Conservation biology of the last Italian population of Cistus laurifolius (Cistaceae): demographic structure, reproductive success and population genetics

Isolated populations are usually subject to low fitness and reduced genetic diversity, both of which may negatively affect their survival and adaptive potential. Hence, these issues cannot be neglected when planning conservation actions for isolated populations. The Italian population of Cistus laurifolius subsp. laurifolius is extremely isolated. Furthermore, it is affected by fragmentation, being constituted by a single larger subpopulation, surrounded by three much smaller subpopulations, a few hundred metres to a few kilometres apart. In order to fill gaps in demographic and genetic knowledge concerning the Italian population, its area of occupancy, size, age-stage structure and phenology were investigated and its reproductive fitness, pollination strategies and genetic variability were assessed. The population was inferred as fully xenogamous and showed good reproductive performance. Despite this, its genetic variability was low and it showed relatively high levels of inbreeding depression (Fis), seemingly not affected by sub-population size. These results suggest that the Italian population recently suffered fragmentation and reduction in size. The low genetic diversity observed could be explained by the high percentage of mature individuals found in the population, possibly established before fragmentation. For these reasons, the Italian population of C. laurifolius subsp. laurifolius should be monitored and concrete actions aimed at its conservation planned.