TRENDS IN POPULATION SIZE OF OPHRYS ARGOLICA SUBSP. BISCUTELLA IN THE APPENNINO LUCANO-VAL D’AGRI-LAGONEGRESE NATIONAL PARK (ITALY)

n this study we focused on population monitoring of Ophrys argolica subsp. biscutella, an orchid endemic to the south of the Italian Peninsula belonging to the section Araniferae. The study concerned its main detected population located within the Appennino Lucano-Val d'Agri-Lagonegrese National Park (Basilicata Region, South Italy). Ten permanent plots of 10 × 10 m were annually surveyed from 2010 to 2015 using total counts of flowering plants. The following characters were measured: height of inflorescences, number of flowers, lost plants, fruiting plants and fruit set. Percentage cover of trees, shrubs, herbs and bare rocks were visually estimated in 1 × 1 m subplots and an accurate vegetation map of each plot was drawn. In regards to plant height and reproductive variables, no significant differences between the plots were detected. Similarly, with respect to population variables, no significant correlations with vegetation and environmental features (i.e. slope, aspect) emerged. On the contrary, a strong negative trend in the population size was observed (from 237 individuals in 2010 to 61 in 2015) and the number of plants per plot decreased from 23.7 individuals to 6.1 individuals. Reproductive variables (i.e. number of flowers, fruit set) showed a similar decreasing pattern. As for the lost of individuals we detected a higher incidence in 2011 (average number of lost plants per plot was 16.6) with 75% of lost spikes and fruit set amounting to zero. Although grazing management can heavily influence demographic parameters of Ophrys populations, there was no evidence of any kind of land cover or land use change. No appreciable differences were observed in vegetation cover, grazing type or grazing load. Moreover, no significant disturbance events occurred in this area. Finally, the inspection of meteorological data recorded during the monitoring interval lead to argue that the strong demographic decline of the Ophrys argolica subsp. biscutella population in the Appennino Lucano-Val d'Agri-Lagonegrese National Park must be mainly related to the late frost event that occurred in the spring of 2011.