Fire avoidance and long-term population decline in the endangered Florida ground lichen Cladonia perforata within a...

Fire is a key ecological process that shapes ecosystems globally, yet fire adaptation strategies remain unclear for many species, especially for ground lichens that are reliant on pyrogenic landscapes but are evidently fire-intolerant. In the pyrogenic Florida scrub, fire-sensitive Cladonia ground lichen species are an important component of the ground layer and influence ecosystem processes. The endangered Cladonia perforata is of special concern because fire regimes can dictate the persistence of the species. We aim to clarify (1) its subpopulation trends, (2) its post-fire recovery, and (3) the influence of microhabitat factors on these patterns.

We analyzed 14 years of detailed monitoring data from nine Cladonia perforata subpopulations on the Lake Wales Ridge that experienced eight fires. We used subpopulation area, occupancy, and fine-scale cover to estimate abundance on multiple spatial scales and analyzed the effects of burn severity, dominant ground cover, and canopy cover on C. perforata abundance over time.

Abundance declined across almost all subpopulations (decreased odds ratio 0.14 for occupancy and 0.20 for cover per year). Severe fire reduced abundance, and subpopulations did not recover. Abundance was highest in litter cover, with a preference for open canopy post-fire.

Cladonia perforata is a fire-sensitive species with very limited growth and recolonization capacity. The detrimental fire effects here indicate a fire avoidance strategy, but litter accumulation may limit this strategy. These results highlight the delicate balance of using fire to promote the conservation of fire-sensitive species in a pyrogenic habitat.