Molluscan fauna of Gueishan Island, Taiwan

Abstract This dataset records the occurrence and inventory of molluscan fauna on Gueishan Island, the only active volcanic island in Taiwan, based on the literature survey and field investigation conducted between 2011 and 2012. The literature review involved seven studies published from 1934 to 2003, which collectively reported 112 species from 61 genera and 37 families of Mollusca on Gueishan Island. Through our field investigation, we identified 34 species from 28 genera and 23 families. Fourteen of these species were new records on Gueishan Island: Liolophura japonica, Lottia luchuana, Nerita costata, Nerita rumphii, Diplommatina suganikeiensis, Littoraria undulata, Solenomphala taiwanensis, Assiminea sp., Siphonaria laciniosa, Laevapex nipponica, Carychium hachijoensis, Succinea erythrophana, Zaptyx crassilamellata, and Allopeas pyrgula. In Total, there are 126 species from 71 genera and 45 families of Mollusca on Gueishan Island. These data have been published through GBIF [http://taibif.org.tw/ipt/resource.do?r=gueishan_island] and integrated into the Taiwan Malacofauna Database (http://shell.sinica.edu.tw/).

Study area descriptions/descriptor: Gueishan Island is located about 10 km from Taiwan. The island was formed via volcanic activity about 1.65 Ma ago and experienced multiple volcanic eruption events until 20 ka ago (Juang et al. 2011). It is considered the only active volcanic island near Taiwan. The land area of the island is about 2.85 km 2 , and the highest peak of the island is 398 meters above sea level. There are two lakes on the island, one of which consist of brackish water (Head Lake) and the other of freshwater (Tail Lake) (Figure 1). Humans colonized Gueishan Island in mid-19th century, by forming a small village. Later in 1977, all residents were moved back to Taiwan due to military requirements for the island. The fauna of this island were not investigated systematically until 2000, when the island came under the management of the Northeast and Yilan Coast National Scenic Area Administration, Tourism Bureau, MOTC and was open to tourists.
Design description: Island species are vulnerable to extinction due to their relatively small population size and limited access to resources. The number of species on an island represents a dynamic equilibrium between immigration and extinction. Volcanic islands provide particularly interesting cases of island biogeography, in that their biota is erased by volcanic activity and recolonized from neighboring regions. Species on Gueishan Island may have under gone several cycles of extinction after volcanic eruption, followed by recolonization from Taiwan when the sea-level dropped during glacial periods. Hu- man activity may also have provided opportunities for colonization of mollusks, either intentionally or accidentally. Investigations of molluscan fauna have been previously conducted on Gueishan Island, but these did not involve a comprehensive examination of land snails. We performed a literature survey using diverse databases, in order to collect previously identified reports on molluscan fauna of Gueishan Island. In addition, we performed field sampling of mollusks in marine, freshwater and terrestrial environments during 2011 and 2012 to establish the inventory of molluscan fauna of Gueishan Island. We considered both the topography of the island and the habitats of mollusks during our field investigation. We focused on the terrestrial environment, as the majority of the earlier investigations examined non-terrestrial habitats. In total, our literature survey and field investigation identified 126 species from 71 genera and 45 families of Mollusca on Gueishan Island. This dataset provides basic information on the island's biodiversity.

Sampling description:
Literature survey: We searched for publications (including journals, project reports, theses and books) associated with the molluscan fauna of Gueishan Island from the following databases: (1) the National Digital Library of Theses and Dissertations in Taiwan (http://ndltd.ncl.edu.tw) (this contains details of theses and dissertations pub-lished since 1956, but did not contain publications relevant to this study); (2) the National Bibliographic Information Network (http://nbinet3.ncl.edu.tw) (this catalog integrates information from National Central Library and 74 other libraries containing all publications with a Taiwan ISBN and selected government project reports; three publications (Wu 2002, National Museum of Marine Biology and Aquarium 2003, Hwang and Lee 2003 from this database met our requirement); (3) the Government Research Bulletin (http://grbsearch.stpi.narl.org.tw/GRB/) (this contains government project reports made since 1993, but did not contain reports relevant to this study); (4) Google Scholar (http://scholar.google.com.tw/) (this contains a wide range of resources, from journals and books to webpages, and it provided two relevant journal articles (Chen and Fu 2007, Lee and Chen 2010)); (5) The Taiwan Malacofauna Database (http://shell.sinica.edu.tw/) (this database contains taxonomy, distribution and references of all mollusks occurred in Taiwan, and provided six relevant publications (Lee and Wu 1998, Jung and Lai 1999, Wu 2002, National Museum of Marine Biology and Aquarium 2003, Hwang and Lee 2003, Chen and Fu 2007). In addition, three relevant publications (Hayasaka and Tan 1934, Kuroda 1938, Kuroda 1941 were identified from citations in Wu (2002). In total, we identified ten relevant publications. Three of these publications Wu 1998, Chen andFu 2007, Lee and Chen 2010) were excluded because they described specimens acquired from fishing ports that had been captured by shrimp fishing or bottom trawling boats near Gueishan Island, without information of the precise sampling location. The seven remaining publications were used to establish the occurrence and inventory data. Sampling sites, names of collectors and the scientific name of each species were recorded using Microsoft EXCEL 2010. All of the publications mentioned above can be accessed in the National Central Library and the National Taiwan Library. Field Sampling: The topology of Gueishan Island and the types of mollusk habitat were considered for field investigation. Visual search was conducted for mollusks in intertidal, freshwater and terrestrial environments (Figure 1). The surface of rocks on the coastline and man-made concrete structures in port were searched for marine mollusks during low tide. Leaf litter and rocks under or near water around Tail Lake (the only freshwater habitat on island) were inspected for freshwater mollusks. We inspected from leaves, trunks, leaves litter, rocks and rotten woods for land snails along three trails: one trail around Tail Lake, another leads to the highest peak (401 Highland) on the island, and the other leads to the northern part of the island. We surveyed for land snails during their active periods: during and after rainfall, early morning, and night. At least one living individual or dead shells of each species was collected as voucher specimens. Living organisms were brought back to laboratory, fixed via freezing in a -80°C freezer, and subsequently transferred to 95% ethanol for long term preservation.
Quality control description: Latitude, longitude and altitude of sampling sites were recorded using Garmin GPSmap 60CSx with uncertainty of less than 10 meters. Sampling sites were georeferenced (WGS84). All the specimens collected during the field investigation were identified independently by Huang and Hsiung. Seven earlier studies described the mollucan fauna of Gueishan Island, but these publications lack clear photos or other information for identifying specimens. Species identification was performed using the following guide books and publications about Taiwan malacofauna: Pace (1973), Lai (1990Lai ( , 1998, Lee and Chen (2003), Wu andLee (2005), andHsieh et al. (2006). Newly recorded species were further confirmed by Dr. Yen-Chen Lee, a Mollusca specialist and postdoctoral researcher in the Biodiversity Research Center, Academia Sinica. Fourteen new recorded species were found to be native to Taiwan but previously unreported on Gueishan Island. The scientific names of all mollusks were checked against the Taiwan Malacofauna Database and World Register of Marine Species (http://www.marinespecies.org/).

Data resources
The data underpinning the analysis reported in this paper are deposited at GBIF, the Global Biodiversity Information Facility, http://taibif.org.tw/ipt/resource. do?r=gueishan_island