Luzon Island Research Articles

Taxonomic revision of the king cobra Ophiophagus hannah (Cantor, 1836) species complex (Reptilia: Serpentes: Elapidae), with the description of two new species

The taxonomy of king cobras (Ophiophagus) was reevaluated using qualitative, mensural and meristic characters, based on 148 entire and five skeletal specimens, and supported by a recent molecular phylogenetic analysis. We provide nomenclatural synopses of both the genus and species-series nomina. We restrict the concept of Ophiophagus hannah s. str. to populations from eastern Pakistan, northern and eastern India, the Andaman Islands, Indo-Burma and Indo-China, south to central Thailand. The nomen Ophiophagus bungarus (Schlegel, 1837) comb. nov. is revived for the populations inhabiting the Sunda Shelf area, including the Malay Peninsula, the Greater Sunda Islands and parts of the southern Philippines. We describe two new species, Ophiophagus kaalinga Gowri Shankar, Das & Ganesh sp. nov. endemic to the Western Ghats of south-western India and Ophiophagus salvatana Gowri Shankar, Das & Wüster sp. nov., inhabiting the island of Luzon in northern Philippines. For the purpose of nomenclatural stability, we designate a neotype for Hamadryas hannah Cantor, 1836. A dichotomous identification key to the four species recognized here is provided.

Morphological and molecular characterization of two potentially toxigenic species of the genus Pseudo-nitzschia (Bacillariophyceae) in Luzon Island, Philippines

Harmful algal blooms are a major concern for the environment and industries like fisheries, healthcare, and tourism in coastal countries such as the Philippines. Blooms of diatoms (Bacillariophyceae) seldom cause harm, but half of the species in the cosmopolitan genus Pseudo-nitzschia produce the neurotoxin domoic acid. Only two published Pseudo-nitzschia surveys in the Philippines carried out morphology-based species identification. Molecular taxonomy has revealed a high level of cryptic diversity corresponding to minute morphological differences. This study sought to explore the diversity of and characterize the genus Pseudo-nitzschia in mariculture zones around Luzon Island using morphological and molecular information. Ten culture strains of Pseudo-nitzschia isolated from shellfish farms were used for morphological and molecular species identification. The secondary structure of the internal transcribed spacer 2 region revealed five strains from Pagbilao Bay to be most similar to P. brasiliana, the first record of this species in Luzon. Meanwhile, four Bacoor isolates and one from Pagbilao clustered within a monophyletic clade representing P. pungens, previously found in Manila Bay. Three single nucleotide polymorphisms and one hemi-compensatory base change were found among the P. pungens strains. Morphological characters, specifically cell shape, apex shape, and poroid density confirmed both species identities. Based on band striae, all P. pungens strains were of the nominal variety, P. pungens var. pungens. This study is among the first culture-based taxonomic studies of diatoms in the Philippines, in this case confirming the presence of harmful microalgae in the coastal ecosystems of the country.

Using detrital zircon U[sbnd]Pb geochronology to track the provenance of Miocene sediments in the northern Pearl River Mouth Basin, South China Sea

The Late Cenozoic provenance study of the Pearl River Mouth Basin (PRMB) holds significant implications for understanding the tectonic-climatic interactions, drainage evolution, and oceanic circulation in the northern South China Sea. However, the Miocene sediment routing system remains poorly understood due to the paucity of zircon geochronological data and the effects of sediment mixing and homogenization. This study reconstructs the ancient source-to-sink system by means of detrital zircon analyses from the northern PRMB and zircon age-based mixture modeling of well-defined provenance end-members. The results disclose varied and complex source-to-sink scenarios since the Early Miocene, involving three primary contributors: the Pearl River drainage system, coastal SE China, and Taiwan Island. In combination with seismic facies and climatic proxies, the intensive addition of Precambrian zircons suggests that, during the Middle and Late Miocene, progressive drainage expansion within the Yangtze Block likely contributed to the increasing sediment supply from the western Pearl River drainage system. Furthermore, the provenance shift in the northern PRMB, as indicated by the Mesozoic ages, may reflect a response to the activation of oceanic circulation and intensification of the East Asian monsoon. Additionally, though less significant, contributions from the Hainan and Luzon Island are also observed, indicating the input of the branch of the Kuroshio Current during the Late Miocene.

