Population biology, ecological niche modelling of endangered and endemic Pittosporum eriocarpum Royle in Western Himalaya, India

Pittosporum eriocarpum, an endemic, endangered, and multipurpose tree of the Indian Himalayan Region, is found in restricted pockets. The available studies on the species reveals that the studies are mostly focused on taxonomy and ethnobotany/resource use patterns. Therefore, the present study assessed the populations; analyzed the physico-chemical properties of soil; developed Ecological Niche Model; and standardized seed germination protocol for conservation. Sixteen populations of P. eriocarpum were surveyed and sampled in Himachal Pradesh. The density of P. eriocarpum ranged from 10 to 40 Ind/ha, it was highest in the rocky habitat (15 Ind/ha) and west aspect (40 Ind/ha). Pinus roxburghii, Pistacia chinensis ssp. integerrima, Grewia optiva, Albizia lebbeck, Quer-cus oblongata and Bauhinia variegata were major associated trees. Soil was analysed for the physico-chemical properties. In most of the populations, P. eriocarpum was in the form of saplings and seedlings. P. eriocarpum density had a significant negative correlation with pH. To predict potentially suitable habitats for P. eriocarpum, species occurrence data, bio-climatic variables, and the maximum entropy distribution modelling approach were used. The model's results revealed that 9.37 % of Himachal Pradesh is appropriate for species reintroduction. Both GA3 and KNO3 were highly effective for increasing germination and decreasing MGT and played a signif-icant role in the seed germination. Despite the high viability of seeds, species cannot regenerate and spread in their native environments. This might be a result of overexploitation, intensive grazing, and competition among associated species. For in-situ conservation, regular monitoring and complete habitat protection are recommended.

Automated summary

Pittosporum eriocarpum is an endemic and endangered tree in the Indian Himalayan Region, with limited distribution. Previous studies on the species focused mainly on taxonomy and ethnobotany/resource use patterns. This study aimed to assess populations, analyze soil properties, develop Ecological Niche Model, and standardize seed germination protocol for conservation purposes. The study surveyed and sampled sixteen populations of P. eriocarpum in Himachal Pradesh. Results showed variations in density among populations, with the highest density in rocky habitats and west-facing aspects. Major associated trees included Pinus roxburghii, Pistacia chinensis ssp. integerrima, Grewia optiva, Albizia lebbeck, Quer-cus oblongata, and Bauhinia variegata. Soil analysis revealed significant negative correlation between P. eriocarpum density and pH. The study also used species occurrence data and bio-climatic variables to predict suitable habitats for reintroducing P. eriocarpum, finding that 9.37% of Himachal Pradesh is appropriate. Furthermore, the study found that GA3 and KNO3 were effective in increasing germination and reducing mean germination time for P. eriocarpum seeds. Despite high seed viability, the species faces challenges in regeneration and spreading due to overexploitation, intensive grazing, and competition from associated species. Regular monitoring and complete habitat protection are recommended for in-situ conservation.