Demography and viability of peripheral populations of Thymus loscosii, an endemic plant of the Ebro Valley

Abstract

Demography and viability of peripheral populations of Thymus loscosii, an endemic plant of the Ebro Valley.

In order to explore the performance of peripheral populations of a restricted plant, I studied the demography, reproductive biology, and the dynamics of some populations of Thymus loscosii (Lamiaceae), an endemic plant of the Ebro valley formerly considered as very endangered. Neither the variables analyzed in isolation nor the deterministic population models generated after assembling all the most important vital rates indicate problems. The stochastic models suggested no population extinction for the next 50 years if current sizes and vital rates persist. The ecological scenarios created to simulate the population response to different problems (predation, increase of mortality in a persistent or stochastic way, reduction of recruitment...), by means of population viability analysis (PVA), suggest that changes in survival of established plants would have a higher influence on population growth rate and extinction probability than changes in vital rates linked to recruitment.