Bridging Species Richness and True Diversity: A Quantitative and Ratio Analysis Approach from Indian Biodiversity Studies

Abstract

Aims: The present study proposes new metrics linking species richness (N​0) and true diversity, calculated as the first-order Hill Number (N1​), viz., Diversity Delta (N0​−N1​), True Diversity-to-Species Richness Ratio (N1​/N0​), and Species Richness-to-True Diversity Multiple (N0​/N1​). Study Design: The proposed metrics were applied on a dataset of 351 observations from 105 published studies. Place and Duration of Study: The analysis was based on observations drawn from ecological studies done across diverse ecosystems in India, published since 2000. Methodology: Calculation of proposed measures and data visualization were performed using MS-Excel and Python. Incorrect and ambiguous observation were excluded from the dataset. Relationships between Shannon’s Index (H) and species richness were also assessed. Results: Diversity Delta ranged from 1 to 517, N0​/N1​ multiple from 1.0333 to 40.6667, and N1​/N0​ ratio from 0.0246 to 0.9677. Shannon’s Index (H) exhibited a characteristic rectangular hyperbolic relationship with species richness (N0​), highlighting diminishing returns of increasing richness on diversity. Conclusion: The proposed metrics offer intuitive and complementary tools to conventional indices. While Diversity Delta (N0–N1) emerged as a robust sanity check to identify miscalculations, high N0/N1 multiples or low N1/N0 ratios acted as benchmarks to assess conservation success. The proposed ratios viz., N1​/N0 Ratio and N0​/N1 multiple offer insights analogous to financial ratios such as Earnings Per Share and Price-to-Earnings multiple, respectively, emphasizing per capita species contribution to true diversity rather than overall site-level equitability or dominance, providing a unique perspective distinct from existing measures. Additionally, the study highlights methodological ambiguities in reported diversity measures and their interpretation in publications, and proposes remedial measures to avoid those in future. The study also provides an exhaustive account of ecological work done in India over the last 25 years, documented in the references, serving as a valuable reference point for future investigations.