Naufraga balearica, a threatened narrow endemism of the Balearic Islands ( western Mediterranean basin): assessing the population dynamics of two subpopulations

Naufraga balearica constitutes a monospecific genus of Majorca (Balearic Islands) and is Critically Endangered according to International Union for Conservation of Nature categories. The species has a narrow distributional area, with one subpopulation at Coves Blanques (CB) and a small set of subpopulations on the Formentor Peninsula. A previous work has shown that the subpopulation in Cap de Catalunya (CC) (located on the Formentor Peninsula) has undergone a distinct decline over the last decade. Herein, we report a comparative study of the population dynamics of N.balearica at the CB and CC sites. By monitoring permanent plots for 6 years (2004-2009), we analyzed the frequency of cells in which the species was present, and, for each annual transition (from November, year t to November, year t+1), we determined the frequency of cells in which the species was stable, decreased or increased for each species and site using a G-test of independence. The same parameters were also analyzed for N.balearica at the quarterly transitions of November-February, February-May, May-August and August-November. The results indicated that the decline of the threatened species was more marked in the CB subpopulation. N.balearica showed a seasonal trend at both sites, with some exceptions. The most common neighboring species were Dactylis glomerata and Erodium reichardii, and they negatively affected N.balearica; however, the neighboring species effect was not homogeneous among the annual transitions analyzed, indicating that other factors are involved. Finally, some conservation measures are proposed.