Factors Controlling the Distribution of Desiccation-Tolerant Plants in West Africa

Abstract

Biodiversity loss driven by human activities is accelerating globally, yet some functional groups remain largely overlooked in conservation planning. Desiccation-tolerant (DT) vascular plants, which can survive extreme dehydration, are among these overlooked taxa and face increasing threats from climate change and anthropogenic pressures. This thesis provides the first comprehensive assessment of desiccation-tolerant vascular plants in West Africa, a region of high biodiversity value and growing vulnerability to land-use change and climate extremes, addressing knowledge gaps in their diversity, distribution, ecological strategies, and conservation needs under global change. First, we compiled a checklist of DT species in the region, systematically reviewed the literature on their conservation status, and evaluated their representation in protected areas relative to anthropogenic threats such as quarrying and climate change. The results of this work show that only 14% of species have been assessed by the IUCN, and conservation needs are rarely discussed in the existing literature. Notably, the species that are the most exposed to threats were also the least represented in protected areas, which proved more effective at reducing quarrying impacts than at mitigating climate change. Second, species distribution models were used under current and projected climate scenarios, and the findings reveal a substantial contraction of distribution ranges, an increased fragmentation, and a significant reduction in species diversity and endemism centers. The findings highlighted the vulnerability of desiccation-tolerant plants to future climate conditions and the need to integrate climate-informed strategies into conservation planning. Third, the role of soil was explored in shaping intraspecific variation in ecological strategies among four selected desiccation-tolerant grasses. Although there are no significant relationships between soil variables and CSR strategies detected, the predominance of stress-tolerant strategies suggests an overriding influence of disturbance or other environmental drivers. Finally, experimental results demonstrated that seed age may compromise early seedling desiccation tolerance, revealing critical vulnerabilities during early life stages. This study stresses the urgent need to integrate desiccation-tolerant plants into biodiversity conservation frameworks through mechanistic, climate-informed approaches that account for species vulnerability in terms of exposure, sensitivity, and adaptive capacity. By combining ecological, physiological, and biogeographic perspectives, this work establishes a foundation for prioritizing desiccation-tolerant plants in conservation planning and provides actionable insights to enhance species persistence under increasingly water-limited conditions and the broader challenges of global change.