Population structure and distribution of Critically Endangered Cycas sancti-lasallei Agoo & Madulid (Cycadaceae) in northern Mindanao, Philippines

Jether S. Suminig; Lynnette Lagria; Hannah P. Lumista; Fulgent P. Coritico; Vanessa Handley; Maria Melanie M. Guiang

Authors

Jether S. Suminig Plant Biology Division, Institute of Biological Sciences, College of Arts and Sciences, Central Mindanao University, Maramag, Bukidnon 8710, Philippines.; Center for Biodiversity Research and Extension in Mindanao (CEBREM), Central Mindanao University, Maramag, Bukidnon 8710, Philippines.
Lynnette Lagria Plant Biology Division, Institute of Biological Sciences, College of Arts and Sciences, Central Mindanao University, Maramag, Bukidnon 8710, Philippines.
Hannah P. Lumista Plant Biology Division, Institute of Biological Sciences, College of Arts and Sciences, Central Mindanao University, Maramag, Bukidnon 8710, Philippines.
Fulgent P. Coritico Plant Biology Division, Institute of Biological Sciences, College of Arts and Sciences, Central Mindanao University, Maramag, Bukidnon 8710, Philippines.; Center for Biodiversity Research and Extension in Mindanao (CEBREM), Central Mindanao University, Maramag, Bukidnon 8710, Philippines.
Vanessa Handley Montgomery Botanical Center, Old Cutler Road, Coral Gables, Florida 33156, United States of America.
Maria Melanie M. Guiang Plant Biology Division, Institute of Biological Sciences, College of Arts and Sciences, Central Mindanao University, Maramag, Bukidnon 8710, Philippines.; Natural Science Research Center, Central Mindanao University, Maramag, Bukidnon 8710, Philippines.

Keywords:

aggregated spatial distribution, endemic gymnosperm, population survey, sex ratio

Abstract

Cycas sancti-lasallei Agoo & Madulid is a Critically Endangered (CR) cycad endemic to Mindanao. Its population structure, sex ratio, and distribution remain poorly understood; therefore, this study aims to provide a more comprehensive characterization of these parameters. Fieldwork was conducted across five plots in Mapawa Nature Park, Barangay Cugman, and one plot in Barangay F.S. Catanico, collectively covering 25,000 ha. Individual locations were mapped using QGIS and GeoCAT. A total of 1,015 individuals were recorded, with the population dominated by juvenile plants with reproductive adults comprised only 4.93% of the total population. This pattern suggests active recruitment but limited progression to reproductive maturity. Reproductive adult density was low (20 plants/ha), with nearly half of these individuals concentrated in a secondary forest site, whereas youngest stage juveniles exhibited the highest density (125.6 plants/ ha). The sex ratio was skewed toward females (0.72:1), which may reflect differences in detectability between sexes during a single survey period rather than a true demographic imbalance. Spatial analysis indicated an aggregated distribution pattern influenced by terrain, soil properties, and vegetation structure. Secondary forests with loamy soils acted as reproductive hubs, supporting nearly half of all coning individuals. In contrast, areas with steep rocky slopes,invasivevegetation,ordensecanopycover supported fewer individuals and showed limited reproductive activity. The skewed stage structure, low abundance of reproductive adults, and spatially constrained distribution suggest potential limitations to the long-term viability of C. sancti-lasallei. These findings highlight the need for targeted conservation strategies and habitat protection.

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