A holistic conservation approach for threatened filmy and grammitid ferns of Sri Lanka

Abstract

Isolated tropical islands support unique biodiversity and high endemism but face high extinction risks for some plant species due to small, fragmented populations and increasing anthropogenic pressures. Sri Lanka, a continental island in the Western Ghats–Sri Lanka biodiversity hotspot, hosts remarkable pteridophyte flora, including two highly threatened groups: the filmy ferns (Hymenophyllaceae) and grammitid ferns (Grammitidoideae). Owing to their narrow ecological niches and dependence on humid, shaded microhabitats, these taxa are highly sensitive to microclimatic shifts and habitat disturbance. This study proposes a holistic conservation approach to safeguard these fern groups by integrating historical and contemporary data, herbarium records, geospatial analyses, hotspot identification, and expert knowledge. Using 752 herbarium specimens from 22 global herbaria, together with recent field collections, we mapped species distributions, examined temporal collection patterns, and identified priority regions and climatic envelopes essential for their survival. Results reveal that high-elevation and southwestern wet-zone forests are key hotspots. Additionally, the analysis identified three hotspots for grammitid ferns and two for filmy ferns. The study outlines a roadmap incorporating species prioritization, targeted field surveys, microhabitat restoration, in situ conservation, ex situ propagation via high-tech greenhouses, community engagement, and collaborative research. Emphasis is placed on strengthening national herbarium resources, integrating citizen science, applying genomic tools, and aligning conservation actions with global frameworks. This holistic, multidisciplinary strategy provides a comprehensive foundation for conserving Sri Lanka’s threatened filmy and grammitid ferns and offers a model applicable to other island flora worldwide.