Where Lineages Persist: Phylogenetic Patterns and Evolutionary Vulnerability in South Africa's Herpetofauna

Abstract

ABSTRACT Aim Conservation under the current global biodiversity crisis demands strategic prioritisation to maximise the impact of limited resources. This study aims to integrate evolutionary history, an often‐overlooked component of biodiversity, alongside extinction risk to identify priority species and regions, assessing both the feasibility and utility of various metrics for phylogenetic diversity. Location South Africa is used as the case study region due to exceptional herpetofaunal diversity and endemism spanning across a highly heterogeneous landscape. Methods We quantified phylogenetic diversity (PD), phylogenetic endemism (PE), expected loss of PD and Evolutionarily Distinct and Globally Endangered (EDGE) metrics for all native amphibians and reptiles of South Africa. National‐scale phylogenetic trees were compiled, and spatial patterns of PD and PE were analysed. Observed values were compared against null models to identify statistically significant deviations. Extinction probabilities derived from IUCN Red List categories were applied to estimate global tree‐of‐life reporting metrics, namely the PD indicator and the EDGE index, both of which were subsequently spatially assessed. Results Distinct spatial patterns revealed a decoupling between PD, PE and species richness. Extinction‐weighted metrics indicated that, without intervention, approximately 6.5% of amphibian PD and 5% of reptile PD are projected to be lost over the next 50 years. Updated EDGE lists and EDGE indices were generated for both groups, identifying priority species for conservation. Spatial distributions of extinction‐weighted metrics largely overlapped with regions of high PE in amphibians and regions of high PD in reptiles, highlighting key areas for evolutionary conservation. Main Conclusions Integrating evolutionary metrics with extinction risk improves our understanding of biodiversity patterns and priorities. This study provides a framework for national‐scale phylogenetic biodiversity monitoring with an approach that aligns with global biodiversity monitoring frameworks, supporting more effective strategies for safeguarding South Africa's evolutionarily unique amphibian and reptile lineages.