The abundance paradox: Integrated morpho-molecular characterization and identification of evolutionarily significant units in Nigerian Piper and Pterocarpus

Abstract

Traditional conservation monitoring often relies on morphological abundance, which can mask critical underlying genetic erosion. This study investigates the ‘Abundance Paradox’ in Southwest Nigeria through a combined morpho-molecular assessment of the Piper and Pterocarpus genera – taxa of significant ethno-medicinal and timber value. We employed a robust integrated approach combining 31 vegetative descriptors with chloroplast Simple Sequence Repeat ( SSR) , nuclear SSR and Amplified Fragment Length Polymorphism ( AFLP) markers to assess genetic diversity across a Lowland Rainforest-Derived Savanna gradient. Sampling covered five distinct land-use types: Primary forest reserves, degraded secondary forests, smallholder farmlands, institutional gardens and sacred groves. Analysis revealed that while Piper guineense appears locally abundant in farmlands, it suffers a significant 12% reduction in expected heterozygosity ( He ) and shows clear signs of a recent bottleneck ( P  < 0.05). In contrast, Pterocarpus erinaceus demonstrated high genetic differentiation ( F _ST  = 0.24), leading to the identification of three distinct evolutionarily significant units aligned with regional ecological zones. Sacred groves were found to maintain biodiversity levels comparable to primary forests, outperforming degraded areas. These data demonstrate that high phenotypic frequency is a misleading proxy for genetic health, and that morphological plasticity in disturbed habitats masks underlying genomic erosion. We provide actionable recommendations for the National Biodiversity Strategy and Action Plan 2025–2030, emphasizing the need for molecular auditing to safeguard the adaptive potential of underutilized tropical genetic resources.