The 3D Density Structure of the South China Sea Based on Wavelet Multi-Scale Analysis of Gravity Data and Its Tectonic Implications

Due to its unique geographical location and complex geological evolution processes, the South China Sea has been a focus of extensive research. Previous studies on the density structure of the South China Sea mostly focused on 2D density structures, with relatively limited research on 3D density structures. A comprehensive study is still needed to refine the expansion mechanism and tectonic evolution of the South China Sea. In this study, we utilized wavelet multi-scale analysis of gravity data to obtain a 3D density model of the South China Sea and discussed its tectonic evolution from the pattern of density anomalies. The inversion results show that (1) the expansion of the South China Sea caused the typical thin oceanic crust and parts of the continent–ocean transition zone may fracture due to the expansion; (2) the low-density anomaly in the upper mantle of Luzon Island may indicate partial melting or the upwelling of asthenosphere materials; and (3) the expansion of the South China Sea is influenced by multiple plate forces and uneven forces affect the distribution of high-density anomalies in the upper mantle.

LOCAL ECOLOGICAL KNOWLEDGE ON LAND SNAIL DIVERSITY IN MOUNT BANAHAW, PHILIPPINES

Local ecological knowledge (LEK) is a community-based conservation effort that promotes sustainable management of natural resources. However, studies on LEK are very limited in the Philippines. To address this information gap, LEK on land snails in Mount Banahaw, Luzon Island, Philippines was investigated. Key informant interviews and focus group discussions were conducted in the four communities (Dolores, Lucban, Tayabas and Majayjay) along the slope of the mountain. A snail calendar was used as a tool for identifying the hunting season and practices of these communities on land snails. The results showed that the communities were knowledgeable on macro land snails (>5 mm shell size) such as the introduced species, Lissachatina fulica and the endemic and edible, Ryssota otaheitana, but were unaware of micro land snails ( 5 mm shell size). Locals also demonstrated an awareness of the snails’ ecosystem functions as a food source for other animals and agents of nutrient cycling. Additionally, sustainable hunting of R. otaheitana in communities was observed. Only adult R. otaheitana were harvested, leaving the juveniles to grow and reproduce. In Lucban, the people hunted while they were waiting for the harvest season of their crops. In Tayabas, the community observed that the snail was abundant during wet and moist soil conditions when leaf litter, its primary food, decomposed easily. In Majayjay, hunting was associated with the blooming of the flowering plant, Erythrina variegata. In Dolores, hunting was practiced after clearing farmland. This research underscores the importance of determining LEK in developing policies and regulations on sustainable utilization and conservation of land snails in a tropical forest setting.

Genome drafts of Pseudogracilibacillus spp. from soil and sediment of Mount Makiling, a dormant volcano in the Philippines.

We present the draft whole-genome sequences of Pseudogracilibacillus spp. isolated from the soils and sediments of Sipit Creek located at Mount Makiling, a dormant volcano in the southern part of Luzon Island, Philippines. This Pseudogracilibacillus spp. genome report extends the body of knowledge on a lesser-known genus of Bacillaceae.

Expert-driven geothermal play fairway analysis for low to medium temperature hidden systems in northwestern Luzon Island, Philippines

The Philippines is the third largest geothermal power-producing country in the world. However, additional opportunities exist to expand the geothermal portfolio of the country with the exploitation of low- and moderate- temperature resources, as well as assessment and development of hidden geothermal systems (i.e., those with no active surface manifestations). As part of the Geothermal Development Initiative (GEODE) funded through the U.S. Department of State award to the University of Nevada, Reno, a collaboration between the Philippines Renewable Energy Management Bureau (REMB) of the Department of Energy and the University of Nevada in Reno, Great Basin Center for Geothermal Energy occurred from September 2022 to March 2024. As part of this collaboration, an expert-driven geothermal Play Fairway Analysis (PFA) was conducted in the northwestern portion of Luzon Island of the Philippines utilizing existing data sets available to the REMB. The goal of this PFA is to identify areas with greater relative geothermal favorability, determine where the data gaps are, and assist in the discovery of hidden geothermal systems. A geothermal PFA requires the compilation and transformation of datasets into appropriate formats (e.g., tables, shapefiles, and raster files) and evaluation of each dataset to determine how it can be used as a proxy for the key attributes of a geothermal system (e.g., heat and permeability). Once the data are organized, they are weighted for integration into the GIS software to develop a favorability model for heat and permeability. The attribute models are then combined to produce two PFA models: the conventional hydrothermal low- to moderate- temperature geothermal favorability and the hidden systems favorability. The data difference between the conventional geothermal favorability and hidden systems models is that hot springs are not used for the hidden systems model. The conventional favorability model of northwestern Luzon Island indicates areas of higher geothermal favorability in the central and southern sections of the study area. Many of the favorable areas identified in the conventional model already have active leases for geothermal exploration, lending more confidence to the methodology and model, and suggesting that the areas with no current leases and high geothermal favorability could represent future exploration targets. The hidden systems model shows favorable zones in the north, central and southern sectors, and can serve as a tool to decide the areas for exploration of potential hidden geothermal systems, particularly, in the Ilocos Norte, Apayao, and Nueva Viscaya regions.

