Analysis of climate changes, habitat fragmentation and germination behavior in Muscari gussonei, Petagnaea gussonei and Poterium spinosum, three Mediterranean plants of conservation interest

Knowing the optimum germination temperatures of endangered plants, as well as the magnitude of climate changes (e.g., rising temperatures) across the spatial range of these species, is essential to assess the level of threat for such species and, consequently, to implement tailored and enduring conservation programs. These analyses should be also integrated by the study of land-cover changes, which can act as an indicator of landscape fragmentation and, therefore, as a proxy of gene flow across metapopulations of species of conservation interest. This study, in particular, investigated both the germination behavior of Muscari gussonei, Petagnaea gussonei and Poterium spinosum, and the trends of climate and land-cover changes occurred in the distributional areas of these species. M. gussonei and P. gussonei are two endangered and narrowly distributed endemic plants from Sicily (Italy), whereas P. spinosum is another biogeographically important species with a highly scattered range across south-eastern Sicily. All the studied plants showed the same narrow germination optimum of 10–15 °C, but different final germination percentage (FGP): 82–98% in M. gussonei, 10–38% in P. gussonei, 5–61% in fruits and 21–68% in seeds of P. spinosum. These optimum germination temperatures are low and limited and, therefore, make the three species much more vulnerable to ever-rising temperatures, which specifically increased by up to 2 °C in the period 1931–2020. Similarly, across the species ranges during 2000–2018, the analysis of CORINE Land Cover classes showed highly fragmented landscapes, where forest and seminatural areas (class 3) declined, and agricultural areas (class 2) increased. The ongoing climate changes will make the suitable germination temperatures harder to be reached by plants with low and narrow germination optimum, such as M. gussonei, P. gussonei and P. spinosum, whose survival is further threatened by a complex fragmented territory with declining natural areas.