Thermal Effects on Early Life Stages of Leptocereus (Cactaceae) Species from Cuban Seasonally Dry Tropical Forests

Rising temperatures are among the most predictable outcomes of climate change, and cacti are particularly vulnerable at the germination stage. We tested seeds of ten Cuban Leptocereus species from coastal and inland habitats under five temperature regimes to evaluate germination responses, thermal buffering capacity for optimal germination, photoblastic behavior, recovery after heat stress, and seedling vigor. Germination declined sharply with increasing temperature, revealing minimal thermal buffering capacity for optimal germination. All species exhibited positively photoblastic seeds, while recovery and the degree of physiological dormancy varied among taxa. Except for one taxon, most displayed partial dormancy that could stagger germination over time. Seedling vigor was not affected by high temperatures in the same way in all species. Overall, our findings suggest that climate warming will further constrain the germination niche of Leptocereus, underscoring the importance of conservation measures such as ex situ propagation.