Bulbophyllum bokodense (section Polymeres, Orchidaceae), a new species from Benguet Province, Luzon Island, Philippines

A new species of orchid, Bulbophyllum bokodense, is herein described and illustrated from Benguet Province, Luzon Island, Philippines. It closely resembles Bulbophyllum rinkei endemic to New Guinea, but is distinct by having a broader leaf, a shorter inflorescence, an acute petal apex, glabrous auricles, a slightly canaliculate labellum, mid lobe and apex of labellum devoid of concavity, and a longer stelidia. A detailed description, photographs, and illustration are also provided. Preliminary conservation assessment of the new species following IUCN guidelines suggest a conservation status of data deficient (DD).

A NEW SPECIES OF THE Odontomachus infandus SPECIES GROUP (HYMENOPTERA: FORMICIDAE) FROM PANGASINAN, PHILIPPINES, WITH NOTES ON SPECIES ECOLOGY

ARTICLE HIGLIGHTS- New species of Odontomachus- Distribution and ecological notes- Updated species key ABSTRACTA new species of Odontomachus Latreille, 1804 named O. ampipitbaybay sp. nov. is illustrated and described from specimens collected along the coastal area of Alaminos City, Pangasinan, Luzon Island, Philippines, with notes on its species ecology. The new species is diagnosed and compared against closely related species from Luzon. A distribution map of selected Philippine Odontomachus species is provided, and a modification to the key to the Philippine Odontomachus is proposed.

The Climatological Perspective of Remote Rainfall Events Triggered by the Northeasterly Wind and the Outer Circulation of Typhoon in Taiwan

AbstractThe climate characteristics of remote rainfall events in Taiwan from September to February over 41 years (1980–2020) are studied. These events are induced by the interaction between the northeasterly flow and the typhoon's outer circulation. Our findings reveal that rainfall in northeastern Taiwan becomes more prominent when tropical cyclones move to the remote rainfall‐prone area, located in the north Philippine area to the northern South China Sea, and when the background northeasterly wind speed exceeds 7 m s−1. Under these criteria, the confluence of the typhoon's outer circulation and the northeasterly flow creates a convergence area that enhances rainfall in northeastern Taiwan, increasing the occurrence of moderate to extreme rainfall (ER) events. This leads to an average enhancement in rainfall amount of 80–220 mm per day. Additionally, when typhoons are in the remote rainfall‐prone area, there is a greater than 20% chance for events with maximum rainfall over 200 mm day−1 to occur, particularly in the region of 20°–22°N, 116°−124°E, and north to Luzon Island. In this area, the occurrence rate can exceed more than a 45% chance. The highest risk of ER events occurs between 20°–22°N and 118°−120°E, with a probability of over 90%. Notably, the convergence area for the Taiwan cases does not necessarily coincide with the baroclinic forcing as that associated with remote rainfall events observed in Japan, Korea, and North America.

A Long Overlooked New Species of Fanged Frog, Genus Limnonectes (Amphibia: Anura: Dicroglossidae), from Luzon Island, Northern Philippines

A Long Overlooked New Species of Fanged Frog, Genus Limnonectes (Amphibia: Anura: Dicroglossidae), from Luzon Island, Northern Philippines

Geochronological advances in human and proboscideans first arrival date in the Philippines archipelago (Cagayan valley, Luzon Island)

The Paleolithic site of Kalinga, in the Cagayan River Basin (Luzon Island), has recorded the oldest known traces of human occupation of the Philippine archipelago dated at 709 ± 68 ka. The island of Luzon is further known for its endemic Hominin Homo luzonensis (Callao cave) recently dated at 134 ± 14 ka, which makes it the oldest human remains in the Philippines.The present study provides new chronological data on the Kalinga site and surrounding localities on the left bank of the Cagayan Valley and tackles the question over the geochronology of the human settlement of the basin. Following the discovery of some abundant paleontological remains and lithic artefacts on surface, several excavations took place since the 1970s. In 2014, new research in the area by our team on a site named Kalinga led to the recovery of hundreds of undisturbed archaeological remains (lithic tools and butchery marks). Apart from the early Middle Pleistocene ages obtained for the Kalinga site, the geochronology of the area is still largely unknown. Through the use of ESR on bleached quartz and 40Ar/39Ar single crystal laser fusion on plagioclase dating methods, the chronology of four archaeological sequences has been here constrained for the first time. Our results highlight a human occupation presence between 796 ± 70 ka and 273 ± 20 ka reducing the chronological gap between Kalinga site and Callao Cave, placing the Cagayan basin as a cornerstone to better understand the human arrival in insular Asia.

