Regional-scale demography of Ramonda myconi: Remnant population dynamics in a preglacial relict species

Remnant population dynamics permit many plant species to persist time spans extending from decades up to several millenia. The regional-scale persistence of these plant species strictly depends on the persistence of local populations within the region. This type of dynamics can explain the existence of preglacial relict species in the Mediterranean today. We studied the population dynamics of the long-lived iteroparous herb Ramonda myconi, a preglacial relict species with a fragmented distribution in Mediterranean mountains, to evaluate the regional-scale persistence of the species. Demographic data were collected from 5 populations placed at La Cerdanya Pyrenean region for up to 6 years. The main life-history features of this species are the great longevity of adult plants and the high mortality of seedlings. Matrix population models were used to investigate its demography. Overall, the population growth rate (λ) ranged from a low of 0.79 to a high of 1.06. However, λ did not differ significantly from the equilibrium point, as indicated by their confidence intervals, except for one population in one year. Despite the small between-year variation in λ, variation in climatic conditions at La Cerdanya from year to year explained an important part of such variation. Elasticity analyses were performed to evaluate the relative importance of demographic parameters for population growth. Stasis transitions made the greatest contribution to λ. Finally, the long-term dynamics of R. myconi populations were analysed by incorporating environmental stochasticity into the models. Projections indicated that local R. myconi populations tend to decline over time but with a long time to extinction, so the persistence of R. myconi all over La Cerdanya is determined by the persistence of its remnant local populations. © 2002 Kluwer Academic Publishers.