll- from 12–72 masl with secondary and old-growth forest. Gergely et al. 2017; Batomalaque and Rosenberg 2018; Five sampling stations were randomly chosen – namely, Páll-Gergely and Schilthuizen 2019; Páll-Gergely and Ari Zero, Ari Zero-1, Bangalao, Maquera, and Tabaco Auffenberg 2019; Lipae et al. 2020). with an approximate total area of 7,878 ha. These sites are forms of conical limestone hills with caves. Likewise, Among the remote karst landscapes in the northern most sites have fragmented secondary forests surrounded region of Luzon is Santa Teresita in Cagayan Province. by agroecosystems (mostly corn and vegetable plantation) This municipality is located in the northeastern region of except for Maquera, which is located in the middle of the the Cagayan Valley Basin (CVB), a north-south trending mature second-growth forest with the presence of large sedimentary basin bounded by the Cordillera mountain trees and thick vegetation adjacent to cornfields and range in the west and Sierra Madre mountain range in vegetable farms. the east. The CVB began to form during the Oligocene as the South China Sea Plate under the Philippine Mobile Belt headed east as the western subduction was Land Snail Sampling ceased along the Luzon Trough (UPLB-MNH 2018). Samples were collected from December 2017–February Sta. Teresita is also within the coverage of the Northeast 2018 using the protocol adapted from Clements et al. Cagayan Key Biodiversity Area (NECKBA), which lies (2006), de Chavez and de Lara (2011), and Uy et al. in the northeastern tip of the Sierra Madre Mountain (2018). Within a station, five 5 x 5 m quadrats were Range. NECKBA covers an area of about 183,430 ha, set randomly located within the outcrops near or at the mouth of the caves and on limestone rocks at least 10 m 526 Philippine Journal of Science Parcon et al.: Diversity and Distribution of Land Vol. 150 No. S1, Special Issue on Biodiversity Snails in Sta. Teresita, Cagayan, Philippines Figure 1. Location of sampling sites in Sta. Teresita Cagayan, Philippines (map source: Google Earth satellite image using QGIS ver 3.4 Madier; photo by J.A. Parcon). to standardize the sampling. Macro snails (> 5 mm) with live and empty shells were searched – particularly on each microhabitat like bark and buttresses of trees, rotting logs, and undersides of epiphytes and palms. To obtain the overall diversity of the sampling sites and to increase the sample size, live snails and empty shells were pooled together (de Winter and Gittenberger 1998; Raheem et al. 2008). Some of the empty shells were collected while live specimens were then photographed and returned to their original habitat after taking their pictures. Empty shells and live snails were identified up to species level and verified using the published literature (Bartsch 1909; Faustino 1930; Springsteen and Leobrera 1986; Hemmen et al. 1987; Bouchet et al. 2017). For micro snails, samples were searched and collected by direct hand-picking on tree branches and on cave entrances Figure 2.