First checklist of Herpetofauna in Mt. Arayat National Park and vicinity, Pampanga Province, Luzon Island, The Philippines

First checklist of Herpetofauna in Mt. Arayat National Park and vicinity, Pampanga Province, Luzon Island, The Philippines

Farming is not a joke: the entrepreneurship ecosystem of agricultural social enterprises

PurposeThis study aims to work toward understanding the entrepreneurship ecosystem of agricultural social enterprises in the Philippines by exploring the interactions between policy, culture, supports and human capital domains.Design/methodology/approachThe authors considered using an exploratory single-embedded case study approach, involving methodological triangulation of document analysis, semistructured interviews and participant observation. The authors analyzed the data using a narrative approach to map the ecosystem.FindingsThrough the research, the authors discovered that while each domain functions effectively individually, disconnects exist when interacting collectively as an ecosystem. The authors come to know that there is no policy consensus on social enterprise definitions, which limits specialized policy support. Although support services like incubators are available, the authors observed that awareness and accessibility vary based on location and business maturity. The authors also noted that human capital helps translate concepts into frameworks, but research tailored to agriculture and social entrepreneurship is limited. The authors come to the conclusion that collaboration and openness across domains are needed to strengthen connections and synergies.Research limitations/implicationsThe study was geographically limited to Luzon Island, and the authors did not include the finance and markets domains of the ecosystem model in the analysis.Practical implicationsBased on the findings, the authors identify strategies to reinforce connections, such as increasing awareness of support services, developing tailored policies for social enterprises, conducting specialized research and promoting collaboration across domains. The authors are convinced that implementing these strategies can further develop the agricultural social entrepreneurship ecosystem.Originality/valueThe study provides unique empirical insights into the agricultural social entrepreneurship ecosystem in the Philippines. The authors captured the narratives and experiences of key ecosystem stakeholders along the process. The authors have confidence that what the authors found can strategically guide policymakers and support organizations, educational institutions and social entrepreneurs to accelerate ecosystem development for greater social impact.

An Emerging New Tourism Destination: Geographic Resources and Tourism Potential of the Province of Masbate (Republic of the Philippines)

The Masbate Province surrounded by the Sibuyan Sea, Visayan Sea and Samar Sea, is located in the central part of the Philippine archipelago and includes 3 large islands (Masbate, Ticao and Burias) and many smaller islands. All the islands within the borders of Masbate Province are just one part of the Luzon Islands Group in terms of physical geography; also in terms of political geography and administrative geography, they are located within the “Bicol Administrative Region”. In terms of administrative structure, there are 20 districts, 1 city (Masbate City) and 550 Barangays in the Masbate Province. Even though the Masbate Province has rich natural resources and mines, great agricultural and fishing potential, it has so far failed to achieve the desired success in international tourism. In this study, Masbate, Ticao and Burias, which are the largest islands of the Masbate province, are investigated and analyzed separately and both their geographical features, tourism potential and tourism attractiveness of these islands are accounted for. In this article, the main accommodation facilities, major nature reserves, islands and beaches within the borders of Masbate Province, as well as natural and cultural tourism attractions are examined; additionally, the tourism advantages and disadvantages of Masbate Province are addressed. The main purpose of the study is to introduce the tourism resources, cultural riches and natural beauties of the Masbate Province, which actually is not very popular among the international tourists, to the readers, both to popularize the name of the Masbate Province to the global tourism markets and offer new holiday options for the inquisitive tourists.

First record of Xeniaria bicornis Maa, 1974 (Dermaptera: Arixeniidae) in Luzon Island, Philippines

ABSTRACT Xeniaria bicornis Maa 1974, an epizoic earwig on molossid bats previously known only from Mindanao Island, is recorded for the first time in Luzon Island, Philippines. The adult female is described for the first time from specimens collected from the floor of Bahay Paniki Cave in Biak-na-Bato National Park, San Miguel, Bulacan Province. Notes on their biogeography, ecology and behaviour are also provided.

