Identification of plant micro-reserves using conservation units and population vulnerability: The case of an endangered endemic Snowflake (Acis nicaeensis) in the Mediterranean Basin hotspot

International audienceErosion of natural habitats due to urban sprawl constitutes a major threat to biodiversity. The development of the Plant Micro-Reserve (PMR) is an efficient concept for the in situ conservation of rare plants with narrow ecological niche and threatened by human impacts. We provide a framework for initiating site selection of PMRs, including evolutionary and ecological uniqueness. The proposed cross-analysis is based on (i) the estimate of population vulnerability, (ii) the contribution of each population to the evolutionary originality of the species by designating conservation units, and (iii) the gap analysis of the current protection status of the populations. As a case study, we apply this framework to the Nice Snowflake Acis nicaeensis, a narrow Mediterranean endemic plant of the French-Italian Riviera which, being caught in the turmoil of urban sprawl, is threatened by tremendous anthropogenic pressures. On the basis of historical data (past land-use and herbarium data) we show that over the last 150 years, the impact of urbanization has been severe for 70 % of the populations and has caused the disappearance of at least 11 of them, i.e. 20 % of the known populations. Similar levels of urban sprawl are observed between the most vulnerable and already extinct populations. In this context of biodiversity decline, our cross-analysis highlights that two of the five conservation units call for a rapid setting up of PMRs because of their high originality and their great risk of extinction: one unit including the populations of the Principality of Monaco and one unit that includes the populations of Nice and its surroundings. This study demonstrates the importance of integrating population vulnerability and conservation units. In a context of huge urbanization our approach makes a clear case for the design of PMR