Heliotropium rottleri Lehm : A lesser known endemic taxa in vulnerable hydrogeomorphic gap areas of Southern Western Ghats, Kerala, India

Heliotropium rottleri Lehm. (Boraginaceae) is a less known endemic taxa recorded from scrub jungles and dry deciduous forests near the gap areas of Southern Western Ghats, Kerala, India. Even though preliminary taxonomic accounts are available, no attempt has been made to assess the distributional range, morpho-anatomical, palynological and ecological features of this endemic taxon. Populations distributed in the vulnerable ephemeral niches determined by specific hydrogeomorphic conditions of rocky plateaus in the gap areas showed morphological variations. The morphometric analysis along with anatomical features including stomatal and trichome traits and pollen features showed less variations except in macro morphology. Leaf trichomes were uniseriate and stomata were anomocytic. The stomatal index varied between155 to 168 among populations and stomatal density ranged from 15.0-16.6 per square centimetre. The scanning electron microscopic analysis of the pollen grains revealed them to be brevipentacolporate with micro punctate exine ornamentation. As the vulnerable microhabitats where the taxon is being distributed faces serious threats of mining, land conversion and grazing, the species might get disappeared in near future due to the narrow ecological amplitude possessed by the taxon.