Ecological Adaptation of Endemic Anthocleista Species under Moisture Gradient in Parts of Niger Delta, Nigeria

Abstract

Background: Knowledge of the anatomy of Anthocleista species is crucial for understanding how these plants adapt to the environment. Aim: This study was aimed at investigating the adaptive relationship of moisture gradient influence on the anatomy of four species in the genus Anthocleista (A djalonesis A Chev; A.  liebrechtsiana De Wild & Th.Dur; A. nobilis G.Don; and A. vogelii Planch) in light of ecological niche adaptation. Place of Study: parts of Akwa-Ibom, Bayelsa, Cross River and Rivers States in the Niger Delta. Methods: Conventional classical anatomical techniques for structural sectioning were used. Results: Though there are similarities and differences in vascular structure among the species, the study has revealed variance in anatomical responses to moisture gradient (ranging from dry mesophytic to mesophytic and wetland conditions) of adaptation. The most important and distinct features observed are the presence of sclerenchymatous idioblast, air sacs and sclereidal idioblast. Sclerenchymatous idioblasts are numerous in A liebrechtsiana, few in A.  nobilis and A. vogelii but lacking in A. djalonesis. The sclerenchymatous idioblast in A. liebrechtsiana, A. nobilis, and A. vogelii confirmed these species to be mesophytic to semi-aquatic in their habitat adaptation; while A. djalonesis is dry-mesophytic in adaptation with thicker epidermal layer, multiple hypodermal layers, thicker mesophyll tissues with increased number of palisade layers and thick leaves. The stem and root modification had abundance sclereidal idioblast distribution in A. liebrechtsiana, and A. nobilis, moderate in A. vogelii and very low in A. djalonesis. Conclusion: The variation observed in the leaf, petiole, stem and root anatomical characters are due to moisture gradient influence with the resultant effect of plant species evolving structures such as idioblast and modification to adapt to the niche and environment where they find themselves.