Entry protocol and fieldwork

Before conducting fieldwork and collecting samples in the forests of Cebu, Wildlife Gratuitous Permits No. 2024-09 and 2024-22 were obtained from the Department of Environment and Natural Resources Region 7, in accordance with the Philippine Republic Act No. 9147 (Wildlife Resources Conservation and Protection Act). The present study specifically conducted fieldwork in Mt. Lantoy in Argao, Cebu (latitude: 9.902500 and longitude: 123.529722) and from the Experimental Forest Station of DENR-CRERDEC in Minglanilla, Cebu (latitude: 10.325278 and longitude: 123.774444) from March to June 2024.

Collection and taxonomic identification

During the fieldwork, the species was primarily identified and collected with the help of forest guards and local guides. Leaves of the specimens were measured with a digital caliper and morphologically characterised, based on published studies by Seidenschwarz (2013) and Lillo et al. (2023). Co's Digital Flora of the Philippines (Pelser et al. 2011), a digital database of the native, naturalised, and invasive vascular plant species of the Philippines, was also used to verify species identity and confirm their presence in the areas. Samples were collected as voucher specimens and deposited in the Philippine Herbarium of Cultivated Plants at the Institute of Crop Science, University of the Philippines Los Baños. Photographs of C. cebuensis in its natural habitat were captured and processed using licensed Adobe Photoshop software to enhance visual clarity.

Mapping the distribution of C. cebuensis

Location coordinates were recorded during sample collection and mapped using QGIS v. 3.36 Maidenhead. A thorough literature review was also conducted to collect and incorporate previously reported coordinates of C. cebuensis from published journals and online databases. All occurrence points collected for this study were incorporated into the updated distribution map.

Cynometra cebuensis was initially discovered and described in Tabunan Forest, located in the Central Cebu Protected Landscape on Cebu Island, Philippines (Seidenschwarz 2013, Lillo et al. 2023). Subsequently, three years later, Pelser and Barcelona (2017) documented the species in Brgy. Cansuje, Argao and in the Municipality of Boljoon, Cebu. This observation was further supported by Lillo et al. (2023), who reported the species' occurrence in Mt. Lantoy in Argao, along with another distribution record in Mt. Kapayas in Carmen, Cebu (Lillo et al. 2021). These reported occurrence points were not integrated into a single map nor submitted to the Global Biodiversity Information Facility (GBIF). In this study, specimens of C. cebuensis were observed in limestone forests at both Mt. Lantoy in Argao and Camp 7 in Minglanilla, Cebu. The species' presence in Minglanilla marks a new distribution record. In addition to previously published data, it can be inferred that the species predominantly inhabits dry forests situated over limestone at an altitude of 400 m above sea level. Notably, younger and smaller individuals, with a maximum height of 3 m, were identified in Mt. Lantoy, while taller counterparts, reaching up to 5 m, were found in Minglanilla, Cebu. Only three wildlings were found on the forest floor of Mt. Lantoy, whereas 18 wildlings were discovered in Minglanilla, Cebu.

The updated distribution map of C. cebuensis generated in this study holds important implications for understanding the suitable habitats of the critically endangered species, providing insights into its current geographical range and distribution patterns. Findings from this study refute the previously held restrictions about the endemicity of C. cebuensis in Tabunan Forest (Seidenschwarz 2013) indicating its wide distribution range and resilience across sites (Lillo et al. 2023). However, it is important to note that the species grows along trails and in nearby residential areas, which can impact its population growth due to the unregulated harvesting of wood from the forests. The medicinal and pharmaceutical potential of the plant also remains largely untapped due to its rarity and slow growth rate. Accessing large amounts of leaves for pharmacological screening is restricted by Department of Environment and Natural Resources (DENR) regulations, as the plant is critically endangered. Acquiring a Wildlife Gratuitous Permit from DENR is necessary for this purpose. As per Seidenschwarz (2013), the species is characterised by slow growth, typically reaching an average height of 8 m with a stem diameter of 8.6 cm after 10 years. The general public is often unaware of their slow growth rate, which can be detrimental to the species. According to a staff member from DENR-Community Environment and Natural Resources Office in Argao, these trees are often cut down for fencing and firewood before they reach maturity. In terms of its phenology, it only begins flowering nine years after planting, making the collection of seeds and fruits challenging (Seidenschwarz 2013). Identifying the species quickly during fieldwork is also difficult due to this factor. We suggest collecting seeds from the species to establish plant sanctuaries to support local pollination and exploring methods such as in vitro micropropagation for its cultivation. We also recommend exploring uncharted areas within Cebu Island to find the species and use ecological niche modelling to predict its distribution, taking into account climate data and the edaphic factors of its environment. By doing so, the current population and its resilience will be assessed, allowing for a re-assessment of its conservation status using the Red List Index (RLI).

The discovery of C. cebuensis in additional locations, especially in key biodiversity areas (KBAs), underscores the significance of these sites in terms of habitat suitability. This suggests that these locations offer optimal environmental conditions for the species' growth and may serve as crucial habitats, highlighting the urgency of their protection and conservation. The collective effort, support and collaborations with various stakeholders such as local government units (LGUs), national government agencies (NGAs), academic and research institutions and non-governmental organisations (NGOs) are essential for the protection of our critically endangered and endemic species like C. cebuensis.