A revolution in understanding SE Asia geodynamics since 20.5–18 Ma

We present an updated evaluation of SE Asian geodynamics that includes the interactions of the South China Sea (SCS) marginal basin with surrounding plates since the end of SCS spreading 20.5–18 Ma. Newly available Ar39/Ar40 ages of SCS oceanic crust drilled at IODP U1431 near the SCS East basin extinct spreading center are older than 18 Ma. Conversely, the oldest ages of the Luzon arc and forearc at Taiwan's Lanyu island, Coastal range and Lichi mélange are 17–18 Ma, suggesting that onset of the Manila subduction zone may have begun a few m.y. earlier. Before ∼20.5 Ma, the northern part of the Manila transcurrent fault (MTF), considered as the western boundary of the Ryukyu subduction zone, was a left-lateral lithospheric-scale shear zone. From ∼20.5–18 Ma to ∼7 Ma, this portion of MTF was connected to the Manila trench. Since ∼7 Ma, the MTF extended into the Taiwan Longitudinal valley and continued southwards to north Luzon island as near-vertical, left-lateral shear zone. Today, south of ∼24°N, the MTF protrudes down to 30 km depths and terminates above the deeper Manila slab. Since ∼7 Ma, the whole MTF shifted 400 km westward with respect to Eurasia and rotated ∼23° clockwise to become oriented ∼NS north of 16°N latitude. We identify a tear fault in the Eurasian (EU) plate north of the Ryukyu trench that is located south of the Myako and Yonaguni islands. Since ∼10 Ma, the tear continuously progressed westward within EU crust, with the Philippine Sea plate progressively subducting northwestward between the two lips of the tear fault. A RFF (ridge-fault-fault) triple junction was active in the EU crust before 20.5 Ma, from 10 to 7 Ma, and since 2 Ma. This triple junction was always located on the MTF with one branch of the MTF on each side of the triple junction, and the third branch being the spreading center.

The larva of the endangered Heterophaea barbata (Martin, 1902), from Luzon Island, the Philippines (Odonata: Euphaeidae)

The larva of the endangered Heterophaea barbata (Martin, 1902), from Luzon Island, the Philippines (Odonata: Euphaeidae)

Gastrointestinal parasitic helminths of bats from a cave in Luzon Island, Philippines.

Bats are often associated with several zoonotic diseases, including helminth infections. Despite their potential detrimental effects on both human and bat populations, information on helminth parasites of Philippine bats remains scarce. Here, we identify gastrointestinal helminths parasitizing bats collected from a cave complex in Cavinti, Laguna Province, Philippines, determine their prevalence (P) and mean intensity (MI), and investigate relationship of helminth prevalence and intensity with bat host characteristics including sex, diet, age, and roosting habit. We isolated 581 individuals of helminths representing six taxa (three trematodes, two nematodes, one cestode) from the gastrointestinal tract of sampled bats. Helminths were observed in 82 out of 172 bats captured (P = 47.67%), with Miniopteruspaululus having the highest infection rate (P = 91.3%) and highest MI (18 ± 4.5/infected bat). Helminths parasitizing endemic bat species from the Philippines, such as Rhinolophus rufus, Rhinolophus inops, Hipposideros pygmaeus, and Ptenochirus jagori were reported here for the first time. We provide new host records for other helminth species and report the presence of two parasites, Plagiorchis sp. and Toxocara sp., known for their zoonotic potential. These data will contribute to efforts in identifying parasites and diseases harbored by bats in the country and develop additional conservation measures for bats.

Morphometric Evaluation of the Relative Uplift Rates along the Vigan–Aggao Fault in Ilocos Norte, Philippines

The Vigan–Aggao Fault (VAF) in northern Luzon Island is a NNE-trending sinistral fault divided by fault bends, which are associated with local variations in the fault’s kinematics. In this study, we examined the relative uplift rates across the fault bend in the San Juan–Vintar segment of the VAF using morphometric indices. Basin-based indices, namely hypsometric integral, basin shape, basin elongation ratio, and basin asymmetry factor, and non-basin-based indices, namely stream length-gradient index, normalized stream length-gradient index, and mountain front sinuosity were calculated to isolate and examine the surface processes that influence landscape development. We then integrated the basin-based results with geological data to create a relative tectonic activity index (RTAI). Clustering analysis of the results revealed hotspots along the bent section of the fault indicating more values that suggest higher relative uplift rates during the development of the landscape. The morphometric indices showed that the highest uplift rates are along the central VAF strands. This study described and evaluated the relative uplift rates of a known active fault system in Ilocos Norte, in the absence of detailed field structural data. This study also reinforces the utility of morphometry in identifying priority sites for detailed paleoseismic and seismic hazard analyses.