such as Eucalyptus (Myrtaceae) and even exceptionally in Erica sessiliflora (Ericaceae). In the northern hemisphere, it is found in a range of conifer taxa, including species of Pinus, Cupressus, Sequoiadendron, and more rarely Picea. Since even non-serotinous cones and woody fruits can provide protection from the heat of fire, the key adaptation of fire-induced serotiny is seed storage in a canopy seed bank, which can be released by fire. The fire-release mechanism is commonly a resin that seals the fruit or cone scales shut, but which melts when heated. This mechanism is refined in some Banksia by the presence inside the follicle of a winged seed separator which blocks the opening, preventing the seed from falling out. Thus, the follicles open after fire, but seed release does not occur. As the cone dries, wetting by rain or humidity causes the cone scales to expand and reflex, promoting seed release. The seed separator thus acts as a lever against the seeds, gradually prying them out of the follicle over the course of one or more wet-dry cycles. The effect of this adaptation is to ensure that seed release occurs not in response to fire, but in response to the onset of rains following fire. The relative importance of serotiny can vary among populations of the same plant species. For example, North American populations of lodgepole pine (Pinus contorta) can vary from being highly serotinous to having no serotiny at all, opening annually to release seed. Different levels of cone serotiny have been linked to variations in the local fire regime: areas that experience more frequent crown-fire tend to have high rates of serotiny, while areas with infrequent crown-fire have low levels of serotiny. Additionally, herbivory of lodgepole pines can make fire-mediated serotiny less advantageous in a population. Red squirrels (Sciurus vulgaris) and red crossbills (Loxia curvirostra) will eat seeds, and so serotinous cones, which last in the canopy longer, are more likely to be chosen. Serotiny occurs less frequently in areas where this seed predation is common. Pyriscence can be understood as an adaptation to an environment in which fires are regular and in which post-fire environments offer the best germination and seedling survival rates. In Australia, for example, fire-mediated serotiny occurs in areas that not only are prone to regular fires but also possess oligotrophic soils and a seasonally dry climate. This results in intense competition for nutrients and moisture,